stream: resume flow when an errored pipe destination is removed

When a source is piped to multiple destinations and one destination
errors synchronously in `_write()`, `write()` returns false without
setting `needDrain` (since the "avoid unnecessary drain for sync
stream" change). The pipe cleanup only re-invoked the source's drain
handler when the destination still had `needDrain` set, so the errored
destination was never removed from the source's `awaitDrainWriters`
set. The source stayed paused forever and any remaining healthy
destination stopped receiving data.

Always invoke the drain handler during cleanup. `pipeOnDrain` only
removes this destination from the awaiting-drain set and resumes the
source once nothing else is awaiting a drain, so it is safe to call
unconditionally and no-ops when this destination was not awaiting a
drain.

Fixes: #53185
Signed-off-by: Mahin Anowar <86069420+MahinAnowar@users.noreply.github.com>

Author: MahinAnowar

lib/internal/streams/readable.js

@@ -985,9 +985,13 @@ Readable.prototype.pipe = function(dest, pipeOpts) {
     // specific writer, then it would cause it to never start
     // flowing again.
     // So, if this is awaiting a drain, then we just call it now.
-    // If we don't know, then assume that we are waiting for one.
-    if (ondrain && state.awaitDrainWriters &&
-        (!dest._writableState || dest._writableState.needDrain))
+    // `pipeOnDrain` only removes this destination from the awaiting-drain set
+    // and resumes the source once nothing else is awaiting a drain, so it is
+    // safe to call unconditionally and no-ops when this writer wasn't awaiting
+    // a drain. Guarding on `needDrain` used to skip this for a destination that
+    // errored synchronously, leaving it stuck in the set and starving other
+    // destinations piped from the same source (see #53185).
+    if (ondrain && state.awaitDrainWriters)
       ondrain();
   }
 

test/parallel/test-stream-pipe-multiple-destinations-error.js

@@ -0,0 +1,48 @@
+'use strict';
+const common = require('../common');
+
+// Regression test for https://github.com/nodejs/node/issues/53185
+// When a source is piped to multiple destinations and one destination errors
+// synchronously in `_write`, the source must keep flowing to the remaining
+// healthy destination(s) instead of stalling forever.
+
+const assert = require('assert');
+const { PassThrough, Writable, finished } = require('stream');
+
+const source = new PassThrough({ highWaterMark: 16 * 1024 });
+
+// A destination that errors synchronously on its first write.
+const failing = new Writable({
+  highWaterMark: 16 * 1024,
+  write(chunk, encoding, callback) {
+    callback(new Error('boom'));
+  },
+});
+failing.on('error', common.mustCall());
+
+// A healthy destination that counts everything it receives.
+let received = 0;
+const healthy = new Writable({
+  highWaterMark: 16 * 1024,
+  write(chunk, encoding, callback) {
+    received += chunk.length;
+    callback();
+  },
+});
+
+source.pipe(failing);
+source.pipe(healthy);
+
+// Two chunks each larger than the highWaterMark so that `write()` returns
+// false and the source is paused awaiting a drain.
+const chunk = Buffer.alloc(20000, 'a');
+source.write(chunk);
+source.write(chunk);
+source.end();
+
+finished(healthy, common.mustSucceed(() => {
+  // Without the fix, the errored destination stays in the source's
+  // awaitDrainWriters set, the source never resumes, and `healthy` only
+  // receives the first chunk.
+  assert.strictEqual(received, chunk.length * 2);
+}));