Better Stackis in the IT Operations Industry

Better Stack

Debugging a Spring WebFlux application can be a challenging task, especially when dealing with complex reactive streams. Unlike traditional blocking applications, where the stack trace provides a clear indication of the root cause of an issue, reactive applications can be harder to debug. Issues such as blocking code, concurrency problems, and race conditions can all cause subtle bugs that are difficult to diagnose. Scenario When dealing with a bug it’s not always a code-related issue. It could be a set of factors, such as recent refactoring, team changes, hard deadlines and so on. In real life, it’s a common thing to end up troubleshooting large applications made by people who left the company a while back, and you just joined. Knowing a little about a domain and technologies isn't going to make your life easier. In the code example below, I wanted to imagine how a buggy code could look like for a person recently joined a team. Consider debugging this code more like a journey rather than challenge. The root cause could be obvious to find for those who are familiar with Reactive apps. However, some practices down below could be still very helpful to revise. @GetMapping("/greeting/{firstName}/{lastName}")
public Mono<String> greeting(@PathVariable String firstName, @PathVariable String lastName) {

    return Flux.fromIterable(Arrays.asList(firstName, lastName))
            .filter(this::wasWorkingNiceBeforeRefactoring)
            .transform(this::senselessTransformation)
            .collect(Collectors.joining())
            .map(names -> "Hello, " + names);
}

private boolean wasWorkingNiceBeforeRefactoring(String aName) {
    // We don't want to greet with John, sorry
    return !aName.equals("John");
}

private Flux<String> senselessTransformation(Flux<String> flux) {
    return flux
            .single()
            .flux()
            .subscribeOn(Schedulers.parallel());
} So, what this piece of code does is: It prepends “Hello, “ to the names provided as parameters. Your colleague John is telling you that everything works on his laptop. That’s true: > curl localhost:8080/greeting/John/Doe 
> Hello, Doe But when you run it like , you see the next stacktrace: curl localhost:8080/greeting/Mick/Jagger java.lang.IndexOutOfBoundsException: Source emitted more than one item
	at reactor.core.publisher.MonoSingle$SingleSubscriber.onNext(MonoSingle.java:134) ~[reactor-core-3.5.5.jar:3.5.5]
	Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Error has been observed at the following site(s):
	*__checkpoint ⇢ Handler com.example.demo.controller.GreetingController#greeting(String, String) [DispatcherHandler]
	*__checkpoint ⇢ HTTP GET "/greeting/Mick/Jagger" [ExceptionHandlingWebHandler]
Original Stack Trace: <18 internal lines>
		at java.base/java.util.concurrent.FutureTask.run(FutureTask.java) ~[na:na] (4 internal lines) Nice, neither of the traces leads to a code sample above. All it reveals is that 1) it occurred in the method, and 2) the client performed an `HTTP GET "/greeting/Mick/Jagger GreetingController#greeting .doOnError() First and the easiest thing to try out is to add `.doOnError()` callback to the end of the greeting chain. @GetMapping("/greeting/{firstName}/{lastName}")
public Mono<String> greeting(@PathVariable String firstName, @PathVariable String lastName) {

    return Flux.fromIterable(Arrays.asList(firstName, lastName))
            // <...>
            .doOnError(e -> logger.error("Error while greeting", e));
} Nice try, but logs don't show any improvement. Nonetheless, Reactor's internal stack trace: Here are some ways can/can’t be helpful during debugging: doOnError : You can use to log error messages and provide more context about what went wrong in your reactive stream. This can be especially helpful when debugging issues in a complex stream with many operators. Logging doOnError : can also be used to recover from errors and continue processing the stream. For example, you can use to provide a fallback value or stream in case of an error. Recovery doOnError onErrorResume : most probably won’t provide any better stacktrace except what you already saw in the logs. Don’t rely on it as a good troubleshooter. Debugging doOnError log() Next stop is to replace previously added by method call. As simple as it gets. observes all Reactive Streams signals and traces them into logs under INFO level by default. doOnError() log() log() Let’s see what additional info we see in logs now: We can see what Reactive methods have been called ( , and ). Additionally, knowing which threads (pools) these methods have been called from can be very useful information. However, it is not relevant to our case. onSubscribe request onError About thread pools Thread name stands for . Reactive methods and were executed on IO thread pool (scheduler). These tasks were executed immediately on a thread that submitted them. ctor-http-nio-2 reactor-http-nio-2 onSubscribe() request() By having inside we’ve instructed Reactor to subscribe further elements on another thread pool. That’s the reason why has been executed on thread. .subscribeOn(Schedulers.parallel()) senselessTransformation onError parallel-1 You can read more about thread pool . in this article method allows you to add logging statements to your stream, making it easier to track the flow of data and diagnose issues. If we were having more complex data flow with things like flatMap, subchains, blocking calls, etc., we would benefit much from having it all logged down. It’s a very easy and nice thing for daily use. However, we still don’t know the root cause. log() Hooks.onOperatorDebug() Instruction tells Reactor to enable debug mode for all operators in reactive streams, allowing for more detailed error messages and stack traces. Hooks.onOperatorDebug() According to the official documentation: When errors are observed later on, they will be enriched with a Suppressed Exception detailing the original assembly line stack. Must be called before producers (e.g. Flux.map, Mono.fromCallable) are actually called to intercept the right stack information. The instruction should be called once per runtime. One of the best places would be Configuration or Main classes. For our use case it would be: public Mono<String> greeting(@PathVariable String firstName, @PathVariable String lastName) {

    Hooks.onOperatorDebug();

    return // <...>
} By adding we can finally make progress in our investigation. Stacktrace is way more useful: Hooks.onOperatorDebug() And on line 42 we have call. single() Don’t scroll up, the looks next: senselessTransformation private Flux<String> senselessTransformation(Flux<String> flux) {
    return flux
            .single()  // line 42
            .flux()
            .subscribeOn(Schedulers.parallel());
} That’s the root cause. emits one item from Flux source or signals for a source with more than one element. That means flux in the method emits more than 1 item. By going up in the call hierarchy we see that originally there is a Flux with two elements . single() IndexOutOfBoundsException Flux.fromIterable(Arrays.asList(firstName, lastName)) Filtering method removes an item from a flux when it equals to . That’s the reason why the code works for a college named John. Huh. wasWorkingNiceBeforeRefactoring John can be particularly useful when debugging complex reactive streams, as it provides more detailed information about how the stream is being processed. However, enabling debug mode can impact the performance of your application (due to the populated stack traces), so it should only be used during development and debugging, and not in production. Hooks.onOperatorDebug() Checkpoints To achieve nearly the same effect as gives with minimum performance impact, there is a special operator. It will enable debug mode for that section of the stream, while leaving the rest of the stream unaffected. Hooks.onOperatorDebug() checkpoint() Let’s add two checkpoints after filtering and after transformation: public Mono<String> greeting(@PathVariable String firstName, @PathVariable String lastName) {

