[metrics] Add file output support

Adds a new command line option, -Xwrite-metrics-to-file=_, which
specifies a file for writing metrics to. This can be used in conjunction
with -Xwrite-metrics-to-log, which will cause the output to go to both
logcat and the file.

Writing metrics to a file can be helpful for testing or benchmarking
environments.

Access to the file is protected using advisory locking, so it is safe to
have multiple processes write metrics to the same file.

Test: test/run-test --host test/2234-write-metrics-to-file
Bug: 175025360, 170149255
Change-Id: I83a4f959cbb96847dc71188035c050a73b915064

1 files changed, 36 insertions, 3 deletions

diff --git a/runtime/metrics/metrics.cc b/runtime/metrics/metrics.cc
index 81ae2b4dab..e85897b19e 100644
--- a/runtime/metrics/metrics.cc
+++ b/runtime/metrics/metrics.cc
@@ -16,12 +16,20 @@
 
 #include "metrics.h"
 
+#include <sstream>
+
+#include "android-base/file.h"
 #include "android-base/logging.h"
 #include "base/macros.h"
+#include "base/scoped_flock.h"
+#include "runtime.h"
+#include "runtime_options.h"
 
 #pragma clang diagnostic push
 #pragma clang diagnostic error "-Wconversion"
 
+using android::base::WriteStringToFd;
+
 namespace art {
 namespace metrics {
 
@@ -116,15 +124,15 @@ std::unique_ptr<MetricsReporter> MetricsReporter::Create(ReportingConfig config,
   std::unique_ptr<MetricsBackend> backend;
 
   // We can't use std::make_unique here because the MetricsReporter constructor is private.
-  return std::unique_ptr<MetricsReporter>{new MetricsReporter{config, metrics}};
+  return std::unique_ptr<MetricsReporter>{new MetricsReporter{std::move(config), metrics}};
 }
 
 MetricsReporter::MetricsReporter(ReportingConfig config, const ArtMetrics* metrics)
-    : config_{config}, metrics_{metrics} {}
+    : config_{std::move(config)}, metrics_{metrics} {}
 
 MetricsReporter::~MetricsReporter() {
   // If we are configured to report metrics, do one final report at the end.
-  if (config_.dump_to_logcat) {
+  if (config_.ReportingEnabled()) {
     LOG_STREAM(INFO) << "\n*** ART internal metrics ***\n\n";
     // LOG_STREAM(INFO) destroys the stream at the end of the statement, which makes it tricky pass
     // it to store as a field in StreamBackend. To get around this, we use an immediately-invoked
@@ -136,6 +144,31 @@ MetricsReporter::~MetricsReporter() {
     }(LOG_STREAM(INFO));
     LOG_STREAM(INFO) << "\n*** Done dumping ART internal metrics ***\n";
   }
+  if (config_.dump_to_file.has_value()) {
+    const auto& filename = config_.dump_to_file.value();
+    std::ostringstream stream;
+    StreamBackend backend{stream};
+    metrics_->ReportAllMetrics(&backend);
+
+    std::string error_message;
+    auto file{
+        LockedFile::Open(filename.c_str(), O_CREAT | O_WRONLY | O_APPEND, true, &error_message)};
+    if (file.get() == nullptr) {
+      LOG(WARNING) << "Could open metrics file '" << filename << "': " << error_message;
+    } else {
+      if (!WriteStringToFd(stream.str(), file.get()->Fd())) {
+        PLOG(WARNING) << "Error writing metrics to file";
+      }
+    }
+  }
+}
+
+ReportingConfig ReportingConfig::FromRuntimeArguments(const RuntimeArgumentMap& args) {
+  using M = RuntimeArgumentMap;
+  return {
+      .dump_to_logcat = args.Exists(M::WriteMetricsToLog),
+      .dump_to_file = args.GetOptional(M::WriteMetricsToFile),
+  };
 }
 
 }  // namespace metrics