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  1. Core Server
  2. SERVER-30261

too many connections to a mongod instance will botch performance

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    • Type: Icon: Bug Bug
    • Resolution: Incomplete
    • Priority: Icon: Major - P3 Major - P3
    • None
    • Affects Version/s: None
    • Component/s: Networking
    • None
    • ALL

      In some workloads, there are a lot of connections to one or many mongod instances which run as a shard. We then start getting these errors in dmesg:
      TCP: request_sock_TCP: Possible SYN flooding on port 10105. Sending cookies. Check SNMP counters.
      TCP: request_sock_TCP: Possible SYN flooding on port 10104. Sending cookies. Check SNMP counters.

      After the workload is gone, the mongod instance responds very slowly to some very simple queries. If we restart the mongod instances, the problem goes away. We have increased somax, tcp syn backlog, and tcp memory (rmem, wmem), but the issue is not fixed. Is this old ticket still related?

      https://jira.mongodb.org/browse/SERVER-2554

      Thank you

            Assignee:
            mark.agarunov Mark Agarunov
            Reporter:
            thestick613 Tudor Aursulesei
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              Created:
              Updated:
              Resolved: