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XTDB

Configuration

Changelog (last updated v2.1)
v2.1: multi-database support

databases was introduced in v2.1.

Prior to that, the log and storage keys were at the top-level of the configuration:

log: !Local
  path: /path/to/log-file

storage: !Local
  path: /path/to/storage-dir

# became

databases:
  xtdb:
    log: !Local
      path: /path/to/log-file

    storage: !Local
      path: /path/to/storage-dir

For more details on the changes to the log and storage configurations, see the Transaction Logs and Object Storage documentation.

XTDB nodes are configured using YAML files.

The two main pluggable components of XTDB are transaction logs and object storage - these can be configured in the databases section of the configuration file.

databases:
  # Currently only one database is supported, named `xtdb`.
  xtdb:
    # -- optional

    # transaction log configuration
    # defaults to an in-memory transaction log
    log: !Local
      path: /path/to/log-file

    # object store configuration
    # defaults to an in-memory object store
    storage: !Local
      path: /path/to/storage-dir

If no databases section is specified, XTDB will use the default configuration - an in-memory transaction log and an in-memory object store.

For more details on the log and storage configurations, including the available components, see the Transaction Logs and Object Storage documentation.

Using !Env

For certain keys, we allow the use of environment variables - typically, the keys where we allow this are things that may change location across environments. Generally, they are either "paths" or "strings".

When specifying a key, you can use the !Env tag to reference an environment variable. As an example:

databases:
  xtdb:
    storage: !Local
      path: !Env XTDB_STORAGE_PATH

Any key that we allow the use of !Env will be documented as such.

Monitoring & Observability

XTDB provides a suite of tools & templates to facilitate monitoring and observability. See Monitoring & Observability.

Authentication

The pg-wire server and the http-server both support authentication which can be configured via authentication rules. See Authentication.

Other configuration:

XTDB nodes accept other optional configuration, as follows:

server:
  # Host on which to start a read-write Postgres wire-compatible server.
  #
  # Default is "localhost", which means the server will only accept connections on the loopback interface.
  # Set to '*' to accept connections on all interfaces.
  host: localhost

  # Port on which to start a read-write Postgres wire-compatible server.
  #
  # Default is 0, to have the server choose an available port.
  # (In the XTDB Docker images, this is defaulted to 5432.)
  # Set to -1 to not start a read-write server.
  port: 0

  # Port on which to start a read-only Postgres wire-compatible server.
  #
  # The server on this port will reject any attempted DML/DDL,
  # regardless of whether the user would otherwise have the permission to do so.
  #
  # Default is -1, to not start a read-only server.
  # Set to 0 to have the server choose an available port.
  readOnlyPort: -1

compactor:
  # Number of threads to use for compaction.

  # Defaults to min(availableProcessors / 2, 1).
  # Set to 0 to disable the compactor.
  threads: 4

CLI tools/flags

Changelog (last updated v2.1)
v2.1: top-level commands

In v2.1, we changed the CLI to use top-level commands (not dissimilar to Git, for example).

Previously, the playground and compact-only nodes were activated using optional flags - --playground-port and --compact-only respectively.

reset-compactor was also added in v2.1.

You can run various tools by passing arguments - either directly to the CLI or via Docker’s arguments:

node (default, can be omitted)

  • -f <file>, --file <file>: specifies the configuration file to use.

playground

Starts a playground - an in-memory server that will accept any database name, creating it if required.

  • -p <port>, --port <port> (default 5432): specifies the port to run the playground server on.

compactor

Starts a compactor-only node - useful for giving the compaction process more compute resources.

  • -f <file>, --file <file>: specifies the configuration file to use.

reset-compactor

Resets the compaction back to L0, deleting any L1+ files - use this if you’ve encountered a compaction bug and need to reset its state.

  1. Spin down all of your XT nodes

  2. Using your container orchestration tool (e.g. Kubernetes), run a one-shot task with an overriden command: ["reset-compactor"]. Optionally, specify --dry-run to list all of the files to be removed.

  3. When the tool has finished, spin up your nodes again.

    You may want to also spin up a compactor-only node to help out with the re-compaction.

At the moment, this can only reset all the way back to L0 - finer-grained reset will be added in a later release.

e.g.

  • Dockerfile: CMD ["playground", "--port", "5439"]

  • docker-compose: command: ["playground", "--port", "5439"]

  • Java uberjar: java -jar xtdb.jar playground --port 5439

  • Clojure (with xtdb-core in your deps.edn): clj -M xtdb.main playground --port 5439

You can also pass --help to any of the commands to get command-specific help.