storage/VacuumManager.cpp
author Nicholas Nethercote <nnethercote@mozilla.com>
Fri, 16 Feb 2018 17:54:16 +1100
changeset 407868 32d6774930e55be5c03e8d631fc067a995623c1e
parent 399161 8357c080dccbe4c6aaba3d9e012b3262f45ff7f6
child 423666 33346f699996421fc8bf22a25f574de470142a41
permissions -rw-r--r--
Bug 1438678 - Pass early prefs via shared memory instead of the command line. r=bobowen,jld,glandium. This patch replaces the large -intPrefs/-boolPrefs/-stringPrefs flags with a short-lived, anonymous, shared memory segment that is used to pass the early prefs. Removing the bloat from the command line is nice, but more important is the fact that this will let us pass more prefs at content process start-up, which will allow us to remove the early/late prefs split (bug 1436911). Although this mechanism is only used for prefs, it's conceivable that it could be used for other data that must be received very early by children, and for which the command line isn't ideal. Notable details: - Much of the patch deals with the various platform-specific ways of passing handles/fds to children. - Linux and Mac: we use a fixed fd (8) in combination with the new GeckoChildProcessHost::AddFdToRemap() function (which ensures the child won't close the fd). - Android: like Linux and Mac, but the handles get passed via "parcels" and we use the new SetPrefsFd() function instead of the fixed fd. - Windows: there is no need to duplicate the handle because Windows handles are system-wide. But we do use the new GeckoChildProcessHost::AddHandleToShare() function to add it to the list of inheritable handles. We also ensure that list is processed on all paths (MOZ_SANDBOX with sandbox, MOZ_SANDBOX without sandbox, non-MOZ_SANDBOX) so that the handles are marked as inheritable. The handle is passed via the -prefsHandle flag. The -prefsLen flag is used on all platforms to indicate the size of the shared memory segment. - The patch also moves the serialization/deserialization of the prefs in/out of the shared memory into libpref, which is a better spot for it. (This means Preferences::MustSendToContentProcesses() can be removed.) MozReview-Commit-ID: 8fREEBiYFvc

/* -*- 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 "mozilla/DebugOnly.h"

#include "VacuumManager.h"

#include "mozilla/Services.h"
#include "mozilla/Preferences.h"
#include "nsIObserverService.h"
#include "nsIFile.h"
#include "nsThreadUtils.h"
#include "mozilla/Logging.h"
#include "prtime.h"

#include "mozStorageConnection.h"
#include "mozIStorageStatement.h"
#include "mozIStorageAsyncStatement.h"
#include "mozIStoragePendingStatement.h"
#include "mozIStorageError.h"
#include "mozStorageHelper.h"
#include "nsXULAppAPI.h"

#define OBSERVER_TOPIC_IDLE_DAILY "idle-daily"
#define OBSERVER_TOPIC_XPCOM_SHUTDOWN "xpcom-shutdown"

// Used to notify begin and end of a heavy IO task.
#define OBSERVER_TOPIC_HEAVY_IO "heavy-io-task"
#define OBSERVER_DATA_VACUUM_BEGIN u"vacuum-begin"
#define OBSERVER_DATA_VACUUM_END u"vacuum-end"

// This preferences root will contain last vacuum timestamps (in seconds) for
// each database.  The database filename is used as a key.
#define PREF_VACUUM_BRANCH "storage.vacuum.last."

