[SERVER-22274] WiredTiger cache size is only configurable in whole gigabytes. Created: 22/Jan/16 Updated: 21/Nov/16 Resolved: 25/Jan/16 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | WiredTiger |
| Affects Version/s: | 3.0.8 |
| Fix Version/s: | None |
| Type: | Bug | Priority: | Minor - P4 |
| Reporter: | Jeroen Vijfhuizen | Assignee: | Kelsey Schubert |
| Resolution: | Cannot Reproduce | Votes: | 0 |
| Labels: | None | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Issue Links: |
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| Operating System: | ALL | ||||||||
| Participants: | |||||||||
| Description |
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Hello, on our development servers we currently run our application server alongside a standalone mongod instance. Ever since WiredTiger was introduced we have the occasional OOM killer issue where app server RAM + WT cache + file system buffers are way higher than these smaller instances have. I was looking into overriding the WT cache size into something smaller and found this option: The problem is that this only allows this value to be specified in whole gigabytes while total RAM of these instances is only 1 or 2 Gb. Specifying this value as a fraction results in parse errors as this field is parsed as an integer. I also tried other key names such as 'cacheSizeMB' or 'cacheSize' without any luck. I also tried using a letter as in indicator ('200M') but that leads to another parsing error. I found a workaround in this post but that does not seem to work (anymore?): Are there plans to specify this value in a more specific way. Also, is there a current workaround for this? |
| Comments |
| Comment by Ramon Fernandez Marina [ 28/Jan/16 ] | ||||||
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jeroen.vijfhuizen@exmachinagames.com, this works for me, please give it a try:
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| Comment by Jeroen Vijfhuizen [ 28/Jan/16 ] | ||||||
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Hi Thomas, thanks for checking the workaround. You were right, when specifying it directly on the commandline it works. I'm having issues with double quoting when sourcing this variable from /etc/default/mongod (don't want to change the upstart file with these sort of settings if I can help it) so I'll get this working on way or another. I'm curious though, are there plans to fix this issue? My bug report was not about the workaround but about the fact that this value is not configurable over what I assume to be the preferred method, the config file. Even with this workaround working I have configuration spread out over multiple places. Thanks! Regards, | ||||||
| Comment by Kelsey Schubert [ 25/Jan/16 ] | ||||||
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Hi jeroenv, The workaround you have have linked appears to be working using MongoDB 3.0.8. I started the mongod with the following command:
In the log, I saw the option was set (ignore the first instance of cache_size):
Additionally, I opened the shell and executed
If you start mongod with the same command and see a different results please comment and we will reopen ticket. Thank you, |