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Use QSaveFile when persisting domain settings to disk

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Prior to this change the `DomainServerSettingsManager::persistToFile()`
method wrote directly to the settings file. It also did limited error
checking. These limitations could lead to a situation where a crashed
domain-server process, a file system backup, a settings file copy, or a
hardware error could corrupt the setting file.

This change swaps the `QFile` class for `QSaveFile` and uses its atomic
saving features, which writes the changes to the settings file to a file
in the same directory as the settings file and then does a rename to
replace the original. If the rename, or any of the file operations, fail
the original settings file remains in place.
This commit is contained in:
Matt Hardcastle 2018-12-02 17:08:27 -08:00
parent 7143689ddf
commit f4b6db5def
1 changed files with 37 additions and 20 deletions
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57
domain-server/src/DomainServerSettingsManager.cpp
View file

@ -22,6 +22,7 @@
#include <QtCore/QThread>
#include <QtCore/QUrl>
#include <QtCore/QUrlQuery>
#include <QSaveFile>
#include <AccountManager.h>
#include <Assignment.h>
@ -1714,28 +1715,44 @@ void DomainServerSettingsManager::sortPermissions() {
}
void DomainServerSettingsManager::persistToFile() {
sortPermissions();
// make sure we have the dir the settings file is supposed to live in
QFileInfo settingsFileInfo(_configMap.getUserConfigFilename());
if (!settingsFileInfo.dir().exists()) {
settingsFileInfo.dir().mkpath(".");
}
QFile settingsFile(_configMap.getUserConfigFilename());
if (settingsFile.open(QIODevice::WriteOnly)) {
// take a read lock so we can grab the config and write it to file
QReadLocker locker(&_settingsLock);
settingsFile.write(QJsonDocument::fromVariant(_configMap.getConfig()).toJson());
} else {
qCritical("Could not write to JSON settings file. Unable to persist settings.");
// failed to write, reload whatever the current config state is
// with a write lock since we're about to overwrite the config map
QString settingsFilename = _configMap.getUserConfigFilename();
QDir settingsDir = QFileInfo(settingsFilename).dir();
if (!settingsDir.exists() && !settingsDir.mkpath(".")) {
// If the path already exists when the `mkpath` method is
// called, it will return true. It will only return false if the
// path doesn't exist after the call returns.
qCritical("Could not create the settings file parent directory. Unable to persist settings.");
QWriteLocker locker(&_settingsLock);
_configMap.loadConfig();
return;
}
QSaveFile settingsFile(settingsFilename);
if (!settingsFile.open(QIODevice::WriteOnly)) {
qCritical("Could not open the JSON settings file. Unable to persist settings.");
QWriteLocker locker(&_settingsLock);
_configMap.loadConfig();
return;
}
sortPermissions();
QVariantMap conf;
{
QReadLocker locker(&_settingsLock);
conf = _configMap.getConfig();
}
QByteArray json = QJsonDocument::fromVariant(conf).toJson();
if (settingsFile.write(json) == -1) {
qCritical("Could not write to JSON settings file. Unable to persist settings.");
QWriteLocker locker(&_settingsLock);
_configMap.loadConfig();
return;
}
if (!settingsFile.commit()) {
qCritical("Could not commit writes to JSON settings file. Unable to persist settings.");
QWriteLocker locker(&_settingsLock);
_configMap.loadConfig();
return; // defend against future code
}
}