[SERVER-52773] Add "resharding" section to server status Created: 11/Nov/20  Updated: 29/Oct/23  Resolved: 06/Jan/21

Status: Closed
Project: Core Server
Component/s: Sharding
Affects Version/s: None
Fix Version/s: 4.9.0

Type: Task Priority: Major - P3
Reporter: Max Hirschhorn Assignee: Amirsaman Memaripour
Resolution: Fixed Votes: 0
Labels: PM-234-M3, PM-234-O-unspecialized, PM-234-T-metrics
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
is depended on by SERVER-52774 Periodically persist metrics about re... Closed
Documented
is documented by DOCS-14084 Investigate changes in SERVER-52773: ... Closed
Related
is related to SERVER-53842 Count the number of resharding attemp... Closed
Backwards Compatibility: Fully Compatible
Sprint: Sharding 2021-01-11
Participants:
Story Points: 1

 Description   

It should have metrics for the following:

  • (Coordinator, Donor, Recipient) Number of resharding operations that succeed
  • (Coordinator, Donor, Recipient) Number of resharding operations that fail with an unrecoverable error
  • (Coordinator, Donor, Recipient) Number of resharding operations that are canceled by the user
  • (Donor) Number of write commands rejected during critical section
  • (Donor) Number of write commands were successful after being queued
  • (Recipient) Number of documents cloned
  • (Recipient) Bytes cloned
  • (Recipient) Number of oplog entries applied


 Comments   
Comment by Githook User [ 06/Jan/21 ]

Author:

{'name': 'Amirsaman Memaripour', 'email': 'amirsaman.memaripour@mongodb.com', 'username': 'samanca'}

Message: SERVER-52773 Add resharding section to server status
Branch: master
https://github.com/mongodb/mongo/commit/7a470e065d48b7871d1552c3c2a093a6a59f7f0d

Comment by Max Hirschhorn [ 24/Dec/20 ]

Hi bruce.lucas, the "(Coordinator, Donor, Recipient)" refers to the role that the config server and shards take on during a resharding operation. So all three being listed means that we want to track success, failure, and cancellation on every mongod within the sharded cluster. For the ones where only "(Donor)" or "(Recipient)" is listed, we'll still include the metric on every mongod but the value is only expected to be != 0 (or != -1 perhaps depending on the situation) on certain shards.

Also of probable interest to you is how we intend for the schema of the new "shardingStatistics.resharding" section to be static. There'll be at most one resharding operation allowed to run in the sharded cluster at a time (SERVER-52730) so we aren't needing to track metrics on a per-collection basis.

Comment by Bruce Lucas (Inactive) [ 24/Dec/20 ]

Does "(Coordinator, Donor, Recpient)" mean exactly 3 metrics or are those placeholder variables for shard names or something like that? If the latter I might be concerned about the number of metrics this could create.

Comment by Max Hirschhorn [ 11/Nov/20 ]

For naming some of these metrics it may be helpful to look at the description of the new/existing metrics for initial sync in SERVER-47863.

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