storage/mozStorageAsyncStatementExecution.cpp
author Chris H-C <chutten@mozilla.com>
Mon, 04 Jul 2016 11:16:05 -0400
changeset 312997 df28918fe2361f0b54ca9ce4773a29c4c0675d06
parent 312382 93657f8dedaafa384bcd49c71b52e195ec968de8
child 313022 9f60d4e661e40a33d866ad5006e8a2f5f9007a89
permissions -rw-r--r--
bug 1218576 - Support remote accumulation via JS histograms. r=gfritzsche The JS histograms, too, need to dispatch their accumulations from child to parent. JSHistograms_Add now only supports histograms that are in gHistogramsMap or that were created in the parent process. After bug 1288745, maybe we'll be able to change this to be less convoluted. MozReview-Commit-ID: 3qTH89YKbGP

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
 * 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 "nsAutoPtr.h"

#include "sqlite3.h"

#include "mozIStorageStatementCallback.h"
#include "mozStorageBindingParams.h"
#include "mozStorageHelper.h"
#include "mozStorageResultSet.h"
#include "mozStorageRow.h"
#include "mozStorageConnection.h"
#include "mozStorageError.h"
#include "mozStoragePrivateHelpers.h"
#include "mozStorageStatementData.h"
#include "mozStorageAsyncStatementExecution.h"

#include "mozilla/DebugOnly.h"
#include "mozilla/Telemetry.h"

namespace mozilla {
namespace storage {

/**
 * The following constants help batch rows into result sets.
 * MAX_MILLISECONDS_BETWEEN_RESULTS was chosen because any user-based task that
 * takes less than 200 milliseconds is considered to feel instantaneous to end
 * users.  MAX_ROWS_PER_RESULT was arbitrarily chosen to reduce the number of
 * dispatches to calling thread, while also providing reasonably-sized sets of
 * data for consumers.  Both of these constants are used because we assume that
 * consumers are trying to avoid blocking their execution thread for long
 * periods of time, and dispatching many small events to the calling thread will
 * end up blocking it.
 */
#define MAX_MILLISECONDS_BETWEEN_RESULTS 75
#define MAX_ROWS_PER_RESULT 15

////////////////////////////////////////////////////////////////////////////////
//// Local Classes

namespace {

typedef AsyncExecuteStatements::ExecutionState ExecutionState;
typedef AsyncExecuteStatements::StatementDataArray StatementDataArray;

/**
 * Notifies a callback with a result set.
 */
class CallbackResultNotifier : public Runnable
{
public:
  CallbackResultNotifier(mozIStorageStatementCallback *aCallback,
                         mozIStorageResultSet *aResults,
                         AsyncExecuteStatements *aEventStatus) :
      mCallback(aCallback)
    , mResults(aResults)
    , mEventStatus(aEventStatus)
  {
  }

  NS_IMETHOD Run() override
  {
    NS_ASSERTION(mCallback, "Trying to notify about results without a callback!");

    if (mEventStatus->shouldNotify()) {
      // Hold a strong reference to the callback while notifying it, so that if
      // it spins the event loop, the callback won't be released and freed out
      // from under us.
      nsCOMPtr<mozIStorageStatementCallback> callback =
        do_QueryInterface(mCallback);

      (void)mCallback->HandleResult(mResults);
    }

    return NS_OK;
  }

private:
  mozIStorageStatementCallback *mCallback;
  nsCOMPtr<mozIStorageResultSet> mResults;
  RefPtr<AsyncExecuteStatements> mEventStatus;
};

/**
 * Notifies the calling thread that an error has occurred.
 */
class ErrorNotifier : public Runnable
{
public:
  ErrorNotifier(mozIStorageStatementCallback *aCallback,
                mozIStorageError *aErrorObj,
                AsyncExecuteStatements *aEventStatus) :
      mCallback(aCallback)
    , mErrorObj(aErrorObj)
    , mEventStatus(aEventStatus)
  {
  }

  NS_IMETHOD Run() override
  {
    if (mEventStatus->shouldNotify() && mCallback) {
      // Hold a strong reference to the callback while notifying it, so that if
      // it spins the event loop, the callback won't be released and freed out
      // from under us.
      nsCOMPtr<mozIStorageStatementCallback> callback =
        do_QueryInterface(mCallback);

      (void)mCallback->HandleError(mErrorObj);
    }

    return NS_OK;
  }

private:
  mozIStorageStatementCallback *mCallback;
  nsCOMPtr<mozIStorageError> mErrorObj;
  RefPtr<AsyncExecuteStatements> mEventStatus;
};

