mirror of
https://github.com/klzgrad/naiveproxy.git
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82 lines
3.0 KiB
C++
82 lines
3.0 KiB
C++
// Copyright (c) 2011 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef NET_PROXY_MULTI_THREADED_PROXY_RESOLVER_H_
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#define NET_PROXY_MULTI_THREADED_PROXY_RESOLVER_H_
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#include <stddef.h>
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#include <memory>
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#include <set>
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#include "base/memory/ref_counted.h"
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#include "net/base/net_export.h"
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#include "net/proxy/proxy_resolver_factory.h"
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namespace net {
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class ProxyResolver;
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// MultiThreadedProxyResolverFactory creates instances of a ProxyResolver
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// implementation that runs synchronous ProxyResolver implementations on worker
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// threads.
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//
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// Threads are created lazily on demand, up to a maximum total. The advantage
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// of having a pool of threads, is faster performance. In particular, being
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// able to keep servicing PAC requests even if one blocks its execution.
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//
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// During initialization (CreateProxyResolver), a single thread is spun up to
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// test the script. If this succeeds, we cache the input script, and will re-use
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// this to lazily provision any new threads as needed.
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//
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// For each new thread that we spawn in a particular MultiThreadedProxyResolver
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// instance, a corresponding new ProxyResolver is created using the
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// ProxyResolverFactory returned by CreateProxyResolverFactory().
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//
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// Because we are creating multiple ProxyResolver instances, this means we
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// are duplicating script contexts for what is ordinarily seen as being a
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// single script. This can affect compatibility on some classes of PAC
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// script:
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//
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// (a) Scripts whose initialization has external dependencies on network or
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// time may end up successfully initializing on some threads, but not
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// others. So depending on what thread services the request, the result
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// may jump between several possibilities.
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//
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// (b) Scripts whose FindProxyForURL() depends on side-effects may now
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// work differently. For example, a PAC script which was incrementing
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// a global counter and using that to make a decision. In the
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// multi-threaded model, each thread may have a different value for this
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// counter, so it won't globally be seen as monotonically increasing!
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class NET_EXPORT_PRIVATE MultiThreadedProxyResolverFactory
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: public ProxyResolverFactory {
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public:
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MultiThreadedProxyResolverFactory(size_t max_num_threads,
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bool factory_expects_bytes);
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~MultiThreadedProxyResolverFactory() override;
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int CreateProxyResolver(
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const scoped_refptr<ProxyResolverScriptData>& pac_script,
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std::unique_ptr<ProxyResolver>* resolver,
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const CompletionCallback& callback,
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std::unique_ptr<Request>* request) override;
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private:
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class Job;
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// Invoked to create a ProxyResolverFactory instance to pass to a
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// MultiThreadedProxyResolver instance.
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virtual std::unique_ptr<ProxyResolverFactory>
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CreateProxyResolverFactory() = 0;
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void RemoveJob(Job* job);
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const size_t max_num_threads_;
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std::set<Job*> jobs_;
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};
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} // namespace net
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#endif // NET_PROXY_MULTI_THREADED_PROXY_RESOLVER_H_
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