[SERVER-64005] Add metric to track the 'fullness' of the TCP accept queue Created: 25/Feb/22  Updated: 29/Oct/23  Resolved: 27/Sep/22

Status: Closed
Project: Core Server
Component/s: None
Affects Version/s: None
Fix Version/s: 6.2.0-rc0

Type: Improvement Priority: Major - P3
Reporter: Blake Oler Assignee: Blake Oler
Resolution: Fixed Votes: 0
Labels: diagnostics
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Documented
is documented by DOCS-15844 Investigate changes in SERVER-64005: ... Closed
Backwards Compatibility: Fully Compatible
Sprint: Service Arch 2022-07-25, Service Arch 2022-08-08, Service Arch 2022-08-22, Service Arch 2022-09-05, Service Arch 2022-09-19, Service Arch 2022-10-03
Participants:
Story Points: 3

 Description   

This ticket concerns connections incoming to a mongos or mongod – we call the incoming connection path the ingress layer. Before the ingress layer accepts a connection, this connection sits in the accept queue on the TCP layer.

The accept queue has a fixed size, and when the queue is full, the OS will start dropping incoming connections at the pre-mongo level. An overflowing queue means that either a mongo process is not accepting connections fast enough, or that the kernel is throttling connection establishment.

Of particular note are generic TCP metrics TcpExtListenOverflows and TcpExtListenDrops.



 Comments   
Comment by Githook User [ 21/Sep/22 ]

Author:

{'name': 'Blake Oler', 'email': 'blake.oler@mongodb.com', 'username': 'BlakeIsBlake'}

Message: SERVER-64005 Add metric tracking listener socket backlog queue depth
Branch: master
https://github.com/mongodb/mongo/commit/02948a5102d2be9f5b727045cf787fc7dda2fcb7

Comment by Bruce Lucas (Inactive) [ 01/Mar/22 ]

This would be great - is there a way to track the accept queue length?

Regarding TcpExtListenOverflows and TcpExtListenDrops - those are already captured in FTDC in the "netstat" section, but of course this only gives a signal once the queue fills up.

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