    return Flux.fromIterable(Arrays.asList(firstName, lastName))
            .filter(this::wasWorkingNiceBeforeRefactoring)
 /* new */  .checkpoint("After filtering")        
            .transform(this::senselessTransformation)
 /* new */  .checkpoint("After transformation")
            .collect(Collectors.joining())
            .map(names -> "Hello, " + names);
} Take a look at the logs: This checkpoints breakdown tells us that the error has been observed after our second checkpoint described as . It doesn’t mean that the first checkpoint hasn’t been reached during execution. It was, but the error started to appear only after the second one. That’s why we don’t see . After transformation After filtering You can also see two more checkpoints mentioned in the breakdown, from and . They were reached after the one we set, down to the call hierarchy. DispatcherHandler ExceptionHandlingWebHandler Besides description, you can force Reactor to generate a stacktrace for your checkpoint by adding as the second parameter to method. It’s important to note that the generated stacktrace will lead you to the line with a checkpoint. It won’t populate a stacktrace for the original exception. So it doesn’t make a lot of sense because you can easily find a checkpoint by providing a description. true checkpoint() Conclusion By following these best practices, you can simplify the debugging process and quickly identify and resolve issues in your Spring WebFlux application. Whether you're a seasoned developer or just starting out with reactive programming, these tips will help you improve the quality and reliability of your code, and deliver better experiences for your users.

How to Debug a Spring WebFlux Application

Cómo depurar una aplicación Spring WebFlux

Comment déboguer une application Spring WebFlux

स्प्रिंग वेबफ्लक्स एप्लिकेशन को कैसे डिबग करें

Spring WebFlux アプリケーションをデバッグする方法

Como depurar um aplicativo Spring WebFlux

Cách gỡ lỗi ứng dụng Spring WebFlux

如何调试 Spring WebFlux 应用程序

Understand how the Symfony project evolves and why it is always worthy to get involved, but differently. In 2011, when I started my studies in computer sciences I learned the PHP using symfony 1.3, and I realized my very first student project on the beta of Symfony 2. At the time, we were moving from a fully integrated full stack framework with a back office provided to a framework that followed what was found in the Java community: besides, many components of Symfony2 were strongly inspired by JEE. PHP 5.3 had just come out and with it the ability to start designing object-oriented correctly. Fabien Potencier finally imposed this prerequisite (initially, Symfony2 required PHP 5.2.7), then Composer was used, and the documentation was complete and in English. Zend Framework 1 was losing his popularity, and no more startup was launched on it (in France) when on the contrary we saw appearing some “Symfony developer” job offers in the most successful french companies. A few years later, nobody could conceive of using anything other than Symfony to make a PHP project. Large Open Source projects have started to migrate on Symfony components: if it was not first, SensioLabs has talked a lot about because it is one of the biggest CMS on the market. EzPublish, PHPBB, PrestaShop and many others followed, some with a full stack framework approach and others by incorporating only a few software bricks. Drupal8 A vibrant and mature ecosystem The Symfony ecosystem has been enriched with ever more specialized solutions and responding to concrete business problems where the Standard Edition framework (so-called “full edition” or “meta-package”) has no scope. Have appeared among the most famous: The framework, easier to access and RAD-oriented framework; Laravel The platform and the entire associated ecosystem: , , , and ; Oro Oro CRM Akeneo OroCommerce Marello The eCommerce framework; Sylius The framework specialized in the design of API RESTful ; API Platform All of these solutions are extremely popular and require real Symfony skills. In 2017, what will be the place of Symfony Standard Edition in the ecosystem? Fabien Potencier decided that there would be no more Standard Edition after the 3.4. Welcome to Symfony Flex! Indeed, the creator of Symfony plans to replace it by a composer plugin called that facilitates the creation of Symfony applications. Flex The developer will have the responsibility to choose and add dependencies that he/she needs. The system works according to a “recipe/template” principle where YAML files describe what Flex should do: add a dependency, configure and register a bundle, or create a folder for example. Flex comes with two sources of “recipes”: validated by SensioLabs and a where everyone can add their recipes and make them available to everyone. an official source community source To put it simply, imagine that you want to realize a RESTful API in 2017 using Flex: the ideal would be to use API Platform. As API Platform is available via Flex you only have one command to run to get to a . complete application that works I have to admit that this approach pleases me a lot and that it reinforces the point of view that I defended for several years: a Symfony project not focused on its framework but the maintenance of software bricks of very high quality and well documented. Perhaps we had to wait for the relative success of Symfony 3 and the popularity of solutions like Akeneo for this awareness, but I’m convinced that the Symfony Core team is now moving in the right direction. If you are looking for more information about Flex, there is not yet any official documentation, but Fabien Potencier has produced that I encourage you to read and experiment since the composer plugin is compatible with Symfony 3.3 and usable independently of the Symfony 4 release ;) a series of articles about the project Ok! But why should I learn Symfony in 2017 then? In 2017, you don’t (necessarily) have to learn the Symfony framework, you have to learn and understand the Symfony ecosystem: How a Symfony application reads an HTTP request and returns a response; How a Symfony application builds and makes available objects (called “services”); How a Symfony application dispatches and listens for events throughout the application lifecycle, and how to look and create its events; Becoming familiar with these notions made you able to quickly be comfortable with API Platform, Akeneo, Marello, Sylius, Drupal8, Laravel, and the Symfony Standard Edition framework. What about the components? I am a huge fan of Symfony components: they are maintained by a big community, very well documented and evolve regularly. The learning or use of a particular component obviously depends on the project. Here is list of the most useful libraries: my The component: provides a complete console with arguments and options management, essential for PHP in CLI mode; Console The and components: they provide a better stack trace in case of error and the function as a replacement of ; Debug VarDumper dump var_dump The and components: they provide a nice API for searching and manipulating folders and files; Finder Filesystem The components: they allow the application to use functions that are not available, either because of the PHP version or the absence of PHP extensions; Polyfill- * All of these components work in “standalone” and are used in the most large PHP projects. So keep learning and investing in the ecosystem: Symfony (framework) is dead, long life to the Symfony project!

