Move policy code into components/policy.

chrome/browser/policy/cloud/external_policy_data_updater.cc

-// Copyright (c) 2013 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.
-
-#include "chrome/browser/policy/cloud/external_policy_data_updater.h"
-
-#include "base/bind.h"
-#include "base/bind_helpers.h"
-#include "base/callback.h"
-#include "base/location.h"
-#include "base/logging.h"
-#include "base/sequenced_task_runner.h"
-#include "base/sha1.h"
-#include "base/stl_util.h"
-#include "chrome/browser/policy/cloud/external_policy_data_fetcher.h"
-#include "net/base/backoff_entry.h"
-#include "url/gurl.h"
-
-namespace policy {
-
-namespace {
-
-// Policies for exponential backoff of failed requests. There are 3 policies for
-// different classes of errors.
-
-// For temporary errors (HTTP 500, RST, etc).
-const net::BackoffEntry::Policy kRetrySoonPolicy = {
-  // Number of initial errors to ignore before starting to back off.
-  0,
-
-  // Initial delay in ms: 60 seconds.
-  1000 * 60,
-
-  // Factor by which the waiting time is multiplied.
-  2,
-
-  // Fuzzing percentage; this spreads delays randomly between 80% and 100%
-  // of the calculated time.
-  0.20,
-
-  // Maximum delay in ms: 12 hours.
-  1000 * 60 * 60 * 12,
-
-  // When to discard an entry: never.
-  -1,
-
-  // |always_use_initial_delay|; false means that the initial delay is
-  // applied after the first error, and starts backing off from there.
-  false,
-};
-
-// For other errors (request failed, server errors).
-const net::BackoffEntry::Policy kRetryLaterPolicy = {
-  // Number of initial errors to ignore before starting to back off.
-  0,
-
-  // Initial delay in ms: 1 hour.
-  1000 * 60 * 60,
-
-  // Factor by which the waiting time is multiplied.
-  2,
-
-  // Fuzzing percentage; this spreads delays randomly between 80% and 100%
-  // of the calculated time.
-  0.20,
-
-  // Maximum delay in ms: 12 hours.
-  1000 * 60 * 60 * 12,
-
-  // When to discard an entry: never.
-  -1,
-
-  // |always_use_initial_delay|; false means that the initial delay is
-  // applied after the first error, and starts backing off from there.
-  false,
-};
-
-// When the data fails validation (maybe because the policy URL and the data
-// served at that URL are out of sync). This essentially retries every 12 hours,
-// with some random jitter.
-const net::BackoffEntry::Policy kRetryMuchLaterPolicy = {
-  // Number of initial errors to ignore before starting to back off.
-  0,
-
-  // Initial delay in ms: 12 hours.
-  1000 * 60 * 60 * 12,
-
-  // Factor by which the waiting time is multiplied.
-  2,
-
-  // Fuzzing percentage; this spreads delays randomly between 80% and 100%
-  // of the calculated time.
-  0.20,
-
-  // Maximum delay in ms: 12 hours.
-  1000 * 60 * 60 * 12,
-
-  // When to discard an entry: never.
-  -1,
-
-  // |always_use_initial_delay|; false means that the initial delay is
-  // applied after the first error, and starts backing off from there.
-  false,
-};
-
-// Maximum number of retries for requests that aren't likely to get a
-// different response (e.g. HTTP 4xx replies).
-const int kMaxLimitedRetries = 3;
-
-}  // namespace
-
-class ExternalPolicyDataUpdater::FetchJob
-    : public base::SupportsWeakPtr<FetchJob> {
- public:
-  FetchJob(ExternalPolicyDataUpdater* updater,
-           const std::string& key,
-           const ExternalPolicyDataUpdater::Request& request,
-           const ExternalPolicyDataUpdater::FetchSuccessCallback& callback);
-  virtual ~FetchJob();
-
-  const std::string& key() const;
-  const ExternalPolicyDataUpdater::Request& request() const;
-
-  void Start();
-
-  void OnFetchFinished(ExternalPolicyDataFetcher::Result result,
-                       scoped_ptr<std::string> data);
-
- private:
-  void OnFailed(net::BackoffEntry* backoff_entry);
-  void Reschedule();
-
-  // Always valid as long as |this| is alive.
-  ExternalPolicyDataUpdater* updater_;
-
-  const std::string key_;
-  const ExternalPolicyDataUpdater::Request request_;
-  ExternalPolicyDataUpdater::FetchSuccessCallback callback_;
-
-  // If the job is currently running, a corresponding |fetch_job_| exists in the
-  // |external_policy_data_fetcher_|. The job must eventually call back to the
-  // |updater_|'s OnJobSucceeded() or OnJobFailed() method in this case.
-  // If the job is currently not running, |fetch_job_| is NULL and no callbacks
-  // should be invoked.
-  ExternalPolicyDataFetcher::Job* fetch_job_;  // Not owned.
