TelemetryGeckoViewPersistence.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "TelemetryGeckoViewPersistence.h"

#include "core/TelemetryHistogram.h"
#include "core/TelemetryScalar.h"
#include "jsapi.h"
#include "js/JSON.h"
#include "mozilla/dom/ScriptSettings.h"  // for AutoJSAPI
#include "mozilla/dom/SimpleGlobalObject.h"
#include "mozilla/ErrorNames.h"
#include "mozilla/JSONWriter.h"
#include "mozilla/Path.h"
#include "mozilla/Preferences.h"
#include "mozilla/ScopeExit.h"
#include "mozilla/StaticPtr.h"
#include "mozilla/SystemGroup.h"
#include "nsDirectoryServiceDefs.h"
#include "nsIFile.h"
#include "nsIInputStream.h"
#include "nsIObserverService.h"
#include "nsIOutputStream.h"
#include "nsISafeOutputStream.h"
#include "nsITimer.h"
#include "nsLocalFile.h"
#include "nsNetUtil.h"
#include "nsXULAppAPI.h"
#include "prenv.h"
#include "prio.h"
#include "xpcpublic.h"

using mozilla::GetErrorName;
using mozilla::MakeScopeExit;
using mozilla::Preferences;
using mozilla::StaticRefPtr;
using mozilla::SystemGroup;
using mozilla::TaskCategory;
using mozilla::dom::AutoJSAPI;
using mozilla::dom::SimpleGlobalObject;

using PathChar = mozilla::filesystem::Path::value_type;
using PathCharPtr = const PathChar*;

// Enable logging by default on Debug builds.
#ifdef DEBUG
// If we're building for Android, use the provided logging facility.
#  ifdef MOZ_WIDGET_ANDROID
#    include <android/log.h>
#    define ANDROID_LOG(fmt, ...) \
      __android_log_print(ANDROID_LOG_DEBUG, "Telemetry", fmt, ##__VA_ARGS__)
#  else
// If we're building for other platforms (e.g. for running test coverage), try
// to print something anyway.
#    define ANDROID_LOG(...) printf_stderr("\n**** TELEMETRY: " __VA_ARGS__)
#  endif  // MOZ_WIDGET_ANDROID
#else
// No-op on Release builds.
#  define ANDROID_LOG(...)
#endif  // DEBUG

// The Gecko runtime can be killed at anytime. Moreover, we can
// have very short lived sessions. The persistence timeout governs
// how frequently measurements are saved to disk.
const uint32_t kDefaultPersistenceTimeoutMs = 60 * 1000;  // 60s

// The name of the persistence file used for saving the
// measurements.
const char16_t kPersistenceFileName[] = u"gv_measurements.json";

// This topic is notified and propagated up to the application to
// make sure it knows that data loading has complete and that snapshotting
// can now be performed.
const char kLoadCompleteTopic[] = "internal-telemetry-geckoview-load-complete";

// The timer used for persisting measurements data.
nsITimer* gPersistenceTimer;
// The worker thread to perform persistence.
StaticRefPtr<nsIThread> gPersistenceThread;

namespace {

void PersistenceThreadPersist();

/**
+ * The helper class used by mozilla::JSONWriter to
+ * serialize the JSON structure to a file.
+ */
class StreamingJSONWriter : public mozilla::JSONWriteFunc {
 public:
  nsresult Open(nsCOMPtr<nsIFile> aOutFile) {
    MOZ_ASSERT(!mStream, "Open must not be called twice");
    nsresult rv =
        NS_NewSafeLocalFileOutputStream(getter_AddRefs(mStream), aOutFile);
    NS_ENSURE_SUCCESS(rv, rv);
    return NS_OK;
  }

  nsresult Close() {
    MOZ_ASSERT(mStream, "Close must be called on an already opened stream");
    // We don't need to care too much about checking if count matches
    // the length of aData: Finish() will do that for us and fail if
    // Write did not persist all the data or mStream->Close() failed.
    // Note that |nsISafeOutputStream| will write to a temp file and only
    // overwrite the destination if no error was reported.
    nsCOMPtr<nsISafeOutputStream> safeStream = do_QueryInterface(mStream);
    MOZ_ASSERT(safeStream);
    return safeStream->Finish();
  }

  void Write(const char* aStr) override {
    uint32_t count;
    mozilla::Unused << mStream->Write(aStr, strlen(aStr), &count);
  }

 private:
  nsCOMPtr<nsIOutputStream> mStream;
};

