Loki

This charm library contains utilities to automatically forward your charm logs to a loki-push-api endpoint.

(yes! charm code, not workload code!)

If your charm isn't already related to Loki using any of the consumers/forwarders from the loki_push_api library, you need to:

charmcraft fetch-lib charms.loki_k8s.v1.loki_push_api

and add the logging consumer that matches your use case. See https://charmhub.io/loki-k8s/libraries/loki_push_apihttps://charmhub.io/loki-k8s/libraries/loki_push_api for more information.

Once your charm is related to, for example, COS' Loki charm (or a Grafana Agent), you will be able to inspect in real time from the Grafana dashboard the logs emitted by your charm.

Labels

The library will inject the following labels into the records sent to Loki:

• model: name of the juju model this charm is deployed to
• model_uuid: uuid of the model
• application: juju application name (such as 'mycharm')
• unit: unit name (such as 'mycharm/0')
• charm_name: name of the charm (whatever is in metadata.yaml) under 'name'.
• juju_hook_name: name of the juju event being processed ` service_name: name of the service this charm represents. Defaults to app name, but can be configured by the user.

Usage

To start using this library, you need to do two things: that returns an http/https endpoint url. If you are using the LokiPushApiConsumer as

1. decorate your charm class with

   @log_charm(loki_push_api_endpoint="my_logging_endpoints")

2. add to your charm a "my_logging_endpoint" (you can name this attribute whatever you like) property

self.logging = LokiPushApiConsumer(self, ...), the implementation could be:

@property
def my_logging_endpoints(self) -> List[str]:
    '''Loki push API endpoints for charm logging.'''
    # this will return an empty list if there is no relation or there is no data yet in the relation
    return ["http://loki-0.loki.svc.cluster.local:3100"]

The log_charm decorator will take these endpoints and set up the root logger (as in python's logging module root logger) to forward all logs to these loki endpoints.

TLS support

If your charm integrates with a tls provider which is also trusted by the logs receiver, you can configure TLS by passing a server_cert parameter to the decorator.

If you're not using the same CA as the loki-push-api endpoint you are sending logs to, you'll need to implement a cert-transfer relation to obtain the CA certificate from the same CA that Loki is using.

@log_charm(loki_push_api_endpoint="my_logging_endpoint", server_cert="my_server_cert")
class MyCharm(...):
    ...

    @property
    def my_server_cert(self) -> Optional[str]:
        '''Absolute path to a server crt if TLS is enabled.'''
        if self.tls_is_enabled():
            return "/path/to/my/server_cert.crt"