-
-  // Some errors should trigger a limited number of retries, even with backoff.
-  // This counts down the number of such retries to stop retrying once the limit
-  // is reached.
-  int limited_retries_remaining_;
-
-  // Various delays to retry a failed download, depending on the failure reason.
-  net::BackoffEntry retry_soon_entry_;
-  net::BackoffEntry retry_later_entry_;
-  net::BackoffEntry retry_much_later_entry_;
-
-  DISALLOW_COPY_AND_ASSIGN(FetchJob);
-};
-
-ExternalPolicyDataUpdater::Request::Request() {
-}
-
-ExternalPolicyDataUpdater::Request::Request(const std::string& url,
-                                            const std::string& hash,
-                                            int64 max_size)
-    : url(url), hash(hash), max_size(max_size) {
-}
-
-bool ExternalPolicyDataUpdater::Request::operator==(
-    const Request& other) const {
-  return url == other.url && hash == other.hash && max_size == other.max_size;
-}
-
-ExternalPolicyDataUpdater::FetchJob::FetchJob(
-    ExternalPolicyDataUpdater* updater,
-    const std::string& key,
-    const ExternalPolicyDataUpdater::Request& request,
-    const ExternalPolicyDataUpdater::FetchSuccessCallback& callback)
-    : updater_(updater),
-      key_(key),
-      request_(request),
-      callback_(callback),
-      fetch_job_(NULL),
-      limited_retries_remaining_(kMaxLimitedRetries),
-      retry_soon_entry_(&kRetrySoonPolicy),
-      retry_later_entry_(&kRetryLaterPolicy),
-      retry_much_later_entry_(&kRetryMuchLaterPolicy) {
-}
-
-ExternalPolicyDataUpdater::FetchJob::~FetchJob() {
-  if (fetch_job_) {
-    // Cancel the fetch job in the |external_policy_data_fetcher_|.
-    updater_->external_policy_data_fetcher_->CancelJob(fetch_job_);
-    // Inform the |updater_| that the job was canceled.
-    updater_->OnJobFailed(this);
-  }
-}
-
-const std::string& ExternalPolicyDataUpdater::FetchJob::key() const {
-  return key_;
-}
-
-const ExternalPolicyDataUpdater::Request&
-    ExternalPolicyDataUpdater::FetchJob::request() const {
-  return request_;
-}
-
-void ExternalPolicyDataUpdater::FetchJob::Start() {
-  DCHECK(!fetch_job_);
-  // Start a fetch job in the |external_policy_data_fetcher_|. This will
-  // eventually call back to OnFetchFinished() with the result.
-  fetch_job_ = updater_->external_policy_data_fetcher_->StartJob(
-      GURL(request_.url), request_.max_size,
-      base::Bind(&ExternalPolicyDataUpdater::FetchJob::OnFetchFinished,
-                 base::Unretained(this)));
-}
-
-void ExternalPolicyDataUpdater::FetchJob::OnFetchFinished(
-    ExternalPolicyDataFetcher::Result result,
-    scoped_ptr<std::string> data) {
-  // The fetch job in the |external_policy_data_fetcher_| is finished.
-  fetch_job_ = NULL;
-
-  switch (result) {
-    case ExternalPolicyDataFetcher::CONNECTION_INTERRUPTED:
-      // The connection was interrupted. Try again soon.
-      OnFailed(&retry_soon_entry_);
-      return;
-    case ExternalPolicyDataFetcher::NETWORK_ERROR:
-      // Another network error occurred. Try again later.
-      OnFailed(&retry_later_entry_);
-      return;
-    case ExternalPolicyDataFetcher::SERVER_ERROR:
-      // Problem at the server. Try again soon.
-      OnFailed(&retry_soon_entry_);
-      return;
-    case ExternalPolicyDataFetcher::CLIENT_ERROR:
-      // Client error. This is unlikely to go away. Try again later, and give up
-      // retrying after 3 attempts.
-      OnFailed(limited_retries_remaining_ ? &retry_later_entry_ : NULL);
-      if (limited_retries_remaining_)
-        --limited_retries_remaining_;
-      return;
-    case ExternalPolicyDataFetcher::HTTP_ERROR:
-      // Any other type of HTTP failure. Try again later.
-      OnFailed(&retry_later_entry_);
-      return;
-    case ExternalPolicyDataFetcher::MAX_SIZE_EXCEEDED:
-      // Received |data| exceeds maximum allowed size. This may be because the
-      // data being served is stale. Try again much later.
-      OnFailed(&retry_much_later_entry_);
-      return;
-    case ExternalPolicyDataFetcher::SUCCESS:
-      break;
-  }
-
-  if (base::SHA1HashString(*data) != request_.hash) {
-    // Received |data| does not match expected hash. This may be because the
-    // data being served is stale. Try again much later.
-    OnFailed(&retry_much_later_entry_);
-    return;
-  }
-
-  // If the callback rejects the data, try again much later.