/**
 * Notifies the calling thread that the statement has finished executing.  Takes
 * ownership of the StatementData so it is released on the proper thread.
 */
class CompletionNotifier : public Runnable
{
public:
  /**
   * This takes ownership of the callback and the StatementData.  They are
   * released on the thread this is dispatched to (which should always be the
   * calling thread).
   */
  CompletionNotifier(mozIStorageStatementCallback *aCallback,
                     ExecutionState aReason)
    : mCallback(aCallback)
    , mReason(aReason)
  {
  }

  NS_IMETHOD Run() override
  {
    if (mCallback) {
      (void)mCallback->HandleCompletion(mReason);
      NS_RELEASE(mCallback);
    }

    return NS_OK;
  }

private:
  mozIStorageStatementCallback *mCallback;
  ExecutionState mReason;
};

} // namespace

////////////////////////////////////////////////////////////////////////////////
//// AsyncExecuteStatements

/* static */
nsresult
AsyncExecuteStatements::execute(StatementDataArray &aStatements,
                                Connection *aConnection,
                                sqlite3 *aNativeConnection,
                                mozIStorageStatementCallback *aCallback,
                                mozIStoragePendingStatement **_stmt)
{
  // Create our event to run in the background
  RefPtr<AsyncExecuteStatements> event =
    new AsyncExecuteStatements(aStatements, aConnection, aNativeConnection,
                               aCallback);
  NS_ENSURE_TRUE(event, NS_ERROR_OUT_OF_MEMORY);

  // Dispatch it to the background
  nsIEventTarget *target = aConnection->getAsyncExecutionTarget();

  // If we don't have a valid target, this is a bug somewhere else. In the past,
  // this assert found cases where a Run method would schedule a new statement
  // without checking if asyncClose had been called. The caller must prevent
  // that from happening or, if the work is not critical, just avoid creating
  // the new statement during shutdown. See bug 718449 for an example.
  MOZ_ASSERT(target);
  if (!target) {
    return NS_ERROR_NOT_AVAILABLE;
  }

  nsresult rv = target->Dispatch(event, NS_DISPATCH_NORMAL);
  NS_ENSURE_SUCCESS(rv, rv);

  // Return it as the pending statement object and track it.
  event.forget(_stmt);
  return NS_OK;
}

AsyncExecuteStatements::AsyncExecuteStatements(StatementDataArray &aStatements,
                                               Connection *aConnection,
                                               sqlite3 *aNativeConnection,
                                               mozIStorageStatementCallback *aCallback)
: mConnection(aConnection)
, mNativeConnection(aNativeConnection)
, mHasTransaction(false)
, mCallback(aCallback)
, mCallingThread(::do_GetCurrentThread())
, mMaxWait(TimeDuration::FromMilliseconds(MAX_MILLISECONDS_BETWEEN_RESULTS))
, mIntervalStart(TimeStamp::Now())
, mState(PENDING)
, mCancelRequested(false)
, mMutex(aConnection->sharedAsyncExecutionMutex)
, mDBMutex(aConnection->sharedDBMutex)
  , mRequestStartDate(TimeStamp::Now())
{
  (void)mStatements.SwapElements(aStatements);
  NS_ASSERTION(mStatements.Length(), "We weren't given any statements!");
  NS_IF_ADDREF(mCallback);
}

AsyncExecuteStatements::~AsyncExecuteStatements()
{
  MOZ_ASSERT(!mHasTransaction, "There should be no transaction at this point");
}

bool
AsyncExecuteStatements::shouldNotify()
{
#ifdef DEBUG
  mMutex.AssertNotCurrentThreadOwns();

  bool onCallingThread = false;
  (void)mCallingThread->IsOnCurrentThread(&onCallingThread);
  NS_ASSERTION(onCallingThread, "runEvent not running on the calling thread!");
#endif

  // We do not need to acquire mMutex here because it can only ever be written
  // to on the calling thread, and the only thread that can call us is the
  // calling thread, so we know that our access is serialized.
  return !mCancelRequested;
}

bool
AsyncExecuteStatements::bindExecuteAndProcessStatement(StatementData &aData,
                                                       bool aLastStatement)
{
  mMutex.AssertNotCurrentThreadOwns();

  sqlite3_stmt *aStatement = nullptr;
  // This cannot fail; we are only called if it's available.
  (void)aData.getSqliteStatement(&aStatement);
  NS_ASSERTION(aStatement, "You broke the code; do not call here like that!");
  BindingParamsArray *paramsArray(aData);

