storage/mozStorageAsyncStatementExecution.cpp
author Jim Blandy <jimb@mozilla.com>
Tue, 12 Feb 2019 08:16:16 +0000
changeset 458932 414b2c238839c321dee78a9d927c968f1e52ae79
parent 448947 6f3709b3878117466168c40affa7bca0b60cf75b
child 472056 e1993a1f09ac53cd1a04fdf6a87f8cad8e44f73e
permissions -rw-r--r--
Bug 1145201: Replace EnqueuePromiseJobCallback and GetIncumbentGlobalCallback with new JobQueue abstract base class. r=arai,smaug While the behavior of ECMAScript Promises and their associated job queue is covered by the ECMAScript standard, the HTML specification amends that with additional behavior the web platform requires. To support this, SpiderMonkey provides hooks the embedding can set to replace SpiderMonkey's queue with its own implementation. At present, these hooks are C-style function-pointer-and-void-pointer pairs, which are awkward to handle and mistake-prone, as passing a function the wrong void* is not a type error. Later patches in this series must add new hooks, making a bad situation worse. A C++ abstract base class is a well-typed alternative. This introduces a new `JS::JobQueue` abstract class, and adapts SpiderMonkey's internal job queue and Gecko's customization to use it. `GetIncumbentGlobalCallback` and `EnqueuePromiseJobCallback` become virtual methods. Within SpiderMonkey, the patch gathers the various fields of JSContext that implement the internal queue into their own type, js::InternalJobQueue. Various jsfriendapi functions become veneers for calls to methods specific to the derived class. The InternalJobQueue type itself remains private to SpiderMonkey, as it uses types like TraceableFifo, derived from Fifo, that are not part of SpiderMonkey's public API. Within Gecko, CycleCollectedJSContext acquires JS::JobQueue as a private base class, and a few static methods are cleaned up nicely. There are a few other hooks defined in js/public/Promise.h that might make sense to turn into virtual methods on JobQueue. For example, DispatchToEventLoopCallback, used for resolving promises of results from off-main-thread tasks, is probably necessarily connected to the JobQueue implementation in use, so it might not be sensible to set one without the other. But it was left unchanged to reduce this patch's size. Differential Revision: https://phabricator.services.mozilla.com/D17544

/* -*- 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

////////////////////////////////////////////////////////////////////////////////
//// 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!");
}

AsyncExecuteStatements::~AsyncExecuteStatements() {
  MOZ_ASSERT(!mCallback, "Never called the Completion callback!");
  MOZ_ASSERT(!mHasTransaction, "There should be no transaction at this point");
  if (mCallback) {
    NS_ProxyRelease("AsyncExecuteStatements::mCallback", mCallingThread,
                    mCallback.forget());
  }
}

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 || mState == CANCELED) 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);
      }
      ::sqlite3_reset(aStatement);
      continue;
    }

    if (rc == SQLITE_INTERRUPT) {
      mState = CANCELED;
      return false;
    }

    // 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;
  }

  // This will take ownership of mCallback and make sure its destruction will
  // happen on the owner thread.
  Unused << mCallingThread->Dispatch(
      NewRunnableMethod("AsyncExecuteStatements::notifyCompleteOnCallingThread",
                        this,
                        &AsyncExecuteStatements::notifyCompleteOnCallingThread),
      NS_DISPATCH_NORMAL);

  return NS_OK;
}

nsresult AsyncExecuteStatements::notifyCompleteOnCallingThread() {
  MOZ_ASSERT(mCallingThread->IsOnCurrentThread());
  // Take ownership of mCallback and responsibility for freeing it when we
  // release it.  Any notifyResultsOnCallingThread and
  // notifyErrorOnCallingThread calls on the stack spinning the event loop have
  // guaranteed their safety by creating their own strong reference before
  // invoking the callback.
  nsCOMPtr<mozIStorageStatementCallback> callback = mCallback.forget();
  if (callback) {
    Unused << callback->HandleCompletion(mState);
  }
  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;

  Unused << mCallingThread->Dispatch(
      NewRunnableMethod<nsCOMPtr<mozIStorageError>>(
          "AsyncExecuteStatements::notifyErrorOnCallingThread", this,
          &AsyncExecuteStatements::notifyErrorOnCallingThread, aError),
      NS_DISPATCH_NORMAL);

  return NS_OK;
}

nsresult AsyncExecuteStatements::notifyErrorOnCallingThread(
    mozIStorageError *aError) {
  MOZ_ASSERT(mCallingThread->IsOnCurrentThread());
  // Acquire our own strong reference so that if the callback spins a nested
  // event loop and notifyCompleteOnCallingThread is executed, forgetting
  // mCallback, we still have a valid/strong reference that won't be freed until
  // we exit.
  nsCOMPtr<mozIStorageStatementCallback> callback = mCallback;
  if (shouldNotify() && callback) {
    Unused << callback->HandleError(aError);
  }
  return NS_OK;
}

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

  // This takes ownership of mResultSet, a new one will be generated in
  // buildAndNotifyResults() when further results will arrive.
  Unused << mCallingThread->Dispatch(
      NewRunnableMethod<RefPtr<ResultSet>>(
          "AsyncExecuteStatements::notifyResultsOnCallingThread", this,
          &AsyncExecuteStatements::notifyResultsOnCallingThread,
          mResultSet.forget()),
      NS_DISPATCH_NORMAL);

  return NS_OK;
}

nsresult AsyncExecuteStatements::notifyResultsOnCallingThread(
    ResultSet *aResultSet) {
  MOZ_ASSERT(mCallingThread->IsOnCurrentThread());
  // Acquire our own strong reference so that if the callback spins a nested
  // event loop and notifyCompleteOnCallingThread is executed, forgetting
  // mCallback, we still have a valid/strong reference that won't be freed until
  // we exit.
  nsCOMPtr<mozIStorageStatementCallback> callback = mCallback;
  if (shouldNotify() && callback) {
    Unused << callback->HandleResult(aResultSet);
  }
  return NS_OK;
}

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->isConnectionReadyOnThisThread());

  // 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