// Time between subsequent vacuum calls for a certain database.
#define VACUUM_INTERVAL_SECONDS 30 * 86400 // 30 days.

extern mozilla::LazyLogModule gStorageLog;

namespace mozilla {
namespace storage {

namespace {

////////////////////////////////////////////////////////////////////////////////
//// BaseCallback

class BaseCallback : public mozIStorageStatementCallback
{
public:
  NS_DECL_ISUPPORTS
  NS_DECL_MOZISTORAGESTATEMENTCALLBACK
  BaseCallback() {}
protected:
  virtual ~BaseCallback() {}
};

NS_IMETHODIMP
BaseCallback::HandleError(mozIStorageError *aError)
{
#ifdef DEBUG
  int32_t result;
  nsresult rv = aError->GetResult(&result);
  NS_ENSURE_SUCCESS(rv, rv);
  nsAutoCString message;
  rv = aError->GetMessage(message);
  NS_ENSURE_SUCCESS(rv, rv);

  nsAutoCString warnMsg;
  warnMsg.AppendLiteral("An error occured during async execution: ");
  warnMsg.AppendInt(result);
  warnMsg.Append(' ');
  warnMsg.Append(message);
  NS_WARNING(warnMsg.get());
#endif
  return NS_OK;
}

NS_IMETHODIMP
BaseCallback::HandleResult(mozIStorageResultSet *aResultSet)
{
  // We could get results from PRAGMA statements, but we don't mind them.
  return NS_OK;
}

NS_IMETHODIMP
BaseCallback::HandleCompletion(uint16_t aReason)
{
  // By default BaseCallback will just be silent on completion.
  return NS_OK;
}

NS_IMPL_ISUPPORTS(
  BaseCallback
, mozIStorageStatementCallback
)

////////////////////////////////////////////////////////////////////////////////
//// Vacuumer declaration.

class Vacuumer : public BaseCallback
{
public:
  NS_DECL_MOZISTORAGESTATEMENTCALLBACK

  explicit Vacuumer(mozIStorageVacuumParticipant *aParticipant);

  bool execute();
  nsresult notifyCompletion(bool aSucceeded);

private:
  nsCOMPtr<mozIStorageVacuumParticipant> mParticipant;
  nsCString mDBFilename;
  nsCOMPtr<mozIStorageConnection> mDBConn;
};

////////////////////////////////////////////////////////////////////////////////
//// Vacuumer implementation.

Vacuumer::Vacuumer(mozIStorageVacuumParticipant *aParticipant)
  : mParticipant(aParticipant)
{
}

bool
Vacuumer::execute()
{
  MOZ_ASSERT(NS_IsMainThread(), "Must be running on the main thread!");

  // Get the connection and check its validity.
  nsresult rv = mParticipant->GetDatabaseConnection(getter_AddRefs(mDBConn));
  NS_ENSURE_SUCCESS(rv, false);
  bool ready = false;
  if (!mDBConn || NS_FAILED(mDBConn->GetConnectionReady(&ready)) || !ready) {
    NS_WARNING("Unable to get a connection to vacuum database");
    return false;
  }

  // Ask for the expected page size.  Vacuum can change the page size, unless
  // the database is using WAL journaling.
  // TODO Bug 634374: figure out a strategy to fix page size with WAL.
  int32_t expectedPageSize = 0;
  rv = mParticipant->GetExpectedDatabasePageSize(&expectedPageSize);
  if (NS_FAILED(rv) || !Service::pageSizeIsValid(expectedPageSize)) {
    NS_WARNING("Invalid page size requested for database, will use default ");
    NS_WARNING(mDBFilename.get());
    expectedPageSize = Service::getDefaultPageSize();
  }

  // Get the database filename.  Last vacuum time is stored under this name
  // in PREF_VACUUM_BRANCH.
  nsCOMPtr<nsIFile> databaseFile;
  mDBConn->GetDatabaseFile(getter_AddRefs(databaseFile));
  if (!databaseFile) {
    NS_WARNING("Trying to vacuum a in-memory database!");
    return false;
  }
  nsAutoString databaseFilename;
  rv = databaseFile->GetLeafName(databaseFilename);
  NS_ENSURE_SUCCESS(rv, false);
  mDBFilename = NS_ConvertUTF16toUTF8(databaseFilename);
  MOZ_ASSERT(!mDBFilename.IsEmpty(), "Database filename cannot be empty");