  // Iterate through all of our parameters, bind them, and execute.
  bool continueProcessing = true;
  BindingParamsArray::iterator itr = paramsArray->begin();
  BindingParamsArray::iterator end = paramsArray->end();
  while (itr != end && continueProcessing) {
    // Bind the data to our statement.
    nsCOMPtr<IStorageBindingParamsInternal> bindingInternal = 
      do_QueryInterface(*itr);
    nsCOMPtr<mozIStorageError> error = bindingInternal->bind(aStatement);
    if (error) {
      // Set our error state.
      mState = ERROR;

      // And notify.
      (void)notifyError(error);
      return false;
    }

    // Advance our iterator, execute, and then process the statement.
    itr++;
    bool lastStatement = aLastStatement && itr == end;
    continueProcessing = executeAndProcessStatement(aStatement, lastStatement);

    // Always reset our statement.
    (void)::sqlite3_reset(aStatement);
  }

  return continueProcessing;
}

bool
AsyncExecuteStatements::executeAndProcessStatement(sqlite3_stmt *aStatement,
                                                   bool aLastStatement)
{
  mMutex.AssertNotCurrentThreadOwns();

  // Execute our statement
  bool hasResults;
  do {
    hasResults = executeStatement(aStatement);

    // If we had an error, bail.
    if (mState == ERROR)
      return false;

    // If we have been canceled, there is no point in going on...
    {
      MutexAutoLock lockedScope(mMutex);
      if (mCancelRequested) {
        mState = CANCELED;
        return false;
      }
    }

    // Build our result set and notify if we got anything back and have a
    // callback to notify.
    if (mCallback && hasResults &&
        NS_FAILED(buildAndNotifyResults(aStatement))) {
      // We had an error notifying, so we notify on error and stop processing.
      mState = ERROR;

      // Notify, and stop processing statements.
      (void)notifyError(mozIStorageError::ERROR,
                        "An error occurred while notifying about results");

      return false;
    }
  } while (hasResults);

#ifndef MOZ_STORAGE_SORTWARNING_SQL_DUMP
  if (MOZ_LOG_TEST(gStorageLog, LogLevel::Warning))
#endif
  {
    // Check to make sure that this statement was smart about what it did.
    checkAndLogStatementPerformance(aStatement);
  }

  // If we are done, we need to set our state accordingly while we still hold
  // our mutex.  We would have already returned if we were canceled or had
  // an error at this point.
  if (aLastStatement)
    mState = COMPLETED;

  return true;
}

bool
AsyncExecuteStatements::executeStatement(sqlite3_stmt *aStatement)
{
  mMutex.AssertNotCurrentThreadOwns();
  Telemetry::AutoTimer<Telemetry::MOZ_STORAGE_ASYNC_REQUESTS_MS> finallySendExecutionDuration(mRequestStartDate);
  while (true) {
    // lock the sqlite mutex so sqlite3_errmsg cannot change
    SQLiteMutexAutoLock lockedScope(mDBMutex);

    int rc = mConnection->stepStatement(mNativeConnection, aStatement);
    // Stop if we have no more results.
    if (rc == SQLITE_DONE)
    {
      Telemetry::Accumulate(Telemetry::MOZ_STORAGE_ASYNC_REQUESTS_SUCCESS, true);
      return false;
    }

    // If we got results, we can return now.
    if (rc == SQLITE_ROW)
    {
      Telemetry::Accumulate(Telemetry::MOZ_STORAGE_ASYNC_REQUESTS_SUCCESS, true);
      return true;
    }

    // Some errors are not fatal, and we can handle them and continue.
    if (rc == SQLITE_BUSY) {
      // Don't hold the lock while we call outside our module.
      SQLiteMutexAutoUnlock unlockedScope(mDBMutex);

      // Yield, and try again
      (void)::PR_Sleep(PR_INTERVAL_NO_WAIT);
      continue;
    }

    // Set an error state.
    mState = ERROR;
    Telemetry::Accumulate(Telemetry::MOZ_STORAGE_ASYNC_REQUESTS_SUCCESS, false);

