David Snowsill created OAK-9112:
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Summary: 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
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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