https://github.com/mmzeeman/breaky

Fusebox provides a way to supervise and manage modules and processes depending on external resources.
https://github.com/mmzeeman/breaky

Last synced: 18 days ago
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Fusebox provides a way to supervise and manage modules and processes depending on external resources.

• Host: GitHub
• URL: https://github.com/mmzeeman/breaky
• Owner: mmzeeman
• Created: 2012-11-20T13:19:43.000Z (almost 12 years ago)
• Default Branch: master
• Last Pushed: 2016-11-30T15:52:02.000Z (almost 8 years ago)
• Last Synced: 2024-10-12T04:32:07.360Z (about 1 month ago)
• Language: Erlang
• Size: 108 KB
• Stars: 47
• Watchers: 5
• Forks: 9
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Breaky

Breaky provides a way to supervise and manage modules and processes depending on external

resources. For these kind of processes standard OTP supervisors will not work. The problem 

is that if something fails, the supervisor can't return the state of an external process 

into a known good state by restarting. The supervisor has no control over it. When that happens 

too often, the supervisor will fail too, and if a supervisor is restarted often enough it 

can take down the whole system down.

![Circuit Breaker](doc/circuit-breaker.jpg "Circuit Breaker")

Photo by [leafbug](http://www.flickr.com/photos/leafbug/) 

Breaky acts as a automatic circuit breaker "middleman" for these kind of processes. The 

process are started and managed in a normal OTP supervision tree. Restarts are managed 

by a circuit breaker FSM. When the FSM detects too many failures it will try to re-establish

the service, but when a certaint threshold of restarts has been reached the restarts will be 

done in a slower rate and calls or casts to the failing process will result in ```off``` to notify 

that the circuit breaker is off and the process is not available. This will prevent the fault 

from cascading through the system.

Example:

```erlang

    %% Start the circuit breaker for the database. It is an external resource.

    Args = [{user, "me"}, {password, "1234"}],

    {ok, _Pid} = breaky:start_circuit_breaker(db, {database, start_link, Args}),

 

    ...

    

    case breaky:call(db, "select * from my_table;") of

        off ->

            error_logger:error_msg("database unavailable"); 

            {error, db_unavailable};

        {ok, Result} ->

            Result

    end,

    ...

```

## Circuit Breaker States

| State |  Description |

| -----: | :------- |

| **Off** | The service is not available |

| **On** | The service is running normally |