[DOCS-10847] Docs for SERVER-4941: collection rename may not replicate / clone properly during initial sync Created: 27/Sep/17 Updated: 02/Sep/19 Resolved: 21/Nov/17 |
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| Status: | Closed |
| Project: | Documentation |
| Component/s: | manual, Server |
| Affects Version/s: | None |
| Fix Version/s: | 3.6.0-rc0 |
| Type: | Task | Priority: | Major - P3 |
| Reporter: | Kay Kim (Inactive) | Assignee: | Nicholas Larew |
| Resolution: | Done | Votes: | 0 |
| Labels: | None | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Issue Links: |
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| Participants: | |||||||||
| Days since reply: | 6 years, 10 weeks, 2 days ago | ||||||||
| Epic Link: | DOCS: 3.6 Server | ||||||||
| Story Points: | 0.2 | ||||||||
| Description |
Documentation Request Summary:Renames no longer result in initial sync failing: https://docs.mongodb.com/manual/core/replica-set-sync/ Engineering Ticket Description:Issue Status as of Sep 25, 2017 ISSUE DESCRIPTION AND IMPACT In addition to the renameCollection command, operations such as aggregations using $out and MapReduce with output to a collection may implicitly use renameCollection operations to create their output collections. Users who attempt to resync a node and, before the process is complete, run any of the of the operations above, may see their initial sync process abort and restart. In extreme cases (e.g.: if users are constantly running aggregations to new collections) initial sync operations may never complete. DIAGNOSIS AND AFFECTED VERSIONS
RATIONALE
At this point the test.aggResults collection on the primary/sync source contains the documents A, B, C and D. On the newly added node however, that collection only contains the documents C and D, and while it believes itself consistent with the primary and caught up, reads from that node will return incomplete results. Additionally, if the user now does any writes to documents A or B this may cause the newly added node to crash as it won’t have any record of A or B. REMEDIATION AND WORKAROUNDS Users mapReduce() may also pause their mapReduce() operations. Alternatively, they may use Output to a collection with an action as a workaround, as this avoids the renameCollection operation performed internally by the out option of mapReduce. For example:
FIX VERSION |
| Comments |
| Comment by Githook User [ 04/Dec/17 ] |
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Author: {'username': 'nlarew', 'email': 'nick.larew@10gen.com', 'name': 'Nick Larew'}Message: |
| Comment by Kay Kim (Inactive) [ 06/Oct/17 ] |
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probably just need to copy a sentence/two from already doc'ed https://docs.mongodb.com/manual/release-notes/3.4-compatibility/#initial-sync-and-renamecollection |