locald

locald is a library that helps run microservices (or even regular services) in local development. It allows you to define service dependencies, restart behavior, etc.

locald utilizes a client-server model whereby a server process manages your running services and cli client (locald) interacts with the server.

Usage

For help, run locald --help.

locald server-start: start the locald daemon.

locald server-stop: stop the locald daemon.

locald start <service>: start the named service, and any dependencies.

locald stop <service>: stop the named service. only stops the named service, not any services it depends on.

locald restart <service>: restart the named service. will stop only the named service and start all dependencies.

locald status ALL: show known services and their status.

To stop all services, it is simplest to stop the server itself: locald server-stop. This will stop all child processes of the server.

Logs can be retrieved with the locald logs command. Specify the name of the service to get logs for just that service as in locald logs cart_api or use the keyword ALL to get the logs for all services known to locald. This command will follow the log output.

Install

pip install locald

Configuration

locald has a configuration file, locald.ini, which is a standard .ini file. In it, you define any locald settings and any services locald should be managing.

A basic configuration that manages two services might look like:

[locald]
pid_path=/tmp/myproject.pid

[cart_api]
service_path=cart.myproject.com/backend/myproject_cart_api/locald.service

[cart_www]
service_path=cart.myproject.com/frontend/locald.service

In this case, we define a pid_path for this specific instance of locald (as you can run many, it is good to make them unique) and two services: a backend API service (for example, flask application that you are running locally and a frontend service, perhaps a react.js application.

Services can be defined either directly in the locald.ini file or using the service_path directive, as shown here.

Configuration files for these services might look like:

id=cart_api
description=Shopping Cart API
restart=always # or, never
restart_seconds=1 # if restarting, how many seconds to wait before doing so
command=/usr/bin/env python3 ../bin/serve.py

id=cart_www
description=Shopping Cart Frontend
restart=always # or, never
restart_seconds=1 # if restarting, how many seconds to wait before doing so
command=yarn run start
requires=cart_api

In this example, cart_www indicates that it requires cart_api. locald will determine that, if locald start cart_www is run, that cart_api must also be running, and will start it if it is not.

Server logs can be configured using Python's standard logging configuration in the locald.ini file like so:

[loggers]
keys=root

[logger_root]
handlers=console,file
level=NOTSET

[handlers]
keys=console,file

[handler_file]
class=FileHandler
formatter=basic
level=NOTSET
args=("/tmp/locald.log", "w")

[handler_console]
class=StreamHandler
formatter=basic
level=NOTSET
args=(sys.stdout,)

[formatters]
keys=basic

[formatter_basic]
format=%(asctime)s - %(name)s - %(levelname)s - %(module)s:%(lineno)d - %(message)s