Refactorings surrounding HostResolver:...

net/base/host_resolver.cc

Index: net/base/host_resolver.cc
===================================================================
--- net/base/host_resolver.cc	(revision 20760)
+++ net/base/host_resolver.cc	(working copy)
@@ -4,616 +4,12 @@
 
 #include "net/base/host_resolver.h"
 
-#if defined(OS_WIN)
-#include <ws2tcpip.h>
-#include <wspiapi.h>  // Needed for Win2k compat.
-#elif defined(OS_POSIX)
-#include <netdb.h>
-#include <sys/socket.h>
-#endif
-#if defined(OS_LINUX)
-#include <resolv.h>
-#endif
-
 #include "base/compiler_specific.h"
-#include "base/message_loop.h"
-#include "base/stl_util-inl.h"
-#include "base/string_util.h"
-#include "base/time.h"
-#include "base/worker_pool.h"
-#include "net/base/address_list.h"
+#include "base/logging.h"
 #include "net/base/net_errors.h"
 
-#if defined(OS_LINUX)
-#include "base/singleton.h"
-#include "base/thread_local_storage.h"
-#endif
-
-#if defined(OS_WIN)
-#include "net/base/winsock_init.h"
-#endif
-
 namespace net {
 
-//-----------------------------------------------------------------------------
-
-static HostMapper* host_mapper;
-
-std::string HostMapper::MapUsingPrevious(const std::string& host) {
-  return previous_mapper_.get() ? previous_mapper_->Map(host) : host;
-}
-
-HostMapper* SetHostMapper(HostMapper* value) {
-  std::swap(host_mapper, value);
-  return value;
-}
-
-#if defined(OS_LINUX)
-// On Linux changes to /etc/resolv.conf can go unnoticed thus resulting in
-// DNS queries failing either because nameservers are unknown on startup
-// or because nameserver info has changed as a result of e.g. connecting to
-// a new network. Some distributions patch glibc to stat /etc/resolv.conf
-// to try to automatically detect such changes but these patches are not
-// universal and even patched systems such as Jaunty appear to need calls
-// to res_ninit to reload the nameserver information in different threads.
-//
-// We adopt the Mozilla solution here which is to call res_ninit when
-// lookups fail and to rate limit the reloading to once per second per
-// thread.
-
-// Keep a timer per calling thread to rate limit the calling of res_ninit.
-class DnsReloadTimer {
- public:
-  DnsReloadTimer() {
-    tls_index_.Initialize(SlotReturnFunction);
-  }
-
-  ~DnsReloadTimer() { }
-
-  // Check if the timer for the calling thread has expired. When no
-  // timer exists for the calling thread, create one.
-  bool Expired() {
-    const base::TimeDelta kRetryTime = base::TimeDelta::FromSeconds(1);
-    base::TimeTicks now = base::TimeTicks::Now();
-    base::TimeTicks* timer_ptr =
-      static_cast<base::TimeTicks*>(tls_index_.Get());
-
-    if (!timer_ptr) {
-      timer_ptr = new base::TimeTicks();
-      *timer_ptr = base::TimeTicks::Now();
-      tls_index_.Set(timer_ptr);
-      // Return true to reload dns info on the first call for each thread.
-      return true;
-    } else if (now - *timer_ptr > kRetryTime) {
-      *timer_ptr = now;
-      return true;
-    } else {
-      return false;
-    }
-  }
-
-  // Free the allocated timer.
-  static void SlotReturnFunction(void* data) {
-    base::TimeTicks* tls_data = static_cast<base::TimeTicks*>(data);
-    delete tls_data;
-  }
-
- private:
-  // We use thread local storage to identify which base::TimeTicks to
-  // interact with.
-  static ThreadLocalStorage::Slot tls_index_ ;
-
-  DISALLOW_COPY_AND_ASSIGN(DnsReloadTimer);
-};
-
-// A TLS slot to the TimeTicks for the current thread.
-// static
-ThreadLocalStorage::Slot DnsReloadTimer::tls_index_(base::LINKER_INITIALIZED);
-
-#endif  // defined(OS_LINUX)
-
-static int HostResolverProc(const std::string& host, struct addrinfo** out) {
-  struct addrinfo hints = {0};
-  hints.ai_family = AF_UNSPEC;
-
-#if defined(OS_WIN)
-  // DO NOT USE AI_ADDRCONFIG ON WINDOWS.
-  //
-  // The following comment in <winsock2.h> is the best documentation I found
-  // on AI_ADDRCONFIG for Windows:
-  //   Flags used in "hints" argument to getaddrinfo()
-  //       - AI_ADDRCONFIG is supported starting with Vista
-  //       - default is AI_ADDRCONFIG ON whether the flag is set or not
-  //         because the performance penalty in not having ADDRCONFIG in
-  //         the multi-protocol stack environment is severe;
-  //         this defaulting may be disabled by specifying the AI_ALL flag,
-  //         in that case AI_ADDRCONFIG must be EXPLICITLY specified to
-  //         enable ADDRCONFIG behavior
-  //
-  // Not only is AI_ADDRCONFIG unnecessary, but it can be harmful.  If the
-  // computer is not connected to a network, AI_ADDRCONFIG causes getaddrinfo
-  // to fail with WSANO_DATA (11004) for "localhost", probably because of the
-  // following note on AI_ADDRCONFIG in the MSDN getaddrinfo page:
-  //   The IPv4 or IPv6 loopback address is not considered a valid global
-  //   address.
-  // See http://crbug.com/5234.
-  hints.ai_flags = 0;
-#else
-  hints.ai_flags = AI_ADDRCONFIG;
-#endif
-
-  // Restrict result set to only this socket type to avoid duplicates.
-  hints.ai_socktype = SOCK_STREAM;
-
-  int err = getaddrinfo(host.c_str(), NULL, &hints, out);
-#if defined(OS_LINUX)
-  net::DnsReloadTimer* dns_timer = Singleton<net::DnsReloadTimer>::get();
-  // If we fail, re-initialise the resolver just in case there have been any
-  // changes to /etc/resolv.conf and retry. See http://crbug.com/11380 for info.
-  if (err && dns_timer->Expired()) {
-    res_nclose(&_res);
-    if (!res_ninit(&_res))
-      err = getaddrinfo(host.c_str(), NULL, &hints, out);
-  }
-#endif
-
-  return err ? ERR_NAME_NOT_RESOLVED : OK;
-}
-
-static int ResolveAddrInfo(HostMapper* mapper, const std::string& host,
-                           struct addrinfo** out) {
-  if (mapper) {
-    std::string mapped_host = mapper->Map(host);
-
-    if (mapped_host.empty())
-      return ERR_NAME_NOT_RESOLVED;
-
-    return HostResolverProc(mapped_host, out);
-  } else {
-    return HostResolverProc(host, out);
-  }
-}
-
-//-----------------------------------------------------------------------------
-
-class HostResolver::Request {
- public:
-  Request(int id, const RequestInfo& info, CompletionCallback* callback,
-          AddressList* addresses)
-      : id_(id), info_(info), job_(NULL), callback_(callback),
-        addresses_(addresses) {}
-
-  // Mark the request as cancelled.
-  void MarkAsCancelled() {
-    job_ = NULL;
-    callback_ = NULL;
-    addresses_ = NULL;
-  }
-
-  bool was_cancelled() const {
-    return callback_ == NULL;
-  }
-
-  void set_job(Job* job) {
-    DCHECK(job != NULL);
-    // Identify which job the request is waiting on.
-    job_ = job;
-  }
-
-  void OnComplete(int error, const AddressList& addrlist) {
-    if (error == OK)
-      addresses_->SetFrom(addrlist, port());
-    callback_->Run(error);
-  }
-
-  int port() const {
-    return info_.port();
-  }
-
-  Job* job() const {
-    return job_;
-  }
-
-  int id() const {
-    return id_;
-  }
-
-  const RequestInfo& info() const {
-    return info_;
-  }
-
- private:
-  // Unique ID for this request. Used by observers to identify requests.
-  int id_;
-
-  // The request info that started the request.
-  RequestInfo info_;
-
-  // The resolve job (running in worker pool) that this request is dependent on.
-  Job* job_;
-
-  // The user's callback to invoke when the request completes.
-  CompletionCallback* callback_;
-
-  // The address list to save result into.
-  AddressList* addresses_;
-
-  DISALLOW_COPY_AND_ASSIGN(Request);
-};
-
-//-----------------------------------------------------------------------------
-
-// This class represents a request to the worker pool for a "getaddrinfo()"
-// call.