Why you should learn Symfony in 2017

My name is Olga Abramova. I am an experienced Design Lead focused on tech products. With this article, I want to explain why design (UX/UI and graphics) is essential for B2B (especially in the IT sector) and how it can contribute to strengthening the business's position in the market. B2B and B2C: Different priorities B2B company owners often believe is insignificant to them. The product works, engineers create cool features, and the clients pay money. Why should they be bothered by design concerns, then? Qualitative client accounting, well-established relationships with the customers, and often distributors, exhibitions, and meet-ups with the partners are the factors that play crucial roles in B2B decision-making in contrast to B2C. design The specificity of B2B is that the customer means a person who chooses in favor of a particular product and a partner company, is not always the product's end-user, as the decision on the usage of the specific product can be made by an IT administrator, CTO, or even CEO. In the , the decision on the choice of the product and its importance, precisely the company from which to purchase it, depends on many factors: including the budget, the existing IT infrastructure, and the narrow sphere of business needs. B2B framework Thus every party engaged is less concerned with the product's usability and the company's marketing image than in the B2C business model, where design and level of usability comfort often play a dominant role. That is why the design does not come in the first place. However, I believe the UX/UI and graphic design in B2B are severely underestimated. For example, revealed that companies that focused on design had 32% higher revenue than the ones that didn’t. a study by McKinsey UX/UI and Graphic Design Importance for B2B Tech Products People use B2C technologies daily, so they have some built-in design & usability expectations. Most customers use modern smartphones with up-to-date Operating Systems and other hi-tech products and B2C programs, where usability and brand design are vital to the product. Moreover, the overall level of design and usability in the world is constantly increasing because of loads of successful IT products. Users get used to a certain level of comfort while using a particular IT product and therefore develop expectations regarding the design and usability quality. It is also worth mentioning that millennials are becoming a group that makes business decisions not only in the B2C sector but also in B2B, and according to visual communication plays a crucial role to them. , the research by TechSmith Below I summarized the main reasons, which shall be taken into consideration by B2B businesses concerning UX/UI and graphic design. Usability flaws are irritating. There are several reasons why there is often a lack of usability in B2B products. First of all, so many B2B digital products created during these years used outlandish usability design solutions that became the basement of their products. Secondly, B2B digital products are harder to update because of the deep system integrations with the clients, complicated processes of decision-making, and overall misunderstanding of the benefits of efficient design solutions and their impact on the company’s revenue. . in the early to mid-2000s, there were fewer established standards in UX/UI, According to Forrester, every dollar spent on improving a brand’s user experience can fetch $100 in return As a result, it often happens that a B2B IT product has been developed for many years and got layers of UX solutions for separate parts, but as an entire product, it loses its usability and needs to be revised. An outdated brand design can downgrade up-to-date technologies. Despite the best tech solutions offered by B2B product-led tech companies, those technologies can be perceived as outdated if the first thing the customer interacts with is an outdated company and product image. It may lead to a situation when the company loses to more modern-looking competitors if there is no critical advantage in favor of the one company. In the end, people perceive visual information easier and primarily, and the product's image should correspond to its essence. On top of this, an outdated design may be perceived as a signal that the company does not seek to embrace changes. Direct B2B competitors earn points quickly if they come with a good brand and UX/UI redesign. Working on the product's UI/UX and graphic design means that the company is alive and dynamically changing for the better; stacking its products is a successful investment of time and money. The indirect competitors are a hidden threat. Nowadays, technologies are growing rapidly. B2C companies are not a danger today, but tomorrow everything can change. We see IT startups popping up every day! Sometimes IT giants buy them to widen or strengthen their possibilities. Usually, these indirect B2C competitors and startups have good UX/UI and marketing design. So, it won't be effortless to catch up with them in a day if the design and usability were not updated to a higher level in the previous years; The price of the product should match its quality. In many cases, are expensive, raising fair expectations among the clients regarding a certain level of design quality. The designer's job is to make the product look and feel appropriate and have superior usability. B2B products Design and usability influence the hiring process. Suppose the business seeks to achieve the top position in a specific market. In that case, an experienced designer is a must, and hiring a professional designer to join a company without good design and usability expertise is more challenging. I learned from HR specialists it will also be much easier to hire experienced engineers and developers for the company with good branding and UX/UI of the products; The industrial design of the devices and packaging is also crucial. Packaging is a handshake, it affects the first impression of the product, and industrial design plays a fundamental role in the everyday usage of the device. Nevertheless, it is not only a part of the offline customer experience. The images of the device and its packaging usually fulfill a significant percentage of a company's website and other marketing materials. Remember, people perceive visual information first, so no matter how good your marketing materials design, weak images of your product and packaging can spoil it. Based on my experience, I want to highlight that good can give to a B2B business: UX/UI and graphic design It attracts new clients and helps them choose favor of your product; It helps to keep old clients. It makes it easier for companies to hire highly qualified employees that help to develop the best quality product. In conclusion, UX/UI and graphic design are essential for B2B companies and benefit this business significantly. B2B, which recognizes this aspect of its product and business development, wins in the long-term perspective.

