IT08971: INDEFINITE HTTP GET REQUEST RETRIES CAN OCCUR WHEN USING SERVICES WITH PERSISTENT CONNECTIONS
Fixes are available
Fix packs for DataPower XML Security Gateway version 6.0
Fix packs for DataPower B2B Appliance version 6.0
Fix packs for DataPower Integration Appliance version 6.0
Fix packs for DataPower Low Latency Appliance version 6.0
Fix packs for DataPower Service Gateway version 6.0
Fix packs for DataPower Service Gateway version 6.0.1
Fix packs for DataPower B2B Appliance version 6.0.1
Fix packs for DataPower Integration Appliance version 6.0.1
Fix packs for DataPower Service Gateway version 7.0
Fix packs for DataPower B2B Appliance version 7.0
Fix packs for DataPower Integration Appliance version 7.0
Fix packs for DataPower Gateway version 7.1
Fix packs for DataPower Gateway version 7.2
Closed as program error.
Affected are customers sending HTTP GET requests to the multiprotocol gateway, web service proxy or web application firewall service. With the present implementation, users may end up in a state with indefinite retries for HTTP GET requests as long as DataPower has at least one live persistent connection to the backend server. After timeout interval for active connection it will terminate the connection and retry using remaining persistent connections to the backend. (If a new connection is opened because of half-dead backend this can continue indefinitely or until the request is served).
This behavior cannot be turned off however it can be mitigated. For some relief out of this, the admin can lower the Back Persistent Timeout and/or User Agent's default Timeout. This should result in less persistent connections to the backend and thus less possible timeout hops Dropping the backend persistent connections option is also a possible workaround, but the consequences should be weighed carefully before making this decision. Not using persistent connections comes with a performance penalty, but it very much depends on the size/type of the transferred data and the speed/ping of the network. SLM is also strongly encouraged to prevent the backend from getting more load than it can handle.
Affected are all customers using the Multi-Protocol Gateway, Web Service Proxy or Web Application Firewall with persistent connection to the backend side. In case the backend server stops responding to HTTP GET requests while there are already some established TCP connections from the time the server worked OK, DataPower will automatically retry those GET requests after a timeout period. This will be retried until there are no established connections to the server. During a high load window, these unwanted retries might eventually keep flooding an already congested backend, especially if it is still able to establish some new connections.
Fix is available in 18.104.22.168, 22.214.171.124, 126.96.36.199, 188.8.131.52 and 184.108.40.206. For a list of the latest fix packs available, please see: http://www-01.ibm.com/support/docview.wss?uid=swg21237631
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