First workflow

Before you begin

Install Aion and have one server running with deployment enabled. These examples use the default gRPC endpoint and namespace. For another server, pass the same endpoint and namespace to every remote command.

Create the project

aion new greet_visitor
cd greet_visitor
aion awl check greet_visitor.awl

The command creates the workflow, a development config and a README. The project name uses lowercase letters, digits and underscores, starting with a letter.

This is the generated workflow:

//! Build a greeting, then choose its tone.
workflow greet_visitor
  input name: String
  input enthusiastic: Bool
  outcome greeted: type Greeting, route success

type Greeting { message: String }

step compose
  "Hello, " + name -> greeting

step punctuate after compose
  greeting + "!" -> excited_greeting

step finish after punctuate
  outcome excited: if enthusiastic,
    route greeted(message: excited_greeting)
  outcome calm: else,
    route greeted(message: greeting + ".")

Each step binds a value. The final step chooses one outcome arm. Both arms supply the record declared by the successful outcome.

Check and compile locally

aion awl check greet_visitor.awl
aion awl emit greet_visitor.awl --target beam --output greet_visitor.beam
aion awl schema greet_visitor.awl

The check reports three steps. The bytecode command writes a BEAM file and its JSON sidecar. Schema prints the input contract. These are local authoring operations.

The bytecode command checks that each construct can compile. A refusal names the construct and source location.

Deploy, start and wait

aion run greet_visitor.awl --input '{"name":"Ada","enthusiastic":true}'

The command compiles the document, checks the input, deploys the archive, starts a run and waits for a terminal event. Its JSON result includes both ids and this result envelope:

{"outcome":"greeted","payload":{"message":"Hello, Ada!"}}

A client wait bound is available in the run command. Reaching that bound stops the client waiting. The run continues on the server.

Start without waiting

aion deploy greet_visitor.awl
aion start greet_visitor --input '{"name":"Ada","enthusiastic":false}'

Copy the returned workflow id and run id into shell variables named in the next example. The calm branch records a greeting ending with a full stop.

aion describe "$WORKFLOW_ID" --run-id "$RUN_ID" --pretty
aion inspect "$WORKFLOW_ID" --run-id "$RUN_ID" --pretty
aion tail "$WORKFLOW_ID" --run-id "$RUN_ID"

Describe reports status and run identity. Inspect reads the event history. Tail follows a live transcript, or replays a finished run and exits.

If the run is refused

A disabled deploy surface, missing deploy grant or invalid input produces a refusal naming the required correction.

If the command cannot connect, read server status and the log. Do not restart a server to clear an unexplained failure.

Continue

Learn durability and replay, then add waits and signals or worker activities.