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