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Type:
Bug
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Resolution: Works as Designed
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Priority:
Major - P3
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None
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Affects Version/s: 4.2.10, 4.4.2
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Component/s: None
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None
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Linux
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When I truncate the log using
: > path-to.log
pattern, the server appears to keep writing the log at the same position where the file was pre-truncation.
Example shell session:
serene% ls -l `find /mnt/zram/mongodb/4.4-scm -name \*.log` -rw-rw-rw- 1 m m 462548363 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/configRepl/rs1/mongod.log -rw-rw-rw- 1 m m 38755955 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/mongos/mongos_14440.log -rw-rw-rw- 1 m m 38488489 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/mongos/mongos_14441.log -rw-rw-rw- 1 m m 57344569 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/shard01/rs1/mongod.log -rw-rw-rw- 1 m m 3191208 Dec 14 15:46 /mnt/zram/mongodb/4.4-scm/shard01/rs2/mongod.log -rw-rw-rw- 1 m m 56094408 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/shard02/rs1/mongod.log -rw-rw-rw- 1 m m 3561329 Dec 14 15:51 /mnt/zram/mongodb/4.4-scm/shard02/rs2/mongod.log serene% :>/mnt/zram/mongodb/4.4-scm/shard01/rs1/mongod.log serene% ls -l `find /mnt/zram/mongodb/4.4-scm -name \*.log` -rw-rw-rw- 1 m m 462549651 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/configRepl/rs1/mongod.log -rw-rw-rw- 1 m m 38756124 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/mongos/mongos_14440.log -rw-rw-rw- 1 m m 38488658 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/mongos/mongos_14441.log -rw-rw-rw- 1 m m 0 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/shard01/rs1/mongod.log -rw-rw-rw- 1 m m 3191208 Dec 14 15:46 /mnt/zram/mongodb/4.4-scm/shard01/rs2/mongod.log -rw-rw-rw- 1 m m 56094408 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/shard02/rs1/mongod.log -rw-rw-rw- 1 m m 3561329 Dec 14 15:51 /mnt/zram/mongodb/4.4-scm/shard02/rs2/mongod.log serene% ls -l `find /mnt/zram/mongodb/4.4-scm -name \*.log` -rw-rw-rw- 1 m m 462549892 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/configRepl/rs1/mongod.log -rw-rw-rw- 1 m m 38756124 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/mongos/mongos_14440.log -rw-rw-rw- 1 m m 38488658 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/mongos/mongos_14441.log -rw-rw-rw- 1 m m 0 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/shard01/rs1/mongod.log -rw-rw-rw- 1 m m 3191208 Dec 14 15:46 /mnt/zram/mongodb/4.4-scm/shard01/rs2/mongod.log -rw-rw-rw- 1 m m 56094408 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/shard02/rs1/mongod.log -rw-rw-rw- 1 m m 3561329 Dec 14 15:51 /mnt/zram/mongodb/4.4-scm/shard02/rs2/mongod.log serene% ls -l `find /mnt/zram/mongodb/4.4-scm -name \*.log` -rw-rw-rw- 1 m m 462550133 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/configRepl/rs1/mongod.log -rw-rw-rw- 1 m m 38756124 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/mongos/mongos_14440.log -rw-rw-rw- 1 m m 38488658 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/mongos/mongos_14441.log -rw-rw-rw- 1 m m 0 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/shard01/rs1/mongod.log -rw-rw-rw- 1 m m 3191208 Dec 14 15:46 /mnt/zram/mongodb/4.4-scm/shard01/rs2/mongod.log -rw-rw-rw- 1 m m 56094408 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/shard02/rs1/mongod.log -rw-rw-rw- 1 m m 3561329 Dec 14 15:51 /mnt/zram/mongodb/4.4-scm/shard02/rs2/mongod.log serene% ls -l `find /mnt/zram/mongodb/4.4-scm -name \*.log` -rw-rw-rw- 1 m m 462550374 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/configRepl/rs1/mongod.log -rw-rw-rw- 1 m m 38756124 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/mongos/mongos_14440.log -rw-rw-rw- 1 m m 38488658 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/mongos/mongos_14441.log -rw-rw-rw- 1 m m 57344811 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/shard01/rs1/mongod.log -rw-rw-rw- 1 m m 3191208 Dec 14 15:46 /mnt/zram/mongodb/4.4-scm/shard01/rs2/mongod.log -rw-rw-rw- 1 m m 56094650 Dec 14 15:53 /mnt/zram/mongodb/4.4-scm/shard02/rs1/mongod.log -rw-rw-rw- 1 m m 3561329 Dec 14 15:51 /mnt/zram/mongodb/4.4-scm/shard02/rs2/mongod.log
You can see how the size of shard01 rs1 log jumped from 0 to 50 megs.
Since the file was earlier truncated, it now has (in the above example) 50 megs of null bytes followed by the log data.
I expected the server to write the log at the current position so that after truncation I just have the post-truncation data starting from the beginning of the file.
I tested 4.2.10 also with same results and the truncate(1) command with also same results.