The Importance of UX/UI and Graphic Design for B2B Business Models

Welcome to other chapters of Let’s Understand Chrome V8 The bytecode is implemented using CodeStubAssembler (CSA), which can be roughly regarded as an assembly. Bytecode is loaded in a de-serialized manner during V8 startup, with no symbol table. So I want to tell you: CAS is obscure in a static analysis. Moreover, we can’t get the source code of the bytecode in debugging. This article will talk about how to debug bytecode at the assembly level and see its execution details. Figure 1 shows the interpreter of bytecodes. The figure is detailed enough for JavaScript developers. But for V8 learners, Figure 1 lacks a lot of detail, such as: the ignition startup, loading the bytecode, and dispatch. Let’s debug bytecode to dive into those details. 1. Preparation Before debugging, you’d better understand stack frames, the encoding of bytecodes and registers, . Note: see here Below is the Invoke which is the last C++ function before debugging. 1.  V8_WARN_UNUSED_RESULT MaybeHandle<Object> Invoke(Isolate* isolate,
2.                                                  const InvokeParams& params) {
3.   if (params.target->IsJSFunction()) {
4.  //............omit...............
5.   }
6.    Object value;
7.     Handle<Code> code =
8.         JSEntry(isolate, params.execution_target, params.is_construct);
9.     {
10.       SaveContext save(isolate);
11.       SealHandleScope shs(isolate);
12.       if (FLAG_clear_exceptions_on_js_entry) isolate->clear_pending_exception();
13.       if (params.execution_target == Execution::Target::kCallable) {
14.         using JSEntryFunction = GeneratedCode<Address(
15.             Address root_register_value, Address new_target, Address target,
16.             Address receiver, intptr_t argc, Address** argv)>;
17.         // clang-format on
18.         JSEntryFunction stub_entry =
19.             JSEntryFunction::FromAddress(isolate, code->InstructionStart());
20.         Address orig_func = params.new_target->ptr();
21.         Address func = params.target->ptr();
22.         Address recv = params.receiver->ptr();
23.         Address** argv = reinterpret_cast<Address**>(params.argv);
24.         RuntimeCallTimerScope timer(isolate, RuntimeCallCounterId::kJS_Execution);
25.         value = Object(stub_entry.Call(isolate->isolate_data()->isolate_root(),
26.                                        orig_func, func, recv, params.argc, argv));
27.       } else {
28.  //............omit...............
29.       }
30.     }
31.     //............omit...............
32.     return Handle<Object>(value, isolate);
33.   } Lines 14 to 23 initialize the JSFunction that will be executed, namely your JavaScript code. The following are five important members that you should remember. These members can help you to locate your position in debugging. They are constant in one debug context, but will be dissimilar in different debug. Line 7, , it is the Builtin::JSEntry pointer, now the value is 1FA 0E06 ED30 (In my debug context). (1) code Line 18, , it is the Ignition’s entrance. Below is the function that gets stub_entry from Builtin::JSEntry. (2) stub_entry Address Code::OffHeapInstructionStart() const {
  DCHECK(is_off_heap_trampoline());
  if (Isolate::CurrentEmbeddedBlob() == nullptr) return raw_instruction_start();
  EmbeddedData d = EmbeddedData::FromBlob();
  return d.InstructionStartOfBuiltin(builtin_index());
} The entry is 1FA 1326 1840. Line21, , it is the address of JSFunction, namely your JavaScript code. The value is 16 2BD8 15A9. (3) func The address of Builtin::InterpreterEntryTrampoline is 52 61C0 8A41. (4) The dispatch_table is 1FA 0E08 CFB0. (5) Figure 2 is the call stack that is going into bytecode. 2. Debug bytecode Let’s start to debug bytecode by stepping into stub_entry.Call(). I’m sorry I can’t go through the line-by-line since the assembly code doesn’t have context. I think the best way is to give the important states during the Ignition execution. In Figure 3, the register RCX is 1FA 1326 1840(stub_entry). As I mentioned, the stub_entry is the entrance of Ignition. In Figure 4, the register RBX is 1FA0E068A00 which is the first argument of stub_entry.Call(), that is isolate->isolate_data()->isolate_root(). Figure 5 is moving the R8 and calling RSI. The register R8 is func, and the RSI is stub_entry, below is the function to which the stub_entry is pointing. 1.  void Builtins::Generate_JSEntry(MacroAssembler* masm) {
2.    Generate_JSEntryVariant(masm, StackFrame::ENTRY,
3.                            Builtins::kJSEntryTrampoline);
4.  }
5.  //==================separation===========================
6.  void Generate_JSEntryVariant(MacroAssembler* masm, StackFrame::Type type,
7.                               Builtins::Name entry_trampoline) {
8.    Label invoke, handler_entry, exit;
9.    Label not_outermost_js, not_outermost_js_2;
10.    {  
11.      NoRootArrayScope uninitialized_root_register(masm);
12.      __ pushq(rbp);
13.      __ movq(rbp, rsp);
14.      __ Push(Immediate(StackFrame::TypeToMarker(type)));
15.      __ AllocateStackSpace(kSystemPointerSize);
16.      __ pushq(r12);
17.      __ pushq(r13);
18.      __ pushq(r14);
19.      __ pushq(r15);
20.  #ifdef _WIN64
21.      __ pushq(rdi);  // Only callee save in Win64 ABI, argument in AMD64 ABI.
22.      __ pushq(rsi);  // Only callee save in Win64 ABI, argument in AMD64 ABI.
23.  #endif
24.      __ pushq(rbx);
25.  #ifdef _WIN64 //Here is True, my OS is Win10!!!!!!!!!!!!!!!!!!
26.      // On Win64 XMM6-XMM15 are callee-save.
27.      __ AllocateStackSpace(EntryFrameConstants::kXMMRegistersBlockSize);
28.      __ movdqu(Operand(rsp, EntryFrameConstants::kXMMRegisterSize * 0), xmm6);
29.      __ movdqu(Operand(rsp, EntryFrameConstants::kXMMRegisterSize * 1), xmm7);
30.      __ movdqu(Operand(rsp, EntryFrameConstants::kXMMRegisterSize * 2), xmm8);
31.      __ movdqu(Operand(rsp, EntryFrameConstants::kXMMRegisterSize * 3), xmm9);
32.      __ movdqu(Operand(rsp, EntryFrameConstants::kXMMRegisterSize * 4), xmm10);
33.      __ movdqu(Operand(rsp, EntryFrameConstants::kXMMRegisterSize * 5), xmm11);
34.      __ movdqu(Operand(rsp, EntryFrameConstants::kXMMRegisterSize * 6), xmm12);
35.      __ movdqu(Operand(rsp, EntryFrameConstants::kXMMRegisterSize * 7), xmm13);
36.      __ movdqu(Operand(rsp, EntryFrameConstants::kXMMRegisterSize * 8), xmm14);
37.      __ movdqu(Operand(rsp, EntryFrameConstants::kXMMRegisterSize * 9), xmm15);
38.      STATIC_ASSERT(EntryFrameConstants::kCalleeSaveXMMRegisters == 10);
39.      STATIC_ASSERT(EntryFrameConstants::kXMMRegistersBlockSize ==
40.                    EntryFrameConstants::kXMMRegisterSize *
41.                        EntryFrameConstants::kCalleeSaveXMMRegisters);
42.  #endif
43.  //............omit...........................
44.  } In lines 12 to 37, we can see that they are the same as the assembly code in Figure 6. Actually, Generate_JSEntryVariant is executing. Builtin:JSEntry is responsible for organizing arguments by std::call standard. Later, the function Builtin::InterpreterEntryTrampoline will use these arguments. Builtin::InterpreterEntryTrampoline lookups at the dispatch_table to find the target bytecode and call it, shown in Figure 7. Let’s examine dispatch in a little more depth, see Figure 7. mark 1: the machine register R15 is the dispatch_table. mark 2: calculate the target bytecode address, that is dispatch_table + the encoding of the bytecode. mark 3: call the target bytecode. In my case, the target bytecode is LdaConstant. 1.  IGNITION_HANDLER(LdaConstant, InterpreterAssembler) {
2.    TNode<Object> constant = LoadConstantPoolEntryAtOperandIndex(0);
3.    SetAccumulator(constant);
4.    Dispatch();
5.  } When LdaConstant exits, lookup at the dispatch_table to find the next bytecode, shown in Figure 8. At the assembly level, we can see the Ignition startup and bytecode execution, which can help us understand the V8 interpreter better. Okay, that wraps it up for this share. I’ll see you guys next time, take care! Please reach out to me if you have any issues. : qq9123013 : WeChat Email v8blink@outlook.com

