Reporting: Implement delivery agent.

net/reporting/reporting_delivery_agent.h

Index: net/reporting/reporting_delivery_agent.h
diff --git a/net/reporting/reporting_delivery_agent.h b/net/reporting/reporting_delivery_agent.h
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+++ b/net/reporting/reporting_delivery_agent.h
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+// 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_DELIVERY_AGENT_H_
+#define NET_REPORTING_REPORTING_DELIVERY_AGENT_H_
+
+#include <memory>
+#include <set>
+#include <string>
+#include <utility>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "net/base/backoff_entry.h"
+#include "net/base/net_export.h"
+#include "net/reporting/reporting_endpoint_manager.h"
+#include "net/reporting/reporting_uploader.h"
+#include "url/gurl.h"
+#include "url/origin.h"
+
+namespace base {
+class TickClock;
+}  // namespace base
+
+namespace net {
+
+class ReportingCache;
+
+// Takes reports from the ReportingCache, assembles reports into deliveries to
+// endpoints, and sends those deliveries using ReportingUploader.
+//
+// Since the Reporting spec is completely silent on issues of concurrency, the
+// delivery agent handles it as so:
+//
+// 1. An individual report can only be included in one delivery at once -- if
+//    SendReports is called again while a report is being delivered, it won't
+//    be included in another delivery during that call to SendReports. (This is,
+//    in fact, made redundant by rule 3, but it's included anyway in case rule 3
+//    changes.)
+//
+// 2. An endpoint can only be the target of one delivery at once -- if
+//    SendReports is called again with reports that could be delivered to that
+//    endpoint, they won't be delivered to that endpoint.
+//
+// 3. Reports for an (origin, group) tuple can only be included in one delivery
+//    at once -- if SendReports is called again with reports in that (origin,
+//    group), they won't be included in any delivery during that call to
+//    SendReports. (This prevents the agent from getting around rule 2 by using
+//    other endpoints in the same group.)
+//
+// 4. Reports for the same origin *can* be included in multiple parallel
+//    deliveries if they are in different groups within that origin.
+//
+// (Note that a single delivery can contain an infinite number of reports.)
+//
+// TODO(juliatuttle): Consider capping the maximum number of reports per
+// delivery attempt.
+class NET_EXPORT ReportingDeliveryAgent {
+ public:
+  // |clock|, |cache|, |uploader|, and |endpoint_backoff_policy| must all
+  // outlive the ReportingDeliveryAgent.
+  ReportingDeliveryAgent(base::TickClock* clock,
+                         ReportingCache* cache,
+                         ReportingUploader* uploader,
+                         const BackoffEntry::Policy* endpoint_backoff_policy);
+  ~ReportingDeliveryAgent();
+
+  // Tries to deliver all of the reports in the cache. Reports that are already
+  // being delivered will not be attempted a second time, and reports that do
+  // not have a viable endpoint will be neither attempted nor removed.
+  void SendReports();
+
+ private:
+  class Delivery;
+
+  using OriginGroup = std::pair<url::Origin, std::string>;
+
+  void OnUploadComplete(const std::unique_ptr<Delivery>& delivery,
+                        ReportingUploader::Outcome outcome);
+
+  base::TickClock* clock_;
+  ReportingCache* cache_;
+  ReportingUploader* uploader_;
+
+  ReportingEndpointManager endpoint_manager_;
+
+  // Tracks OriginGroup tuples for which there is a pending delivery running.
+  // (Would be an unordered_set, but there's no hash on pair.)
+  std::set<OriginGroup> pending_origin_groups_;
+
+  base::WeakPtrFactory<ReportingDeliveryAgent> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ReportingDeliveryAgent);
+};
+
+}  // namespace net
+
+#endif  // NET_REPORTING_REPORTING_DELIVERY_AGENT_H_