-class HostResolver::Job : public base::RefCountedThreadSafe<HostResolver::Job> {
- public:
-  Job(HostResolver* resolver, const std::string& host)
-      : host_(host),
-        resolver_(resolver),
-        origin_loop_(MessageLoop::current()),
-        host_mapper_(host_mapper),
-        error_(OK),
-        results_(NULL) {
-  }
-
-  ~Job() {
-    if (results_)
-      freeaddrinfo(results_);
-
-    // Free the requests attached to this job.
-    STLDeleteElements(&requests_);
-  }
-
-  // Attaches a request to this job. The job takes ownership of |req| and will
-  // take care to delete it.
-  void AddRequest(HostResolver::Request* req) {
-    req->set_job(this);
-    requests_.push_back(req);
-  }
-
-  // Called from origin loop.
-  void Start() {
-    // Dispatch the job to a worker thread.
-    if (!WorkerPool::PostTask(FROM_HERE,
-            NewRunnableMethod(this, &Job::DoLookup), true)) {
-      NOTREACHED();
-
-      // Since we could be running within Resolve() right now, we can't just
-      // call OnLookupComplete().  Instead we must wait until Resolve() has
-      // returned (IO_PENDING).
-      error_ = ERR_UNEXPECTED;
-      MessageLoop::current()->PostTask(
-          FROM_HERE, NewRunnableMethod(this, &Job::OnLookupComplete));
-    }
-  }
-
-  // Cancels the current job. Callable from origin thread.
-  void Cancel() {
-    HostResolver* resolver = resolver_;
-    resolver_ = NULL;
-
-    // Mark the job as cancelled, so when worker thread completes it will
-    // not try to post completion to origin loop.
-    {
-      AutoLock locked(origin_loop_lock_);
-      origin_loop_ = NULL;
-    }
-
-    // We don't have to do anything further to actually cancel the requests
-    // that were attached to this job (since they are unreachable now).
-    // But we will call HostResolver::CancelRequest(Request*) on each one
-    // in order to notify any observers.
-    for (RequestsList::const_iterator it = requests_.begin();
-         it != requests_.end(); ++it) {
-      HostResolver::Request* req = *it;
-      if (!req->was_cancelled())
-        resolver->CancelRequest(req);
-    }
-  }
-
-  // Called from origin thread.
-  bool was_cancelled() const {
-    return resolver_ == NULL;
-  }
-
-  // Called from origin thread.
-  const std::string& host() const {
-    return host_;
-  }
-
-  // Called from origin thread.
-  const RequestsList& requests() const {
-    return requests_;
-  }
-
- private:
-  void DoLookup() {
-    // Running on the worker thread
-    error_ = ResolveAddrInfo(host_mapper_, host_, &results_);
-
-    Task* reply = NewRunnableMethod(this, &Job::OnLookupComplete);
-
-    // The origin loop could go away while we are trying to post to it, so we
-    // need to call its PostTask method inside a lock.  See ~HostResolver.
-    {
-      AutoLock locked(origin_loop_lock_);
-      if (origin_loop_) {
-        origin_loop_->PostTask(FROM_HERE, reply);
-        reply = NULL;
-      }
-    }
-
-    // Does nothing if it got posted.
-    delete reply;
-  }
-
-  // Callback for when DoLookup() completes (runs on origin thread).
-  void OnLookupComplete() {
-    // Should be running on origin loop.
-    // TODO(eroman): this is being hit by URLRequestTest.CancelTest*,
-    // because MessageLoop::current() == NULL.
-    //DCHECK_EQ(origin_loop_, MessageLoop::current());
-    DCHECK(error_ || results_);
-
-    if (was_cancelled())
-      return;
-
-    DCHECK(!requests_.empty());
-
-     // Adopt the address list using the port number of the first request.
-    AddressList addrlist;
-    if (error_ == OK) {
-      addrlist.Adopt(results_);
-      addrlist.SetPort(requests_[0]->port());
-      results_ = NULL;
-    }
-
-    resolver_->OnJobComplete(this, error_, addrlist);
-  }
-
-  // Set on the origin thread, read on the worker thread.
-  std::string host_;
-
-  // Only used on the origin thread (where Resolve was called).
-  HostResolver* resolver_;
-  RequestsList requests_;  // The requests waiting on this job.