/**
 * Get the path to the Android Data dir.
 *
 * @param {nsTString<PathChar>} aOutDir - the variable holding the path.
 * @return {nsresult} NS_OK if the data dir path was found, a failure value
 *                    otherwise.
 */
nsresult GetAndroidDataDir(nsTString<PathChar>& aOutDir) {
  // This relies on the Java environment to set the location of the
  // cache directory. If that happens, the following variable is set.
  // This should always be the case.
  const char* dataDir = PR_GetEnv("MOZ_ANDROID_DATA_DIR");
  if (!dataDir || !*dataDir) {
    ANDROID_LOG(
        "GetAndroidDataDir - Cannot find the data directory in the "
        "environment.");
    return NS_ERROR_FAILURE;
  }

  aOutDir.AssignASCII(dataDir);
  return NS_OK;
}

/**
 * Get the path to the persistence file in the Android Data dir.
 *
 * @param {nsCOMPtr<nsIFile>} aOutFile - the nsIFile pointer holding the file
 *                                       info.
 * @return {nsresult} NS_OK if the persistence file was found, a failure value
 *                          otherwise.
 */
nsresult GetPersistenceFile(nsCOMPtr<nsIFile>& aOutFile) {
  nsTString<PathChar> dataDir;
  nsresult rv = GetAndroidDataDir(dataDir);
  NS_ENSURE_SUCCESS(rv, rv);

  // Append the extension to the filename.
  nsAutoString fileName;
  fileName.Assign(kPersistenceFileName);

  aOutFile = new nsLocalFile(dataDir);
  aOutFile->Append(fileName);
  ANDROID_LOG("GetPersistenceFile -  %s", aOutFile->HumanReadablePath().get());
  return NS_OK;
}

/**
 * Read and parses JSON content from a file.
 *
 * @param {nsCOMPtr<nsIFile>} aFile - the nsIFile handle to the file.
 * @param {nsACString} fileContent - the content of the file.
 * @return {nsresult} NS_OK if the file was correctly read, an error code
 *                          otherwise.
 */
nsresult ReadFromFile(const nsCOMPtr<nsIFile>& aFile, nsACString& fileContent) {
  int64_t fileSize = 0;
  nsresult rv = aFile->GetFileSize(&fileSize);
  if (NS_FAILED(rv)) {
    return rv;
  }

  nsCOMPtr<nsIInputStream> inStream;
  rv = NS_NewLocalFileInputStream(getter_AddRefs(inStream), aFile, PR_RDONLY);
  NS_ENSURE_SUCCESS(rv, rv);

  // Make sure to close the stream.
  auto scopedStreamClose = MakeScopeExit([inStream] { inStream->Close(); });

  rv = NS_ReadInputStreamToString(inStream, fileContent, fileSize);
  NS_ENSURE_SUCCESS(rv, rv);

  return NS_OK;
}

/**
 * Arms the persistence timer and instructs to run the persistence
 * task off the main thread.
 */
void MainThreadArmPersistenceTimer() {
  MOZ_ASSERT(NS_IsMainThread());
  ANDROID_LOG("MainThreadArmPersistenceTimer");

  // We won't have a persistence timer the first time this runs, so take
  // care of that.
  if (!gPersistenceTimer) {
    gPersistenceTimer =
        NS_NewTimer(SystemGroup::EventTargetFor(TaskCategory::Other)).take();
    if (!gPersistenceTimer) {
      ANDROID_LOG("MainThreadArmPersistenceTimer - Timer creation failed.");
      return;
    }
  }

  // Define the callback for the persistence timer: it will dispatch the
  // persistence task off the main thread. Once finished, it will trigger the
  // timer again.
  nsTimerCallbackFunc timerCallback = [](nsITimer* aTimer, void* aClosure) {
    gPersistenceThread->Dispatch(
        NS_NewRunnableFunction("PersistenceThreadPersist",
                               []() -> void { ::PersistenceThreadPersist(); }));
  };

  uint32_t timeout =
      Preferences::GetUint("toolkit.telemetry.geckoPersistenceTimeout",
                           kDefaultPersistenceTimeoutMs);

  // Schedule the timer to automatically run and reschedule
  // every |kPersistenceTimeoutMs|.
  gPersistenceTimer->InitWithNamedFuncCallback(
      timerCallback, nullptr, timeout, nsITimer::TYPE_ONE_SHOT_LOW_PRIORITY,
      "TelemetryGeckoViewPersistence::Persist");
}

