AmbiguousTimeoutException during upsert

Hi, we are getting following error when trying to upsert few documents, while other work fine -
com.couchbase.client.core.error.AmbiguousTimeoutException: UpsertRequest, Reason: TIMEOUT {“cancelled”:true,“completed”:true,“coreId”:“0x6abbe164”,“idempotent”:false,“lastChannelId”:“6ABBE16/0000000054”,“lastDispatchedFrom”:“”,“lastDispatchedTo”:“”,“reason”:“TIMEOUT”,“requestId”:883822,“requestType”:“UpsertRequest”,“retried”:14,“retryReasons”:[“KV_TEMPORARY_FAILURE”],“service”:{“bucket”:“test”,“collection”:"_default",“documentId”:“unpublished::test-doc”,“opaque”:“0xd7c91”,“scope”:"_default",“type”:“kv”},“timeoutMs”:2500,“timings”:{“dispatchMicros”:1281,“encodingMicros”:18,“totalDispatchMicros”:18559,“totalServerMicros”:0,“totalMicros”:2505368,“serverMicros”:0}}

Also, when we try to look up the same document in couchbase UI, it gives “Internal Server Error” while the document that doesnt exist, it generally gives “Document not found”.
We are using Couchbase server 6.6.3 and java sdk 3.2.3
Any pointers will be greatly appreciated.

This part of the error context indicates that the SDK has retried sending the request 14 times, each time getting a TEMPORARY_FAILURE error back from the data service. It fails on hitting the timeout after 2.5 seconds.
It might be worth looking at the latest memcached.log in your logs directory to see if there’s any indication why the data service is returning the error.
TEMPORARY_FAILURE is usually a transient error. You could try increasing the KV timeout to give the SDK more time to retry.

Thanks for your reply. Will try to increase the KV timeout. Also, any idea why its showing message “Internal Server Error” when we try to lookup the document in Couchbase UI?

There was some issue with one of the nodes. The issue got resolved after restarting that node.