Enabling reliable disk-based buffering

The following destination drivers can use the disk-buffer option: amqp(), elasticsearch2(), file(), hdfs(), http(), kafka(), mongodb(), program(), redis(), riemann(), smtp(), sql(), stomp(), unix-dgram(), and unix-stream(). The network(), syslog(), tcp(), and tcp6() destination drivers can also use the disk-buffer option, except when using the udp transport method. (The other destinations or protocols do not provide the necessary feedback mechanisms required for the disk-buffer option.)

To enable reliable disk-based buffering, use the disk-buffer(reliable(yes)) parameter in the destination. Use reliable disk-based buffering if you do not want to lose logs in case of reload/restart, unreachable destination or AxoSyslog crash. This solution provides a slower, but reliable disk-buffer option. It is created and initialized at startup and gradually grows as new messages arrive. The filename of the reliable disk buffer file is the following: <syslog-ng path>/var/syslog-ng-00000.rqf.

Example: Example for using reliable disk-based buffering

   destination d_BSD {
        network("127.0.0.1"
            port(3333)
            disk-buffer(
                flow-control-window-bytes(10000)
                capacity-bytes(2000000)
                reliable(yes)
            )
        );
    }; 

For details on the differences between normal and reliable disk-based buffering, see also About disk queue files.