Command Line Interface

Nameko ships with a command line interface to make hosting and interacting with services as easy as possible.

Running a Service

$ nameko run <module>[:<ServiceClass>]

Discover and run a service class. This will start the service in the foreground and run it until the process terminates.

It is possible to override the default settings using a --config switch

$ nameko run --config ./foobar.yaml <module>[:<ServiceClass>]

and providing a simple YAML configuration file:

# foobar.yaml

AMQP_URI: 'pyamqp://guest:guest@localhost'
WEB_SERVER_ADDRESS: '0.0.0.0:8000'
rpc_exchange: 'nameko-rpc'
max_workers: 10
parent_calls_tracked: 10

LOGGING:
    version: 1
    handlers:
        console:
            class: logging.StreamHandler
    root:
        level: DEBUG
        handlers: [console]

The LOGGING entry is passed to logging.config.dictConfig() and should conform to the schema for that call.

Config values can be read via the built-in Config dependency provider.

Environment variable substitution

YAML configuration files have support for environment variables. You can use bash style syntax: ${ENV_VAR}. Optionally you can provide default values ${ENV_VAR:default_value}. Default values can contains environment variables recursively ${ENV_VAR:default_${OTHER_ENV_VAR:value}} (note: this feature requires regex package).

# foobar.yaml
AMQP_URI: pyamqp://${RABBITMQ_USER:guest}:${RABBITMQ_PASSWORD:password}@${RABBITMQ_HOST:localhost}

To run your service and set environment variables for it to use:

$ RABBITMQ_USER=user RABBITMQ_PASSWORD=password RABBITMQ_HOST=host nameko run --config ./foobar.yaml <module>[:<ServiceClass>]

If you need to quote the values in your YAML file, the explicit !env_var resolver is required:

# foobar.yaml
AMQP_URI: !env_var "pyamqp://${RABBITMQ_USER:guest}:${RABBITMQ_PASSWORD:password}@${RABBITMQ_HOST:localhost}"

You can provide many levels of default values

# foobar.yaml
AMQP_URI: ${AMQP_URI:pyamqp://${RABBITMQ_USER:guest}:${RABBITMQ_PASSWORD:password}@${RABBITMQ_HOST:localhost}}

this config accepts AMQP_URI as an environment variable, if provided RABBITMQ_* nested variables will not be used.

The environment variable value is interpreted as YAML, so it is possible to use rich types:

# foobar.yaml
...
THINGS: ${A_LIST_OF_THINGS}
$ A_LIST_OF_THINGS=[A,B,C] nameko run --config ./foobar.yaml <module>[:<ServiceClass>]

the parser for environment variables will pair all brackets.

# foobar.yaml
LANDING_URL_TEMPLATE: ${LANDING_URL_TEMPLATE:https://example.com/{path}}

so the default value for this config will be https://example.com/{path}

Interacting with running services

$ nameko shell

Launch an interactive python shell for working with remote nameko services. This is a regular interactive interpreter, with a special module n added to the built-in namespace, providing the ability to make RPC calls and dispatch events.

Making an RPC call to “target_service”:

$ nameko shell
>>> n.rpc.target_service.target_method(...)
# RPC response

Dispatching an event as “source_service”:

$ nameko shell
>>> n.dispatch_event("source_service", "event_type", "event_payload")