LogFlush

LogFlush is a term used in logging and durability systems to refer to the operation of flushing buffered log records to a durable sink. It can be exposed as a function or invoked by a system component. The goal is to ensure that logs reach stable storage and are recoverable after a crash or power failure.

Mechanism and durability: A LogFlush typically forces the in-memory log buffers to be written to the underlying storage and may invoke an OS-level flush (such as fsync) to guarantee persistence and ordering. Depending on the system, it may apply to a single log file or to the entire log stream. Some implementations distinguish between flushing buffers (log data in memory) and synchronously persisting metadata (like file headers, commit records).

Use cases: Log flushing is central to write-ahead logging in databases, durable messaging systems, and critical event logging where crash recovery relies on persisted log records. Flushing is often balanced against performance: more frequent flushes reduce risk of data loss but increase I/O overhead; asynchronous logging reduces latency but defers durability.

Variants and examples: In application code, libraries may provide Log.Flush() or Log.FlushSync() functions. In databases and message brokers, the equivalent operation is often described as syncing the log to disk or ensuring durability before acknowledging a commit or message delivery. Differences exist in the reader/writer ordering guarantees and whether metadata is flushed with the logs.

See also: fsync, write-ahead log, durability, logging library, log rotation.