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217 lines
6.2 KiB
ReStructuredText
217 lines
6.2 KiB
ReStructuredText
.. _Tasking_model_in_PolyORB:
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************************
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Tasking model in PolyORB
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************************
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.. index:: Tasking model
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.. _PolyORB_Tasking_runtimes:
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PolyORB Tasking runtimes
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========================
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.. index:: Tasking runtime
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PolyORB may use any of three different tasking runtimes to manage and
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synchronize tasks, if any. Tasking runtime capabilities are defined
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in the Ada Reference Manual :cite:`ada-rm`.
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The choice of a specific tasking runtime is a compile-time parameter,
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:ref:`Tasking_runtimes` for more details on their configuration.
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Full tasking runtime
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--------------------
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Full tasking runtime refers to the configuration in which there are
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dependencies on the tasking constructs defined in chapter 9 of
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:cite:`ada-rm`. It makes use of all capabilities defined in this section
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to manage and synchronize tasks.
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In this configuration, a PolyORB application must be compiled and
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linked with a tasking-capable Ada runtime.
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No tasking runtime
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------------------
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No tasking runtime refers to the configuration in which there is no
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dependency on tasking constructs. Thus, no tasking is required.
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In this configuration, a PolyORB application may be compiled and
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linked with a tasking-capable Ada runtime or a no-tasking Ada runtime.
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Ravenscar tasking runtime
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-------------------------
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.. index:: Ravenscar
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Ravenscar tasking runtime refers to the configuration in which tasking
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constructs are compliant with the *Ravenscar tasking restricted
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profile*.
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In this configuration, a PolyORB application may be compiled and
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linked with a tasking-capable Ada runtime or a Ravenscar Ada runtime.
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To configure tasking constructs used by PolyORB, one must instantiate
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the `PolyORB.Setup.Tasking.Ravenscar` generic package shown below
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to set up tasks and protected objects used by PolyORB core.
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.. literalinclude:: ../src/setup/polyorb-setup-tasking-ravenscar.ads
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:language: ada
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.. _PolyORB_ORB_Tasking_policies:
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PolyORB ORB Tasking policies
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============================
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PolyORB ORB Tasking policies control the creation of tasks to
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process all middleware internal jobs, e.g. request processing, I/O
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monitoring.
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*Note: there is a dependency between ORB Tasking policies, and the runtime used, as detailed below.*
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No Tasking
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----------
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Under the No Tasking ORB policy, no tasks are created within the
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middleware instance: it uses the environment task to process all
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jobs. Note that this policy is not thread safe and is compatible with
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the No tasking runtime only.
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Thread Pool
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-----------
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Under the Thread Pool ORB policy, the middleware creates a pool of
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threads during initialization of PolyORB. This pool processes all
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jobs. The number of tasks in the thread pool can be configured by three
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parameters in the `[tasking]` configuration section.
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* `min_spare_threads` indicates the number of tasks
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created at startup.
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* `max_spare_threads` is a ceiling. When a remote subprogram
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call is completed, its anonymous task is deallocated if the number of
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unused tasks already in the pool is greater than the ceiling. If not,
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then the task is queued in the pool.
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* `max_threads` indicates the maximum number of tasks in the pool.
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:ref:`PolyORB_Tasking_configuration`, for more information on how to
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configure the number of tasks in the thread pool.
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Thread Per Session
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------------------
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Under the Thread Per Session ORB policy, the middleware creates one
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task when a new session (one active connection) is opened. The task
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terminates when the session is closed.
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Thread Per Request
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------------------
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Under the Thread Per Request ORB policy, the middleware creates one
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task per incoming request. The task terminates when the request is
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completed.
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.. _PolyORB_Tasking_configuration:
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PolyORB Tasking configuration
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=============================
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The following parameters allow the user to set up some of the tasking
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parameters.
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::
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###############################################################################
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# Parameters for tasking
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#
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[tasking]
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# Default storage size for all threads spawned by PolyORB
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#storage_size=262144
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# Number of threads by Thread Pool tasking policy
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#min_spare_threads=4
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#max_spare_threads=4
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#max_threads=4
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.. _PolyORB_ORB_Controller_policies:
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PolyORB ORB Controller policies
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===============================
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The PolyORB ORB Controller policies are responsible for the management
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of the global state of the middleware: they assign middleware internal
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jobs, or I/Os monitoring to middleware tasks.
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ORB Controller policies grant access to middleware internals and
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affect one action for each middleware task. They ensure that all
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tasks work concurrently in a thread-safe manner.
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No Tasking
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----------
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The No Tasking ORB Controller policy is dedicated to no-tasking
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middleware configurations; the middleware task executes the following
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loop: process internal jobs, then monitor I/Os.
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Workers
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-------
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The Workers ORB Controller policy is a simple controller policy: all
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tasks are equal, they may alternatively and randomly process requests
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or wait for I/O sources.
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*Note: this is the default configuration provided by PolyORB sample setup files, :ref:`Sample_files*.`
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Half Sync/Half Async
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--------------------
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The Half Sync/Half Async ORB Controller policy implements the "Half
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Sync/Half Async" design pattern: it discriminates between one thread
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dedicated to I/O monitoring that queue middleware jobs; another pool
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of threads dequeue jobs and process them.
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*Note: this pattern is well-suited to process computation-intensive requests.*
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Leader/Followers
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----------------
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The Leader/Followers ORB Controller policy implements the
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'Leader/Followers ' design pattern: multiple tasks take turns to
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monitor I/O sources and then process requests that occur on the event
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sources.
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*Note: this pattern is adapted to process a lot of light requests.*
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.. _PolyORB_ORB_Controller_configuration:
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PolyORB ORB Controller configuration
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====================================
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The following parameters allow the user to set up parameters for ORB
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Controllers.
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::
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###############################################################################
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# Parameters for ORB Controllers
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#
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[orb_controller]
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# Interval between two polling actions on one monitor
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#polyorb.orb_controller.polling_interval=0
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# Timeout when polling on one monitor
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#polyorb.orb_controller.polling_timeout=0
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