STEPN

Tool to execute commands in sequence.

Install

cargo install --git https://github.com/rnitta/stepn

Practical Usage

Assuming web development with Ruby on Rails and webpack(-dev-server). When you run Rails app in local env, you must run commands below:

1. bundle exec rails db:migrate && bundle exec rails s
2. yarn start
3. docker-compose -f datastores.yml up

Now, Command 1 is dependent to Command 3, because the database migration cannot be done without datastores booted. So, you should follow these steps manually:

• execute docker-compose -f datastores.yml up
• execute yarn start
• wait until docker-compose's startup process is done and the middlewares(such as postgresql, redis) is ready to accept connection.
• execute bundle exec rails db:migrate && bundle exec rails s

Irritating.

Write proc.toml and execute stepn.

How it works

1

2

3

proc.toml

Config

name	required	default	type	explain
services	yes	-	HashMap<String, Service>	list of service and its name

Service

name	required	default	type	explain
command	yes	None	String	command run in the service
depends_on	no	None	Vec	names of the other services waiting to be started when that service is started
health_checker	no	None	HealthChecker	conditions for certifying that the service has booted
environments	no	None	HashMap<String, String>	environment variables: <key, value>
delay_sec	no	None	u64	seconds to wait before starting that service

HealthChecker

name	required	default	type	explain
output_trigger	no	None	Vec	string to mark the service as booted if it appears in the log output to stdout

see src/stepn_config.rs for detail.

example1:

[services.a]
command = "for i in {0..10}; do echo a$i; sleep 1; done"

# conditions of assuming the startup is done
[services.a.health_checker]
output_trigger = [
    "2",
    "5"
]

[services.b]
command = "for i in {0..10}; do echo b$i; sleep 1; done"
depends_on = ["a"]

[services.b.health_checker]
output_trigger = [
    "4"
]

[services.c]
command = "for i in {0..10}; do echo c$i; sleep 1; done"
depends_on = ["b"]

example2:

[services.middleware]
command = "docker-compose --file dc-ds.yml up"

# conditions of assuming the startup is done
[services.middleware.health_check]
output_trigger = [
    "Ready to accept connections", # redis
    "database system is ready to accept connections" # postgresql
]

[services.web]
command = "bundle exec rails db:migrate && bundle exec rails s"
# migration can be executed after postgresql is booted.
depends_on = [ "middleware" ]
[services.web.environments]
PORT = "3000"
BINDING = "0.0.0.0"

[services.frontend]
command = "yarn webpack-dev-server"