[jira] [Commented] (OAK-9112) High CPU IOWAIT on Mongo due to Oak background task

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

    [ https://issues.apache.org/jira/browse/OAK-9112?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17135939#comment-17135939 ] 

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

The query on the MongoDB side only targets a single document and does not show what is causing the load on the system.

You write:
bq. Oak background task

Do you have a stacktrace you can share that shows more details of the background task?

> High CPU IOWAIT on Mongo due to Oak background task
> ---------------------------------------------------
>
>                 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
>             Fix For: 1.8.22
>
>         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:
> { 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" } } } } }
> and appears to be iterating over the entire collection.
> Can anyone provide any guidance on what is happening?



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