stream: fix pipe deadlock when starting with needDrain

Fixes: #36544 PR-URL: #36563 Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
nodejs · Dec 21, 2020 · 3f33d0b · 3f33d0b
1 parent 95c80f5
commit 3f33d0b
Show file tree

Hide file tree

Showing 2 changed files with 35 additions and 28 deletions.
diff --git a/lib/internal/streams/readable.js b/lib/internal/streams/readable.js
@@ -716,35 +716,39 @@ Readable.prototype.pipe = function(dest, pipeOpts) {
       ondrain();
   }
 
+  function pause() {
+    // If the user unpiped during `dest.write()`, it is possible
+    // to get stuck in a permanently paused state if that write
+    // also returned false.
+    // => Check whether `dest` is still a piping destination.
+    if (!cleanedUp) {
+      if (state.pipes.length === 1 && state.pipes[0] === dest) {
+        debug('false write response, pause', 0);
+        state.awaitDrainWriters = dest;
+        state.multiAwaitDrain = false;
+      } else if (state.pipes.length > 1 && state.pipes.includes(dest)) {
+        debug('false write response, pause', state.awaitDrainWriters.size);
+        state.awaitDrainWriters.add(dest);
+      }
+      src.pause();
+    }
+    if (!ondrain) {
+      // When the dest drains, it reduces the awaitDrain counter
+      // on the source.  This would be more elegant with a .once()
+      // handler in flow(), but adding and removing repeatedly is
+      // too slow.
+      ondrain = pipeOnDrain(src, dest);
+      dest.on('drain', ondrain);
+    }
+  }
+
   src.on('data', ondata);
   function ondata(chunk) {
     debug('ondata');
     const ret = dest.write(chunk);
     debug('dest.write', ret);
     if (ret === false) {
-      // If the user unpiped during `dest.write()`, it is possible
-      // to get stuck in a permanently paused state if that write
-      // also returned false.
-      // => Check whether `dest` is still a piping destination.
-      if (!cleanedUp) {
-        if (state.pipes.length === 1 && state.pipes[0] === dest) {
-          debug('false write response, pause', 0);
-          state.awaitDrainWriters = dest;
-          state.multiAwaitDrain = false;
-        } else if (state.pipes.length > 1 && state.pipes.includes(dest)) {
-          debug('false write response, pause', state.awaitDrainWriters.size);
-          state.awaitDrainWriters.add(dest);
-        }
-        src.pause();
-      }
-      if (!ondrain) {
-        // When the dest drains, it reduces the awaitDrain counter
-        // on the source.  This would be more elegant with a .once()
-        // handler in flow(), but adding and removing repeatedly is
-        // too slow.
-        ondrain = pipeOnDrain(src, dest);
-        dest.on('drain', ondrain);
-      }
+      pause();
     }
   }
 
@@ -793,7 +797,7 @@ Readable.prototype.pipe = function(dest, pipeOpts) {
 
   if (dest.writableNeedDrain === true) {
     if (state.flowing) {
-      src.pause();
+      pause();
     }
   } else if (!state.flowing) {
     debug('pipe resume');

diff --git a/test/parallel/test-stream-pipe-needDrain.js b/test/parallel/test-stream-pipe-needDrain.js
@@ -5,12 +5,13 @@ const assert = require('assert');
 const Readable = require('_stream_readable');
 const Writable = require('_stream_writable');
 
-// Pipe should not continue writing if writable needs drain.
+// Pipe should pause temporarily if writable needs drain.
 {
   const w = new Writable({
     write(buf, encoding, callback) {
-
-    }
+      process.nextTick(callback);
+    },
+    highWaterMark: 1
   });
 
   while (w.write('asd'));
@@ -20,10 +21,12 @@ const Writable = require('_stream_writable');
   const r = new Readable({
     read() {
       this.push('asd');
+      this.push(null);
     }
   });
 
-  w.write = common.mustNotCall();
+  r.on('pause', common.mustCall(2));
+  r.on('end', common.mustCall());
 
   r.pipe(w);
 }