Bairdy
Bairdy•2y ago

Deno.serve AbortController onError. How?

When I run my new Deno.serve() updated implementation I get a type error. Perhaps I'm doing it wrong. Maybe it is the way I am trying to use the Abort Controller or maybe the onError handler must always return something? 
// You can stop the server with an AbortSignal.
// The abort signal needs to be passed as the signal option in the options bag.
const ac = new AbortController();

const server = Deno.serve({
  // The port to listen on.
  port: config.http.server.port,
  // A literal IP address or host name that can be resolved to an IP address.
  hostname: "0.0.0.0",
  // An AbortSignal to close the server and all connections.
  signal: ac.signal,
  // The callback which is called when the server starts listening.
  onListen({ port, hostname }) {
    // console.log(`Server started at http://${hostname}:${port}`);
    console.log(
      `%cApplication..... fsrv v2.0 - A Deno HTTP Server
Deno v${Deno.version.deno} : Typescript v${Deno.version.typescript} : V8 v${Deno.version.v8}
Gateway URL..... http://${hostname}:${port}
Server Root..... ${pathJoin(CWD, config.http.server.www)}
Internal Pages.. ${pathJoin(CWD, config.http.server.internal)}
Site Root....... ${pathJoin(CWD, config.http.server.public)}`,
      "color: #7986cb",
    );
  },
  // The handler to invoke when route handlers throw an error.
  onError(error) {
    console.error(error);
    log("HTTP 500");

    // FATAL ERROR!

    // The server aborts when the abort signal is sent to the abort controller.
    console.log("Closing server...");
    ac.abort();
    // To wait for the server to close, await the promise returned from the Deno.serve API.
    server.finished.then(() => console.log("Server closed"));

  },
}, handler);
// You can stop the server with an AbortSignal.
// The abort signal needs to be passed as the signal option in the options bag.
const ac = new AbortController();

const server = Deno.serve({
  // The port to listen on.
  port: config.http.server.port,
  // A literal IP address or host name that can be resolved to an IP address.
  hostname: "0.0.0.0",
  // An AbortSignal to close the server and all connections.
  signal: ac.signal,
  // The callback which is called when the server starts listening.
  onListen({ port, hostname }) {
    // console.log(`Server started at http://${hostname}:${port}`);
    console.log(
      `%cApplication..... fsrv v2.0 - A Deno HTTP Server
Deno v${Deno.version.deno} : Typescript v${Deno.version.typescript} : V8 v${Deno.version.v8}
Gateway URL..... http://${hostname}:${port}
Server Root..... ${pathJoin(CWD, config.http.server.www)}
Internal Pages.. ${pathJoin(CWD, config.http.server.internal)}
Site Root....... ${pathJoin(CWD, config.http.server.public)}`,
      "color: #7986cb",
    );
  },
  // The handler to invoke when route handlers throw an error.
  onError(error) {
    console.error(error);
    log("HTTP 500");

    // FATAL ERROR!

    // The server aborts when the abort signal is sent to the abort controller.
    console.log("Closing server...");
    ac.abort();
    // To wait for the server to close, await the promise returned from the Deno.serve API.
    server.finished.then(() => console.log("Server closed"));

  },
}, handler);
I get the following error: 
error: TS2322 [ERROR]: Type '(error: unknown) => void' is not assignable to type '(error: unknown) => Response | Promise<Response>'.
  Type 'void' is not assignable to type 'Response | Promise<Response>'.
  onError(error) {
error: TS2322 [ERROR]: Type '(error: unknown) => void' is not assignable to type '(error: unknown) => Response | Promise<Response>'.
  Type 'void' is not assignable to type 'Response | Promise<Response>'.
  onError(error) {
3 Replies
MrKleeblatt
MrKleeblatt•2y ago
That's because onError needs a return value. Although never called because of the ac.abort() call, just add 
return new Response("never");
return new Response("never");
at the end of the onError function.
guest271314
guest271314•2y ago
Technically a reason should be passed to AbortController.abort('Stream aborted') so that reason can be propagated to abort() methods and/or catch()/catch (e) {}.
Bairdy
BairdyOP•2y ago
Thank you both for such simple solutions. I now have 2 working example scenarios. Scenario #1 * Once started, the server runs regardless of encountering route handler errors. * onError, a warning HTTP 500 response is still returned to the client. * There is no Abort Controller. 
Deno.serve({
  // The port to listen on.
  port: config.http.server.port,
  // A literal IP address or host name that can be resolved to an IP address.
  hostname: "0.0.0.0",
  // The callback which is called when the server starts listening.
  onListen({ port, hostname }) {
    console.log(
      `%cApplication..... fsrv v2.0 - A Deno HTTP Server
Deno v${Deno.version.deno} : Typescript v${Deno.version.typescript} : V8 v${Deno.version.v8}
Permissions: --allow-sys --allow-read --allow-net
Gateway URL..... http://${hostname}:${port}
Server Root..... ${config.http.server.www}
Internal Pages.. ${config.http.server.internal}
Site Root....... ${config.http.server.public}\n\n`,
      "color: #7986cb",
    );
  },
  // The handler to invoke when route handlers throw an error.
  onError(error: unknown) {    
    console.error(error);
    console.log("HTTP 500");

    // WARNING!
      
