[DOCS-13635] Investigate changes in SERVER-47672: Add minSnapshotHistoryWindowInSeconds parameter Created: 07/May/20  Updated: 13/Nov/23  Resolved: 24/Feb/21

Status: Closed
Project: Documentation
Component/s: manual, Server
Affects Version/s: None
Fix Version/s: 4.7.0, Server_Docs_20231030, Server_Docs_20231106, Server_Docs_20231105, Server_Docs_20231113

Type: Task Priority: Major - P3
Reporter: Backlog - Core Eng Program Management Team Assignee: Naomi Pentrel (Inactive)
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Documented
documents SERVER-47672 Add minSnapshotHistoryWindowInSeconds... Closed
Related
is related to DOCS-14828 Fix documentation for minSnapshotHist... Closed
Participants:
Days since reply: 2 years, 50 weeks ago
Epic Link: DOCSP-9747
Story Points: 2

 Description   

Description

Downstream Change Summary

Removed startup/runtime --setParameter maxTargetSnapshotHistoryWindowInSeconds=int (default: 5) Maximum target snapshot history window, in seconds
Removed startup/runtime --setParameter snapshotWindowMultiplicativeDecrease=double (default: 0.75) Snapshot window multiplicative decrease
Removed startup/runtime --setParameter snapshotWindowAdditiveIncreaseSeconds=int (default: 2) Snapshot window multiplicative increase, in seconds
Removed startup/runtime --setParameter minMillisBetweenSnapshotWindowInc=int (default: 500) Minimum duration between snapshot window increment, in milliseconds
Removed startup/runtime --setParameter minMillisBetweenSnapshotWindowDec=int (default: 500) Minimum duration between snapshot window decrement, in milliseconds
Removed startup/runtime --setParameter checkCachePressurePeriodSeconds=int (default: 5) Check cache pressure period, in seconds

Added startup/runtime --setParameter minSnapshotHistoryWindowInSeconds=int (default: 5) Minimum target snapshot history data to keep, in seconds. Snapshot (point-in-time) reads that read data at a version older than this will get SnapshotTooOld errors.

Deleted metrics in the "snapshot-window-settings" subsection of the wiredTiger serverStatus section that are no longer relevant.

  • "max target available snapshots window size in seconds”
  • "target available snapshots window size in seconds"

Add metric "minimum target snapshots window size in seconds" in the "snapshot-window-settings" subsection of the wiredTiger serverStatus section – this reports the minSnapshotHistoryWindowInSeconds configuration.

Description of Linked Ticket

Add a new startup and runtime server parameter minSnapshotHistoryWindowInSeconds for mongod, which is the amount of history in seconds stored by the system. Remove support for maxTargetSnapshotHistoryWindowInSeconds.

Also remove snapshot window adjustment logic, see SERVER-31767.

  • This logic was used to dynamically change the amount of history stored to avoid cache pressure. Given durable history is available now, this is no longer needed.
  • Delete metrics in the "snapshot-window-settings" subsection of the wiredTiger serverStatus section that are no longer relevant.
    • "max target available snapshots window size in seconds”
    • "target available snapshots window size in seconds"

Add metric "minimum target snapshots window size in seconds".

Scope of changes

Impact to Other Docs

MVP (Work and Date)

Resources (Scope or Design Docs, Invision, etc.)



 Comments   
Comment by Githook User [ 24/Feb/21 ]

Author:

{'name': 'Naomi Pentrel', 'email': '5212232+npentrel@users.noreply.github.com', 'username': 'npentrel'}

Message: DOCS-13635 add minSnapshotHistoryWindowInSeconds
Branch: v5.0
https://github.com/mongodb/docs/commit/59beccfd63f779b829a6167f7f96a95a484e4d21

Comment by Lingzhi Deng [ 08/Jul/20 ]

Snapshot reads that are older than minSnapshotHistoryWindowInSeconds will return SnapshotTooOld errors.

Comment by Lingzhi Deng [ 08/Jul/20 ]

In sharded clusters, specifying minSnapshotHistoryWindowInSeconds against the config servers will also make them keep minSnapshotHistoryWindowInSeconds of chunk history.

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