  // Check interval from last vacuum.
  int32_t now = static_cast<int32_t>(PR_Now() / PR_USEC_PER_SEC);
  int32_t lastVacuum;
  nsAutoCString prefName(PREF_VACUUM_BRANCH);
  prefName += mDBFilename;
  rv = Preferences::GetInt(prefName.get(), &lastVacuum);
  if (NS_SUCCEEDED(rv) && (now - lastVacuum) < VACUUM_INTERVAL_SECONDS) {
    // This database was vacuumed recently, skip it.
    return false;
  }

  // Notify that we are about to start vacuuming.  The participant can opt-out
  // if it cannot handle a vacuum at this time, and then we'll move to the next
  // one.
  bool vacuumGranted = false;
  rv = mParticipant->OnBeginVacuum(&vacuumGranted);
  NS_ENSURE_SUCCESS(rv, false);
  if (!vacuumGranted) {
    return false;
  }

  // Notify a heavy IO task is about to start.
  nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
  if (os) {
    rv =
      os->NotifyObservers(nullptr, OBSERVER_TOPIC_HEAVY_IO,
                          OBSERVER_DATA_VACUUM_BEGIN);
    MOZ_ASSERT(NS_SUCCEEDED(rv), "Should be able to notify");
  }

  // Execute the statements separately, since the pragma may conflict with the
  // vacuum, if they are executed in the same transaction.
  nsCOMPtr<mozIStorageAsyncStatement> pageSizeStmt;
  nsAutoCString pageSizeQuery(MOZ_STORAGE_UNIQUIFY_QUERY_STR
                              "PRAGMA page_size = ");
  pageSizeQuery.AppendInt(expectedPageSize);
  rv = mDBConn->CreateAsyncStatement(pageSizeQuery,
                                     getter_AddRefs(pageSizeStmt));
  NS_ENSURE_SUCCESS(rv, false);
  RefPtr<BaseCallback> callback = new BaseCallback();
  nsCOMPtr<mozIStoragePendingStatement> ps;
  rv = pageSizeStmt->ExecuteAsync(callback, getter_AddRefs(ps));
  NS_ENSURE_SUCCESS(rv, false);

  nsCOMPtr<mozIStorageAsyncStatement> stmt;
  rv = mDBConn->CreateAsyncStatement(NS_LITERAL_CSTRING(
    "VACUUM"
  ), getter_AddRefs(stmt));
  NS_ENSURE_SUCCESS(rv, false);
  rv = stmt->ExecuteAsync(this, getter_AddRefs(ps));
  NS_ENSURE_SUCCESS(rv, false);

  return true;
}

////////////////////////////////////////////////////////////////////////////////
//// mozIStorageStatementCallback

NS_IMETHODIMP
Vacuumer::HandleError(mozIStorageError *aError)
{
  int32_t result;
  nsresult rv;
  nsAutoCString message;

#ifdef DEBUG
  rv = aError->GetResult(&result);
  NS_ENSURE_SUCCESS(rv, rv);
  rv = aError->GetMessage(message);
  NS_ENSURE_SUCCESS(rv, rv);

  nsAutoCString warnMsg;
  warnMsg.AppendLiteral("Unable to vacuum database: ");
  warnMsg.Append(mDBFilename);
  warnMsg.AppendLiteral(" - ");
  warnMsg.AppendInt(result);
  warnMsg.Append(' ');
  warnMsg.Append(message);
  NS_WARNING(warnMsg.get());
#endif

  if (MOZ_LOG_TEST(gStorageLog, LogLevel::Error)) {
    rv = aError->GetResult(&result);
    NS_ENSURE_SUCCESS(rv, rv);
    rv = aError->GetMessage(message);
    NS_ENSURE_SUCCESS(rv, rv);
    MOZ_LOG(gStorageLog, LogLevel::Error,
           ("Vacuum failed with error: %d '%s'. Database was: '%s'",
            result, message.get(), mDBFilename.get()));
  }
  return NS_OK;
}

NS_IMETHODIMP
Vacuumer::HandleResult(mozIStorageResultSet *aResultSet)
{
  NS_NOTREACHED("Got a resultset from a vacuum?");
  return NS_OK;
}

