Setup

• OS: Ubuntu 20.04.4
• mongod --version
  db version v6.0.16
  Build Info: {
      "version": "6.0.16",
      "gitVersion": "1bbe71e91a41b097b19d036dee47b861b3f27181",
      "openSSLVersion": "OpenSSL 1.1.1f  31 Mar 2020",
      "modules": [],    "allocator": "tcmalloc",
      "environment": {
          "distmod": "ubuntu2004",
          "distarch": "x86_64",
          "target_arch": "x86_64"
      }{}}

Step to reproduce

Exactly same as in NODE-4783.

Issue

After mongod1 becomes PRIMARY again, find() requests stuck for up to 20 seconds.

NODE-4783 was fixed for driver 4.x and it works properly, new issue found in 6.12.

Acceptance Criteria

Implementation Requirements

• Add multi-message processing to the SizedMessageTransform
  • A single chunk may contain multiple messages, all of them should be pushed to the stream as they arrive

Testing Requirements

• Check that the SizedMessageTransform handles multiple messages
  • multiple full messages and partials
  • check no full messages need to be "pushed" out by the arrival of another

Documentation Requirements

• None

Follow Up Requirements

• Consider re-introducing the hello-skipping as an optimization