[ZOOKEEPER-4210] Zookeeper c client: detect connection loss during opportunistic async send

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.7.0, 3.4.14, 3.6.2
• Fix Version/s: 3.8.0
• Component/s: c client
• Labels: pull-request-available

Environment

Observed on Linux 3.x 4.x 5.x Centos distributions.

• Assignee: Unassigned
• Reporter: Sam Mikes
• Created: 15/Feb/21 14:50
• Updated: 09/Mar/21 20:31
• Resolved: 09/Mar/21 20:30

Description

When an async operation is performed in the C client, the client will attempt to send the command to the server if this would not block.

When this send reports an error (eg: EPIPE) this is reported up to the async message, but the return code is not stored and checked, making it impossible for the user of the c client library to identify this case.

This can eventually trigger an assertion in some IO libraries, eg libev, because the file descriptor libev is watching is not associated with a valid stream. 

Issue Links

• links to: GitHub Pull Request #1602