[FLINK-19490] Document SOMAXCONN OS limit on blob server backlog

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.13.0
• Component/s: Documentation, Runtime / Coordination
• Labels: pull-request-available
• Assignee: Chesnay Schepler
• Reporter: Chesnay Schepler
• Created: 02/Oct/20 09:20
• Updated: 13/Dec/20 22:45
• Resolved: 13/Dec/20 22:45

Description

The BlobServer has a blob.fetch.backlog setting that controls how many connections can be queued when blob.fetch.num-concurrent is exceeded.
However, the backlog relies on OS functionality, which has it's own maximum limit (SOMAXCONN). Put another way, our backlog setting is just a hint to the OS.

This should be documented so that users who are thinking about this option are aware of it's limitations.

Issue Links

• links to: GitHub Pull Request #14351