grpc-js: Stop leaking freed message buffer placeholder objects

packages/grpc-js/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@grpc/grpc-js",
-  "version": "1.8.10",
+  "version": "1.8.11",
   "description": "gRPC Library for Node - pure JS implementation",
   "homepage": "https://grpc.io/",
   "repository": "https://github.com/grpc/grpc-node/tree/master/packages/grpc-js",

packages/grpc-js/src/retrying-call.ts

@@ -151,6 +151,12 @@ export class RetryingCall implements Call {
   private initialMetadata: Metadata | null = null;
   private underlyingCalls: UnderlyingCall[] = [];
   private writeBuffer: WriteBufferEntry[] = [];
+  /**
+   * The offset of message indices in the writeBuffer. For example, if
+   * writeBufferOffset is 10, message 10 is in writeBuffer[0] and message 15
+   * is in writeBuffer[5].
+   */
+  private writeBufferOffset = 0;
   /**
    * Tracks whether a read has been started, so that we know whether to start
    * reads on new child calls. This only matters for the first read, because
@@ -203,14 +209,8 @@ export class RetryingCall implements Call {
   private reportStatus(statusObject: StatusObject) {
     this.trace('ended with status: code=' + statusObject.code + ' details="' + statusObject.details + '"');
     this.bufferTracker.freeAll(this.callNumber);
-    for (let i = 0; i < this.writeBuffer.length; i++) {
-      if (this.writeBuffer[i].entryType === 'MESSAGE') {
-        this.writeBuffer[i] = {
-          entryType: 'FREED',
-          allocated: false
-        };
-      }
-    }
+    this.writeBufferOffset = this.writeBufferOffset + this.writeBuffer.length;
+    this.writeBuffer = [];
     process.nextTick(() => {
       // Explicitly construct status object to remove progress field
       this.listener?.onReceiveStatus({
@@ -236,20 +236,27 @@ export class RetryingCall implements Call {
     }
   }
 
-  private maybefreeMessageBufferEntry(messageIndex: number) {
+  private getBufferEntry(messageIndex: number): WriteBufferEntry {
+    return this.writeBuffer[messageIndex - this.writeBufferOffset] ?? {entryType: 'FREED', allocated: false};
+  }
+
+  private getNextBufferIndex() {
+    return this.writeBufferOffset + this.writeBuffer.length;
+  }
+
+  private clearSentMessages() {
     if (this.state !== 'COMMITTED') {
       return;
     }
-    const bufferEntry = this.writeBuffer[messageIndex];
-    if (bufferEntry.entryType === 'MESSAGE') {
+    const earliestNeededMessageIndex = this.underlyingCalls[this.committedCallIndex!].nextMessageToSend;
+    for (let messageIndex = this.writeBufferOffset; messageIndex < earliestNeededMessageIndex; messageIndex++) {
+      const bufferEntry = this.getBufferEntry(messageIndex);
       if (bufferEntry.allocated) {
         this.bufferTracker.free(bufferEntry.message!.message.length, this.callNumber);
       }
-      this.writeBuffer[messageIndex] = {
-        entryType: 'FREED',
-        allocated: false
-      };
     }
+    this.writeBuffer = this.writeBuffer.slice(earliestNeededMessageIndex - this.writeBufferOffset);
+    this.writeBufferOffset = earliestNeededMessageIndex;
   }
 
   private commitCall(index: number) {
@@ -272,9 +279,7 @@ export class RetryingCall implements Call {
       this.underlyingCalls[i].state = 'COMPLETED';
       this.underlyingCalls[i].call.cancelWithStatus(Status.CANCELLED, 'Discarded in favor of other hedged attempt');
     }
-    for (let messageIndex = 0; messageIndex < this.underlyingCalls[index].nextMessageToSend - 1; messageIndex += 1) {
-      this.maybefreeMessageBufferEntry(messageIndex);
-    }
+    this.clearSentMessages();
   }
 
   private commitCallWithMostMessages() {
@@ -555,8 +560,8 @@ export class RetryingCall implements Call {
   private handleChildWriteCompleted(childIndex: number) {
     const childCall = this.underlyingCalls[childIndex];
     const messageIndex = childCall.nextMessageToSend;
-    this.writeBuffer[messageIndex].callback?.();
-    this.maybefreeMessageBufferEntry(messageIndex);
+    this.getBufferEntry(messageIndex).callback?.();
+    this.clearSentMessages();
     childCall.nextMessageToSend += 1;
     this.sendNextChildMessage(childIndex);
   }
@@ -566,10 +571,10 @@ export class RetryingCall implements Call {
     if (childCall.state === 'COMPLETED') {
       return;
     }
-    if (this.writeBuffer[childCall.nextMessageToSend]) {
-      const bufferEntry = this.writeBuffer[childCall.nextMessageToSend];
+    if (this.getBufferEntry(childCall.nextMessageToSend)) {
+      const bufferEntry = this.getBufferEntry(childCall.nextMessageToSend);
       switch (bufferEntry.entryType) {
-        case 'MESSAGE': 
+        case 'MESSAGE':
           childCall.call.sendMessageWithContext({
             callback: (error) => {
               // Ignore error
@@ -594,13 +599,13 @@ export class RetryingCall implements Call {
       message,
       flags: context.flags,
     };
-    const messageIndex = this.writeBuffer.length;
+    const messageIndex = this.getNextBufferIndex();
     const bufferEntry: WriteBufferEntry = {
       entryType: 'MESSAGE',
       message: writeObj,
       allocated: this.bufferTracker.allocate(message.length, this.callNumber)
     };
-    this.writeBuffer[messageIndex] = bufferEntry;
+    this.writeBuffer.push(bufferEntry);
     if (bufferEntry.allocated) {
       context.callback?.();
       for (const [callIndex, call] of this.underlyingCalls.entries()) {
@@ -642,11 +647,11 @@ export class RetryingCall implements Call {
   }
   halfClose(): void {
     this.trace('halfClose called');
-    const halfCloseIndex = this.writeBuffer.length;
-    this.writeBuffer[halfCloseIndex] = {
+    const halfCloseIndex = this.getNextBufferIndex();
+    this.writeBuffer.push({
       entryType: 'HALF_CLOSE',
       allocated: false
-    };
+    });
     for (const call of this.underlyingCalls) {
       if (call?.state === 'ACTIVE' && call.nextMessageToSend === halfCloseIndex) {
         call.nextMessageToSend += 1;