13.3. Configuring the message journal

The location of the message journal. The default value is data/journal. For best performance, this journal should be located on its own physical volume to minimize disk head movement. If this journal is stored on a storage area network, each journal instance on the network should have its own logical unit.

If true, the journal directory is created at the location specified in journal-directory. The default value is true.

Valid values are NIO or ASYNCIO. If NIO, the Java NIO journal is used. If ASYNCIO, Linux asynchronous IO is used. If ASYNCIO is set on a non-Linux or non-libaio system, HornetQ detects this and falls back to NIO.

If true, HornetQ ensures all transaction data is flushed to disk on transaction boundaries (commit, prepare, and rollback). The default is true.

If true, HornetQ ensures non-transactional message data (sends and acknowledgments) are flushed to disk. The default is true.

The size of each journal file in bytes. The default value is 10485760 bytes (10 megabytes).

The minimum number of files the journal maintains. When HornetQ starts and there is no initial data, HornetQ pre-creates this number of files. Creating and padding journal files is an expensive operation, so to be avoided at run-time as files are filled. Pre-creating files means that as one is filled the journal can immediately resume with the next file without pausing to create it.

The maximum number of write requests to hold in the IO queue. Write requests are queued here before being submitted to the system for execution. If the queue fills, writes are blocked until space becomes available in the queue. For NIO, this must be 1. For AIO, this should be 500. A different default value is maintained depending on whether NIO or AIO is used (1 for NIO, 500 for AIO). The total max AIO must not be higher than what is configured at the operating system level (/proc/sys/fs/aio-max-nr), generally at 65536.

HornetQ maintains a buffer of flush requests, and flushes the entire buffer either when it is full or when this timeout expires - whichever is soonest. This is used for both NIO and AIO and allows improved scaling when many concurrent writes and flushes are required.

The size of the timed buffer on AIO. The default value is 490 kilobytes.

The minimum number of files before the journal will be compacted. The default value is 10.

When less than this percentage of a journal is considered live data compacting will occur. The default value is 30. journal-compact-min-files must also be fulfilled before compacting.