[SERVER-13748] Global Lock in Reduce Phase of Map/Reduce Created: 25/Apr/14 Updated: 10/Dec/14 Resolved: 25/Apr/14 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | MapReduce |
| Affects Version/s: | 2.4.9, 2.6.0 |
| Fix Version/s: | None |
| Type: | Question | Priority: | Major - P3 |
| Reporter: | Andre Spiegel | Assignee: | Mathias Stearn |
| Resolution: | Duplicate | Votes: | 0 |
| Labels: | None | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Issue Links: |
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| Description |
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When writing results to an output collection, the map/reduce engine acquires a global write lock, effectively blocking the server for all other operations. Even when the nonAtomic option is used, the global lock is acquired for every single document that is written, and since this happens pre-emptively, the effect is very much the same. This effectively prevents any kind of concurrency while doing map/reduce computations and should therefore be changed. |