# Circuit Breaker

Janus has a circuit breaker plugin that can be configured for each endpoint. You can check our [example](https://github.com/hellofresh/janus/tree/master/examples/plugin-cb) on how to use the plugin.

## Configuration

The plain cb config:

```javascript
{
    "name" : "cb",
    "enabled" : true,
    "config" : {
        "name": "my-circuit-breaker",
        "timeout" : 1000,
        "max_concurrent_requests": 100,
        "error_percent_threshold": 50,
        "request_volume_threshold": 20,
        "sleep_window": 5000,
        "predicate": "statusCode == 0 || statusCode >= 500"
    }
}
```

| Configuration              | Description                                                                                                                                                                |    |                     |
| -------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -- | ------------------- |
| name                       | Circuit Breaker name to group stats                                                                                                                                        |    |                     |
| timeout                    | Timeout that the CB will wait till the request responds                                                                                                                    |    |                     |
| max\_concurrent\_requests  | How many commands of the same type can run at the same time                                                                                                                |    |                     |
| error\_percent\_threshold  | Causes circuits to open once the rolling measure of errors exceeds this percent of requests                                                                                |    |                     |
| request\_volume\_threshold | Is the minimum number of requests needed before a circuit can be tripped due to health                                                                                     |    |                     |
| sleep\_window              | Is how long, in milliseconds, to wait after a circuit opens before testing for recovery                                                                                    |    |                     |
| predicate                  | The rule that we will check to define if the request was successful or not. You have access to `statusCode` and all the `request` object. Defaults to \`statusCode == 0 \\ | \\ | statusCode >= 500\` |


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