Add support for tracing with tempo_k8s (#250)

## Issue
We would like to be able to instrument our charm and generate traces to
discover inefficiencies in charm code execution. The observability team
has developed a charm for
[tempo](https://github.com/canonical/tempo-k8s-operator) that we would
like to integrate with.

## Solution
Integrate with the tempo charm

## Considerations
1. We must use COS lite with edge until it is release to stable with
some
2. We are sending traces with HTTP until some rough edges are rounded
with HTTPS


![image](https://github.com/canonical/mysql-router-k8s-operator/assets/99665202/7049fee1-2fd2-4df6-911c-059a3d43fd83)

.github/workflows/ci.yaml

@@ -31,7 +31,7 @@ jobs:
   unit-test:
     name: Unit test charm
     runs-on: ubuntu-latest
-    timeout-minutes: 15
+    timeout-minutes: 20
     steps:
       - name: Checkout
         uses: actions/checkout@v4

lib/charms/data_platform_libs/v0/data_interfaces.py

@@ -331,7 +331,7 @@ def _on_topic_requested(self, event: TopicRequestedEvent):
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 35
+LIBPATCH = 37
 
 PYDEPS = ["ops>=2.0.0"]
 
@@ -642,22 +642,26 @@ def _move_to_new_label_if_needed(self):
             return
 
         # Create a new secret with the new label
-        old_meta = self._secret_meta
         content = self._secret_meta.get_content()
+        self._secret_uri = None
 
         # I wish we could just check if we are the owners of the secret...
         try:
             self._secret_meta = self.add_secret(content, label=self.label)
         except ModelError as err:
             if "this unit is not the leader" not in str(err):
                 raise
-        old_meta.remove_all_revisions()
+        self.current_label = None
 
     def set_content(self, content: Dict[str, str]) -> None:
         """Setting cached secret content."""
         if not self.meta:
             return
 
+        # DPE-4182: do not create new revision if the content stay the same
+        if content == self.get_content():
+            return
+
         if content:
             self._move_to_new_label_if_needed()
             self.meta.set_content(content)
@@ -1586,7 +1590,7 @@ def _register_secret_to_relation(
         """
         label = self._generate_secret_label(relation_name, relation_id, group)
 
-        # Fetchin the Secret's meta information ensuring that it's locally getting registered with
+        # Fetching the Secret's meta information ensuring that it's locally getting registered with
         CachedSecret(self._model, self.component, label, secret_id).meta
 
     def _register_secrets_to_relation(self, relation: Relation, params_name_list: List[str]):
@@ -2309,7 +2313,7 @@ def _secrets(self) -> dict:
         return self._cached_secrets
 
     def _get_secret(self, group) -> Optional[Dict[str, str]]:
-        """Retrieveing secrets."""
+        """Retrieving secrets."""
         if not self.app:
             return
         if not self._secrets.get(group):

lib/charms/grafana_k8s/v0/grafana_dashboard.py

@@ -219,7 +219,7 @@ def __init__(self, *args):
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
 
-LIBPATCH = 35
+LIBPATCH = 36
 
 logger = logging.getLogger(__name__)
 
@@ -1050,6 +1050,7 @@ def __init__(
 
         self.framework.observe(self._charm.on.leader_elected, self._update_all_dashboards_from_dir)
         self.framework.observe(self._charm.on.upgrade_charm, self._update_all_dashboards_from_dir)
+        self.framework.observe(self._charm.on.config_changed, self._update_all_dashboards_from_dir)
 
         self.framework.observe(
             self._charm.on[self._relation_name].relation_created,

lib/charms/loki_k8s/v0/loki_push_api.py

@@ -16,9 +16,10 @@
   applications such as pebble, or charmed operators of workloads such as grafana-agent or promtail,
   that can communicate with loki directly.
 
-- `LogProxyConsumer`: This object can be used by any Charmed Operator which needs to
-send telemetry, such as logs, to Loki through a Log Proxy by implementing the consumer side of the
-`loki_push_api` relation interface.
+- `LogProxyConsumer`: DEPRECATED.
+This object can be used by any Charmed Operator which needs to send telemetry, such as logs, to
+Loki through a Log Proxy by implementing the consumer side of the `loki_push_api` relation
+interface.
 
 Filtering logs in Loki is largely performed on the basis of labels. In the Juju ecosystem, Juju
 topology labels are used to uniquely identify the workload which generates telemetry like logs.
@@ -38,13 +39,14 @@
 - `charm`: A reference to the parent (Loki) charm.
 
 - `relation_name`: The name of the relation that the charm uses to interact
-  with its clients, which implement `LokiPushApiConsumer` or `LogProxyConsumer`.
+  with its clients, which implement `LokiPushApiConsumer` or `LogProxyConsumer`
+  (note that LogProxyConsumer is deprecated).
 
   If provided, this relation name must match a provided relation in metadata.yaml with the
   `loki_push_api` interface.
 
   The default relation name is "logging" for `LokiPushApiConsumer` and "log-proxy" for
-  `LogProxyConsumer`.
+  `LogProxyConsumer` (note that LogProxyConsumer is deprecated).
 
   For example, a provider's `metadata.yaml` file may look as follows:
 
@@ -219,6 +221,9 @@ def __init__(self, *args):
 
 ## LogProxyConsumer Library Usage
 
+> Note: This object is deprecated. Consider migrating to LogForwarder (see v1/loki_push_api) with
+> the release of Juju 3.6 LTS.
+
 Let's say that we have a workload charm that produces logs, and we need to send those logs to a
 workload implementing the `loki_push_api` interface, such as `Loki` or `Grafana Agent`.
 
@@ -480,7 +485,7 @@ def _alert_rules_error(self, event):
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 29
+LIBPATCH = 30
 
 PYDEPS = ["cosl"]
 
@@ -1539,7 +1544,8 @@ def __init__(
         the Loki API endpoint to push logs. It is intended for workloads that can speak
         loki_push_api (https://grafana.com/docs/loki/latest/api/#push-log-entries-to-loki), such
         as grafana-agent.
-        (If you only need to forward a few workload log files, then use LogProxyConsumer.)
+        (If you need to forward workload stdout logs, then use v1/loki_push_api.LogForwarder; if
+        you need to forward log files, then use LogProxyConsumer.)
 
         `LokiPushApiConsumer` can be instantiated as follows:
 
@@ -1728,6 +1734,9 @@ class LogProxyEvents(ObjectEvents):
 class LogProxyConsumer(ConsumerBase):
     """LogProxyConsumer class.
 
+    > Note: This object is deprecated. Consider migrating to v1/loki_push_api.LogForwarder with the
+    > release of Juju 3.6 LTS.
+
     The `LogProxyConsumer` object provides a method for attaching `promtail` to
     a workload in order to generate structured logging data from applications
     which traditionally log to syslog or do not have native Loki integration.