gRPC is not really the relevant part for comparison, it&#39;s that gRPC uses HTTP/2 which can certainly be compared to WebSockets.

https://www.infoq.com/articles/websocket-and-http2-coexist

This article outlines them quite well. Essentially, HTTP/2 is Client/Server with Server Push on the background, so you can make your request and simply stay on that connection listening for updates without the need for polling, for example. 

Whilst WebSockets are not going away because of HTTP/2, they might not be considered necessary for use cases that center around &quot;let me know when updates happen related to the thing I just did&quot;.

gRPC is an API/Protocol on top of HTTP/2, so it is more relevant to compare HTTP/2 and Websockets.

Note: _HTTP/2 Server Push_ is **not** relevant here either. That is a [website optimization technique][1] for cacheable (GET) resources.

Websocket and HTTP/2 support binary data frames with low overhead (a few bytes), however frames (whole payload) in Websocket is _masked_ at sender and then _unmasked_ at receiver. See [What is the mask in a WebSocket frame?][2].

With HTTP/2 you can have multiple streams multiplexed over the same connection. This need to be handled by application developer or a library when using Websocket - if desired.

If your client is a browser, the answer to [HTTP/2 or Websockets for low latency client to server messages][3] may be relevant.


  [1]: https://en.wikipedia.org/wiki/HTTP/2_Server_Push
  [2]: https://stackoverflow.com/questions/14174184/what-is-the-mask-in-a-websocket-frame
  [3]: https://stackoverflow.com/a/59690386/213269

I am trying a nested reactive form in Angular 4. It is working fine but when I try to build AOT it&#39;s throwing the error 

&gt; &#39;controls&#39; does not exist on type &#39;AbstractControl&#39;

I googled and tried few things but no luck. Could anyone tell me how to fix this issue? 

    &lt;div [formGroup]=&quot;myForm&quot;&gt;
        &lt;div formArrayName=&quot;addresses&quot;&gt;
            &lt;div *ngFor=&quot;let address of myForm.get(&#39;addresses&#39;).controls; let i=index&quot; 
                        class=&quot;panel panel-default&quot;&gt;
                &lt;span *ngIf=&quot;myForm.get(&#39;addresses&#39;).length &gt; 1&quot;
                        (click)=&quot;removeAddress(i)&quot;&gt;Remove&lt;/span&gt;
                &lt;div [formGroupName]=&quot;i&quot;&gt;
                    &lt;mat-form-field&gt;
                        &lt;input matInput formControlName=&quot;city&quot; placeholder=&quot;city&quot; value=&quot;&quot;&gt;
                    &lt;/mat-form-field&gt;
                &lt;/div&gt;
    
            &lt;/div&gt;
        &lt;/div&gt;
        &lt;a (click)=&quot;addAddress()&quot; style=&quot;cursor: default&quot;&gt; Add +&lt;/a&gt;
    &lt;/div&gt;


typescript code below

    constructor(private _fb: FormBuilder) {     
    }
    
    ngOnInit() {
        this.myForm = this._fb.group({
            addresses: this._fb.array([
                this.initAddress(),
            ])
        });
    }
    initAddress() {
        return this._fb.group({
            city: [&#39;&#39;]
        });
    }
    addAddress() {
        const control = &lt;FormArray&gt;this.myForm.get(&#39;addresses&#39;);
        control.push(this.initAddress());
    }
    removeAddress(i: number) {
        const control = &lt;FormArray&gt;this.myForm.get(&#39;addresses&#39;);
        control.removeAt(i);
    }




Property &#39;controls&#39; does not exist on type &#39;AbstractControl&#39; Angular 4

I have this code:

    package tests;

    import java.util.Hashtable;

    public class Tests {

	    public static void main(String[] args) {

		    Hashtable&lt;String, Boolean&gt; modifiedItems = new Hashtable&lt;String, Boolean&gt;();
		
		    System.out.println(&quot;TEST 1&quot;);
		    System.out.println(modifiedItems.get(&quot;item1&quot;)); // Prints null
		    System.out.println(&quot;TEST 2&quot;);
		    System.out.println(modifiedItems.get(&quot;item1&quot;) == null); // Prints true
		    System.out.println(&quot;TEST 3&quot;);
		    System.out.println(Boolean.valueOf(null)); // Prints false
		    System.out.println(&quot;TEST 4&quot;);
		    System.out.println(Boolean.valueOf(modifiedItems.get(&quot;item1&quot;))); // Produces NullPointerException
		    System.out.println(&quot;FINISHED!&quot;); // Never executed
	    }
    }

My problem is that I don&#39;t understand why *Test 3* works fine (it prints `false` and doesn&#39;t produce `NullPointerException`) meanwhile *Test 4* throws a `NullPointerException`. As you can see in tests *1* and *2*, `null` and `modifiedItems.get(&quot;item1&quot;)` are equals and `null`.

