Writable Stream problem with end() callback #6868

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1. addaleax

   added

   questionIssues asking questions about Node.js.Issues asking questions about Node.js.

   streamIssues and PRs related to Node.js streams.Issues and PRs related to Node.js streams.

   on May 18, 2016
2. addaleax commented on May 18, 2016

   

   addaleax

   on May 18, 2016

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   Could you provide e.g. a minimal snippet of code with an example where calling .end(…) does not work?
3. tysenmoore-xse commented on May 18, 2016

   

   tysenmoore-xse

   on May 18, 2016

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   The code is rather large. To get a working example would be a bit of work, but basically the code is:

   wavFile = fs.createReadStream( filename );
   usbAudioWriter = getWritableStreamSomehow(); // calls a module that inherits from the Writable to stream over our USB API (The end code calls the Writeable.end as is.
   wavFile.pipe( usbAudioWriter );
   ...
   // When closing the stream down
   usbAudioWriter.end(  function() {
        // Do the close here...
        console.log("End Called");    
   } );
   

   Like I mentioned before, when end() is called state.finished is false.

   If I attempt to force the afterWrite() with something like the following code:
   usbAudioWriter.write( Buffer("\0") );
   I get the error: write after end

   If this is not enough to go on, please let me know. I can attempt to reduce the problem to a testable use case. I am just working off of code inspection, but it seems if state.finished is false when endWritable() is called, the callback passed into end() will never be called--I could however be wrong. I am still rather new to all the streaming code.
4. addaleax commented on May 18, 2016

   

   addaleax

   on May 18, 2016

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   Ah! The docs for .pipe() might help clarify things. Normally, when piping from a stream to another, when the reading side ends, the writing sides ends, too, so you can’t call .end() again. If you want to know when writing to a stream ended, use the 'finish' event, i.e.

   // When closing the stream down
   usbAudioWriter.on( 'finish', function() {
        // Do the close here...
        console.log("End Called");    
   } );

   If there’s something you need to do before the writer stream ends, you should be able to override the default behaviour using {end: false} and ending the writable stream yourself:

   wavFile = fs.createReadStream( filename );
   usbAudioWriter = getWritableStreamSomehow(); // calls a module that inherits from the Writable to stream over our USB API (The end code calls the Writeable.end as is.
   wavFile.pipe( usbAudioWriter, { end: false } );
   ...
   // When closing the stream down
   wavFile.on('finish', function() {
        // do things...
        usbAudioWriter.end(  function() {
             // Do the close here...
             console.log("End Called");    
        } );
   } );

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5. tysenmoore-xse commented on May 19, 2016

   

   tysenmoore-xse

   on May 19, 2016

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   In my use case the wav file being played is on a continuous loop, so its end() is never called.

   However, based on your suggestions I was able to get it working similar to your solution. Thanks so much for the time and help.
6. tysenmoore-xse

   closed this as completedon May 19, 2016
7. akshita31 commented on May 1, 2018

   

   akshita31

   on May 1, 2018

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   I am working on a similar thing where I need to download a zip into to an already open file(that has a valid file descriptor) and also use this file descriptor later on to unzip the file. If I dont use pipe: false then the filestream end is coming and accessing the file descriptor for the unzip is giving an error because it is already closed. Is there a way to just know when the data has been flushed to the underlying stream without closing it ?

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