Sending data in loop fails about node-unix-dgram HOT 6 CLOSED

-9 is EBADF, -11 is EAGAIN on Linux, -55 is ENOBUFS on OS X. I should probably add string error names but in the mean time consult errno.h on your system; the error code is the negated errno.

EBADF means you are trying to send on a socket you closed earlier. ENOBUFS means you've exhausted the kernel's resources and need to back off.

EAGAIN should have been handled by unix-dgram, I think. @santigimeno Why is it that send() starts the poll watcher but sendto() simply returns the error?

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@santigimeno Why is it that send() starts the poll watcher but sendto() simply returns the error?

@bnoordhuis IIRC send() just adds the UV_WRITABLE flag to the handle. The socket should already be watching for UV_READABLE events. bindings.send() should only be used for connected sockets and the UV_WRITABLE flag is needed for the congestion and writable events, see: https://github.com/bnoordhuis/node-unix-dgram#socketconnectremote_path.

EAGAIN should have been handled by unix-dgram

AFAICT, EAGAIN was never handled with non-connected sockets. In fact, that's one of the reasons I added the connected sockets functionality.

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For this issue I would use code similar to the one in https://github.com/bnoordhuis/node-unix-dgram#socketsendbuf-callback that allows implementing some congestion control.

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I tried the example code you just linked, but the writable / congestion events are never received on mac os

var unix = require('unix-dgram');
var client = unix.createSocket('unix_dgram');
var socketPath = __dirname + '/test.socket';

client.on('error', function (err) {
  console.error(err);
  client.close();
});

client.on('congestion', function() {
  console.log('congestion * * * * * * *');
  /* The server is not accepting data */
});

client.on('writable', function() {
  console.log('writable * * * * * * *');
  /* The server can accept data */
});

client.on('connect', function() {
  console.log('connected');
  for (var i = 0; i < 1000; i++) {
    var message = 'message ' + i;
    console.log('sending ' + message);
    client.send(Buffer.from(message));
  }
});

client.connect(socketPath);

Using this test code, here are the logs:

...
sending message 64
sending message 65
{ [Error: send -55] code: -55, errno: -55, syscall: 'send' }
sending message 66
{ [Error: send -9] code: -9, errno: -9, syscall: 'send' }
Assertion failed: (iter != watchers.end()), function StopWatcher, file ../src/unix_dgram.cc, line 166.
Abort trap: 6

On Debian, the events are well received and when having a congestion, the write pause and restart when socket is writable again

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@jbdemonte can you try the following patch?

diff --git a/src/unix_dgram.cc b/src/unix_dgram.cc
index 4c6e9e8..370b1e4 100644
--- a/src/unix_dgram.cc
+++ b/src/unix_dgram.cc
@@ -317,7 +317,7 @@ NAN_METHOD(Send) {
   err = 0;
   if (r == -1) {
     err = -errno;
-    if ((errno == EAGAIN) || (errno == EWOULDBLOCK)) {
+    if ((errno == EAGAIN) || (errno == EWOULDBLOCK) || (errno == ENOBUFS)) {
       watchers_t::iterator iter = watchers.find(fd);
       assert(iter != watchers.end());
       SocketContext* sc = iter->second;

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I confirm this patch works like a charm 👍

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