http2: fix tracking received data for maxSessionMemory

Track received data correctly. Specifically, for the buffer that is used for receiving data, we previously would try to increment the current memory usage by its length, and later decrement it by that, but in the meantime the buffer had been turned over to V8 and its length reset to zero. This gave the impression that more and more memory was consumed by the HTTP/2 session when it was in fact not. Fixes: #27416 Refs: #26207
nodejs · addaleax · May 26, 2019 · May 26, 2019 · 4b5176fe0afc2d0ec47d140a8a1278deb14db3c1
commit 4b5176fe0afc2d0ec47d140a8a1278deb14db3c1
diff --git a/src/node_http2.cc b/src/node_http2.cc
@@ -1782,11 +1782,13 @@ void Http2Session::OnStreamRead(ssize_t nread, const uv_buf_t& buf_) {
   // Shrink to the actual amount of used data.
   buf.Resize(nread);
 
-  IncrementCurrentSessionMemory(buf.size());
+  IncrementCurrentSessionMemory(nread);
   OnScopeLeave on_scope_leave([&]() {
     // Once finished handling this write, reset the stream buffer.
     // The memory has either been free()d or was handed over to V8.
-    DecrementCurrentSessionMemory(buf.size());
+    // We use `nread` instead of `buf.size()` here, because the buffer is
+    // cleared as part of the `.ToArrayBuffer()` call below.
+    DecrementCurrentSessionMemory(nread);
     stream_buf_ab_ = Local<ArrayBuffer>();
     stream_buf_ = uv_buf_init(nullptr, 0);
   });

diff --git a/test/parallel/test-http2-max-session-memory-leak.js b/test/parallel/test-http2-max-session-memory-leak.js
@@ -0,0 +1,46 @@
+'use strict';
+const common = require('../common');
+if (!common.hasCrypto)
+  common.skip('missing crypto');
+const http2 = require('http2');
+
+// Regression test for https://github.com/nodejs/node/issues/27416.
+// Check that received data is accounted for correctly in the maxSessionMemory
+// mechanism.
+
+const bodyLength = 8192;
+const maxSessionMemory = 1;  // 1 MB
+const requestCount = 1000;
+
+const server = http2.createServer({ maxSessionMemory });
+server.on('stream', (stream) => {
+  stream.respond();
+  stream.end();
+});
+
+server.listen(common.mustCall(() => {
+  const client = http2.connect(`http://localhost:${server.address().port}`, {
+    maxSessionMemory
+  });
+
+  function request() {
+    return new Promise((resolve, reject) => {
+      const stream = client.request({
+        ':method': 'POST',
+        'content-length': bodyLength
+      });
+      stream.on('error', reject);
+      stream.on('response', resolve);
+      stream.end('a'.repeat(bodyLength));
+    });
+  }
+
+  (async () => {
+    for (let i = 0; i < requestCount; i++) {
+      await request();
+    }
+
+    client.close();
+    server.close();
+  })().then(common.mustCall());
+}));