Automatically rejecting work requests when no servant is available to process these requests
When a controller determines that a servant has terminated, the controller normally cleans up any other work requests that were dispatched in that servant. If that servant is the last servant, new work requests are placed in the request queue until a servant is available. Depending on how long it takes for a servant to become available, these requests might terminate because the time allowed to process a request has expired. To prevent this from happening, you can change the configuration settings for an application server to prevent the controller from accepting new requests.
About this task
When a new servant is ready to start accepting requests, the next request in the queue might be so close to timing out that the dispatch process for the request cannot complete and the servant again is terminated by timeout processing. Again requests accumulate in the queue until another new servant is ready and potentially the same timeout problem occurs. When this problem keeps reoccurring, it is sometimes referred to as a bouncing servant problem. You can handle this problem in one of the following ways:
- You can configure the server to automatically detect a no-server situation and stop accepting requests until the minimum configured number of servants are ready to accept work. This is the simplest approach.
- You can create an automation routine to handle the problem if
you are able to detect that you are having a system problem before
servants are terminated because of timeouts. This automation routine
can issue the
f
server,pauselisteners
command to prevent requests from being accepted by this server. The routine must then detect when circumstances have changed and issue thef
server,resumelisteners
command when the detected system problem is resolved. - You can configure the server to detect a no-server condition and
stop accepting requests, and create the previously discussed automation
routine. The automation routine must recognize the different processing
that can take place because the server is configured to detect a no-server
condition:
- If the last servant terminates even though the
f
server,pauselisteners
command is issued, the server starts to reject all requests and issues message BBOO0299I. The server automatically starts to accept requests when the minimum number of servants, for which the server is configured, are ready to accept work. It also issues message BBOO0300I to indicate that requests are again being processed. Therefore, the automation routine must be sensitive to the fact that the server might have resumed accepting requests upon detecting that the minimal number of servants are available. - If the control_region_confirm_recovery_on_no_srs custom property is specified for the server, the server issues WTOR message BBOO0297A after it detects that the minimal number of servants, for which the server is configured, are ready to process new requests. You must enter a response to this message before the server actually starts to accept work.
- If the automation routine prevents the server from terminating
the servants because of timeout processing, it must also recognize
when it is safe for the server to resume taking requests and issue
the
f
server,resumelisteners
command at that point in time. The automation routine can be set up to determine whether or not it needs to issue thef
server,resumelisteners
command based on whether or not the message BBOO0299I is issued. This message indicates that the server ran out of servants and is rejecting requests. This approach is the most complex, but provides the most flexibility.
- If the last servant terminates even though the
Complete the following steps if you want to configure the server to handle no-server conditions.
Procedure
- In the administrative console, click , and select the application server for which you want to automatically detect no-servant conditions.
- Under Additional Properties, click .
- Specify
control_region_dreg_on_no_srs
in the Name field and1
in the Value field.When this custom property is set to 1, the server rejects all requests targeted for dispatch when it detects that there are no servants ready to process the requests. Setting this property to 0 (zero) turns off this function. - Specify
control_region_confirm_recovery_on_no_srs
in the Name field and either0
(zero) or1
in the Value field.If you enter0
in the Value field, the controller resumes taking requests as soon as the minimum number of servants are ready to receive requests. If you enter1
in the Value field, the controller issues WTOR message BBOO0297A as soon as it detects that the minimum number of servants for which the server is configured are ready to accept work. The server waits until it receives a response to this message before it actually resumes taking requests. - Click Review, select Synchronize changes with Nodes, and then click Save to update the repository with your changes.