[FEATURE][needs-doc] Introduce QGIS_SERVER_LOG_STDERR and deprecate file logging

python/server/auto_generated/qgsserverlogger.sip.in

@@ -47,9 +47,16 @@ Set the current log level
 .. versionadded:: 3.0
 %End
 
-    void setLogFile( const QString &f );
+    void setLogFile( const QString &filename = QString() );
 %Docstring
 Set the current log file
+%End
+
+    void setLogStderr();
+%Docstring
+Activates logging to stderr.
+
+.. versionadded:: 3.4.
 %End
 
   public slots:

python/server/auto_generated/qgsserversettings.sip.in

@@ -94,6 +94,15 @@ Returns the QGS project file to use.
 Returns the log file.
 
 :return: the path of the log file or an empty string if none is defined.
+%End
+
+    bool logStderr() const;
+%Docstring
+Returns whether logging to stderr is activated.
+
+:return: true if logging to stderr is activated, false otherwise.
+
+.. versionadded:: 3.4
 %End
 
     qint64 cacheSize() const;

src/server/qgsserver.cpp

@@ -186,7 +186,14 @@ bool QgsServer::init()
   // init and configure logger
   QgsServerLogger::instance();
   QgsServerLogger::instance()->setLogLevel( sSettings.logLevel() );
-  QgsServerLogger::instance()->setLogFile( sSettings.logFile() );
+  if ( ! sSettings.logFile().isEmpty() )
+  {
+    QgsServerLogger::instance()->setLogFile( sSettings.logFile() );
+  }
+  else if ( sSettings.logStderr() )
+  {
+    QgsServerLogger::instance()->setLogStderr();
+  }
 
   // log settings currently used
   sSettings.logSummary();

src/server/qgsserverlogger.cpp

@@ -52,7 +52,7 @@ void QgsServerLogger::logMessage( const QString &message, const QString &tag, Qg
     mTextStream << formattedMessage;
     mTextStream.flush();
   }
-  else if ( QString::compare( mLogFile.fileName(), QStringLiteral( "stderr" ), Qt::CaseInsensitive ) == 0 )
+  else if ( mLogStderr )
   {
     QgsMessageLogConsole::logMessage( message, tag, level );
   }
@@ -63,17 +63,20 @@ void QgsServerLogger::setLogLevel( const Qgis::MessageLevel level )
   mLogLevel = level;
 }
 
-void QgsServerLogger::setLogFile( const QString &f )
+void QgsServerLogger::setLogFile( const QString &filename )
 {
   mTextStream.flush();
   mLogFile.close();
+  mLogFile.setFileName( filename );
 
-  mLogFile.setFileName( f );
-
-  if ( ( ! f.isEmpty() ) &&
-       QString::compare( f, QStringLiteral( "stderr" ), Qt::CaseInsensitive ) != 0 &&
-       mLogFile.open( QIODevice::Append ) )
+  if ( ( ! filename.isEmpty() ) && mLogFile.open( QIODevice::Append ) )
   {
     mTextStream.setDevice( &mLogFile );
   }
 }
+
+void QgsServerLogger::setLogStderr()
+{
+  setLogFile();
+  mLogStderr = true;
+}

src/server/qgsserverlogger.h

@@ -59,7 +59,13 @@ class SERVER_EXPORT QgsServerLogger : public QgsMessageLogConsole
     /**
       * Set the current log file
       */
-    void setLogFile( const QString &f );
+    void setLogFile( const QString &filename = QString() );
+
+    /**
+     * Activates logging to stderr.
+     * \since QGIS 3.4.
+     */
+    void setLogStderr();
 
   public slots:
 
@@ -79,6 +85,7 @@ class SERVER_EXPORT QgsServerLogger : public QgsMessageLogConsole
     static QgsServerLogger *sInstance;
 
     QFile mLogFile;
+    bool mLogStderr = false;
     QTextStream mTextStream;
     Qgis::MessageLevel mLogLevel = Qgis::None;
 };

src/server/qgsserversettings.cpp

@@ -87,6 +87,17 @@ void QgsServerSettings::initSettings()
                            };
   mSettings[ sLogFile.envVar ] = sLogFile;
 
+  // log to stderr
+  const Setting sLogStderr = { QgsServerSettingsEnv::QGIS_SERVER_LOG_STDERR,
+                               QgsServerSettingsEnv::DEFAULT_VALUE,
+                               "Activate/Deactivate logging to stderr",
+                               "",
+                               QVariant::Bool,
+                               QVariant( false ),
+                               QVariant()
+                             };
+  mSettings[ sLogStderr.envVar ] = sLogStderr;
+
   // project file
   const Setting sProject = { QgsServerSettingsEnv::QGIS_PROJECT_FILE,
                              QgsServerSettingsEnv::DEFAULT_VALUE,
@@ -281,6 +292,11 @@ QString QgsServerSettings::logFile() const
   return value( QgsServerSettingsEnv::QGIS_SERVER_LOG_FILE ).toString();
 }
 
+bool QgsServerSettings::logStderr() const
+{
+  return value( QgsServerSettingsEnv::QGIS_SERVER_LOG_STDERR ).toBool();
+}
+
 Qgis::MessageLevel QgsServerSettings::logLevel() const
 {
   return static_cast<Qgis::MessageLevel>( value( QgsServerSettingsEnv::QGIS_SERVER_LOG_LEVEL ).toInt() );

src/server/qgsserversettings.h

@@ -56,6 +56,7 @@ class SERVER_EXPORT QgsServerSettingsEnv : public QObject
       QGIS_SERVER_MAX_THREADS,
       QGIS_SERVER_LOG_LEVEL,
       QGIS_SERVER_LOG_FILE,
+      QGIS_SERVER_LOG_STDERR,
       QGIS_PROJECT_FILE,
       MAX_CACHE_LAYERS,
       QGIS_SERVER_CACHE_DIRECTORY,
@@ -148,6 +149,13 @@ class SERVER_EXPORT QgsServerSettings
       */
     QString logFile() const;
 
+    /**
+     * Returns whether logging to stderr is activated.
+     * \returns true if logging to stderr is activated, false otherwise.
+     * \since QGIS 3.4
+     */
+    bool logStderr() const;
+
     /**
      * Returns the cache size.
       * \returns the cache size.

tests/src/python/test_qgsserverlogger.py

@@ -46,7 +46,12 @@ class TestQgsServerLogger(unittest.TestCase):
         exists = os.access(self.log_file, os.R_OK)
         self.assertTrue(exists)
 
-    def test_logging_stderr(self):
+    def test_logging_log_file_stderr(self):
         self.logger.setLogFile('stderr')
         exists = os.access(self.log_file, os.R_OK)
         self.assertFalse(exists)
+
+    def test_logging_stderr(self):
+        self.logger.setLogStderr()
+        exists = os.access(self.log_file, os.R_OK)
+        self.assertFalse(exists)