fsyncLock on csrs secondary for backup cause query timeout issue

For some reason, we want have full and incremental backup to support point in time restore, so we’ve follow the mongodb official doc to do backup for sharded cluster , but when we lock a secondary of config server to do mongodump, it would cause query timeout in production, something related to “uptime reporter” which is refreshing config setting with a majority read , but isn’t fsyncLock only lock writes ? i don’t get it , can anyone expain why it will cause production query timeout , is it a block method that would block all the query to the cluster ? what if we does not lock config but just lock shard secondary for backup ?
Plus, no exact point in time backup needed, just almost point in time backup is enough for us.

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fsynclock a single secondary shouldn’t be a problem as long as you have other 2 functioning nodes… in any case I suggest you give a try to Percona Backup for MongoDB which will automatically backup the sharded cluster for you

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