Let’s Understand Chrome V8 - Chapter 18: Understanding Bytecode and How to Debug it

Welcome to other chapters of Let’s Understand Chrome V8 In this paper, we’ll talk about the stack frame of two common function calls, “the arguments are less than the declared parameters” and “the arguments are more than the declared parameters”. Explain why these two function calls( ) do not cause a stack overflow, but can still run and output results correctly. arguments mismatch 1. Introduction The stack frame is used to store arguments, the return of callee, local variables, and registers. The steps of creating a stack frame is below: Callee’s parameters. Push the stack if there are params. Push the return of the callee. Step into callee, Push ESP. Make EBP = ESP. Reserve stack space for local variables if there are. Push the register to be protected onto the stack. Here’s an example: Figure 1 shows the call stack when add42 is executed. When the add42 executes, Ignition generates it’s bytecode, installs the stack, enters the add42’s stack space, and finally returns to the caller. Figure 2 is the stack frame of add42, which is created by InterpreterPushArgsThenCall that there are more details. Let’s look at the following two cases： call add42 without argument — add42() call add32 with three arguments — add42(91,1,2) In sloppy mode, both two calls execute normally and the add(91,1,2) can return the expected result — 133. How does the stack frame work? 2. Register, Bytecode Before diving into the stack frame, let’s take a look at the registers and bytecodes, which helps to understand the stack better. The call of add42(91) is below. V8 uses non-negative hexadecimal integers to encode registers, fa is registers-r1, f9 is r2… In the last line — CallNoFeedback r1, r2-r3, fa is r1, f9 is r2, 02 is length. The combination of f9 and 02 means: a register list of length 2 starting with r2. 5f fa f9 02 The add42’s bytecde is below: In 1st line of code, the encoding of the parameter a0 is 02, which is the offset of the parameter in the stack frame, shown in Figure 2. The complement of fa is 6, and FP -6 is exactly register r1; FP +2 is exactly argument 91. By moving the FP pointer, you can quickly access parameters and registers, which simplifies the design of bytecodes. Register addressing formula: r[i]=FP-2-kFixedFrameHeaderSize-i. Arguments addressing formula: a[i]=FP+2+parameter_count-i-1. 3. Adaptor Frame Although the adaptor frame has been abandoned, learning it still helps to learn stack frame better. () (91,1,2,) add42 add42 We know that add42() returns Nan, add42(91,1,2) returns 133. Figure 3 shows the adaptor frame. The adaptor frame has two important members: Number of arguments, the number records the number of arguments, it comes from JSFunction. For add42(x), it is 1; Arguments slot, the slot is used to store the arguments, the number of slots is (1). For add42(), one argument is missing, so fill slot with Undefined, see left side in Figure 3. For add42(91,1,2), although there are three arguments, Number of arguments is 1, so fill the slot with the first argument — 91. No matter how many arguments are passed in, the add42 always can get the correct arguments, so it executes correctly and returns the expected value. The adaptor frame uses Number of parameters and slot to normalize arguments mismatch so that a function can be called correctly. Why is the adapter framework scrapped? Of course, for improving performance!When a function is called, two stack frames are created. One is the adapter framework, and the other is the called framework, which is too time-consuming. 4. Stack Frame The new stack frame removes adaptor frame, but still uses number of arguments, as shown in Figure 4. The intention of the new stack frame is to meet the four requirements below: Get parameters and registers using FP pointer and offset. (1) Normalize arguments mismatch, add42() and add42(91,1,2) can be called correctly. (2) The stack can be rolled back correctly when callee returns. (3) Abandon adaptor frame, reduce the number of stack builds. (4) Let’s explain how to meet these four requirements. For (1): The push order and encoding are not changed, so it is met. For (2): Number of arguments is here. When the length of args >= Number, only the args[0:Number-1] are retained. When it < Number, use Undefined as the missing parameter. For (3): From figure 4, we met this requirement. For (4): The adaptor frame has already gone. The code to build stack frame is below. The above code shows the process of building stack frame, it also includes some architecture-related preparations, see builtins-x64.cc for details. The above code is the entry to execute callee, the Add42’s bytecodes will be executed. Okay, that wraps it up for this share. I’ll see you guys next time, take care! Please reach out to me if you have any issues. : qq9123013 : v8blink@outlook.com WeChat Email Also published . here