-
-  // Used to post ourselves onto the origin thread.
-  Lock origin_loop_lock_;
-  MessageLoop* origin_loop_;
-
-  // Hold an owning reference to the host mapper that we are going to use.
-  // This may not be the current host mapper by the time we call
-  // ResolveAddrInfo, but that's OK... we'll use it anyways, and the owning
-  // reference ensures that it remains valid until we are done.
-  scoped_refptr<HostMapper> host_mapper_;
-
-  // Assigned on the worker thread, read on the origin thread.
-  int error_;
-  struct addrinfo* results_;
-
-  DISALLOW_COPY_AND_ASSIGN(Job);
-};
-
-//-----------------------------------------------------------------------------
-
-HostResolver::HostResolver(int max_cache_entries, int cache_duration_ms)
-    : cache_(max_cache_entries, cache_duration_ms), next_request_id_(0),
-      shutdown_(false) {
-#if defined(OS_WIN)
-  EnsureWinsockInit();
-#endif
-}
-
-HostResolver::~HostResolver() {
-  // Cancel the outstanding jobs. Those jobs may contain several attached
-  // requests, which will also be cancelled.
-  for (JobMap::iterator it = jobs_.begin(); it != jobs_.end(); ++it)
-    it->second->Cancel();
-
-  // In case we are being deleted during the processing of a callback.
-  if (cur_completing_job_)
-    cur_completing_job_->Cancel();
-}
-
-// TODO(eroman): Don't create cache entries for hostnames which are simply IP
-// address literals.
-int HostResolver::Resolve(const RequestInfo& info,
-                          AddressList* addresses,
-                          CompletionCallback* callback,
-                          Request** out_req) {
-  if (shutdown_)
-    return ERR_UNEXPECTED;
-
-  // Choose a unique ID number for observers to see.
-  int request_id = next_request_id_++;
-
-  // Notify registered observers.
-  NotifyObserversStartRequest(request_id, info);
-
-  // If we have an unexpired cache entry, use it.
-  if (info.allow_cached_response()) {
-    const HostCache::Entry* cache_entry = cache_.Lookup(
-        info.hostname(), base::TimeTicks::Now());
-    if (cache_entry) {
-      addresses->SetFrom(cache_entry->addrlist, info.port());
-      int error = OK;
-
-      // Notify registered observers.
-      NotifyObserversFinishRequest(request_id, info, error);
-
-      return error;
-    }
-  }
-
-  // If no callback was specified, do a synchronous resolution.
-  if (!callback) {
-    struct addrinfo* results;
-    int error = ResolveAddrInfo(host_mapper, info.hostname(), &results);
-
-    // Adopt the address list.
-    AddressList addrlist;
-    if (error == OK) {
-      addrlist.Adopt(results);
-      addrlist.SetPort(info.port());
-      *addresses = addrlist;
-    }
-
-    // Write to cache.
-    cache_.Set(info.hostname(), error, addrlist, base::TimeTicks::Now());
-
-    // Notify registered observers.
-    NotifyObserversFinishRequest(request_id, info, error);
-
-    return error;
-  }
-
-  // Create a handle for this request, and pass it back to the user if they
-  // asked for it (out_req != NULL).
-  Request* req = new Request(request_id, info, callback, addresses);
-  if (out_req)
-    *out_req = req;
-
-  // Next we need to attach our request to a "job". This job is responsible for
-  // calling "getaddrinfo(hostname)" on a worker thread.
-  scoped_refptr<Job> job;
-
-  // If there is already an outstanding job to resolve |info.hostname()|, use
-  // it. This prevents starting concurrent resolves for the same hostname.
-  job = FindOutstandingJob(info.hostname());
-  if (job) {
-    job->AddRequest(req);
-  } else {
-    // Create a new job for this request.
-    job = new Job(this, info.hostname());
-    job->AddRequest(req);
-    AddOutstandingJob(job);
-    // TODO(eroman): Bound the total number of concurrent jobs.
-    // http://crbug.com/9598
-    job->Start();
-  }
-
-  // Completion happens during OnJobComplete(Job*).
-  return ERR_IO_PENDING;
-}
-
-// See OnJobComplete(Job*) for why it is important not to clean out
-// cancelled requests from Job::requests_.