/**
 * Parse the string data into a JSON structure, using
 * the native JS JSON parser.
 */
void MainThreadParsePersistedProbes(const nsACString& aProbeData) {
  // We're required to run on the main thread since we're using JS.
  MOZ_ASSERT(NS_IsMainThread());
  ANDROID_LOG("MainThreadParsePersistedProbes");

  // We need a JS context to run the parsing stuff in.
  JS::Rooted<JSObject*> cleanGlobal(
      mozilla::dom::RootingCx(),
      SimpleGlobalObject::Create(
          SimpleGlobalObject::GlobalType::BindingDetail));
  if (!cleanGlobal) {
    ANDROID_LOG(
        "MainThreadParsePersistedProbes - Failed to create a JS global object");
    return;
  }

  AutoJSAPI jsapi;
  if (NS_WARN_IF(!jsapi.Init(cleanGlobal))) {
    ANDROID_LOG("MainThreadParsePersistedProbes - Failed to get JS API");
    return;
  }

  // Parse the JSON using the JS API.
  JS::RootedValue data(jsapi.cx());
  NS_ConvertUTF8toUTF16 utf16Content(aProbeData);
  if (!JS_ParseJSON(jsapi.cx(), utf16Content.BeginReading(),
                    utf16Content.Length(), &data)) {
    ANDROID_LOG(
        "MainThreadParsePersistedProbes - Failed to parse the persisted JSON");
    return;
  }

  // Get the data for the scalars.
  JS::RootedObject dataObj(jsapi.cx(), &data.toObject());
  JS::RootedValue scalarData(jsapi.cx());
  if (JS_GetProperty(jsapi.cx(), dataObj, "scalars", &scalarData)) {
    // If the data is an object, try to parse its properties. If not,
    // silently skip and try to load the other sections.
    if (!scalarData.isObject() ||
        NS_FAILED(TelemetryScalar::DeserializePersistedScalars(jsapi.cx(),
                                                               scalarData))) {
      ANDROID_LOG(
          "MainThreadParsePersistedProbes - Failed to parse 'scalars'.");
      MOZ_ASSERT(!JS_IsExceptionPending(jsapi.cx()),
                 "Parsers must suppress exceptions themselves");
    }
  } else {
    // Getting the "scalars" property failed, suppress the exception
    // and continue.
    JS_ClearPendingException(jsapi.cx());
  }

  JS::RootedValue keyedScalarData(jsapi.cx());
  if (JS_GetProperty(jsapi.cx(), dataObj, "keyedScalars", &keyedScalarData)) {
    // If the data is an object, try to parse its properties. If not,
    // silently skip and try to load the other sections.
    if (!keyedScalarData.isObject() ||
        NS_FAILED(TelemetryScalar::DeserializePersistedKeyedScalars(
            jsapi.cx(), keyedScalarData))) {
      ANDROID_LOG(
          "MainThreadParsePersistedProbes - Failed to parse 'keyedScalars'.");
      MOZ_ASSERT(!JS_IsExceptionPending(jsapi.cx()),
                 "Parsers must suppress exceptions themselves");
    }
  } else {
    // Getting the "keyedScalars" property failed, suppress the exception
    // and continue.
    JS_ClearPendingException(jsapi.cx());
  }

  // Get the data for the histograms.
  JS::RootedValue histogramData(jsapi.cx());
  if (JS_GetProperty(jsapi.cx(), dataObj, "histograms", &histogramData)) {
    // If the data is an object, try to parse its properties. If not,
    // silently skip and try to load the other sections.
    nsresult rv = NS_OK;
    if (!histogramData.isObject() ||
        NS_FAILED(rv = TelemetryHistogram::DeserializeHistograms(
                      jsapi.cx(), histogramData))) {
      nsAutoCString errorName;
      GetErrorName(rv, errorName);
      ANDROID_LOG(
          "MainThreadParsePersistedProbes - Failed to parse 'histograms', %s.",
          errorName.get());
      MOZ_ASSERT(!JS_IsExceptionPending(jsapi.cx()),
                 "Parsers must suppress exceptions themselves");
    }
  } else {
    // Getting the "histogramData" property failed, suppress the exception
    // and continue.
    JS_ClearPendingException(jsapi.cx());
  }

