.. _pg_autoctl_watch:

pg_autoctl watch
======================

pg_autoctl watch - Display an auto-updating dashboard

Synopsis
--------

This command outputs the events that the pg_auto_failover events records
about state changes of the pg_auto_failover nodes managed by the monitor::

  usage: pg_autoctl watch  [ --pgdata --formation --group ]

  --pgdata      path to data directory
  --monitor     show the monitor uri
  --formation   formation to query, defaults to 'default'
  --group       group to query formation, defaults to all
  --json        output data in the JSON format

Options
-------

--pgdata

  Location of the Postgres node being managed locally. Defaults to the
  environment variable ``PGDATA``. Use ``--monitor`` to connect to a monitor
  from anywhere, rather than the monitor URI used by a local Postgres node
  managed with ``pg_autoctl``.

--monitor

  Postgres URI used to connect to the monitor. Must use the ``autoctl_node``
  username and target the ``pg_auto_failover`` database name. It is possible
  to show the Postgres URI from the monitor node using the command
  :ref:`pg_autoctl_show_uri`.

--formation

  List the events recorded for nodes in the given formation. Defaults to
  ``default``.

--group

  Limit output to a single group in the formation. Default to including all
  groups registered in the target formation.

Environment
-----------

PGDATA

  Postgres directory location. Can be used instead of the ``--pgdata``
  option.

PG_AUTOCTL_MONITOR

  Postgres URI to connect to the monitor node, can be used instead of the
  ``--monitor`` option.

XDG_CONFIG_HOME

  The pg_autoctl command stores its configuration files in the standard
  place XDG_CONFIG_HOME. See the `XDG Base Directory Specification`__.

  __ https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html
  
XDG_DATA_HOME

  The pg_autoctl command stores its internal states files in the standard
  place XDG_DATA_HOME, which defaults to ``~/.local/share``. See the `XDG
  Base Directory Specification`__.

  __ https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html

Description
-----------

The ``pg_autoctl watch`` output is divided in 3 sections.

The first section is a single header line which includes the name of the
currently selected formation, the formation replication setting
:ref:`number_sync_standbys`, and then in the right most position the current
time.

The second section displays one line per node, and each line contains a list
of columns that describe the current state for the node. This list can
includes the following columns, and which columns are part of the output
depends on the terminal window size. This choice is dynamic and changes if
your terminal window size changes:

  - Name

	Name of the node.

  - Node, or Id

	Node information. When the formation has a single group (group zero),
	then this column only contains the nodeId.

	Only Citus formations allow several groups. When using a Citus formation
	the Node column contains the groupId and the nodeId, separated by a
	colon, such as ``0:1`` for the first coordinator node.

  - Last Report, or Report

	Time interval between now and the last known time when a node has
	reported to the monitor, using the ``node_active`` protocol.

	This value is expected to stay under 2s or abouts, and is known to
	increment when either the ``pg_autoctl run`` service is not running, or
	when there is a network split.

  - Last Check, or Check

	Time interval between now and the last known time when the monitor could
	connect to a node's Postgres instance, via its health check mechanism.

	This value is known to increment when either the Postgres service is not
	running on the target node, when there is a network split, or when the
	internal machinery (the health check worker background process)
	implements jitter.

  - Host:Port

	Hostname and port number used to connect to the node.

  - TLI: LSN

	Timeline identifier (TLI) and Postgres Log Sequence Number (LSN).

	The LSN is the current position in the Postgres WAL stream. This is a
	hexadecimal number. See `pg_lsn`__ for more information.

	__ https://www.postgresql.org/docs/current/datatype-pg-lsn.html

	The current `timeline`__ is incremented each time a failover happens, or
	when doing Point In Time Recovery. A node can only reach the secondary
	state when it is on the same timeline as its primary node.

	__ https://www.postgresql.org/docs/current/continuous-archiving.html#BACKUP-TIMELINES

  - Connection

	This output field contains two bits of information. First, the Postgres
	connection type that the node provides, either ``read-write`` or
	``read-only``. Then the mark ``!`` is added when the monitor has failed
	to connect to this node, and ``?`` when the monitor didn't connect to
	the node yet.

  - Reported State

	The current FSM state as reported to the monitor by the pg_autoctl
	process running on the Postgres node.

  - Assigned State

	The assigned FSM state on the monitor. When the assigned state is not
	the same as the reported start, then the pg_autoctl process running on
	the Postgres node might have not retrieved the assigned state yet, or
	might still be implementing the FSM transition from the current state to
	the assigned state.

The third and last section lists the most recent events that the monitor has
registered, the more recent event is found at the bottom of the screen.

To quit the command hit either the ``F1`` key or the ``q`` key.
