Preparing LogWriter API for rotation and flushing.

src/LogWriter.h

@@ -50,6 +50,37 @@ protected:
     // should be reported via Error().
     virtual bool DoWrite(int num_fields, LogField** fields, LogVal** vals) = 0;
 
+	// Called when the flushing status for this writer is changed. If
+	// flushing is enabled, the writer should attempt to write out
+	// information as quickly as possible even if that may have an
+	// performance impact. If disabled (which the writer should assume to be
+	// the default), then it can buffer things up as necessary and write out
+	// in a way optimized for performance.
+	//
+	// A writer may ignore flushing if it doesn't fit with its semantics.
+	virtual void DoSetFlushing(bool enabled) = 0;
+
+	// Called when a log output is to be rotated. Most directly, this only
+	// applies to writers outputting files, thoug a writer may also trigger
+	// other regular actions if that fits a similar model
+	//
+	// The string "rotate_path" is interpreted in writer-specific way, yet
+	// should generally should have similar semantics that the "path" passed
+	// into DoInit(), except that now it reflects the name to where the
+	// rotated output is to be moved. After rotation, output should continue
+	// normally with the standard "path". As an example, for file-based
+	// output, the rotate_path may be the original filename with an embedded
+	// timestamp.
+	//
+	// The writer must return false if an error occured that prevent the
+	// writer for continuing operation; it will then be disabled. The error
+	// reason should be reported via Error(). If a recoverable error occurs,
+	// still call Error(), but return true.
+	//
+	// A writer may ignore rotation requests if it doesn't fit with its
+	// semantics. In that case, still return true.
+	virtual bool DoRotate(string rotated_path) = 0;
+
 	// Called once on termination. Not called when any of the other methods
 	// has previously signaled an error, i.e., executing this method signals
 	// a regular shutdown.

src/LogWriterAscii.cc

@@ -127,3 +127,14 @@ bool LogWriterAscii::DoWrite(int num_fields, LogField** fields, LogVal** vals)
 
 	return true;
 	}
+
+bool LogWriterAscii::DoRotate(string rotated_path)
+	{
+	return true;
+	}
+
+void LogWriterAscii::DoSetFlushing(bool enabled)
+	{
+	}
+
+

src/LogWriterAscii.h

@@ -15,9 +15,11 @@ public:
 	static LogWriter* Instantiate()	{ return new LogWriterAscii; }
 
 protected:
-    bool DoInit(string path, int num_fields, LogField** fields);
-    bool DoWrite(int num_fields, LogField** fields, LogVal** vals);
-    void DoFinish();
+    virtual bool DoInit(string path, int num_fields, LogField** fields);
+    virtual bool DoWrite(int num_fields, LogField** fields, LogVal** vals);
+	virtual void DoSetFlushing(bool enabled);
+	virtual bool DoRotate(string rotated_path);
+    virtual void DoFinish();
 
 private:
 	FILE* file;