This information might help you diagnose the trouble if you are
having a workload distribution problem.
What kind of problem are you seeing?
If none of these problem solution descriptions fix your problem:
- Browse the JVM logs of the problem deployment manager and
application servers:
- Look up any error messages by selecting the Reference view of the
information center navigation and expanding Messages in the navigation
tree.
If Java exceptions appear in the log files, try to determine the actual
subcomponent that is directly involved in the problem by examining the trace
stack and looking for a WebSphere Application Server-related class near the
top of the stack (names beginning with com.ibm.websphere or com.ibm.ws)
that created the exception. If appropriate, review the steps for troubleshooting
the appropriate subcomponent under the Troubleshooting WebSphere applications section
of the Information Center.
For example, if the exception appears to
have been thrown by a class in the com.ibm.websphere.naming package, review
the Naming Services Component troubleshooting tips topic.
- Ensure that all the machines in your configuration have TCP/IP connectivity
to each other by running the ping command:
- From each physical server to the deployment manager
- From the deployment manager to each physical server
- Although the problem is happening in a clustered environment, the actual
cause might be only indirectly related, or unrelated, to clustering. Investigate
all relevant possibilities:
- If an enterprise bean on one or more servers is not serving requests,
review the "Cannot access an enterprise bean from a servlet, JSP, stand-alone
program, or other client" and "Cannot look up an object hosted by WebSphere
Application Server from a servlet, JSP file, or other client" topics.
- If problems seem to appear after enabling security, review the "Errors
or access problems after enabling security" topic.
- If an application server stops responding to requests, or spontaneously
dies (its process closes), review the "Web module or application server dies
or hangs" topic.
- If SOAP requests are not being served by some or all servers, review the
"Errors returned to client trying to send a SOAP request" topic.
- Check to see if the problem is identified and documented by looking at
available online support (hints and tips, technotes, and fixes).
HTTP requests are not distributed to all servers
If
HTTP requests are not being distributed to all servers:
- Check your Primary Servers list. The plug-in load balances across all
servers that are defined in the Primary Servers list, if affinity has not
been established. If you do not have a Primary Servers list defined, the plug-in
load balances across all servers defined in the cluster, if affinity has not
been established. In the case where affinity has been established, the plug-in
should go directly to that server, for all requests within the same HTTP session.
- If some servers are servicing requests and one or more others are not,
try accessing a problem server directly to verify that it works, apart from
workload management issues. If that does not work:
- Use the administrative console to ensure that the affected server is running.
- See the topic "Web resource does not display" for more information.
- See the "HTTP plug-in component troubleshooting tips" topic for more information.
Enterprise bean requests are not distributed to
all servers
If a client cannot reach a server in a cluster thought
to be reachable, a server might be marked unusable, or is down. To verify
this:
- Use the administrative console to verify that the server is started. Try
starting it, or if started, stop and restart it.
- Browse the administrative console and verify that the node that runs the
server having the problem appears. If it does not:
- Review the steps for adding a node to a cluster.
- Review the steps in the section One or more nodes do not show up
in the administrative console.
- If possible, try accessing the enterprise bean directly on the problem
server to see if there is a problem with TCP/IP connectivity, application
server health, or other problem not related to workload management. If this
fails, review the "Cannot access enterprise bean from a servlet, JSP, stand-alone
program , or other client" topic.
Enterprise bean requests are not distributed
evenly
There are a number of possible reasons for this behavior,
which generally fall into one or more of these categories:
- Improper configuration
- Environment issues such as the availability of servers or applications.
- A large numbers of requests that involve transactional affinity, or
- A small number of clients
Workload management in WebSphere Application
Server is based on a round robin scheme of request distribution. This results
in balance being determined by numbers of requests rather than by any other
measure. A true balance problem is determined by comparing the number of requests
processed by each member of the cluster with the weights that have been set
for each of those members.
- When the percentage of requests that arrive for each member of the cluster
is consistent with the weights then further analysis of the application is
required to determine the cause for the workload being imbalanced even when
the number of requests is balanced.
- When the number of numIncomingNonWLMObjectRequests is
not balanced among the members of the cluster and is large in relation to
the numIncomingRequests then the reason for the imbalance is the non-distributable
components installed on the members of the cluster. A modification to the
configuration will yield a more balanced environment.
- When the number of numIncomingStrongAffinityRequests is not balanced
among the members of the cluster and is large in relation to the numIncomingRequests then
the reason for the imbalance is the requests which are invoked within a transaction.
These can be reduced by installing the objects involved within a transaction
within the same cluster.
A failing server still receives enterprise bean
requests (failover is not completed)
Some possible causes of this
problem are:
- The client might have been in a transaction with an enterprise bean on
the server that went down. Check the JVM logs of the application server hosting
the problem enterprise bean instance. If a request is returned with CORBA
SystemException COMM_FAILURE org.omg.CORBA.completion_status.COMPLETED_MAYBE,
this might be working as designed. The design is to let this particular exception
flow back to the client, since the transaction might have completed. Failing
over this request to another server could result in this request being serviced
twice.
- If the requests sent to the servers come back to the client with any other
exceptions consistently, it might be that no servers are available.
Stopped or unresponsive servers do
not share the workload after being restored
This error occurs when
previously unavailable servers are not recognized by the workload management
component after those servers are restored. There is an unusable interval
determined by the property com.ibm.websphere.wlm.unusable.interval during
which the workload manager waits to send to a server that has been marked
unusable. By default this is 5 minutes.
You can confirm that this is
the problem by ensuring that servers that were down are now up and capable
of servicing requests. Then wait for the unusable interval to elapse before
checking to determine whether failover occurs.