Events

When should I use events instead of a build step?

Unlike build steps events will run every time so it is advisable to use them for automating common steps like compiling sass before or after your app starts and not installing lower level dependencies like node modules or php extensions.

Events allow you to automate commands or tasks you might often or always run either before or after something happens. Generally, you can hook into pre and post events for every part of the Lando and App runtime. At time of writing, those events were as follows:

LANDO	APP
pre-bootstrap-config	pre-destroy
pre-bootstrap-tasks	post-destroy
pre-bootstrap-engine	pre-init
pre-bootstrap-app	post-init
post-bootstrap-config	pre-rebuild
post-bootstrap-tasks	post-rebuild
post-bootstrap-engine	pre-start
post-bootstrap-app	post-start
pre-engine-build	pre-stop
post-engine-build	post-stop
pre-engine-destroy	pre-uninstall
post-engine-destroy	post-uninstall
pre-engine-run	ready
post-engine-run
pre-engine-start
post-engine-start
pre-engine-stop
post-engine-stop

You can also hook into pre and post events for all tooling commands. For example, the command lando db-import should expose pre-db-import and post-db-import.

Discovering Events

While the above lists are great starting point, they may be out of date. You can explicitly discover what events are available by running as shown below:

# Discover hookable events for the `lando start` command
lando start --debug | grep "emitting"

# Discover hookable events for the `lando test` command
# NOTE: This assumed you've defined a `test` command in tooling
lando test --debug | grep "emitting"

Specifically, you need to hook into an event where the service you are running the command against exists and is running.

Usage

It's fairly straightforward to add events to your Landofile using the events top level config.

Note that due to the nature of events eg automating steps that the user usually runs, all commands are run as "you" and do not have sudo or root access. In Lando 4 this will likely change.

Also note that some events are "silly" eg you will find it difficult to use the post-destroy event.

Default commands

If you do not specify a service then the command will run on the default service. Generally this will be the appserver service.

events:
  pre-start:
    - yarn install
    - echo "I JUST YARNED"

An exception for this is events that are based on tooling commands which will use the tooling service as the default.

events:
  post-thing:
    - some-command
tooling:
  thing:
    service: web

In the above scenario, some-command will run on the web service by default instead of the appserver. For dynamic tooling routes, events will use the default of the dynamic route.

events:
  post-dynamic:
    - some-command
tooling:
  dynamic:
    cmd: env
    service: :host
    options:
      host:
        default: web2
        alias:
          - h
        describe: Run a different service

In the above lando dynamic scenario, some-command will run on web2 by default. However if you run lando dynamic --host web then some-command will run on web.

Service commands

Make it explicit!

While the defaults above are good to know, we highly recommend you just explicitly define which commands should run on which services by keying the command with a service as shown below.

events:
  pre-start:
    - appserver: composer install
    - database: echo "I JUST COMPOSERED"
  post-start:
    - node: yarn sass
    - appserver: composer compile-templates

Backgrounding

You can also background a command using &

events:
  post-some-command:
    - node: npm run worker-process &