[jira] [Commented] (OAK-9112) High CPU IOWAIT on Mongo due to Oak Version Garbage Collection

["Marcel Reutegger (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OAK-9112?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17148359#comment-17148359 ] 

Marcel Reutegger commented on OAK-9112:
---------------------------------------

Thanks for the feedback [~djsnowsill]. I'd still be interested in a thread dump if you can share it. The node type should be irrelevant to the revision GC.

> High CPU IOWAIT on Mongo due to Oak Version Garbage Collection
> --------------------------------------------------------------
>
>                 Key: OAK-9112
>                 URL: https://issues.apache.org/jira/browse/OAK-9112
>             Project: Jackrabbit Oak
>          Issue Type: Bug
>          Components: mongomk
>    Affects Versions: 1.8.22
>         Environment: Mongo: 3.4.9
> Hosteding: Scalegrid
> Instance Size: Small
>            Reporter: David Snowsill
>            Priority: Major
>         Attachments: image-2020-06-15-19-41-04-852.png, image-2020-06-15-19-41-40-385.png
>
>
> Over the previous weekend, our existing application went from having 100,000 documents in the "nodes" collection to 600,000 documents in the "nodes" collection. Since that time there appears to be an Oak background task that commences running near 100% CPU IOWAIT and heavy disk activity (read only). Please refer to charts below
> !image-2020-06-15-19-41-04-852.png!
> !image-2020-06-15-19-41-40-385.png!
> According to currentOp Mongo command, the queries being running look as follows:
> {code}
> { desc: "conn4944", threadId: "140061124310784", connectionId: 4944, client: "18.207.114.70:47008", clientMetadata: \{ driver: { name: "mongo-java-driver", version: "unknown" }, os: \{ type: "Linux", name: "Linux", architecture: "amd64", version: "4.4.115-k8s" }, platform: "Java/IcedTea/1.8.0_212-b04" }, active: true, opid: 2215767, secs_running: 2, microsecs_running: \{ "$numberLong": "2280333" }, op: "query", ns: "prod-content-service.nodes", query: \{ find: "nodes", filter: { _id: "2:/prod/18d6b4d0-9ee8-4a06-804e-b3669f67dda8" }, limit: 1, singleBatch: true }, planSummary: "IDHACK", numYields: 0, locks: \{ Global: "r", Database: "r", Collection: "r" }, waitingForLock: false, lockStats: \{ Global: { acquireCount: { r: { "$numberLong": "2" } } }, Database: \{ acquireCount: { r: { "$numberLong": "1" } } }, Collection: \{ acquireCount: { r: { "$numberLong": "1" } } } } }
> {code}
> and appears to be iterating over the entire collection.
> Can anyone provide any guidance on what is happening?



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