-  if (!callback_.Run(*data)) {
-    OnFailed(&retry_much_later_entry_);
-    return;
-  }
-
-  // Signal success.
-  updater_->OnJobSucceeded(this);
-}
-
-void ExternalPolicyDataUpdater::FetchJob::OnFailed(net::BackoffEntry* entry) {
-  if (entry) {
-    entry->InformOfRequest(false);
-
-    // This function may have been invoked because the job was obsoleted and is
-    // in the process of being deleted. If this is the case, the WeakPtr will
-    // become invalid and the delayed task will never run.
-    updater_->task_runner_->PostDelayedTask(
-        FROM_HERE,
-        base::Bind(&FetchJob::Reschedule, AsWeakPtr()),
-        entry->GetTimeUntilRelease());
-  }
-
-  updater_->OnJobFailed(this);
-}
-
-void ExternalPolicyDataUpdater::FetchJob::Reschedule() {
-  updater_->ScheduleJob(this);
-}
-
-ExternalPolicyDataUpdater::ExternalPolicyDataUpdater(
-    scoped_refptr<base::SequencedTaskRunner> task_runner,
-    scoped_ptr<ExternalPolicyDataFetcher> external_policy_data_fetcher,
-    size_t max_parallel_fetches)
-    : task_runner_(task_runner),
-      external_policy_data_fetcher_(external_policy_data_fetcher.release()),
-      max_parallel_jobs_(max_parallel_fetches),
-      running_jobs_(0),
-      shutting_down_(false) {
-  DCHECK(task_runner_->RunsTasksOnCurrentThread());
-}
-
-ExternalPolicyDataUpdater::~ExternalPolicyDataUpdater() {
-  DCHECK(task_runner_->RunsTasksOnCurrentThread());
-  shutting_down_ = true;
-  STLDeleteValues(&job_map_);
-}
-
-void ExternalPolicyDataUpdater::FetchExternalData(
-    const std::string key,
-    const Request& request,
-    const FetchSuccessCallback& callback) {
-  DCHECK(task_runner_->RunsTasksOnCurrentThread());
-
-  // Check whether a job exists for this |key| already.
-  FetchJob* job = job_map_[key];
-  if (job) {
-    // If the current |job| is handling the given |request| already, nothing
-    // needs to be done.
-    if (job->request() == request)
-      return;
-
-    // Otherwise, the current |job| is obsolete. If the |job| is on the queue,
-    // its WeakPtr will be invalidated and skipped by StartNextJobs(). If |job|
-    // is currently running, it will call OnJobFailed() immediately.
-    delete job;
-    job_map_.erase(key);
-  }
-
-  // Start a new job to handle |request|.
-  job = new FetchJob(this, key, request, callback);
-  job_map_[key] = job;
-  ScheduleJob(job);
-}
-
-void ExternalPolicyDataUpdater::CancelExternalDataFetch(
-    const std::string& key) {
-  DCHECK(task_runner_->RunsTasksOnCurrentThread());
-
-  // If a |job| exists for this |key|, delete it. If the |job| is on the queue,
-  // its WeakPtr will be invalidated and skipped by StartNextJobs(). If |job| is
-  // currently running, it will call OnJobFailed() immediately.
-  std::map<std::string, FetchJob*>::iterator job = job_map_.find(key);
-  if (job != job_map_.end()) {
-    delete job->second;
-    job_map_.erase(job);
-  }
-}
-
-void ExternalPolicyDataUpdater::StartNextJobs() {
-  if (shutting_down_)
-    return;
-
-  while (running_jobs_ < max_parallel_jobs_ && !job_queue_.empty()) {
-    FetchJob* job = job_queue_.front().get();
-    job_queue_.pop();
-
-    // Some of the jobs may have been invalidated, and have to be skipped.
-    if (job) {
-      ++running_jobs_;
-      // A started job will always call OnJobSucceeded() or OnJobFailed().
-      job->Start();
-    }
-  }
-}
-
-void ExternalPolicyDataUpdater::ScheduleJob(FetchJob* job) {
-  DCHECK_EQ(job_map_[job->key()], job);
-
-  job_queue_.push(job->AsWeakPtr());
-
-  StartNextJobs();
-}
-
-void ExternalPolicyDataUpdater::OnJobSucceeded(FetchJob* job) {
-  DCHECK(running_jobs_);
-  DCHECK_EQ(job_map_[job->key()], job);
-
-  --running_jobs_;
-  job_map_.erase(job->key());
-  delete job;
-
-  StartNextJobs();
-}
-
-void ExternalPolicyDataUpdater::OnJobFailed(FetchJob* job) {
-  DCHECK(running_jobs_);
-  DCHECK_EQ(job_map_[job->key()], job);
-
-  --running_jobs_;
-
-  // The job is not deleted when it fails because a retry attempt may have been
-  // scheduled.
-  StartNextJobs();
-}
-
-}  // namespace policy