## Rule of Thumb
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All classes are not thread safe for access from multiple
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threads simultaneously unless it is stated explicitly otherwise.
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In general there are several thread safe classes
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in the CppCMS that their member functions
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can be accessed simultaneously from several threads:
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- `cppcms::service`
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- `cppcms::applications_pool`
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- `cppcms::thread_pool`
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- `cppcms::views::pool`
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- `booster::aio::io_service`
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In all other cases special measures should be
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taken in order to prevent accessing same class
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from multiple threads.
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## Threads in CppCMS
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There are several types of threads in CppCMS:
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- Event Loop - the main thread, the thread that runs
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the `cppcms::service::run()` threads.
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- Thread Pool - the special pool of threads that
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every synchronous requests are executed there
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- Some background threads auxiliary threads
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that are in general of no interest to you.
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## Cross Thread Interactions
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Once the CppCMS service started all synchronous
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applications are executed in the thread pool.
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If CppCMS synchronous application wants to perform
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some operation withing event loop, for example,
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interact with some asynchronous application by
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sending some data or by transferring its HTTP
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context to it, it should do it using
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`cppcms::service::post()` member function
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and an appropriate execution handler.
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This handler would be dispatched to the event loop
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queue and executed in its thread.
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If asynchronous application or any other object
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that runs in the event wants to execute some long
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running, blocking or heavy operation, it may do it
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by submitting an execution handler to the thread pool.
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Note, once the job is complete, the handler should notify
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its completion by posting some handler to the event
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loop, the same way as described above.
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Different applications should never access their
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internal states directly as it is not safe.
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---
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← [Understanding Application Lifetime][prev]
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| [Top](#maincontent)
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| [Configure CppCMS to run with different web servers][next] →
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[prev]: /wikipp/en/page/cppcms_1x_application_lifetime
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[next]: /wikipp/en/page/cppcms_1x_tut_web_server_config |
## Related
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- [Event Loop](/wikipp/en/page/cppcms_1x_event_loop)
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- [Understanding Application Lifetime](/wikipp/en/page/cppcms_1x_application_lifetime)
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← [Understanding Application Lifetime](http://cppcms.com/wikipp/en/page/cppcms_1x_application_lifetime)
|
[Configure CppCMS to run with different web servers](http://cppcms.com/wikipp/en/page/cppcms_1x_tut_web_server_config)→ |
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## Browse
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[CppCMS 1.x.x - Stable][toc]
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|
← [Understanding Application Lifetime][prev]
|
[Configure CppCMS to run with different web servers][next] →
|
|
[toc]: /wikipp/en/page/cppcms_1x
|
[prev]: /wikipp/en/page/cppcms_1x_application_lifetime
|
[next]: /wikipp/en/page/cppcms_1x_tut_web_server_config |