    // Construct the error message before giving up the mutex (which we cannot
    // hold during the call to notifyError).
    nsCOMPtr<mozIStorageError> errorObj(
      new Error(rc, ::sqlite3_errmsg(mNativeConnection))
    );
    // We cannot hold the DB mutex while calling notifyError.
    SQLiteMutexAutoUnlock unlockedScope(mDBMutex);
    (void)notifyError(errorObj);

    // Finally, indicate that we should stop processing.
    return false;
  }
}

nsresult
AsyncExecuteStatements::buildAndNotifyResults(sqlite3_stmt *aStatement)
{
  NS_ASSERTION(mCallback, "Trying to dispatch results without a callback!");
  mMutex.AssertNotCurrentThreadOwns();

  // Build result object if we need it.
  if (!mResultSet)
    mResultSet = new ResultSet();
  NS_ENSURE_TRUE(mResultSet, NS_ERROR_OUT_OF_MEMORY);

  RefPtr<Row> row(new Row());
  NS_ENSURE_TRUE(row, NS_ERROR_OUT_OF_MEMORY);

  nsresult rv = row->initialize(aStatement);
  NS_ENSURE_SUCCESS(rv, rv);

  rv = mResultSet->add(row);
  NS_ENSURE_SUCCESS(rv, rv);

  // If we have hit our maximum number of allowed results, or if we have hit
  // the maximum amount of time we want to wait for results, notify the
  // calling thread about it.
  TimeStamp now = TimeStamp::Now();
  TimeDuration delta = now - mIntervalStart;
  if (mResultSet->rows() >= MAX_ROWS_PER_RESULT || delta > mMaxWait) {
    // Notify the caller
    rv = notifyResults();
    if (NS_FAILED(rv))
      return NS_OK; // we'll try again with the next result

    // Reset our start time
    mIntervalStart = now;
  }

  return NS_OK;
}

nsresult
AsyncExecuteStatements::notifyComplete()
{
  mMutex.AssertNotCurrentThreadOwns();
  NS_ASSERTION(mState != PENDING,
               "Still in a pending state when calling Complete!");

  // Reset our statements before we try to commit or rollback.  If we are
  // canceling and have statements that think they have pending work, the
  // rollback will fail.
  for (uint32_t i = 0; i < mStatements.Length(); i++)
    mStatements[i].reset();

  // Release references to the statement data as soon as possible. If this
  // is the last reference, statements will be finalized immediately on the
  // async thread, hence avoiding several bounces between threads and possible
  // race conditions with AsyncClose().
  mStatements.Clear();

  // Handle our transaction, if we have one
  if (mHasTransaction) {
    if (mState == COMPLETED) {
      nsresult rv = mConnection->commitTransactionInternal(mNativeConnection);
      if (NS_FAILED(rv)) {
        mState = ERROR;
        (void)notifyError(mozIStorageError::ERROR,
                          "Transaction failed to commit");
      }
    }
    else {
      DebugOnly<nsresult> rv =
        mConnection->rollbackTransactionInternal(mNativeConnection);
      NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "Transaction failed to rollback");
    }
    mHasTransaction = false;
  }

  // Always generate a completion notification; it is what guarantees that our
  // destruction does not happen here on the async thread.
  RefPtr<CompletionNotifier> completionEvent =
    new CompletionNotifier(mCallback, mState);

  // We no longer own mCallback (the CompletionNotifier takes ownership).
  mCallback = nullptr;

  (void)mCallingThread->Dispatch(completionEvent, NS_DISPATCH_NORMAL);

  return NS_OK;
}

nsresult
AsyncExecuteStatements::notifyError(int32_t aErrorCode,
                                    const char *aMessage)
{
  mMutex.AssertNotCurrentThreadOwns();
  mDBMutex.assertNotCurrentThreadOwns();

  if (!mCallback)
    return NS_OK;

  nsCOMPtr<mozIStorageError> errorObj(new Error(aErrorCode, aMessage));
  NS_ENSURE_TRUE(errorObj, NS_ERROR_OUT_OF_MEMORY);

  return notifyError(errorObj);
}

nsresult
AsyncExecuteStatements::notifyError(mozIStorageError *aError)
{
  mMutex.AssertNotCurrentThreadOwns();
  mDBMutex.assertNotCurrentThreadOwns();

  if (!mCallback)
    return NS_OK;

  RefPtr<ErrorNotifier> notifier =
    new ErrorNotifier(mCallback, aError, this);
  NS_ENSURE_TRUE(notifier, NS_ERROR_OUT_OF_MEMORY);

  return mCallingThread->Dispatch(notifier, NS_DISPATCH_NORMAL);
}

nsresult
AsyncExecuteStatements::notifyResults()
{
  mMutex.AssertNotCurrentThreadOwns();
  NS_ASSERTION(mCallback, "notifyResults called without a callback!");