The behavior is the same in Java 7 and 8.

Boolean.valueOf() produces NullPointerException sometimes

I want to develop a client-server application in a bi-directional streaming manner.

what is more suitable technology for this, grpc or websocket?

What is difference between grpc and websocket? Which one is more suitable for bidirectional streaming connection?

<p>I want to develop a client-server application in a bi-directional streaming manner.</p>
<p>what is more suitable technology for this, grpc or websocket?</p>


In this function that handles a REST API call, any of the called functions to handle parts of the request might throw an error to signal that an error code should be sent as response. However, the function itself might also discover an error, at which point it should jump into the exception handling block.

    static async handleRequest(req) {
        try {
            let isAllowed = await checkIfIsAllowed(req);
            if (!isAllowed) {
                throw new ForbiddenException(&quot;You&#39;re not allowed to do that.&quot;);
            }
            let result = await doSomething(req); // can also raise exceptions
            sendResult(result);
        } catch(err) {
            sendErrorCode(err);
        }
    }

Webstorm will underline the `throw` with the following message: `&#39;throw&#39; of exception caught locally. This inspection reports any instances of JavaScript throw statements whose exceptions are always caught by containing try statements. Using throw statements as a &quot;goto&quot; to change the local flow of control is likely to be confusing.`

However, I&#39;m not sure how to refactor the code to improve the situation.

I could copypaste the code from the `catch` block into the `if` check, but I believe this would make my code less readable and harder to maintain.

I could write a new function that does the `isAllowed` check and throws an exception if it doesn&#39;t succeed, but that seems to be sidestepping the issue, rather than fixing a design problem that Webstorm is supposedly reporting.

Are we using exceptions in a bad way, and that&#39;s why we&#39;re encountering this problem, or is the Webstorm error simply misguiding and should be disabled?

How to fix &quot;&#39;throw&#39; of exception caught locally&quot;?

I am trying to use a Node.JS application to make and receive API requests. It does a get request to another server using Axios with data it receives from an API call it receives. The second snippet is when the script returns the data from the call in. It will actually take it and write to the console, but it won&#39;t send it back in the second API.

    function axiosTest() {
        axios.get(url)
            .then(function (response) {
                console.log(response.data);
                // I need this data here ^^
                return response.data;
            })
            .catch(function (error) {
                console.log(error);
            });
    }

...

    axiosTestResult = axiosTest(); 
    response.json({message: &quot;Request received!&quot;, data: axiosTestResult});

I&#39;m aware this is wrong, I&#39;m just trying to find a way to make it work. The only way I can seem to get data out of it is through console.log, which isn&#39;t helpful in my situation.

Returning data from Axios API

I am newbie in spring boot rest services. I have developed some rest api in spring boot using maven project.

I have successfully developed **Get** and **Post** Api. My **GET** Method working properly in postman and mobile. **when i am trying to hit post method from postman its working properly but from mobile its gives 403 forbidden error.**

This is my Configuration:

    spring.datasource.url = jdbc:mysql://localhost/sampledb?useSSL=false
    spring.datasource.username = te
    spring.datasource.password = test
    spring.jpa.properties.hibernate.dialect= org.hibernate.dialect.MySQL5InnoDBDialect
    Hibernate ddl auto (create, create-drop, validate, update)
    spring.jpa.hibernate.ddl-auto = update

Please Suggest me how to solve error.

[![enter image description here][1]][1]


  [1]: https://i.stack.imgur.com/sdY6h.png

How to Solve 403 Error in Spring Boot Post Request

**Background:**

I am building an application and the proposed architecture is Event/Message Driven on a microservice architecture. 

The monolithic way of doing thing is that I&#39;ve a `User/HTTP request` and that actions some commands that have a direct `synchronous response`. Thus, to respond to the same User/HTTP request is &#39;hassle free&#39;.


[![enter image description here][1]][1]

**The problem:**

The user sends an `HTTP request` to the **UI Service** (there are multiple UI Services) that fires some events to a queue (Kafka/RabbitMQ/any). a N of services picks up that Event/Message do some magic along the way and **then at some point that same UI Service should pick that up a response and give that back to the user that originated HTTP request.** Request processing is `ASYNC` but the `User/HTTP REQUEST-&gt;RESPONSE` is `SYNC` as per your typical HTTP interaction.

