Reporting: Implement endpoint manager.

net/reporting/reporting_endpoint_manager.h

+// Copyright 2017 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_REPORTING_REPORTING_ENDPOINT_MANAGER_H_
+#define NET_REPORTING_REPORTING_ENDPOINT_MANAGER_H_
+
+#include <map>
+#include <memory>
+#include <set>
+#include <string>
+
+#include "base/macros.h"
+#include "net/base/backoff_entry.h"
+#include "net/base/net_export.h"
+
+class GURL;
+
+namespace base {
+class TickClock;
+}  // namespace base
+
+namespace url {
+class Origin;
+}  // namespace url
+
+namespace net {
+
+class ReportingCache;
+
+// Keeps track of which endpoints are pending (have active delivery attempts to
+// them) or in exponential backoff after one or more failures, and chooses an
+// endpoint from an endpoint group to receive reports for an origin.
+class NET_EXPORT ReportingEndpointManager {
+ public:
+  // Note: All three parameters must outlive the endpoint manager.
+  ReportingEndpointManager(base::TickClock* clock,
+                           const ReportingCache* cache,
+                           const BackoffEntry::Policy* backoff_policy);
+  ~ReportingEndpointManager();
+
+  // Finds an endpoint configured by |origin| in group |group| that is not
+  // pending, backed-off (according to BackoffEntry), or expired.
+  //
+  // Deliberately chooses an endpoint randomly to ensure sites aren't relying on
+  // any sort of fallback ordering.
+  //
+  // Returns true and sets |*endpoint_url_out| to the endpoint URL if an
+  // endpoint was chosen; returns false (and leaves |*endpoint_url_out| invalid)
+  // if no endpoint was found.
+  bool FindEndpointForOriginAndGroup(const url::Origin& origin,
+                                     const std::string& group,
+                                     GURL* endpoint_url_out);
+
+  // Adds |endpoint| to the set of pending endpoints, preventing it from being
+  // chosen for a second parallel delivery attempt.
+  void SetEndpointPending(const GURL& endpoint);
+
+  // Removes |endpoint| from the set of pending endpoints.
+  void ClearEndpointPending(const GURL& endpoint);
+
+  // Informs the BackoffEntry for |endpoint| of a successful or not (according

[Randy Smith (Not in Mondays), 2017/03/31 15:14:08]

BackoffEntry isn't an exported concept, so shouldn't be referenced in consumer
documentation.  "Inform the manager of a request result (successful or
unsuccessful) for use in managing exponential backoff" would be better.

[Julia Tuttle, 2017/03/31 15:40:27]

Done.

+  // to |succeeded|) request.

[Randy Smith (Not in Mondays), 2017/03/31 15:14:08]

nit, suggestion: I"d phrase this as "of a successful or unsuccessful request." 
I think the use of the bool is pretty obvious in context and doesn't need to be
referenced explicitly.

[Julia Tuttle, 2017/03/31 15:40:27]

Done.

+  void InformOfEndpointRequest(const GURL& endpoint, bool succeeded);
+
+ private:
+  base::TickClock* clock_;
+  const ReportingCache* cache_;
+  const BackoffEntry::Policy* backoff_policy_;
+
+  std::set<GURL> pending_endpoints_;
+  std::map<GURL, std::unique_ptr<net::BackoffEntry>> endpoint_backoff_;
+
+  DISALLOW_COPY_AND_ASSIGN(ReportingEndpointManager);
+};
+
+}  // namespace net
+
+#endif  // NET_REPORTING_REPORTING_ENDPOINT_MANAGER_H_