docs/walkthroughs/daprrun.md

Sequence of Events on a dapr run in Self Hosting Mode

The doc describes the sequence of events that occur when dapr run is executed in self hosting mode (formerly known as standalone mode). It uses sample 1 as an example.

Terminology used below:

• Dapr CLI - the Dapr command line tool. The binary name is dapr (dapr.exe on Windows)
• Dapr runtime - this runs alongside each app. The binary name is daprd (daprd.exe on Windows)

In self hosting mode, running dapr init copies the Dapr runtime onto your box and starts the placement service (used for actors) and Redis in containers. These must be present before running dapr run. The Dapr CLI also creates the default components directory which for Linux/MacOS is: $HOME/.dapr/components and for Windows: %USERPROFILE%\.dapr\components if it does not already exist.

What happens when dapr run is executed?

dapr run --app-id nodeapp --app-port 3000 --port 3500 node app.js

First, the Dapr CLI loads the components from the default directory (specified above) for the state store and pub/sub: statestore.yaml and pubsub.yaml, respectively. Code.

You can either add components to the default directory or create your own components directory and provide the path to the CLI using the --components-path flag.

In order to switch components, simply replace or add the YAML files in the components directory and run dapr run again. For example, by default Dapr will use the Redis state store in the default components dir. You can either override it with a different YAML, or supply your own components path.

Then, the Dapr CLI will launch two proceses: the Dapr runtime and your app (in this sample node app.js).

If you inspect the command lines of the Dapr runtime and the app, observe that the Dapr runtime has these args:

daprd.exe --app-id mynode --dapr-http-port 3500 --dapr-grpc-port 43693 --log-level info --max-concurrency -1 --protocol http --app-port 3000 --placement-address localhost:50005

And the app has these args, which are not modified from what was passed in via the CLI:

node app.js

Dapr runtime

The daprd process is started with the args above. --app-id, "nodeapp", which is the dapr app id, is forwarded from the Dapr CLI into daprd as the --app-id arg. Similarly:

• the --app-port from the CLI, which represents the port on the app that daprd will use to communicate with it has been passed into the --app-port arg.
• the --port arg from the CLI, which represents the http port that daprd is listening on is passed into the --dapr-http-port arg. (Note to specify grpc instead you can use --grpc-port). If it's not specified, it will be -1 which means the Dapr CLI will chose a random free port. Below, it's 43693, yours will vary.

The app

The Dapr CLI doesn't change the command line for the app itself. Since node app.js was specified, this will be the command it runs with. However, two environment variables are added, which the app can use to determine the ports the Dapr runtime is listening on. The two ports below match the ports passed to the Dapr runtime above:

DAPR_GRPC_PORT=43693
DAPR_HTTP_PORT=3500