Add session metric pruning.

[ Merge of http://go/wvgerrit/65983 ]

Add support to drop closed metrics in order to save space for
long-running applications (and CdmEngine instances). The code now keeps
only a limited number of metrics collections after the session is closed.
As a session (and its metrics session) is closed, the oldest, closed metrics
session is dropped. This means those metrics will not be reported nor
accessible in the client.

Bug: http://b/118664842

Test: CDM Unit tests. Android Unit Test. Ran GPLay Manually.
Change-Id: I27d6e61a8fe4148ad1ef2a433c8e5f4cdd84cc72

libwvdrmengine/cdm/metrics/src/metrics_collections.cpp

@@ -13,13 +13,15 @@ using ::google::protobuf::RepeatedPtrField;
 using ::wvcdm::metrics::EventMetric;
 
 namespace {
+
 // Helper struct for comparing session ids.
 struct CompareSessionIds {
   const std::string &target_;
 
   CompareSessionIds(const wvcdm::CdmSessionId &target) : target_(target){};
 
-  bool operator()(const wvcdm::metrics::SessionMetrics *metrics) const {
+  bool operator()(const std::shared_ptr<wvcdm::metrics::SessionMetrics> metrics)
+      const {
     return metrics->GetSessionId() == target_;
   }
 };
@@ -258,31 +260,60 @@ EngineMetrics::EngineMetrics() {
 
 EngineMetrics::~EngineMetrics() {
   std::unique_lock<std::mutex> lock(session_metrics_lock_);
-  std::vector<SessionMetrics *>::iterator i;
-  if (!session_metrics_list_.empty()) {
-    LOGV("EngineMetrics::~EngineMetrics. Session count: %d",
-         session_metrics_list_.size());
+  if (!active_session_metrics_list_.empty()
+      || !completed_session_metrics_list_.empty()) {
+    LOGV("EngineMetrics::~EngineMetrics. Session counts: "
+         "active %d. completed %d.", active_session_metrics_list_.size(),
+         completed_session_metrics_list_.size());
   }
-  for (i = session_metrics_list_.begin(); i != session_metrics_list_.end();
-       i++) {
-    delete *i;
-  }
-  session_metrics_list_.clear();
 }
 
 SessionMetrics *EngineMetrics::AddSession() {
   std::unique_lock<std::mutex> lock(session_metrics_lock_);
-  SessionMetrics *metrics = new SessionMetrics();
-  session_metrics_list_.push_back(metrics);
-  return metrics;
+  active_session_metrics_list_.push_back(std::make_shared<SessionMetrics>());
+  return active_session_metrics_list_.back().get();
 }
 
 void EngineMetrics::RemoveSession(wvcdm::CdmSessionId session_id) {
   std::unique_lock<std::mutex> lock(session_metrics_lock_);
-  session_metrics_list_.erase(
-      std::remove_if(session_metrics_list_.begin(), session_metrics_list_.end(),
+  active_session_metrics_list_.erase(
+      std::remove_if(active_session_metrics_list_.begin(),
+                     active_session_metrics_list_.end(),
                      CompareSessionIds(session_id)),
-      session_metrics_list_.end());
+      active_session_metrics_list_.end());
+  completed_session_metrics_list_.erase(
+      std::remove_if(completed_session_metrics_list_.begin(),
+                     completed_session_metrics_list_.end(),
+                     CompareSessionIds(session_id)),
+      completed_session_metrics_list_.end());
+}
+
+void EngineMetrics::ConsolidateSessions() {
+  auto completed_filter =
+      [] (const std::shared_ptr<SessionMetrics>& session_metrics) {
+        return session_metrics->IsCompleted();
+      };
+
+  std::unique_lock<std::mutex> lock(session_metrics_lock_);
+  std::copy_if(active_session_metrics_list_.begin(),
+               active_session_metrics_list_.end(),
+               std::back_inserter(completed_session_metrics_list_),
+               completed_filter);
+  active_session_metrics_list_.erase(
+      std::remove_if(active_session_metrics_list_.begin(),
+                     active_session_metrics_list_.end(),
+                     completed_filter),
+      active_session_metrics_list_.end());
+
+  // TODO(b/118664842): Add support to merge older metrics into one
+  // consolidated metric.
+  int excess_completed = completed_session_metrics_list_.size()
+                         - kMaxCompletedSessions;
+  if (excess_completed > 0) {
+    completed_session_metrics_list_.erase(
+        completed_session_metrics_list_.begin(),
+        completed_session_metrics_list_.begin() + excess_completed);
+  }
 }
 
 void EngineMetrics::Serialize(WvCdmMetrics *wv_metrics) const {
@@ -299,8 +330,12 @@ void EngineMetrics::Serialize(WvCdmMetrics *wv_metrics) const {
   }
   SerializeEngineMetrics(engine_metrics);
 
-  for (std::vector<metrics::SessionMetrics *>::const_iterator it =
-       session_metrics_list_.begin(); it != session_metrics_list_.end(); it++) {
+  for (auto it = completed_session_metrics_list_.begin();
+       it != completed_session_metrics_list_.end(); it++) {
+    (*it)->Serialize(wv_metrics->add_session_metrics());
+  }
+  for (auto it = active_session_metrics_list_.begin();
+       it != active_session_metrics_list_.end(); it++) {
     (*it)->Serialize(wv_metrics->add_session_metrics());
   }
 }