A Go library for service orchestration, inspired by Conductor.
Tasks are the fundamental building blocks of Orchestrator. They are similar to primitive types or statements in a programming language.
Typically, a task accepts an input and returns an output. Each parameter in the input can be a literal value or an expression.
Built-in tasks:
A flow is used to define a piece of logic, which usually consists of one or more tasks. Flows are similar to functions or routines in a programming language.
In Orchestrator, a flow is essentially a composite task (i.e. a Serial task). Therefore, just like a task, a flow accepts an input and returns an output. Furthermore, a flow can be embedded into another flow by leveraging a Call task, thus serving as a sub-flow.
Expressions are used to extract values out of the flow input and other tasks in the flow.
For example, a flow is supplied with an input by the client/caller when a new execution is triggered. The flow input is available via an expression of the form ${input.<var>} (see dialects). Likewise, the output of a previously executed task can also be extracted using an expression (e.g. ${<task>.<output_var>}) for use in the input of a subsequent task.
Currently supported expression dialects:
-
In addition to Starlark's built-in functions, there are some more pre-declared functions:
getenv(key): Retrieve the value of the environment variable named by the key.isiterator(v): Whether the given value v is an Orchestrator Iterator.jsonencode(v): Encode the given value v to a JSON string (go.starlark.net/lib/json).jsondecode(v): Decode the given JSON string to a value (go.starlark.net/lib/json).
Examples:
${input.value} // Value from the input. ${tool.status == 200} // Whether the status code (from an HTTP task `tool`) is 200 ${len(tool.body.entities)} // Length of the response entities (from an HTTP task `tool`) ${[s*2 for s in input.scores]} // List comprehension ${{k: v.upper() for k, v in input.properties.items()}} // Dictionary comprehension -
(- expand -)
Examples:
#{input.value} // Value from the input. #{tool.status == 200} // Whether the status code (from an HTTP task `tool`) is 200 #{len(tool.body.entities)} // Length of the response entities (from an HTTP task `tool`) //#{[s*2 for s in input.scores]} // UNSUPPORTED //#{{k: v.upper() for k, v in input.properties.items()}} // UNSUPPORTED -
JSONPath (spec and implementation)
(- expand -)
Examples:
@{input.value} // Value from the input. //@{tool.status == 200} // UNSUPPORTED //@{len(tool.body.entities)} // UNSUPPORTED //@{[s*2 for s in input.scores]} // UNSUPPORTED //@{{k: v.upper() for k, v in input.properties.items()}} // UNSUPPORTED
Orchestrator provides three ways to build a flow.
flow := builtin.NewSerial("get_todo_user").Timeout(3*time.Second).Tasks(
builtin.NewHTTP("get_todo").Timeout(2*time.Second).Get(
"https://jsonplaceholder.typicode.com/todos/${input.todoId}",
),
builtin.NewHTTP("get_user").Timeout(2*time.Second).Get(
"https://jsonplaceholder.typicode.com/users/${get_todo.body.userId}",
),
).Build()See Example for the complete example.
name: get_todo_user
type: serial
timeout: 3s
input:
tasks:
- name: get_todo
type: http
timeout: 2s
input:
method: GET
uri: https://jsonplaceholder.typicode.com/todos/${input.todoId}
- name: get_user
type: http
timeout: 2s
input:
method: GET
uri: https://jsonplaceholder.typicode.com/users/${get_todo.body.userId}See Example (Yaml) for the complete example.
{
"name": "get_todo_user",
"type": "serial",
"timeout": "3s",
"input": {
"tasks": [
{
"name": "get_todo",
"type": "http",
"timeout": "2s",
"input": {
"method": "GET",
"uri": "https://jsonplaceholder.typicode.com/todos/${input.todoId}"
}
},
{
"name": "get_user",
"type": "http",
"timeout": "2s",
"input": {
"method": "GET",
"uri": "https://jsonplaceholder.typicode.com/users/${get_todo.body.userId}"
}
}
]
}
}See Example (Json) for the complete example.
Checkout the Godoc.