-void HostResolver::CancelRequest(Request* req) {
-  DCHECK(req);
-  DCHECK(req->job());
-  // NULL out the fields of req, to mark it as cancelled.
-  req->MarkAsCancelled();
-  NotifyObserversCancelRequest(req->id(), req->info());
-}
-
-void HostResolver::AddObserver(Observer* observer) {
-  observers_.push_back(observer);
-}
-
-void HostResolver::RemoveObserver(Observer* observer) {
-  ObserversList::iterator it =
-      std::find(observers_.begin(), observers_.end(), observer);
-
-  // Observer must exist.
-  DCHECK(it != observers_.end());
-
-  observers_.erase(it);
-}
-
-void HostResolver::Shutdown() {
-  shutdown_ = true;
-
-  // Cancel the outstanding jobs.
-  for (JobMap::iterator it = jobs_.begin(); it != jobs_.end(); ++it)
-    it->second->Cancel();
-  jobs_.clear();
-}
-
-void HostResolver::AddOutstandingJob(Job* job) {
-  scoped_refptr<Job>& found_job = jobs_[job->host()];
-  DCHECK(!found_job);
-  found_job = job;
-}
-
-HostResolver::Job* HostResolver::FindOutstandingJob(
-    const std::string& hostname) {
-  JobMap::iterator it = jobs_.find(hostname);
-  if (it != jobs_.end())
-    return it->second;
-  return NULL;
-}
-
-void HostResolver::RemoveOutstandingJob(Job* job) {
-  JobMap::iterator it = jobs_.find(job->host());
-  DCHECK(it != jobs_.end());
-  DCHECK_EQ(it->second.get(), job);
-  jobs_.erase(it);
-}
-
-void HostResolver::OnJobComplete(Job* job,
-                                 int error,
-                                 const AddressList& addrlist) {
-  RemoveOutstandingJob(job);
-
-  // Write result to the cache.
-  cache_.Set(job->host(), error, addrlist, base::TimeTicks::Now());
-
-  // Make a note that we are executing within OnJobComplete() in case the
-  // HostResolver is deleted by a callback invocation.
-  DCHECK(!cur_completing_job_);
-  cur_completing_job_ = job;
-
-  // Complete all of the requests that were attached to the job.
-  for (RequestsList::const_iterator it = job->requests().begin();
-       it != job->requests().end(); ++it) {
-    Request* req = *it;
-    if (!req->was_cancelled()) {
-      DCHECK_EQ(job, req->job());
-
-      // Notify registered observers.
-      NotifyObserversFinishRequest(req->id(), req->info(), error);
-
-      req->OnComplete(error, addrlist);
-
-      // Check if the job was cancelled as a result of running the callback.
-      // (Meaning that |this| was deleted).
-      if (job->was_cancelled())
-        return;
-    }
-  }
-
-  cur_completing_job_ = NULL;
-}
-
-void HostResolver::NotifyObserversStartRequest(int request_id,
-                                               const RequestInfo& info) {
-  for (ObserversList::iterator it = observers_.begin();
-       it != observers_.end(); ++it) {
-    (*it)->OnStartResolution(request_id, info);
-  }
-}
-
-void HostResolver::NotifyObserversFinishRequest(int request_id,
-                                                const RequestInfo& info,
-                                                int error) {
-  bool was_resolved = error == OK;
-  for (ObserversList::iterator it = observers_.begin();
-       it != observers_.end(); ++it) {
-    (*it)->OnFinishResolutionWithStatus(request_id, was_resolved, info);
-  }
-}
-
-void HostResolver::NotifyObserversCancelRequest(int request_id,
-                                                const RequestInfo& info) {
-  for (ObserversList::iterator it = observers_.begin();
-       it != observers_.end(); ++it) {
-    (*it)->OnCancelResolution(request_id, info);
-  }
-}
-
-//-----------------------------------------------------------------------------
-
 SingleRequestHostResolver::SingleRequestHostResolver(HostResolver* resolver)
     : resolver_(resolver),
       cur_request_(NULL),
@@ -634,7 +30,7 @@
                                        CompletionCallback* callback) {
   DCHECK(!cur_request_ && !cur_request_callback_) << "resolver already in use";
 
-  HostResolver::Request* request = NULL;
+  HostResolver::RequestHandle request = NULL;
 
   // We need to be notified of completion before |callback| is called, so that
   // we can clear out |cur_request_*|.