**Question:**
How do I send a response to the same UI Service that originated the action (The service thats interacting with the user over HTTP) in this Agnostic/Event driven world?

**My research so far** 
I&#39;ve been looking around and it seems that some people are solving that problem using WebSockets.

But the layer of complexity is that there needs to be some table that maps `(RequestId-&gt;Websocket(Client-Server))` which is used to ‘discover’ which node in the gateway has the websocket connection for some particular response. But even if I understand the problem and complexity I&#39;m stuck that I can&#39;t find any articles that would give me info on how to solve this problem at the implementation layer. **AND** this still is not a viable option because of 3rd party integrations such as payments providers(WorldPay) that expect `REQUEST-&gt;RESPONSE` - specially on the 3DS validation.


So I am somehow reluctant to think that WebSockets is an option. But even if WebSockets are ok for Webfacing apps, for API that connects to external systems is not a great architecture.


** ** ** **Update:** ** ** ** 

Even if long polling is an possible solution for a WebService API with a `202 Accepted` a `Location header` and a `retry-after header` it wouldn&#39;t be performant for a high concurrency &amp; high ability website. 
Imagine a huge number of people trying to get the transaction status update on EVERY request they make and you have to invalidate CDN cache (go and play with that problem now! ha).

But most important and relatable to my case I&#39;ve 3rd party APIs such as payment systems where the 3DS systems have automatic redirects that are handled by the payment provider system and they expect a typical `REQUEST/RESPONSE flow`, thus this model would not work for me nor the sockets model would work. 

Because of this use-case the `HTTP REQUEST/RESPONSE` should be handled in the typical fashion where i have a dumb client that expect that the complexity of the precessing is handled in back-end.

**So i am looking for a solution where externally I have a typical `Request-&gt;Response`(SYNC) and the complexity of the status(ASYNCrony of the system) is handled internally** 

 
An example of the long polling, but this model wouldn&#39;t work for 3rd party API such as payments provider on `3DS Redirects` that are not within my control.

     POST /user
        Payload {userdata}
        RETURNs: 
            HTTP/1.1 202 Accepted
            Content-Type: application/json; charset=utf-8
            Date: Mon, 27 Nov 2018 17:25:55 GMT
            Location: https://mydomain/user/transaction/status/:transaction_id
            Retry-After: 10
    
    GET 
       https://mydomain/user/transaction/status/:transaction_id



[![enter image description here][2]][2]




  [1]: https://i.stack.imgur.com/rP5nf.png
  [2]: https://i.stack.imgur.com/rznNC.png


How to handle HTTP requests in a Microservice / Event Driven Architecture?

I have my REST API where I put my pdf file, now I want my angular app to download it on click via my web browser but I got HttpErrorResponse 

&quot;Unexpected token % in JSON at position 0&quot;

&quot;SyntaxError: Unexpected token % in JSON at position 0↵    at JSON.parse (&lt;anonymous&gt;

this is my endpoint

        @GetMapping(&quot;/help/pdf2&quot;)
    public ResponseEntity&lt;InputStreamResource&gt; getPdf2(){

        Resource resource = new ClassPathResource(&quot;/pdf-sample.pdf&quot;);
        long r = 0;
        InputStream is=null;

        try {
            is = resource.getInputStream();
            r = resource.contentLength();
        } catch (IOException e) {
            e.printStackTrace();
        }

            return ResponseEntity.ok().contentLength(r)
                    .contentType(MediaType.parseMediaType(&quot;application/pdf&quot;))
                    .body(new InputStreamResource(is));

    }

this is my service 

      getPdf() {

    this.authKey = localStorage.getItem(&#39;jwt_token&#39;);

    const httpOptions = {
      headers: new HttpHeaders({
        &#39;Content-Type&#39;:  &#39;application/pdf&#39;,
        &#39;Authorization&#39; : this.authKey,
        responseType : &#39;blob&#39;,
        Accept : &#39;application/pdf&#39;,
        observe : &#39;response&#39;
      })
    };
    return this.http
      .get(&quot;http://localhost:9989/api/download/help/pdf2&quot;, httpOptions);


  }

and invocation 

    this.downloadService.getPdf()
      .subscribe((resultBlob: Blob) =&gt; {
      var downloadURL = URL.createObjectURL(resultBlob);
      window.open(downloadURL);});



Angular 6 Downloading file from rest api

Writing a bash script to connect to [GDAX&#39;s Websocket Feed](https://docs.gdax.com/#websocket-feed) at wss://ws-feed.gdax.com but curl doesn&#39;t seem to support this as I get 

    curl &quot;wss://ws-feed.gdax.com&quot;
    curl: (1) Protocol &quot;wss&quot; not supported or disabled in libcurl

How to read websocket response in linux shell

I need to connect to WebSockets server and log it&#39;s messages. With React class component I&#39;d put this logic in `componentDidMount` lifecycle hook and move on happily, but I&#39;m not sure how to properly implement it with hooks.

