Connection to MongoDB is unavailable

About the Community The Treehouse
1

hi,
I have a replica set version 3.6.63 and almost every evening around 21:00 the server goes down, when I open the log file I see this message:

2023-07-30T21:06:48.847+0300 I COMMAND [conn14689698] command local.oplog.rs command: find { find: “oplog.rs”, filter: { ts: { $exists: true } }, sort: { $natural: 1 }, skip: 0, limit: 1, batchSize: 1, singleBatch: true, maxTimeMS: 3000, $readPreference: { mode: “secondaryPreferred” }, $db: “local” } planSummary: COLLSCAN exception: operation exceeded time limit code:ExceededTimeLimit numYields:0 reslen:246 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, oplog: { acquireCount: { r: 1 } } } protocol:op_query 3417ms

Has anyone encountered this phenomenon? Why does the system scan the file oplog.rs?

2

Try setting higher timeout.

db.adminCommand( { setParameter: 1, maxTransactionLockRequestTimeoutMillis: 60000 });
Your error contains COLLSCAN, which is a collection scan, meaning the server must read all the documents in the collection to answer the query. This is typically the cause of a slow query. You can follow these guidelines to create indexes which can improve query performance.

Hope this helps!

3

OK. I know this well…
The question was why was LOCAL’s collection even scanned?
Is this an automatic operation?

4

This topic was automatically closed after 180 days. New replies are no longer allowed.