Let’s Understand Chrome V8 — Chapter 7: Stack Frame 

Most people know Matt Odell from the podcast he co-hosts with Marty Bent. He is also cofounder of , and an advisor for and . For more background and history on the Bitcoin Bull Market Diaries check out Bitcoin Bull Market Diaries Volume 1 Interview with Hodlonaut . Tales From the Crypt Final Message Bitcoin Citadel Bottlepay givebitcoin I met Matt over the last year and really appreciate his Bitcoin perspective and his authentic personality. He may not have invented the saying, "Stay humble. Stack sats," - but I give him credit for making it commonly used saying among Bitcoiners. Name Matt Odell Country USA How do people know you? Destroyed my Op-Sec on Twitter and then I doubled down by hosting a podcast with Marty Bent. You may have read my , my views have not changed much so make sure you check that one out too. previous interview in the bear market version of this series How long have you been into Bitcoin? ~360000 blocks Best Bitcoin experience? Bitcoiners are awesome. Worst Bitcoin experience? Didn't buy enough. How did you get involved in the Tales From the Crypt podcast? Marty seduced me on twitter and after a couple of weeks finally got me to come on the show as a guest. The episode went great, we hit it off, and quickly became friends. When he later approached me to join him for a weekly news show, I said yes immediately. What do you think is Bitcoin's biggest threat? . Specifically the US Gov. Expect laws that require routine disclosure of bitcoin holdings and moves to restrict self custody altogether. Governments What are your thoughts on the various Bitcoin forks? . Minority forks tend to zero What are you optimistic about in this space? Btcpayserver, bisq, lightning, hardware nodes, hardware wallets, multisig tools, and using all of those in combination easily. Biggest regret during the last Bear market and what did you learn? . We will see the same narratives play out every bear market. No regrets What is the biggest fail you observed during the last bear market? Generally speaking, insecure shitcoiners attacking bitcoiners as their bags continue to lose value when measured in bitcoin. Specific instance, Fred Wilson straight up lying about Kin usage. What do you think help turn things around to the current Bull market? Millions of bitcoiners stacking sats and the builders who have made it easier than ever. Who are the heroes of the last Bear market? Too many to list. I love you all. Why do you think alt-coins are still struggling? The key value prop has always been censorship resistance, specifically State resistance, but most altcoins failed to prioritize that. They often prefer vanity metrics that can pump the price short term which results in their networks getting more centralized rather than less. Bitcoin is still too centralized in my opinion, but it's by far the most distributed and censorship resistant network in the space – it's not even close. Everything ultimately trends to zero when priced in bitcoin. What do you have to say to those who claim alt-season is coming? Lol altseason isn't a real thing, the 2017 pump was unprecedented and fueled by dumb money after the eth pump. Do you hold any alts? If not, why? Holding alts isn't diversification, it's high risk leverage. Trading is brutal. The overwhelming majority of people are better off stacking sats than trading. Long term everything tends to zero when priced in bitcoin. What do you think about the upcoming Bitcoin halving and what it will do to the price of Bitcoin? It's not priced in. We heard the same thing before the last halving. Halvings are a strange beast, they are the first time in history where there is a known supply shock. Usually supply shocks are a surprise, hence the name shock, but with bitcoin that's not the case. That said, even though it is known ahead of time, people aren't capable of fully appreciating how much that reduced supply will impact price. Most miners are professionals who have to sell their earned bitcoin to pay for their expenses – electricity, rent, labor, taxes, etc – that selling pressure will be reduced by half while buying pressure will continue to increase with adoption. TL;DR Number go up. What do you think makes Bitcoin superior to anything else out there? Bitcoin is a new type of money that is digital and independent of world governments or corporations. It is hard to seize, block, or inflate and easy to send around the world. It is the best money we have ever had. . As more people realize this, the price should rise Do you think central banks are or will be accumulating Bitcoin? Yes. It's the only smart move. Smaller countries - especially those that are sanctioned - will be the first movers. Some may have already started but it is in their best interest not to admit it until they have accumulated a substantial amount. How do you feel about the current state and future of lightning network? Bullish. Huge improvements in usability over the last year and we should see even bigger improvements over the next few years. Next step, make it easy enough for grandma to use. What are your thoughts on HODLing Bitcoin? Slow and steady constant accumulation is the most conservative investment move you can make when it comes to bitcoin. Short term bitcoin is highly volatile, but long term the price should rise with adoption. Dollar cost averaging with money you are willing to lose – stacking sats – allows you to average out that short term volatility while gaining exposure to the long term upside. Trading is brutal and most people will lose more money than if they had avoided it in the first place. If you started stacking sats at any time in bitcoin history you would be in profit right now. You can check the numbers yourself at stackingsats.com. What are your thoughts on Bitcoin Maximalism? Bitcoin maximalism is a straw man argument created by Vitalik to sell his token ICO. “The only reason you don't like ethereum is because it's not bitcoin.” Thoughts on the notion of bitcoinization? Gradually, then suddenly. There are few things more powerful than free speech and sound money. Where do you think Bitcoin dominance will do as the price increases? Bitcoin dominance is a flawed metric and we shouldn't focus on it. It is extremely easy to inflate market caps of altchains through large supplies and low wash traded volumes. What will someone have to do to prove they are the real Satoshi Nakamoto? Anyone who claims they are Satoshi should first prove ownership of early keys, either through a signed message or by moving them. If they don't do that then you can safely ignore their claims, it is a waste of time. That said, doing that alone would still not be definitive proof, other supplemental evidence would need to be presented if a credible claim is ever made. I would prefer if Satoshi remains anonymous and I expect that to be the case. He/she/they pulled off an extremely impressive level of opsec over the last 10 years so I find it hard to believe Satoshi would throw that all away now. What Bitcoin startups are you excited about? ZkSnacks, Samourai, Nodl, Casa, Unchained Cap, Zap, Lightning Labs, ACINQ, Blockstream, OpenNode, Coinkite, Trezor, Ledger, Zap, Joule, Bitrefill, Satoshi Games, GoTenna, HodlHodl, Bitmex, Chaincode, Kraken, Bottlepay, Breez, Bittr, BullBitcoin, Foldapp, Lolli. Special mention to Square, although no longer a startup, their bitcoin push is a big deal. Another special mention to the teams at btcpayserver and bisq, they aren't companies but are arguably more important projects than any of the companies I listed above. What “crypto influencers” do you think get it wrong and why? 90%. Some are legitimately confused, but there’s a special place in hell for the ones who know what they are doing and intentionally mislead their followers. Here's a list of people who have blocked me on twitter after I called them out on their bullshit: Vinny Lingham, Kyle Samani, Preethi Kasireddy, Tiffany Hayden, Ari Paul, Emin Gun Sirer, Erim Finman, Bitfinexed, George Kikvadze, Nouriel Roubini. What “crypto influencers” do you think get it right and why? This is a pretty good place to start: https://hive.one/bitcoin/ Nobody is perfect, myself included, but if you follow me on twitter, it should become pretty obvious who has earned my respect. Also the term “crypto influencer” should die. Where do you envision the market heading in the next 5 years? Moon. Just not sure which one. What is Bitcoin Citadel and Final Message, and where do you see them going? is an educational effort that I started with Evan Kaloudis, Joshua Stokes, and a handful of other NYC bitcoiners with the goal of running bitcoin focused workshops. It is not being run for profit but rather is our way to give back to the community. The first workshop is tomorrow and we are very excited. Bitcoin Citadel is a privacy focused dead man's switch service that is ideal for use with multisig and shamir secret schemes but can be used for any text based delivery need. When you stop renewing your subscription your encrypted message is automatically sent to your desired recipients. We have plans to improve upon our base design with additional features and delivery options. Final Message Best tips for storing Bitcoin? Buy a coldcard. Consider using it with multisig. There's at least two user friendly multisig tools in development currently: Junction and Spectre. If you haven't already moved to multisig I would wait a month or two for them to be tested and released fully. They will make it much easier than the current standard process using electrum. Any tips you want to give to people new to Bitcoin? This community is extremely welcoming and many of us are happy to help. Stay humble and don’t overextend yourself. You have to look out for yourself or you will get burned. Name some of your favorite information sources and/or podcasts in the space. Twitter can be extremely useful. The hard part is learning how to cut out useless noise. Publications: Bitcoin Magazine Newsletters: Marty's Bent, Coinmetrics, Bitcoin Optech Podcasts: TFTC, Stephan Livera, Noded, Block Digest, What Bitcoin Did Resources: bitcoin.page, coinmetrics.io, bitcoinacks.com, onchainfx.com, oxt.me, blockstream.info, fork.lol, mempool.space, jochen-hoenicke.de/queue/#0,30d, coin.dance, 1ml.com, bitcoin-only.com Sites you should avoid: bitcoin.com, ccn.com, bitcoinist.com, newsbtc.com, blockchain.com Any last words of wisdom? Stay humble. Stack sats. Stay tuned for the next Bitcoin Bull Market Diaries. I have some awesome interviews in the queue and will be dropping new volumes regularly. Special thanks to Matt Odell and all of our fellow Taco Carnivore Bitcoin Plebs out there!

