[SERVER-20459] pingMs and lastHearbeatMessage fields are sporadic Created: 17/Sep/15  Updated: 07/Oct/15  Resolved: 21/Sep/15

Status: Closed
Project: Core Server
Component/s: Diagnostics
Affects Version/s: None
Fix Version/s: 3.1.9

Type: Bug Priority: Major - P3
Reporter: Bruce Lucas (Inactive) Assignee: Eric Milkie
Resolution: Done Votes: 0
Labels: FTDC
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Backwards Compatibility: Fully Compatible
Operating System: ALL
Sprint: RPL A (10/09/15)
Participants:

 Description   

The pingMs and lastHearbeatMessage fields in the members array of the replSetGetStatus command occur sporadically. The fields appear to be alternately present for a couple of seconds and missing for a couple of seconds.

This creates frequent schema changes that reduce the compression efficiency of FTDC storage by a factor of 5-10x.

Observed behavior in 3.0 is that pingMs is always present (and lastHearbeatMessage seems to be new for 3.1).



 Comments   
Comment by Githook User [ 21/Sep/15 ]

Author:

{u'username': u'milkie', u'name': u'Eric Milkie', u'email': u'milkie@10gen.com'}

Message: SERVER-20459 repl pings start as -1 ms to avoid collisions with 0 ms
Branch: master
https://github.com/mongodb/mongo/commit/1282823cdb82747323435d05b0bd79b33c032177

Comment by Bruce Lucas (Inactive) [ 17/Sep/15 ]

It would have been significant effort to set up a cluster with a ping time consistently >1ms, so instead I tried the proposed patch and it (or equivalent) would fix the problem, thanks.

Comment by Eric Milkie [ 17/Sep/15 ]

I believe the new behavior is that if the recent ping time happens to be less than 1ms, it rounds to 0 and then doesn't display the pingMs field. The old behavior in 3.0 was to display the field even if the ping time was 0.
Does the problem still occur if you are running replica set members on separate devices?
The lastHeartbeatMessage can only appear if the pingMs field appears.

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