Here&#39;s my first attempt.
```js
import React, {useEffect} from &#39;react&#39;;

export default function AppWs() {
  useEffect(() =&gt; {
    let ws = new WebSocket(&#39;wss://ws.kraken.com/&#39;);
    ws.onopen = () =&gt; console.log(&#39;ws opened&#39;);
    ws.onclose = () =&gt; console.log(&#39;ws closed&#39;);

    ws.onmessage = e =&gt; {
      const message = JSON.parse(e.data);
      console.log(&#39;e&#39;, message);
    };

    return () =&gt; {
      ws.close();
    }
  }, []);

  return (
    &lt;div&gt;hooks + ws&lt;/div&gt;
  )
}
```
I added connection and log logic to `useEffect`, provided empty array with dependencies, and everything worked great. Until I needed to add `pause` state to pause logging.
```js
export default function AppWs() {
  const [isPaused, setPause] = useState(false);

  useEffect(() =&gt; {
    let ws = new WebSocket(&#39;wss://ws.kraken.com/&#39;);
    ws.onopen = () =&gt; console.log(&#39;ws opened&#39;);
    ws.onclose = () =&gt; console.log(&#39;ws closed&#39;);

    ws.onmessage = e =&gt; {
      if (isPaused) return;
      const message = JSON.parse(e.data);
      console.log(&#39;e&#39;, message);
    };

    return () =&gt; {
      ws.close();
    }
  }, []);

  return (
    &lt;div&gt;
      &lt;button onClick={() =&gt; setPause(!isPaused)}&gt;{isPaused ? &#39;Resume&#39; : &#39;Pause&#39;}&lt;/button&gt;
    &lt;/div&gt;
  )
}
```
ESLint started to yell at me that I should add `isPaused` state as a dependency to `useEffect`.  
Well, ok, done.  
But I noticed re-connection to WS server after every time I click the button. This is clearly not what I want.

My next iteration was to use two `useEffect`s: one for connection and one for message processing.
```js
export default function AppWs() {
  const [isPaused, setPause] = useState(false);
  const [ws, setWs] = useState(null);

  useEffect(() =&gt; {
    const wsClient = new WebSocket(&#39;wss://ws.kraken.com/&#39;);
    wsClient.onopen = () =&gt; {
      console.log(&#39;ws opened&#39;);
      setWs(wsClient);
    };
    wsClient.onclose = () =&gt; console.log(&#39;ws closed&#39;);

    return () =&gt; {
      wsClient.close();
    }
  }, []);

  useEffect(() =&gt; {
    if (!ws) return;

    ws.onmessage = e =&gt; {
      if (isPaused) return;
      const message = JSON.parse(e.data);
      console.log(&#39;e&#39;, message);
    };
  }, [isPaused, ws]);

  return (
    &lt;div&gt;
      &lt;button onClick={() =&gt; setPause(!isPaused)}&gt;{isPaused ? &#39;Resume&#39; : &#39;Pause&#39;}&lt;/button&gt;
    &lt;/div&gt;
  )
}
```
This works as expected, but I have a feeling that I miss something and this task can be solved easier, with one `useEffect`.
Please help to refactor the code on convince me that I&#39;m using React hooks in a proper way. Thanks!


Proper way of using React hooks + WebSockets

I try to understand protobuf and gRPC and how I can use both. Could you help me understand the following:

 - Considering the [OSI model][1] what is where, for example is Protobuf at layer 4?
 - Thinking through a message transfer how is the &quot;flow&quot;, what is gRPC doing what protobuf misses?
 - If the sender uses protobuf can the server use gRPC or does gRPC add something which only a gRPC client can deliver?
 - If gRPC can make synchronous and asynchronous communication possible, Protobuf is just for the marshalling and therefore does not have anything to do with state - true or false?
 - Can I use gRPC in a frontend application communicating instead of REST or GraphQL?

