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Type:
Bug
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Resolution: Done
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Priority:
Major - P3
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Affects Version/s: 3.0.0-rc7
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Component/s: WiredTiger
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Labels:None
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Fully Compatible
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ALL
While doing perf testing of an insert only workload, I noticed that the oplog collection's btree was deepening faster than expected. After only ~1 minute, the tree depth grows to 4 and after ~2 minutes it grows to 5.
I'm not sure this is a problem per se, but seems abnormal.
I couldn't seem to reproduce this with an oplog size of 1GB or 3GB, but happens very quickly with 5GB. Tested with rc7 and latest master (git hash: e4c60053b2967e16f765fa25d16aa6d629faa196)
Running mongodb with --master and --oplogSize 5000:
./mongod --dbpath /home/dan/wt-data/ --storageEngine wiredTiger --master --oplogSize 5000
Run workload:
mongo deep_tree.js
Tracking the btree depth here:
> use local
switched to db local
> while(1) {print(""+ Date()+" " + db.oplog.$main.stats().wiredTiger.btree['maximum tree depth']);sleep(5000)}
Wed Feb 04 2015 15:32:58 GMT-0500 (EST) 3
Wed Feb 04 2015 15:32:59 GMT-0500 (EST) 3
Wed Feb 04 2015 15:33:00 GMT-0500 (EST) 3
Wed Feb 04 2015 15:33:05 GMT-0500 (EST) 3
Wed Feb 04 2015 15:33:10 GMT-0500 (EST) 3
Wed Feb 04 2015 15:33:15 GMT-0500 (EST) 3
Wed Feb 04 2015 15:33:20 GMT-0500 (EST) 3
Wed Feb 04 2015 15:33:25 GMT-0500 (EST) 3
Wed Feb 04 2015 15:33:30 GMT-0500 (EST) 3
Wed Feb 04 2015 15:33:35 GMT-0500 (EST) 3
Wed Feb 04 2015 15:33:40 GMT-0500 (EST) 4
.
.
.
Wed Feb 04 2015 15:34:37 GMT-0500 (EST) 5
Workload generated using dead simple insertion of identical 565 byte docs.