[SERVER-64015] Add metrics to track the number of connections that mongos currently has open to each mongod Created: 25/Feb/22  Updated: 06/Dec/22  Resolved: 26/Jul/22

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

Type: Improvement Priority: Major - P3
Reporter: Blake Oler Assignee: Backlog - Service Architecture
Resolution: Won't Do Votes: 0
Labels: diagnostics
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Assigned Teams:
Service Arch
Participants:
Story Points: 3

 Description   

This ticket concerns connections outgoing from a mongos to a mongod – we call the outgoing path the egress layer.

Track and expose via serverStatus/FTDC the number of connections currently open to each mongod.



 Comments   
Comment by Vojislav Stojkovic [ 26/Jul/22 ]

As per the discussion in the comments above, closing as "won't do" to avoid overwhelming FTDC and t2.

Comment by Blake Oler [ 07/Mar/22 ]

Heard regarding measuring averages. Will change ticket.

Comment by Blake Oler [ 07/Mar/22 ]

bruce.lucas what is the usual upper limit of mongod processes? Is it on the order of tens, hundreds?

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

Tracking statistics per mongod needs to be done with care as large installations can have a very large number of mongod processes. There are already some stats in the connPoolStats section, e.g. totalCreated, that may capture this information?

Regarding connections created in the last X seconds - generally we prefer cumulative metrics to fixed durations for averages, because then you can compute an average over any time period given two samples (e.g. from FTDC).

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