Bitcoin Bull Market Diaries Volume 5 Interview with Matt Odell

You probably heard it a thousand times before and you’ll hear it a hundred times more – you need to keep learning if you want to stay relevant! This is true for any field, especially in the world of programming languages. Learning is the key to our success, and that means constantly branching out from the fields we are comfortable with into new and upcoming fields. It means at least grasping the core concepts in a variety of developmental fields to be as well rounded as possible, because you never know when your company might need X problem solved and you’d be the dream candidate they’ve been searching for (or at least you will be so long as you keep learning). Stagnation is as dangerous as invalid input validation, so unless you want your career to be open to input manipulation vulnerabilities you’d better take control of your future, set the course you want, and start learning. History as a Loop The history of computer programming can effectively be traced back to 1949 with the creation of the Assembly Language. Yes, technically we can go back as far as 1883 with Lovelace and Babbage’s Analytical Engine for computing Bernoulli numbers, but we’d be digging up fossils at that point. So, 1949 was the dawn of modern programming, and since then there have been major advances and major setbacks, the latter of which are much clearer as we look into the past from the present. Source: dilbert.com There are major trends that can be observed, and they typically go like this: Language A is invented for a specific purpose. After a while, another (better) language, B, is written to replace language A. But, instead, they exist in parallel until language A eventually becomes outdated (from the programmer’s perspective). So, language A continues to be used even though language B is better. Moreover, language A continues to hold market share simply because it was first to market. We see this in programming languages ( ), operating systems ( ), and nearly everything computer related ( , for instance). There is a certain mindset held by developers and companies of not letting go with things related to computers, and it tends to stifle progress in the respective field. the dreaded VBA/Objective-C 1/3rd of companies still running XP ATMs running COBOL But you, as a developer, don’t care about everything related to computers, you care about your day-to-day tools: programming languages. By investigating the past perhaps we can shine some light on the current state of things, and with any luck, help prevent the same situation from happening in the world of smart contracts and blockchains before it even begins. Breaking down the Data We are 70 years in since Assembly Language was first created, and since then we’ve seen so many languages that it’s hard to keep track of them all. Only some of them made it big and are worth noting, and over the next few decades we saw a lot of the major languages introduced (Basic, Pascal, Python, all the C varieties, etc.). A lot of these languages still plague developers today, since the industry refuses to move past them and onto new, better, languages. Stack Overflow (you may have heard of them) does an annual to get a sense of where the programming community is at. The survey this year had nearly 90,000 respondents ranging from dozens of countries and developer roles. Based on their section labeled “ ” we can see some interesting data straight from the developers. First, the top 10 most dreaded languages are at least a decade old, if not more ancient (VBA, Objective-C, Assembly, etc). The most loved languages are all far, far newer, with one exception. Developer Survey Most Loved, Dreaded, and Wanted Languages Rust 1.0 - 2015 Python 1.0 - 1994 TypeScript 1.0 - 2014 Kotlin 1.0 - 2016 WebAssembly 1.0 - 2019 Swift 1.0 - 2014 And it makes sense to have such a ranking. If you were a young developer-to-be about to start your first day of college, would you want to study Visual Basic? Would you seek out courses to learn Objective-C? No, you’d want to learn Rust and Swift, the languages that people want to write in. But you probably aren’t a student anymore, so you’re out of luck right? Well, that depends on where you see your field going. We are currently experiencing the dawn of a new type of programming with new languages and possibilities: blockchains with an emphasis on smart contracts. This field has only been in existence for half a decade, but things are moving rather fast. There’s a market leader, , but is it already moving into the realm of antiquity? Solidity Solidity first released in 2014 as THE smart contract language for a variety of reasons: Back then, there was only one main blockchain to run smart contracts on (Ethereum). There weren’t any competing languages (unless you count Lisp-Like Language as a real competitor). And it had first-to-market advantage. Solidity took the smart contract world by storm, but does that mean it will always be the best option for smart contract developers? Take iOS programming, for instance. Objective-C was the primary language for a long time until Swift entered the scene. When Swift came along programmers flocked to it because it was better, but there was still a struggle since Objective-C had a strong hold on the iOS market because of its first-to-market advantage and the fact that it was a household name. Companies that have apps older than 2014 probably still have apps running on Objective-C, but most newer apps are written in Swift, as it is far superior and more liked. Source: liberaldictionary.com Ending the loop When it comes to traditional programming there isn’t much we can do except beg our employers to let us write in more modern code so that every work day isn’t a dreaded typing experience. But there is hope for us to end this vicious loop before it can even start in the smart contract world, and that is by considering other languages than Solidity now instead of in 10 years. There are two major contenders that may become the Swift to smart contracts’ Objective-C, if you catch my drift. is one of the newly developed programming languages being created by and the Ethereum Foundation, though we have no real timeline as to when it will officially go live (it is on v0.1.0-beta.11, last I checked). Vyper is a simple language that is extremely easy to audit, has things like overflow checking, decidability, strong typing, and understandable compiler code. Its strengths come from its simplicity and the fact that the creators purposefully excluded things like recursive calling, class inheritance, inline assembly, and the like. Vyper Vitalik Buterin However, Vyper falls short for a few reasons. First, there is no real timeline for its release or even any clear direction as to what its purpose is. Some that it is to be used alongside Solidity to create more secure contracts, while others think it will completely This confusion is unsettling, and the fact that it has been delayed time and time again isn’t reassuring either. sources say replace Solidity all together. On the other hand, built by Waves is a new programming language already up and running in its entirety. It’s running on the Waves blockchain and it’s joining a whole suite of services the team built. Based on the performance of their past creations we can assume Ride will be equally as impactful. Ride has all of the same perks as Vyper, it’s already up and running, and more: Ride Intentionally non-turing complete ( that turing completeness in Solidity smart contracts is only used 7% of the time, the other 93% of occasions just cause security problems). studies have shown Basic, no nonsense scripting functions. Functional programming language based on side-effect-free expressions as basic building blocks. Built-in smart contract complexity evaluation (to predict the cost of running said contract). Waves’ blockchain currently uses LPOS (Leased Proof of Stake), something Ethereum (and Solidity) hopes to shift to in the next few years. Between the two of them, Ride and Vyper, I’d love to see Vyper shift the Solidity front, but Ride is already doing it. The more developers it can shift away from Solidity the better, and, to be fair, Vyper just became a crutch that keeps Solidity hobbling along. Ride is a standalone product that is more secure, more straightforward, and cheaper to use in a direct contract comparison. So, my fantastic community of developers, the decision is up to you. Do we want to start the loop all over, this time in the decentralized world? Do we want to make the bane of future programmers’ existence the languages we refused to move away from, or do we want to constantly push forward and adapt to new languages that are actually better. Source: xkcd.com If you’re a decentralized programmer, please consider that the world is larger than Solidity, and if you aren’t a decentralized programmer please realize that expanding your skillset is . We have the power to shape the future of programming, so let’s leave it in better shape than we found it, deal? extremely marketable

