IT08971: INDEFINITE HTTP GET REQUEST RETRIES CAN OCCUR WHEN USING SERVICES WITH PERSISTENT CONNECTIONS

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

APAR status

• Closed as program error.

Error description

• 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).
  

Local fix

• 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.
  

Problem summary

• 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.
  

Problem conclusion

• Fix is available in 6.0.0.16, 6.0.1.12, 7.0.0.9, 7.1.0.6 and
  7.2.0.2.
  
  For a list of the latest fix packs available, please see:
  http://www-01.ibm.com/support/docview.wss?uid=swg21237631
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  DATAPOWER

• Fixed component ID

  DP1234567

Applicable component levels

• R600 PSN

     UP

• R601 PSN

     UP

• R602 PSN

     UP

• R700 PSN

     UP

• R710 PSN

     UP

• R720 PSN

     UP