I already know - or assume I do - that:

[Protobuf][2]

 - Binary protocol for data interchange
 - Designed by Google
 - Uses generated &quot;Struct&quot; like description at client and server to un-/-marshall message

[gRPC][3]

 - Uses protobuf (v3)
 - Again from Google
 - Framework for RPC calls
 - Makes use of HTTP/2 as well
 - Synchronous and asynchronous communication possible

I again assume its an easy question for someone already using the technology. I still would thank you to be patient with me and help me out. I would also be really thankful for any network deep dive of the technologies.


  [1]: https://en.wikipedia.org/wiki/OSI_model
  [2]: https://developers.google.com/protocol-buffers/docs/reference/overview
  [3]: https://grpc.io/docs/guides/

protobuf vs gRPC

I am running my NodeJs App and i am getting an error.      
        
    sudo /usr/local/bin/node app.js    
        Error: Failed to load gRPC binary module because it was not installed for the current system
    Expected directory: node-v57-linux-x64-glibc
    Found: [node-v59-linux-x64-glibc]
    This problem can often be fixed by running &quot;npm rebuild&quot; on the current system
    Original error: Cannot find module &#39;/home/projects/kj_app/node_modules/grpc/src/node/extension_binary/node-v57-linux-x64-glibc
    /grpc_node.node&#39;
        at Object.&lt;anonymous&gt; (/home/projects/kj_app/node_modules/grpc/src/grpc_extension.js:53:17)
        at Module._compile (module.js:652:30)
        at Object.Module._extensions..js (module.js:663:10)
        at Module.load (module.js:565:32)
        at tryModuleLoad (module.js:505:12)
        at Function.Module._load (module.js:497:3)
        at Module.require (module.js:596:17)
        at require (internal/module.js:11:18)
        at Object.&lt;anonymous&gt; (/home/projects/kj_app/node_modules/grpc/src/client.js:37:12)
        at Module._compile (module.js:652:30)
        at Object.Module._extensions..js (module.js:663:10)
        at Module.load (module.js:565:32)
        at tryModuleLoad (module.js:505:12)
        at Function.Module._load (module.js:497:3)
        at Module.require (module.js:596:17)
        at require (internal/module.js:11:18)

    
**Edit**

        sudo /usr/local/bin/npm rebuild
  
        &gt; protobufjs@6.8.6 postinstall /home/projects/kj_app/node_modules/protobufjs
    &gt; node scripts/postinstall
    &gt; grpc@1.10.1 install /home/projects/kj_app/node_modules/grpc
    &gt; node-pre-gyp install --fallback-to-build --library=static_library
    [grpc] Success: &quot;/home/projects/kj_app/node_modules/grpc/src/node/extension_binary/node-v59-linux-x64-glibc/grpc_node.node&quot; al
    ready installed
    Pass --update-binary to reinstall or --build-from-source to recompile
    &gt; @google-cloud/profiler@0.1.14 install /home/projects/kj_app/node_modules/@google-cloud/profiler
    &gt; node-gyp rebuild
    gyp ERR! clean error 
    gyp ERR! stack Error: EACCES: permission denied, rmdir &#39;build&#39;
    gyp ERR! System Linux 4.9.0-6-amd64
    gyp ERR! command &quot;/opt/bitnami/nodejs/bin/.node.bin&quot; &quot;/usr/local/lib/node_modules/npm/node_modules/node-gyp/bin/node-gyp.js&quot; &quot;
    rebuild&quot;
    gyp ERR! cwd /home/projects/kj_app/node_modules/@google-cloud/profiler
    gyp ERR! node -v v9.8.0
    gyp ERR! node-gyp -v v3.6.2
    gyp ERR! not ok 
    npm ERR! code ELIFECYCLE
    npm ERR! errno 1
    npm ERR! @google-cloud/profiler@0.1.14 install: `node-gyp rebuild`
    npm ERR! Exit status 1
    npm ERR! 
    npm ERR! Failed at the @google-cloud/profiler@0.1.14 install script.
    npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
    npm ERR! A complete log of this run can be found in:
    npm ERR!     /root/.npm/_logs/2018-04-10T16_06_40_444Z-debug.log

NodeJs Error - Failed to load gRPC binary module because it was not installed for the current system Expected directory?