  // Get the data for the keyed histograms.
  JS::RootedValue keyedHistogramData(jsapi.cx());
  if (JS_GetProperty(jsapi.cx(), dataObj, "keyedHistograms",
                     &keyedHistogramData)) {
    // If the data is an object, try to parse its properties. If not,
    // silently skip and try to load the other sections.
    nsresult rv = NS_OK;
    if (!keyedHistogramData.isObject() ||
        NS_FAILED(rv = TelemetryHistogram::DeserializeKeyedHistograms(
                      jsapi.cx(), keyedHistogramData))) {
      nsAutoCString errorName;
      GetErrorName(rv, errorName);
      ANDROID_LOG(
          "MainThreadParsePersistedProbes - Failed to parse 'keyedHistograms', "
          "%s.",
          errorName.get());
      MOZ_ASSERT(!JS_IsExceptionPending(jsapi.cx()),
                 "Parsers must suppress exceptions themselves");
    }
  } else {
    // Getting the "keyedHistogramData" property failed, suppress the exception
    // and continue.
    JS_ClearPendingException(jsapi.cx());
  }
}

/**
 * The persistence worker function, meant to be run off the main thread.
 */
void PersistenceThreadPersist() {
  MOZ_ASSERT(XRE_IsParentProcess(),
             "We must only persist from the parent process.");
  MOZ_ASSERT(!NS_IsMainThread(),
             "This function must be called off the main thread.");
  ANDROID_LOG("PersistenceThreadPersist");

  // If the function completes or fails, make sure to spin up the persistence
  // timer again.
  auto scopedArmTimer = MakeScopeExit([&] {
    NS_DispatchToMainThread(NS_NewRunnableFunction(
        "MainThreadArmPersistenceTimer",
        []() -> void { MainThreadArmPersistenceTimer(); }));
  });

  nsCOMPtr<nsIFile> persistenceFile;
  if (NS_FAILED(GetPersistenceFile(persistenceFile))) {
    ANDROID_LOG(
        "PersistenceThreadPersist - Failed to get the persistence file.");
    return;
  }

  // Open the persistence file.
  mozilla::UniquePtr<StreamingJSONWriter> jsonWriter =
      mozilla::MakeUnique<StreamingJSONWriter>();

  if (!jsonWriter || NS_FAILED(jsonWriter->Open(persistenceFile))) {
    ANDROID_LOG(
        "PersistenceThreadPersist - There was an error opening the persistence "
        "file.");
    return;
  }

  // Build the JSON structure: give up the ownership of jsonWriter.
  mozilla::JSONWriter w(std::move(jsonWriter));
  w.Start();

  w.StartObjectProperty("scalars");
  if (NS_FAILED(TelemetryScalar::SerializeScalars(w))) {
    ANDROID_LOG("Persist - Failed to persist scalars.");
  }
  w.EndObject();

  w.StartObjectProperty("keyedScalars");
  if (NS_FAILED(TelemetryScalar::SerializeKeyedScalars(w))) {
    ANDROID_LOG("Persist - Failed to persist keyed scalars.");
  }
  w.EndObject();

  w.StartObjectProperty("histograms");
  if (NS_FAILED(TelemetryHistogram::SerializeHistograms(w))) {
    ANDROID_LOG("Persist - Failed to persist histograms.");
  }
  w.EndObject();

  w.StartObjectProperty("keyedHistograms");
  if (NS_FAILED(TelemetryHistogram::SerializeKeyedHistograms(w))) {
    ANDROID_LOG("Persist - Failed to persist keyed histograms.");
  }
  w.EndObject();

  // End the building process.
  w.End();

  // Android can kill us while we are writing to disk and, if that happens,
  // we end up with a corrupted json overwriting the old session data.
  // Luckily, |StreamingJSONWriter::Close| is smart enough to write to a
  // temporary file and only overwrite the original file if nothing bad
  // happened.
  nsresult rv = static_cast<StreamingJSONWriter*>(w.WriteFunc())->Close();
  if (NS_FAILED(rv)) {
    ANDROID_LOG(
        "PersistenceThreadPersist - There was an error writing to the "
        "persistence file.");
    return;
  }
}

/**
 * This function loads the persisted metrics from a JSON file
 * and adds them to the related storage. After it completes,
 * it spins up the persistence timer.
 *
 * Please note that this function is meant to be run off the
 * main-thread.
 */
void PersistenceThreadLoadData() {
  MOZ_ASSERT(XRE_IsParentProcess(),
             "We must only persist from the parent process.");
  MOZ_ASSERT(!NS_IsMainThread(), "We must perform I/O off the main thread.");
  ANDROID_LOG("PersistenceThreadLoadData");

  // If the function completes or fails, make sure to spin up the persistence
  // timer.
  nsAutoCString fileContent;
  auto scopedArmTimer = MakeScopeExit([&] {
    NS_DispatchToMainThread(NS_NewRunnableFunction(
        "MainThreadArmPersistenceTimer", [fileContent]() -> void {
          // Try to parse the probes if the file was not empty.
          if (!fileContent.IsEmpty()) {
            MainThreadParsePersistedProbes(fileContent);
          }

