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How Multithreading and Multicontexting Work in a Server
The events that occur in a server when a multithreaded and multicontexted application is active can be described in three phases:
What happens during the start-up phase depends on the value of the MINDISPATCHTHREADS and MAXDISPATCHTHREADS parameters in the configuration file.
If the value of MINDISPATCHTHREADS is . . . |
And the value of MAXDISPATCHTHREADS |
Then . . . |
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0 |
> 1 |
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> 0 |
> 1 |
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Work Phase
In this phase, the following activities occur:
Server-dispatched Threads Are Used
In response to clients' requests for a service, the server dispatcher creates multiple threads (up to a configurable maximum) in one server that can be assigned to various client requests concurrently. A server cannot become a client by calling tpinit().
Each dispatched thread is associated with a separate context. This feature is useful in both conversational and RPC servers. It is especially useful for conversational servers which otherwise sit idle, waiting for the client side of a conversation while other conversational connections are waiting for service.
This functionality is controlled by the following parameters in the SERVERS section of the UBBCONFIG(5) file and the TM_MIB(5).
UBBCONFIG Parameter |
MIB Parameter |
Default |
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MINDISPATCHTHREADS |
TA_MINDISPATCHTHREADS |
0 |
MAXDISPATCHTHREADS |
TA_MAXDISPATCHTHREADS |
1 |
THREADSTACKSIZE |
TA_THREADSTACKSIZE |
0 (representing the OS default) |
Application-created Threads Are Used
Using your operating system functions, you may create additional threads within an application server. Application-created threads may:
Some restrictions govern what you can do if you create threads in your application.
BBL Verifies Sanity of System Processes
The BBL periodically checks servers. If a server is taking too long to execute a particular service request, the BBL kills that server. (If specified, the BBL then restarts the server.) If the BBL kills a multicontexted server, the other service calls that are currently being executed are also terminated as a result of the process being killed.
The BBL also sends a message to any process or thread that has been waiting longer than its timeout value to receive a message. The blocking message receive call then returns an error indicating a timeout.
System Keeps Statistics on Server Threads
For each server, the BEA Tuxedo system maintains statistics for the following information:
Userlog Maintains Thread-specific Information
For each thread in each application, userlog(3c) records the following identifying information:
process_ID.thread_ID.context_ID
Placeholders are printed in the thread_ID and context_ID fields of entries for non-threaded platforms and single-contexted applications.
The TM_MIB(5) supports this functionality in the TA_THREADID and TA_CONTEXTID fields in the T_ULOG class.
Completion Phase
When the application is shut down, tpsvrthrdone(3c) and tpsvrdone(3c) are called to perform any termination processing that is necessary, such as closing a resource manager.
See Also
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Copyright © 2000 BEA Systems, Inc. All rights reserved.
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