I am getting error while installing grpcio using pip install grpcio on my windows machine.I read here - https://github.com/grpc/grpc/issues/17829 that it may be due to error in a version of setuptools. I upgraded my setuptools to the latest version i.e. 41.0.1 . Still getting the same build error. Its not happening for any other package. I have tried reinstalling pip and python both on my laptop. I&#39;m attaching my error 

    Building wheels for collected packages: grpcio
    Building wheel for grpcio (setup.py) ... error
    ERROR: Complete output from command &#39;c:\python27\python.exe&#39; -u -c &#39;import setuptools, tokenize;__file__=&#39;&quot;&#39;&quot;&#39;c:\\users\\s\\appdata\\local\\temp\\pip-install-ge5zhq\\grpcio\\setup.py&#39;&quot;&#39;&quot;&#39;;f=getattr(tokenize, &#39;&quot;&#39;&quot;&#39;open&#39;&quot;&#39;&quot;&#39;, open)(__file__);code=f.read().replace(&#39;&quot;&#39;&quot;&#39;\r\n&#39;&quot;&#39;&quot;&#39;, &#39;&quot;&#39;&quot;&#39;\n&#39;&quot;&#39;&quot;&#39;);f.close();exec(compile(code, __file__, &#39;&quot;&#39;&quot;&#39;exec&#39;&quot;&#39;&quot;&#39;))&#39; bdist_wheel
    -d &#39;c:\users\s\appdata\local\temp\pip-wheel-txjhlh&#39; --python-tag cp27:
      ERROR: Found cython-generated files...
      running bdist_wheel
      running build
      running build_py
      running build_project_metadata
      creating python_build
      creating python_build\lib.win-amd64-2.7
      creating python_build\lib.win-amd64-2.7\grpc
      copying src\python\grpcio\grpc\_auth.py -&gt; python_build\lib.win-amd64-2.7\grpc
      copying src\python\grpcio\grpc\_channel.py -&gt; python_build\lib.win-amd64-2.7\grpc
      copying src\python\grpcio\grpc\_common.py -&gt; python_build\lib.win-amd64-2.7\grpc
      copying src\python\grpcio\grpc\_compression.py -&gt; python_build\lib.win-amd64-2.7\grpc
      copying src\python\grpcio\grpc\_grpcio_metadata.py -&gt; python_build\lib.win-amd64-2.7\grpc
      copying src\python\grpcio\grpc\_interceptor.py -&gt; python_build\lib.win-amd64-2.7\grpc
      copying src\python\grpcio\grpc\_plugin_wrapping.py -&gt; python_build\lib.win-amd64-2.7\grpc
      copying src\python\grpcio\grpc\_server.py -&gt; python_build\lib.win-amd64-2.7\grpc
      copying src\python\grpcio\grpc\_utilities.py -&gt; python_build\lib.win-amd64-2.7\grpc
      copying src\python\grpcio\grpc\__init__.py -&gt; python_build\lib.win-amd64-2.7\grpc
      creating python_build\lib.win-amd64-2.7\grpc\beta
      copying src\python\grpcio\grpc\beta\implementations.py -&gt; python_build\lib.win-amd64-2.7\grpc\beta
      copying src\python\grpcio\grpc\beta\interfaces.py -&gt; python_build\lib.win-amd64-2.7\grpc\beta
      copying src\python\grpcio\grpc\beta\utilities.py -&gt; python_build\lib.win-amd64-2.7\grpc\beta
      copying src\python\grpcio\grpc\beta\_client_adaptations.py -&gt; python_build\lib.win-amd64-2.7\grpc\beta
          copying src\python\grpcio\grpc\beta\_metadata.py -&gt; python_build\lib.win-amd64-2.7\grpc\beta
          copying src\python\grpcio\grpc\beta\_server_adaptations.py -&gt; python_build\lib.win-amd64-2.7\grpc\beta
          copying src\python\grpcio\grpc\beta\__init__.py -&gt; python_build\lib.win-amd64-2.7\grpc\beta
          creating python_build\lib.win-amd64-2.7\grpc\experimental
          copying src\python\grpcio\grpc\experimental\gevent.py -&gt; python_build\lib.win-amd64-2.7\grpc\experimental
          copying src\python\grpcio\grpc\experimental\session_cache.py -&gt; python_build\lib.win-amd64-2.7\grpc\experimental
          copying src\python\grpcio\grpc\experimental\__init__.py -&gt; python_build\lib.win-amd64-2.7\grpc\experimental
          creating python_build\lib.win-amd64-2.7\grpc\framework
          copying src\python\grpcio\grpc\frame`enter code here`work\__init__.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework
          creating python_build\lib.win-amd64-2.7\grpc\_cython
          copying src\python\grpcio\grpc\_cython\__init__.py -&gt; python_build\lib.win-amd64-2.7\grpc\_cython
          creating python_build\lib.win-amd64-2.7\grpc\framework\common
          copying src\python\grpcio\grpc\framework\common\cardinality.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\common
          copying src\python\grpcio\grpc\framework\common\style.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\common
          copying src\python\grpcio\grpc\framework\common\__init__.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\common
          creating python_build\lib.win-amd64-2.7\grpc\framework\foundation
          copying src\python\grpcio\grpc\framework\foundation\abandonment.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\foundation
          copying src\python\grpcio\grpc\framework\foundation\callable_util.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\foundation
          copying src\python\grpcio\grpc\framework\foundation\future.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\foundation
          copying src\python\grpcio\grpc\framework\foundation\logging_pool.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\foundation
          copying src\python\grpcio\grpc\framework\foundation\stream.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\foundation
          copying src\python\grpcio\grpc\framework\foundation\stream_util.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\foundation
          copying src\python\grpcio\grpc\framework\foundation\__init__.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\foundation
          creating python_build\lib.win-amd64-2.7\grpc\framework\interfaces
          copying src\python\grpcio\grpc\framework\interfaces\__init__.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\interfaces
          creating python_build\lib.win-amd64-2.7\grpc\framework\interfaces\base
          copying src\python\grpcio\grpc\framework\interfaces\base\base.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\interfaces\base
          copying src\python\grpcio\grpc\framework\interfaces\base\utilities.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\interfaces\base
          copying src\python\grpcio\grpc\framework\interfaces\base\__init__.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\interfaces\base
          creating python_build\lib.win-amd64-2.7\grpc\framework\interfaces\face
          copying src\python\grpcio\grpc\framework\interfaces\face\face.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\interfaces\face
          copying src\python\grpcio\grpc\framework\interfaces\face\utilities.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\interfaces\face
          copying src\python\grpcio\grpc\framework\interfaces\face\__init__.py -&gt; python_build\lib.win-amd64-2.7\grpc\framework\interfaces\face
          creating python_build\lib.win-amd64-2.7\grpc\_cython\_cygrpc
          copying src\python\grpcio\grpc\_cython\_cygrpc\__init__.py -&gt; python_build\lib.win-amd64-2.7\grpc\_cython\_cygrpc
          creating python_build\lib.win-amd64-2.7\grpc\_cython\_credentials
          copying src\python\grpcio\grpc\_cython\_credentials\roots.pem -&gt; python_build\lib.win-amd64-2.7\grpc\_cython\_credentials
          running build_ext
          error: [Error 2] The system cannot find the file specified
          ----------------------------------------
          ERROR: Failed building wheel for grpcio
          Running setup.py clean for grpcio
        Failed to build grpcio

