Bug 1844133 - [remote] WebSocketConnection logs should be truncated for huge objects r=webdriver-reviewers,Sasha

Puppeteer happens to send huge payloads as part of their test suite when using their $$eval API.
This is because they pass back and forth nodeLists for which all children are serialized by default.
This could be avoided by changing the serialization options (see https://github.com/puppeteer/puppeteer/issues/10582)

But without such a fix, we need to cap the size of the websocket logs, otherwise the logparser is unable to handle the
logs from the bidi puppeteer job.

Differential Revision: https://phabricator.services.mozilla.com/D184108

remote/shared/WebSocketConnection.sys.mjs

@@ -17,6 +17,8 @@ ChromeUtils.defineESModuleGetters(lazy, {
 
 XPCOMUtils.defineLazyGetter(lazy, "logger", () => lazy.Log.get());
 
+const MAX_LOG_LENGTH = 2500;
+
 export class WebSocketConnection {
   /**
    * @param {WebSocket} webSocket
@@ -45,12 +47,20 @@ export class WebSocketConnection {
         return value;
       }
 
-      const payload = JSON.stringify(
+      let payload = JSON.stringify(
         data,
         replacer,
         lazy.Log.verbose ? "\t" : null
       );
 
+      if (payload.length > MAX_LOG_LENGTH) {
+        // Even if we truncate individual values, the resulting message might be
+        // huge if we are serializing big objects with many properties or items.
+        // Truncate the overall message to avoid issues in logs.
+        const truncated = payload.substring(0, MAX_LOG_LENGTH);
+        payload = `${truncated} [... truncated after ${MAX_LOG_LENGTH} characters]`;
+      }
+
       lazy.logger.debug(
         `${this.constructor.name} ${this.id} ${direction} ${payload}`
       );