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107 lines
3.4 KiB
C++
107 lines
3.4 KiB
C++
// @file background.h
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/* Copyright 2009 10gen Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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namespace mongo {
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/**
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* Background thread dispatching.
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* subclass and define run()
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*
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* It is ok to call go(), that is, run the job, more than once -- if the
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* previous invocation has finished. Thus one pattern of use is to embed
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* a backgroundjob in your object and reuse it (or same thing with
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* inheritance). Each go() call spawns a new thread.
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*
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* Thread safety:
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* note when job destructs, the thread is not terminated if still running.
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* generally if the thread could still be running, allocate the job dynamically
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* and set deleteSelf to true.
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*
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* go() and wait() are not thread safe
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* run() will be executed on the background thread
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* BackgroundJob object must exist for as long the background thread is running
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*/
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class BackgroundJob : boost::noncopyable {
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protected:
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/**
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* sub-class must intantiate the BackgrounJob
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*
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* @param selfDelete if set to true, object will destruct itself after the run() finished
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* @note selfDelete instantes cannot be wait()-ed upon
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*/
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explicit BackgroundJob(bool selfDelete = false);
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virtual string name() const { return ""; }
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/**
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* define this to do your work.
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* after this returns, state is set to done.
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* after this returns, deleted if deleteSelf true.
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*
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* NOTE:
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* if run() throws, the exception will be caught within 'this' object and will ultimately lead to the
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* BackgroundJob's thread being finished, as if run() returned.
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*
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*/
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virtual void run() = 0;
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public:
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enum State {
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NotStarted,
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Running,
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Done
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};
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virtual ~BackgroundJob() { }
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/**
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* starts job.
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* returns immediatelly after dispatching.
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*
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* @note the BackgroundJob object must live for as long the thread is still running, ie
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* until getState() returns Done.
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*/
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BackgroundJob& go();
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/**
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* wait for completion.
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*
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* @param msTimeOut maximum amount of time to wait in millisecons
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* @return true if did not time out. false otherwise.
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*
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* @note you can call wait() more than once if the first call times out.
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* but you cannot call wait on a self-deleting job.
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*/
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bool wait( unsigned msTimeOut = 0 );
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// accessors
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State getState() const;
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bool running() const;
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private:
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struct JobStatus;
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boost::shared_ptr<JobStatus> _status; // shared between 'this' and body() thread
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void jobBody( boost::shared_ptr<JobStatus> status );
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};
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} // namespace mongo
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