As a Blockchain Developer, you Need to Keep Learning to Stay Ahead of the Game

Quality mobile SDK tools are the building blocks of a quality mobile app. According to stats from , the apps that top the charts on the Apple App Store and Google Play all use some of the leading mobile app SDKs: Firebase, AppsFlyer, Crashlytics, Adjust, and AdMob, just to name a few. You’ll find a great free resource with all the top tools at the bottom of this post. 42matters However, with so many tools on the market today, mobile app professionals often suffer from choice overload. . Trying to manage all the different SDK tools that you, your app, and your team need can leave you feeling like this: SafeDK calls it “SDK fatigue” Image Source: Giphy How do you survive the mobile SDK shopping trip without losing your mind — or worse, your precious time? Here are a few things to keep in mind when building or refining your SDK tool stack. Better together: Power up your mobile SDK tools with integrations shows a steady increase in the number of SDKs app publishers use. In 2016, the average was 15 SDKs per app. Now, app publishers are using an average of 18 SDKs per app. Will 2019 see that number grow to 19, 20, or even 25 SDKs? As the graph below shows, that number may be plateauing, as existing SDKs continue to improve in quality, merge to create stronger tools together, or offer integrations that create extra-powerful combinations, like , , and . SafeDK’s 2018 report on the state of mobile SDKs Mixpanel with Braze Optimizely with Appsee Adjust with AdColony Image source: SafeDK As mentioned earlier, there is such a thing as too many tools. If you’re hesitant to add another SDK to your stack, you’re not wrong: there are a lot of factors that will have to go into that decision, from your company’s legal bureaucracy and privacy policy to setting up the tool, technical syncing, and onboarding. However, this doesn’t mean that you have to give up on adding a tool that can help you out. Instead, see if you can integrate the new SDK with tools you’re already using or would like to use. Integration means that the tools can sync with each other and offer you a comprehensive picture of your app’s status, often in a single dashboard. For example, enables you to use the already-powerful Crashlytics tool and also use Appsee’s session recordings to recreate crashes. This powerful combination of two market leaders ensures that no bug or crash will escape get past your defenses. By integrating two SDK tools, you get the best of both worlds without having to jump from one software to another. Crashlytics’ integration with Appsee Pick mobile SDK tools that work for you, not the other way around Your job is to create and publish awesome apps that users love. It’s a tough job, and you need all the time you can spare to do it right. You pay for mobile SDKs to make that job easier, leaving you to code, design, market, and manage your app while they do the work that can be automated. Your mobile SDK tools of choice should work for you, not make you work for them. They should provide you with the fastest possible service, the easiest setup, and the most accessible, actionable data. That’s why your SDK of choice should be used directly , with as much automation as possible, so that you can start getting results the same day. out of the box For example, if a tool requires you to manually tag UI elements or native app events, that’s an exhausting and time-consuming process. It means you’ll have to work to make the tool work for you, and it’ll take time and effort before you can actually get the results you paid for. A tool that works for you is a tool that can do and recognize elements without any work on your part. automatic event tagging How do you know if the tool can be used out of the box? Here’s a clue: . If the company doesn’t have a free trial, that’s a pretty good indication that the tool requires more manual setup and can’t give insights on the fly. look for a free trial option Don’t get lost. Use a map to find the best mobile SDK tools If you’ve ever gotten lost at the mall as a kid, you probably remember it as a terrifying experience. (The adult who was with you was probably even more terrified.) Shopping for mobile SDKs can leave you just as lost and confused, and in this case, Googling will only lead to a hundred open tabs and no actual decisions. If you want to quickly find the top mobile SDK tools, all you need is a reliable market guide. It’s not surprising that one of the top downloaded resources in the mobile industry is titled the , which you’ll find at the bottom of this post. Now released in an updated version for 2019, it sets the tone for the coming year by listing the best mobile SDK tools in each category. Ultimate SDK Guide for Mobile Apps Why should you use this guide? The best reason: . The guide will reduce the job of researching and choosing new tools from hours to minutes, by pointing you directly to the best mobile SDK tools currently on the market. The guide includes fourteen specific categories of mobile SDK tools: it’ll save you time Quantitative analytics Qualitative analytics Attribution Crash reporting/bug reporting A/B testing Marketing and push notifications Beta testing/user testing Voice of customer Monetization/advertising Acquisition/Re-targeting Payments Geolocation Business intelligence/App Store intelligence Data Management You can get a free download of the mobile SDK Guide for Mobile Apps 2019 here:

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