There's obviously a bug or something in `mqttmarionette` because it
occasionally gets "stuck" in a state where it is running but does
not reconnect to the MQTT broker. In such situations, it has to be
restarted (and even then it doesn't shut down correctly but has to
be killed with SIGKILL, usually). I have been doing this manually, but
with this shell script and a corresponding "shell command" integration
in Home Assistant, it can be done automatically. This is similar to
how Home Assistant restarts Mopidy on the living room stereo when it
gets into the same kind of state.
Zigbee2MQTT commits the cardinal sin of storing state in its
configuration file. This means the file has to be writable and thus
stored in persistent storage rather than in a ConfigMap. As a
consequence, making changes to the configuration when the application is
not running is rather difficult. Case in point: when I added the
internal alias for _mqtt.pyrocufflink.blue_ pointing to the in-cluster
service, Zigbee2MQTT became unable to connect to the broker because it
was using the node port instead of the internal port. Since it could
not connect to the broker, it refused to start, and thus the container
would not stay running long enough to fix the configuration to point
to the correct port.
Fortunately, Zigbee2MQTT also allows configuring settings via
environment variables, which can be managed with a ConfigMap. Luckily,
the values read from environment variables override those from the
configuration file, so pointing to the correct broker port with the
environment variable was sufficient to allow the application to start.
Home Assistant uses PostgreSQL for recording the history of entity
states. Since we had been using the in-cluster database server for
this, the data were migrated to the new external PostgreSQL server
automatically when the backup from the former was restored on the
latter. It follows, then, that we can point Home Assistant to the
new server as well.
Home Assistant uses SQLAlchemy, which in turn uses _libpq_ via
_psycopg_, as a client for PostgreSQL. It doesn't expose any
configuration parameters beyond the "database URL" directly, but we
can use the standard environment variables to specify the certificate
and private key for authentication. In fact, the empty `postgresql://`
URL is sufficient, and indicates that _all_ of the connection parameters
should be taken from environment variables. This makes specifying the
parameters for both the `wait-for-db` init container and the main
container take the exact same environment variables, so we can use
YAML anchors to share their definitions.
The digital photo frame in the kitchen is powered by a server service,
which exposes a minimal HTTP API. Using this API, we can e.g. advance
or backtrack the displayed photo. Exposing `rest_command` services
for these operations allows us to add buttons to dashboards to control
the frame.
When Home Assistant starts, if PostgreSQL is unavailable, it will come
up successfully, but without the history component. It never tries
again to connect and enable the component. This makes it difficult to
detect the problem and thus easy to overlook the missing functionality.
To avoid having extended periods of missing state history, we'll force
Home Assistant to wait for PostgreSQL to come up before starting.
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Dustin
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