          TelemetryScalar::ApplyPendingOperations();

          // Arm the timer.
          MainThreadArmPersistenceTimer();
          // Notify that we're good to take snapshots!
          nsCOMPtr<nsIObserverService> os =
              mozilla::services::GetObserverService();
          if (os) {
            os->NotifyObservers(nullptr, kLoadCompleteTopic, nullptr);
          }
        }));
  });

  // Attempt to load the persistence file. This could fail if we're not able
  // to allocate enough memory for the content. See bug 1460911.
  nsCOMPtr<nsIFile> persistenceFile;
  if (NS_FAILED(GetPersistenceFile(persistenceFile)) ||
      NS_FAILED(ReadFromFile(persistenceFile, fileContent))) {
    ANDROID_LOG("PersistenceThreadLoadData - Failed to load cache file at %s",
                persistenceFile->HumanReadablePath().get());
    return;
  }
}

}  // anonymous namespace

// This namespace exposes testing only helpers to simplify writing
// gtest cases.
namespace TelemetryGeckoViewTesting {

void TestDispatchPersist() {
  gPersistenceThread->Dispatch(NS_NewRunnableFunction(
      "Persist", []() -> void { ::PersistenceThreadPersist(); }));
}

}  // namespace TelemetryGeckoViewTesting

void TelemetryGeckoViewPersistence::InitPersistence() {
  MOZ_ASSERT(NS_IsMainThread());

  if (gPersistenceThread) {
    ANDROID_LOG("Init must only be called once.");
    return;
  }

  // Only register the persistence timer in the parent process in
  // order to persist data for all the processes.
  if (!XRE_IsParentProcess()) {
    ANDROID_LOG("InitPersistence - Bailing out on child process.");
    return;
  }

  ANDROID_LOG("InitPersistence");

  // Spawn a new thread for handling GeckoView Telemetry persistence I/O.
  // We just spawn it once and re-use it later.
  nsCOMPtr<nsIThread> thread;
  nsresult rv = NS_NewNamedThread("TelemetryGVIO", getter_AddRefs(thread));
  if (NS_WARN_IF(NS_FAILED(rv))) {
    ANDROID_LOG("InitPersistence -  Failed to instantiate the worker thread.");
    return;
  }

  gPersistenceThread = ToRefPtr(std::move(thread));

  // From now on all scalar operations should be recorded.
  TelemetryScalar::DeserializationStarted();

  // Trigger the loading of the persistence data. After the function
  // completes it will automatically arm the persistence timer.
  gPersistenceThread->Dispatch(NS_NewRunnableFunction(
      "PersistenceThreadLoadData", &PersistenceThreadLoadData));
}

void TelemetryGeckoViewPersistence::DeInitPersistence() {
  MOZ_ASSERT(NS_IsMainThread());

  // Bail out if this is not the parent process.
  if (!XRE_IsParentProcess()) {
    ANDROID_LOG("DeInitPersistence - Bailing out.");
    return;
  }

  // Even though we need to implement this function, it might end up
  // not being called: Android might kill us without notice to reclaim
  // our memory in case some other foreground application needs it.
  ANDROID_LOG("DeInitPersistence");

  if (gPersistenceThread) {
    gPersistenceThread->Shutdown();
    gPersistenceThread = nullptr;
  }

  if (gPersistenceTimer) {
    // Always make sure the timer is canceled.
    MOZ_ALWAYS_SUCCEEDS(gPersistenceTimer->Cancel());
    NS_RELEASE(gPersistenceTimer);
  }
}

void TelemetryGeckoViewPersistence::ClearPersistenceData() {
  // This can be run on any thread, as we just dispatch the persistence
  // task to the persistence thread.
  MOZ_ASSERT(gPersistenceThread);

  ANDROID_LOG("ClearPersistenceData");

  // Trigger clearing the persisted measurements off the main thread.
  gPersistenceThread->Dispatch(
      NS_NewRunnableFunction("ClearPersistedData", []() -> void {
        nsCOMPtr<nsIFile> persistenceFile;
        if (NS_FAILED(GetPersistenceFile(persistenceFile)) ||
            NS_FAILED(persistenceFile->Remove(false))) {
          ANDROID_LOG(
              "ClearPersistenceData - Failed to remove the persistence file.");
          return;
        }
      }));
}