    /**
     * onError returns HTTP response.
     * Server proceeds to next request. 
     *
     */
    return serverResponse(
      "HTTP 500: Internal Server Error",
      500,
      "text/plain",
    );
    
  },
}, handler); // <-- The handler goes here
Deno.serve({
  // The port to listen on.
  port: config.http.server.port,
  // A literal IP address or host name that can be resolved to an IP address.
  hostname: "0.0.0.0",
  // The callback which is called when the server starts listening.
  onListen({ port, hostname }) {
    console.log(
      `%cApplication..... fsrv v2.0 - A Deno HTTP Server
Deno v${Deno.version.deno} : Typescript v${Deno.version.typescript} : V8 v${Deno.version.v8}
Permissions: --allow-sys --allow-read --allow-net
Gateway URL..... http://${hostname}:${port}
Server Root..... ${config.http.server.www}
Internal Pages.. ${config.http.server.internal}
Site Root....... ${config.http.server.public}\n\n`,
      "color: #7986cb",
    );
  },
  // The handler to invoke when route handlers throw an error.
  onError(error: unknown) {    
    console.error(error);
    console.log("HTTP 500");

    // WARNING!
      
    /**
     * onError returns HTTP response.
     * Server proceeds to next request. 
     *
     */
    return serverResponse(
      "HTTP 500: Internal Server Error",
      500,
      "text/plain",
    );
    
  },
}, handler); // <-- The handler goes here
Scenario #2 * Once started, the server runs until the first error is thrown by the route handlers. * onError, the abort signal is sent to the AbortController. * The abort signal needs to be passed as the signal option in the options bag. 
const ac = new AbortController();

const server = Deno.serve({
  // The port to listen on.
  port: config.http.server.port,
  // A literal IP address or host name that can be resolved to an IP address.
  hostname: "0.0.0.0",
  // An AbortSignal to close the server and all connections.
  signal: ac.signal,
  // The callback which is called when the server starts listening.
  onListen({ port, hostname }) {
    // console.log(`Server started at http://${hostname}:${port}`);
    console.log(
      `%cApplication..... fsrv v2.0 - A Deno HTTP Server
Deno v${Deno.version.deno} : Typescript v${Deno.version.typescript} : V8 v${Deno.version.v8}
Gateway URL..... http://${hostname}:${port}
Server Root..... ${config.http.server.www}
Internal Pages.. ${config.http.server.internal}
Site Root....... ${config.http.server.public}`,
      "color: #7986cb",
    );
  },
  // The handler to invoke when route handlers throw an error.
  onError(error: unknown) {
    console.error(error);
    log("HTTP 500");

    // FATAL ERROR!

    // The server aborts when the abort signal is sent to the abort controller.
    console.log("Closing server...");
      
    // Send the abort signal!
    ac.abort("Stream aborted");
      
    // To wait for the server to close, await the promise returned from the Deno.serve API.
    server.finished.then(() => console.log("Server closed"));

    /**
     * onError needs a return value or error Type 'void' is not assignable 
     * to type 'Response | Promise<Response>' occurs.
     *
     * return here is NEVER reached because of the ac.abort() call that preceeds it.
     * 
     */
    return new Response("Stream aborted");

  },
}, handler); // <-- The handler goes here
const ac = new AbortController();

const server = Deno.serve({
  // The port to listen on.
  port: config.http.server.port,
  // A literal IP address or host name that can be resolved to an IP address.
  hostname: "0.0.0.0",
  // An AbortSignal to close the server and all connections.
  signal: ac.signal,
  // The callback which is called when the server starts listening.
  onListen({ port, hostname }) {
    // console.log(`Server started at http://${hostname}:${port}`);
    console.log(
      `%cApplication..... fsrv v2.0 - A Deno HTTP Server
Deno v${Deno.version.deno} : Typescript v${Deno.version.typescript} : V8 v${Deno.version.v8}
Gateway URL..... http://${hostname}:${port}
Server Root..... ${config.http.server.www}
Internal Pages.. ${config.http.server.internal}
Site Root....... ${config.http.server.public}`,
      "color: #7986cb",
    );
  },
  // The handler to invoke when route handlers throw an error.
  onError(error: unknown) {
    console.error(error);
    log("HTTP 500");

    // FATAL ERROR!

    // The server aborts when the abort signal is sent to the abort controller.
    console.log("Closing server...");
      
    // Send the abort signal!
    ac.abort("Stream aborted");
      
    // To wait for the server to close, await the promise returned from the Deno.serve API.
    server.finished.then(() => console.log("Server closed"));

    /**
     * onError needs a return value or error Type 'void' is not assignable 
     * to type 'Response | Promise<Response>' occurs.
     *
     * return here is NEVER reached because of the ac.abort() call that preceeds it.
     * 
     */
    return new Response("Stream aborted");

  },
}, handler); // <-- The handler goes here

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