[SERVER-6640] Strict balancing guarantees with sharding tags Created: 30/Jul/12 Updated: 06/Dec/22 Resolved: 07/Oct/16 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | Sharding |
| Affects Version/s: | 2.2.0-rc0 |
| Fix Version/s: | None |
| Type: | Improvement | Priority: | Major - P3 |
| Reporter: | Vadim Semenov | Assignee: | [DO NOT USE] Backlog - Sharding Team |
| Resolution: | Duplicate | Votes: | 1 |
| Labels: | None | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Issue Links: |
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| Assigned Teams: |
Sharding
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| Participants: | |||||||||
| Case: | (copied to CRM) | ||||||||
| Description |
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In 2.2.0-rc0 tag aware sharding behaves strange: it doesn't offer strict guarantee to which chunk a document will be placed when inserted. So if we have 2 tags for 2 shards (e.g. 'US-West' and 'US-East') on an empty collection, inserting 2 documents which map to different tags will place both documents into one chunk; and the chunk location will depend on to which of the tags we've made insertion first. This behavior scales to any number of documents: there's always a high chance to have documents "misplaced" this way after automatic chunk splitting. |
| Comments |
| Comment by Kaloian Manassiev [ 07/Oct/16 ] |
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Please follow |
| Comment by Greg Studer [ 07/Mar/14 ] |
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Strict balancing guarantees aren't possible until the chunks are initially distributed, but agree the initial distribution should happen automatically when possible with tagged shards. |