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Cisco Bug: CSCvj04438 - [cmc/cos-aic-client] : should only create one TCP connection to docserver

Last Modified

Jun 13, 2018

Products (1)

  • Cisco Content Delivery Engine Series

Known Affected Releases

3.19(0)

Description (partial)

Symptom:
COS AIC Client & CMC AIC Client check the status of various system health parameters (e.g. disks, interfaces, critical services) every 2 seconds, and report the status to COS Mgmt. System (via DocServer) if any of these change. The status is attempted to be sent at least once an hour, and maybe attempted to be sent more often (as often as every 2 seconds) if these parameters change more frequently.

Each attempt by COS/CMC AIC Client to send COS/CMC Node status to the COS Management System (via DocServer) leads to a new TCP connection being opened by the DocClient library from the COS/CMC Node to the management node running the DocServer master.

Normally, the attempted send completes quickly with either a success or error message returned to the client.

However, if DocServer is overloaded or hung, or if there is a network delay (e.g. a delay in resolving the DocServer FQDN via DNS), an attempted status send may not return for a long time. During this time, the TCP connection may remain open. Then, as soon as another status is ready to be sent, a new connection will be opened.

If each attempted send takes a long time to return with a success/failure, more and more TCP connections will remain open. 

Example:
c3260-g4b:/arroyo/log/# netstat -an | grep '5088.*ESTABLISH' | wc -l
80


This might further overload the DocServer with too many open connections.

Conditions:
This can happen if:

1) COS/CMC AIC Client attempts to send COS/CMC Node status updates frequently, i.e. if one or more of the monitored elements on the node change frequently.

AND

2) Each attempted send takes a long time to complete (i.e. neither success nor failure returned for a long time), e.g. if:
a) DocServer is overloaded, OR
b) DocServer FQDN resolution is slow. This can happen if the local DNS configuration is incorrect, e.g. the first listed name server is not "127.0.0.1".
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