Unable to install grpcio using pip install grpcio

I am trying to build a sample application with Go [gRPC][1], but I am unable to generate the code using &quot;protoc&quot;

I have installed the required libraries and Go packages using:

1. `go get -u google.golang.org/grpc`
2. `go get -u github.com/golang/protobuf/protoc-gen-go`

I have tried setting the path as well, but no luck.

Sample &quot;proto&quot; file:

```
syntax = &quot;proto3&quot;;

package greet;
option go_package=&quot;greetpb&quot;;

service GreetService{}
```

Error message:

&gt; &quot;protoc-gen-go: program not found or is not executable \
--go_out: protoc-gen-go: Plugin failed with status code 1.&quot;

  [1]: https://en.wikipedia.org/wiki/GRPC





Error &quot;protoc-gen-go: program not found or is not executable&quot;

There are a lot of topics about the [HTTP/2][1] protocol, but I wonder if there is a working website with this protocol.

I.e.

We can decide to use `http://` or `https://`, but how can we write a HTTP/2 request?

I am aware that this protocol depends on the server capability, but I can not find a way to check if a website, e.g. `google.com`, has HTTP/2 support enabled.

[![HTTP/2 browser support][2]][2]

As I can see in this picture, all modern browsers support this protocol.
I have not seen any link that could look like a new generation protocol.

Are we using the HTTP/2 protocol without knowing or it is just a fairy tale?

  [1]: https://en.wikipedia.org/wiki/HTTP/2
  [2]: https://i.stack.imgur.com/pyhyL.png


How to check if a website has HTTP/2 protocol support

I&#39;m currently working on a website, which triggers a ```net::ERR_HTTP2_PROTOCOL_ERROR 200``` error on Google Chrome. I&#39;m not sure exactly what can provoke this error, I just noticed it pops out only when accessing the website in HTTPS. I can&#39;t be 100% sure it is related, but it looks like it prevents JavaScript to be executed properly.

