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  1. Couchbase Server
  2. MB-38978

STAT "dcp" and "dcpagg" adversely affect front-end operation latency

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Details

    • Bug
    • Status: Closed
    • Critical
    • Resolution: Fixed
    • 6.5.0, 6.0.0, 5.5.0, 5.5.1, 5.5.2, 5.5.3, 6.0.1, 6.0.2, 5.5.4, 6.0.3, 5.5.5, 5.5.6, 6.0.4, 6.5.1, 7.0.0
    • 7.0.2
    • couchbase-bucket
    • 1
    • KV-Engine Sprint 2021 July

    Description

      Problem

      Currently the "dcp" and "dcpagg" stats are collated by the front-end thread. This can be an expensive operation, and hence the STAT command can take a significant time to return. This means the STAT operation is tying-up a front-and thread which means that operations that happen to be allocated to the same thread get delayed for an unacceptable length of time.

      Solutions

      1. Move the expensive part(s) of these stat groups to a background task, allowing the client operation to EWOULDBLOCK and yield execution back to the front-end thread.
      2. Investigate what part(s) of these stat groups ns_server needs. If the stat(s) needed are cheap then consider new stat groups which only contain the specific elements ns_server needs.

      Note we might want both of these; given that dcp and dcpagg are recorded by cbcollect_info and we wouldn't want to remove them there.

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              ashwin.govindarajulu Ashwin Govindarajulu
              owend Daniel Owen
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              Dates

                Created:
                Updated:
                Resolved:

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