NS_IMETHODIMP
Vacuumer::HandleCompletion(uint16_t aReason)
{
  if (aReason == REASON_FINISHED) {
    // Update last vacuum time.
    int32_t now = static_cast<int32_t>(PR_Now() / PR_USEC_PER_SEC);
    MOZ_ASSERT(!mDBFilename.IsEmpty(), "Database filename cannot be empty");
    nsAutoCString prefName(PREF_VACUUM_BRANCH);
    prefName += mDBFilename;
    DebugOnly<nsresult> rv = Preferences::SetInt(prefName.get(), now);
    MOZ_ASSERT(NS_SUCCEEDED(rv), "Should be able to set a preference");
  }

  notifyCompletion(aReason == REASON_FINISHED);

  return NS_OK;
}

nsresult
Vacuumer::notifyCompletion(bool aSucceeded)
{
  nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
  if (os) {
    os->NotifyObservers(nullptr, OBSERVER_TOPIC_HEAVY_IO,
                        OBSERVER_DATA_VACUUM_END);
  }

  nsresult rv = mParticipant->OnEndVacuum(aSucceeded);
  NS_ENSURE_SUCCESS(rv, rv);

  return NS_OK;
}

} // namespace

////////////////////////////////////////////////////////////////////////////////
//// VacuumManager

NS_IMPL_ISUPPORTS(
  VacuumManager
, nsIObserver
)

VacuumManager *
VacuumManager::gVacuumManager = nullptr;

already_AddRefed<VacuumManager>
VacuumManager::getSingleton()
{
  //Don't allocate it in the child Process.
  if (!XRE_IsParentProcess()) {
    return nullptr;
  }

  if (!gVacuumManager) {
    auto manager = MakeRefPtr<VacuumManager>();
    MOZ_ASSERT(gVacuumManager == manager.get());
    return manager.forget();
  }
  return do_AddRef(gVacuumManager);
}

VacuumManager::VacuumManager()
  : mParticipants("vacuum-participant")
{
  MOZ_ASSERT(!gVacuumManager,
             "Attempting to create two instances of the service!");
  gVacuumManager = this;
}

VacuumManager::~VacuumManager()
{
  // Remove the static reference to the service.  Check to make sure its us
  // in case somebody creates an extra instance of the service.
  MOZ_ASSERT(gVacuumManager == this,
             "Deleting a non-singleton instance of the service");
  if (gVacuumManager == this) {
    gVacuumManager = nullptr;
  }
}

////////////////////////////////////////////////////////////////////////////////
//// nsIObserver

NS_IMETHODIMP
VacuumManager::Observe(nsISupports *aSubject,
                       const char *aTopic,
                       const char16_t *aData)
{
  if (strcmp(aTopic, OBSERVER_TOPIC_IDLE_DAILY) == 0) {
    // Try to run vacuum on all registered entries.  Will stop at the first
    // successful one.
    nsCOMArray<mozIStorageVacuumParticipant> entries;
    mParticipants.GetEntries(entries);
    // If there are more entries than what a month can contain, we could end up
    // skipping some, since we run daily.  So we use a starting index.
    static const char* kPrefName = PREF_VACUUM_BRANCH "index";
    int32_t startIndex = Preferences::GetInt(kPrefName, 0);
    if (startIndex >= entries.Count()) {
      startIndex = 0;
    }
    int32_t index;
    for (index = startIndex; index < entries.Count(); ++index) {
      RefPtr<Vacuumer> vacuum = new Vacuumer(entries[index]);
      // Only vacuum one database per day.
      if (vacuum->execute()) {
        break;
      }
    }
    DebugOnly<nsresult> rv = Preferences::SetInt(kPrefName, index);
    MOZ_ASSERT(NS_SUCCEEDED(rv), "Should be able to set a preference");
  }

  return NS_OK;
}

} // namespace storage
} // namespace mozilla