Transaction Log

One of the key components of an XTDB node is the transaction log - this is a totally ordered log of all transaction operations that have been applied to the database, generally persistent & shared between nodes.

Implementations

We offer a number of separate implementations of the transaction log, currently:

• Single-node log implementations, within xtdb-core:

  • In memory: transient in-memory log.

  • Local disk: log using the local filesystem.

• Log implementations within their own modules:

  • Kafka

In memory

By default, the transaction log is a transient, in-memory log:

# default, no need to explicitly specify
# txLog: !InMemory

If configured as an in-process node, you can also specify an InstantSource implementation - this is used to override the local machine’s clock when providing a system-time timestamp for each transaction.

For examples on how to enable/configure the in-memory transaction log as part of your node, see the individual client library documentation:

Local disk

A single-node persistent transaction log implementation that writes to a local directory.

txLog: !Local
  # -- required

  # The path to the local directory to store the transaction log in.
  # (Can be set as an !Env value)
  path: /var/lib/xtdb/log

  # -- optional

  # The number of entries of the buffer to use when writing to the transaction log.
  # bufferSize: 4096

  # The duration to sleep for when polling for new transactions written to the transaction log.
  # pollSleepDuration: PT0.1S

If configured as an in-process node, you can also specify an InstantSource implementation - this is used to override the local machine’s clock when providing a system-time timestamp for each transaction.

For examples on how to enable/configure the local-disk transaction log as part of your node, see the individual client library documentation: