DMS (Dead Man's Switch)

A simple OTP Application (and eventually an HTTP API) which enables short circuiting when a service becomes unavailable.

Used as a learning project for members of Belfast Elixir.

• Build: mix do deps.get, compile
• Test: mix test
• Documentation: mix docs
• REPL: iex -S mix
• Observe: :observer.start

API Examples

# Ping will register service with that id as alive
id = "my-svc-id"
DMS.ping(id) # => :pong
DMS.alive?(id) # => true ~ Service with id responds as alive
# After @timeout period and no further pings
DMS.alive?(id) # => false ~ Service with id responds as dead

# An id which has never pinged will also respond as dead
false = DMS.alive?("another-svc-id") #=> false

Checklist

• (#13) Model a Service as a Process (DMS.Service)
• (#1) Register Service against an id (DMS.Servce.Registry)
• (#2) Add a supervisor for Service Process (DMS.Service.Supervisor)
• (#3) Add ping(id) function which will init Service if doesn't exist
• (#4) Add alive?(id) function which returns true if service alive otherwise false
• (#5) Add timer to service process which will terminate the process if it hasn't been pinged within @timeout
• (#12) Add Documentation with ExDoc
• (#6) Add Credo & Dialyzer for linting and static analysis.
• (#7) Add API to set service as down (before timeout).
• (#8) Enhance DMS.id to contain service id and account token + hash it before use as key in DMS.Servise.Registry.
• (#9) Add HTTP API.
• (#10) Add Pub/Sub push based API to notify when service is down.
• (#11) Publish on HEX package manager.