NOTE:
I have already created Stackoverslow question for this issue and was asked by a Google Cloud Employee (Kamal Aboul-Hosn) to raise the issue over here.

Environment details

• OS:
• Node.js version: v18.16.1
• npm version: 9.5.1
• @google-cloud/pubsub version: ^3.7.1

Steps to reproduce

I am using Node JS client for Google PubSub (RPC StreamingPullRequest API) with flow control. My subscription options look like that:

 {
      streamingOptions: {
        // decrease this to reduce re-deliveries
        maxStreams: 2, // default: 5
      },
      flowControl: {
        allowExcessMessages: false,
        maxMessages: 4000, // No issues at 2000
      },
    },

I reduced maxStreams from 5 (default) to 2 to reduce re-deliveries, as mentioned here in the docs. When I set the maxMessages to 4000, I get the following debug warning, which causes re-deliveries of messages:

Pubsub subscription received debug message: Failed to "ack" for 3000 message(s). Reason: 3 INVALID_ARGUMENT: Request payload size exceeds the limit: 524288 bytes.

Why am I getting the warning, and how can I increase the payload size?