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  1. Couchbase Server
  2. MB-38283

memcached log wrapped due to excessive DCP "no memory" messages

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    Description

      As seen when investigating CBSE-8003, a large number of log messages are printed when DCP consumer stalls due to high memory usage:

      $ grep -c "Got error 'no memory' while trying to process mutation" memcached.log 
      207611
      

      However, the number of actual unique messages is small:

      $ grep "Got error 'no memory' while trying to process mutation" memcached.log | cut -d ' ' -f 2- | sort | uniq | wc -l
           108
      

      They are however intermixed, i.e. we see different vbids in consecutive log messages:

      $ grep "Got error 'no memory' while trying to process mutation" memcached.log |head -n 5
      2020-02-21T12:31:54.019542-07:00 WARNING 278: (bucket_1) DCP (Consumer) eq_dcpq:replication:ns_1@node_a->ns_1@node_b:bucket_1 - vb:309 Got error 'no memory' while trying to process mutation with seqno:153492
      2020-02-21T12:31:54.019545-07:00 WARNING 278: (bucket_1) DCP (Consumer) eq_dcpq:replication:ns_1@node_a->ns_1@node_b:bucket_1 - vb:311 Got error 'no memory' while trying to process mutation with seqno:163927
      2020-02-21T12:31:54.019548-07:00 WARNING 278: (bucket_1) DCP (Consumer) eq_dcpq:replication:ns_1@node_a->ns_1@node_b:bucket_1 - vb:883 Got error 'no memory' while trying to process mutation with seqno:159181
      2020-02-21T12:31:54.019552-07:00 WARNING 278: (bucket_1) DCP (Consumer) eq_dcpq:replication:ns_1@node_a->ns_1@node_b:bucket_1 - vb:894 Got error 'no memory' while trying to process mutation with seqno:164317
      2020-02-21T12:31:54.019555-07:00 WARNING 278: (bucket_1) DCP (Consumer) eq_dcpq:replication:ns_1@node_a->ns_1@node_b:bucket_1 - vb:890 Got error 'no memory' while trying to process mutation with seqno:160836
      

      We should modify the logging of this message to be edge-triggered instead of level-triggered. Would also be useful to add a log message when returning to a normal memory situation.

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              ashwin.govindarajulu Ashwin Govindarajulu
              drigby Dave Rigby (Inactive)
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                Updated:
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                PagerDuty