  RefPtr<CallbackResultNotifier> notifier =
    new CallbackResultNotifier(mCallback, mResultSet, this);
  NS_ENSURE_TRUE(notifier, NS_ERROR_OUT_OF_MEMORY);

  nsresult rv = mCallingThread->Dispatch(notifier, NS_DISPATCH_NORMAL);
  if (NS_SUCCEEDED(rv))
    mResultSet = nullptr; // we no longer own it on success
  return rv;
}

NS_IMPL_ISUPPORTS(
  AsyncExecuteStatements,
  nsIRunnable,
  mozIStoragePendingStatement
)

bool
AsyncExecuteStatements::statementsNeedTransaction()
{
  // If there is more than one write statement, run in a transaction.
  // Additionally, if we have only one statement but it needs a transaction, due
  // to multiple BindingParams, we will wrap it in one.
  for (uint32_t i = 0, transactionsCount = 0; i < mStatements.Length(); ++i) {
    transactionsCount += mStatements[i].needsTransaction();
    if (transactionsCount > 1) {
      return true;
    }
  }
  return false;
}

////////////////////////////////////////////////////////////////////////////////
//// mozIStoragePendingStatement

NS_IMETHODIMP
AsyncExecuteStatements::Cancel()
{
#ifdef DEBUG
  bool onCallingThread = false;
  (void)mCallingThread->IsOnCurrentThread(&onCallingThread);
  NS_ASSERTION(onCallingThread, "Not canceling from the calling thread!");
#endif

  // If we have already canceled, we have an error, but always indicate that
  // we are trying to cancel.
  NS_ENSURE_FALSE(mCancelRequested, NS_ERROR_UNEXPECTED);

  {
    MutexAutoLock lockedScope(mMutex);

    // We need to indicate that we want to try and cancel now.
    mCancelRequested = true;
  }

  return NS_OK;
}

////////////////////////////////////////////////////////////////////////////////
//// nsIRunnable

NS_IMETHODIMP
AsyncExecuteStatements::Run()
{
  MOZ_ASSERT(!mConnection->isClosed());

  // Do not run if we have been canceled.
  {
    MutexAutoLock lockedScope(mMutex);
    if (mCancelRequested)
      mState = CANCELED;
  }
  if (mState == CANCELED)
    return notifyComplete();

  if (statementsNeedTransaction() && mConnection->getAutocommit()) {
    if (NS_SUCCEEDED(mConnection->beginTransactionInternal(mNativeConnection,
                                                           mozIStorageConnection::TRANSACTION_IMMEDIATE))) {
      mHasTransaction = true;
    }
#ifdef DEBUG
    else {
      NS_WARNING("Unable to create a transaction for async execution.");
    }
#endif
  }

  // Execute each statement, giving the callback results if it returns any.
  for (uint32_t i = 0; i < mStatements.Length(); i++) {
    bool finished = (i == (mStatements.Length() - 1));

    sqlite3_stmt *stmt;
    { // lock the sqlite mutex so sqlite3_errmsg cannot change
      SQLiteMutexAutoLock lockedScope(mDBMutex);

      int rc = mStatements[i].getSqliteStatement(&stmt);
      if (rc != SQLITE_OK) {
        // Set our error state.
        mState = ERROR;

        // Build the error object; can't call notifyError with the lock held
        nsCOMPtr<mozIStorageError> errorObj(
          new Error(rc, ::sqlite3_errmsg(mNativeConnection))
        );
        {
          // We cannot hold the DB mutex and call notifyError.
          SQLiteMutexAutoUnlock unlockedScope(mDBMutex);
          (void)notifyError(errorObj);
        }
        break;
      }
    }

    // If we have parameters to bind, bind them, execute, and process.
    if (mStatements[i].hasParametersToBeBound()) {
      if (!bindExecuteAndProcessStatement(mStatements[i], finished))
        break;
    }
    // Otherwise, just execute and process the statement.
    else if (!executeAndProcessStatement(stmt, finished)) {
      break;
    }
  }

  // If we still have results that we haven't notified about, take care of
  // them now.
  if (mResultSet)
    (void)notifyResults();

  // Notify about completion
  return notifyComplete();
}

} // namespace storage
} // namespace mozilla