For instance, the following scenario happens :

1. I&#39;m accessing the website in HTTPS

2. My Twitter feed integrated via https://publish.twitter.com  isn&#39;t loaded at all 

3. I can notice in the console the ERR_HTTP2_PROTOCOL_ERROR

4. If I remove the code to load the Twitter feed, the error remains

5. If I access the website in HTTP, the Twitter feed appears and the error disappears 

Google Chrome is the only web browser triggering the error: it works well on both Edge and Firefox.
(NB: I tried with Safari, and I have a similar ```kcferrordomaincfnetwork 303``` error)

I was wondering if it could be related to the header returned by the server since there is this &#39;200&#39; mention in the error, and a 404 / 500 page isn&#39;t triggering anything. 

Thing is the error isn&#39;t documented at all. Google search gives me very few results. Moreover, I noticed it appears on very recent Google Chrome releases; the error doesn&#39;t pop on v.64.X, but it does on v.75+ (regardless of the OS; I&#39;m working on Mac tho).

----------


Might be related to https://stackoverflow.com/questions/49927327/website-ok-on-firefox-but-not-on-safari-kcferrordomaincfnetwork-error-303-neit


----------


Findings from further investigations are the following:

 - **error doesn&#39;t pop on the exact same page if server returns 404 instead of 2XX**
 - error doesn&#39;t pop on local with a HTTPS certificate
 - error pops on a different server (both are OVH&#39;s), which uses a different certificate
 - error pops no matter what PHP version is used, from 5.6 to 7.3 (framework used : Cakephp 2.10)

As requested, below is the returned header for the failing ressource, which is the whole web page. Even if the error is triggering on each page having a HTTP header 200, those pages are always loading on client&#39;s browser, but sometimes an element is missing (in my exemple, the external Twitter feed). Every other asset on the Network tab has a success return, except the whole document itself. 
[![line that failed in console][1]][1]

Google Chrome header (with error):

[![Chrome header][2]][2]


Firefox header (without error):

[![Firefox header][3]][3]

A ```curl --head --http2``` request in console returns the following success:
```
HTTP/2 200 
date: Fri, 04 Oct 2019 08:04:51 GMT
content-type: text/html; charset=UTF-8
content-length: 127089
set-cookie: SERVERID31396=2341116; path=/; max-age=900
server: Apache
x-powered-by: PHP/7.2
set-cookie: xxxxx=0919c5563fc87d601ab99e2f85d4217d; expires=Fri, 04-Oct-2019 12:04:51 GMT; Max-Age=14400; path=/; secure; HttpOnly
vary: Accept-Encoding
```

----------

Trying to go deeper with the chrome://net-export/ and https://netlog-viewer.appspot.com tools is telling me the request ends with a RST_STREAM :
```
t=123354 [st=5170]    HTTP2_SESSION_RECV_RST_STREAM
                      --&gt; error_code = &quot;2 (INTERNAL_ERROR)&quot;
                      --&gt; stream_id = 1
```
For what I read in [this other post][4], &quot;*In HTTP/2, if the client wants to abort the request, it sends a RST_STREAM. When the server receives a RST_STREAM, it will stop sending DATA frames to the client, thereby stopping the response (or the download). The connection is still usable for other requests, and requests/responses that were concurrent with the one that has been aborted may continue to progress.
[...]
It is possible that by the time the RST_STREAM travels from the client to the server, the whole content of the request is in transit and will arrive to the client, which will discard it. However, for large response contents, sending a RST_STREAM may have a good chance to arrive to the server before the whole response content is sent, and therefore will save bandwidth.*&quot;

The described behavior is the same as the one I can observe. But that would mean the browser is the culprit, and then I wouldn&#39;t understand why it happens on two identical pages with one having a 200 header and the other a 404 (same goes if I disable JS).
 

  [1]: https://i.stack.imgur.com/ZkdHo.png
  [2]: https://i.stack.imgur.com/0wCrD.png
  [3]: https://i.stack.imgur.com/AAtn8.png
  [4]: https://stackoverflow.com/questions/28736463/rst-stream-frame-in-http2

Content Type	Original Author	Original Content on Stackoverflow
Question	prashant sindhu	View Question on Stackoverflow
Solution 1 - Rest	Phil Sturgeon	View Answer on Stackoverflow
Solution 2 - Rest	Jonas	View Answer on Stackoverflow

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