[DPE-5312] Update tracing charm libs to retrieve them from tempo coordinator repo (#324)

## Issue
There are a bunch of tempo tracing related updates:
1. tempo-k8s has been deprecated in favor of tempo ha
2. tracing charm libs need to be fetch-ed from tempo_coordinator_k8s
3. tracing traffic is now relayed through grafana-agent-k8s (like the
remaining COS traffic)

## Solution
2. update tracing charm libs from new repo
Test integration with tempo ha + test relay of traffic through
grafana-agent-k8s

## To be done simultaneously
Update mysql-router-k8s tracing related documentation (in progress)

Author: shayancanonical

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 = 39
+LIBPATCH = 40
 
 PYDEPS = ["ops>=2.0.0"]
 
@@ -391,6 +391,10 @@ class IllegalOperationError(DataInterfacesError):
     """To be used when an operation is not allowed to be performed."""
 
 
+class PrematureDataAccessError(DataInterfacesError):
+    """To be raised when the Relation Data may be accessed (written) before protocol init complete."""
+
+
 ##############################################################################
 # Global helpers / utilities
 ##############################################################################
@@ -1453,6 +1457,8 @@ def _on_relation_changed_event(self, event: RelationChangedEvent) -> None:
 class ProviderData(Data):
     """Base provides-side of the data products relation."""
 
+    RESOURCE_FIELD = "database"
+
     def __init__(
         self,
         model: Model,
@@ -1618,6 +1624,15 @@ def _fetch_my_specific_relation_data(
     def _update_relation_data(self, relation: Relation, data: Dict[str, str]) -> None:
         """Set values for fields not caring whether it's a secret or not."""
         req_secret_fields = []
+
+        keys = set(data.keys())
+        if self.fetch_relation_field(relation.id, self.RESOURCE_FIELD) is None and (
+            keys - {"endpoints", "read-only-endpoints", "replset"}
+        ):
+            raise PrematureDataAccessError(
+                "Premature access to relation data, update is forbidden before the connection is initialized."
+            )
+
         if relation.app:
             req_secret_fields = get_encoded_list(relation, relation.app, REQ_SECRET_FIELDS)
 
@@ -3290,6 +3305,8 @@ class KafkaRequiresEvents(CharmEvents):
 class KafkaProviderData(ProviderData):
     """Provider-side of the Kafka relation."""
 
+    RESOURCE_FIELD = "topic"
+
     def __init__(self, model: Model, relation_name: str) -> None:
         super().__init__(model, relation_name)
 
@@ -3539,6 +3556,8 @@ class OpenSearchRequiresEvents(CharmEvents):
 class OpenSearchProvidesData(ProviderData):
     """Provider-side of the OpenSearch relation."""
 
+    RESOURCE_FIELD = "index"
+
     def __init__(self, model: Model, relation_name: str) -> None:
         super().__init__(model, relation_name)
 

lib/charms/loki_k8s/v1/loki_push_api.py

@@ -480,6 +480,25 @@ def _alert_rules_error(self, event):
 
 Units of consumer charm send their alert rules over app relation data using the `alert_rules`
 key.
+
+## Charm logging
+The `charms.loki_k8s.v0.charm_logging` library can be used in conjunction with this one to configure python's
+logging module to forward all logs to Loki via the loki-push-api interface.
+
+```python
+from lib.charms.loki_k8s.v0.charm_logging import log_charm
+from lib.charms.loki_k8s.v1.loki_push_api import charm_logging_config, LokiPushApiConsumer
+
+@log_charm(logging_endpoint="my_endpoints", server_cert="cert_path")
+class MyCharm(...):
+    _cert_path = "/path/to/cert/on/charm/container.crt"
+    def __init__(self, ...):
+        self.logging = LokiPushApiConsumer(...)
+        self.my_endpoints, self.cert_path = charm_logging_config(
+            self.logging, self._cert_path)
+```
+
+Do this, and all charm logs will be forwarded to Loki as soon as a relation is formed.
 """
 
 import json
@@ -527,7 +546,7 @@ 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 = 12
+LIBPATCH = 13
 
 PYDEPS = ["cosl"]
 
@@ -577,7 +596,11 @@ def _alert_rules_error(self, event):
 GRPC_LISTEN_PORT_START = 9095  # odd start port
 
 
-class RelationNotFoundError(ValueError):
+class LokiPushApiError(Exception):
+    """Base class for errors raised by this module."""
+
+
+class RelationNotFoundError(LokiPushApiError):
     """Raised if there is no relation with the given name."""
 
     def __init__(self, relation_name: str):
@@ -587,7 +610,7 @@ def __init__(self, relation_name: str):
         super().__init__(self.message)
 
 
-class RelationInterfaceMismatchError(Exception):
+class RelationInterfaceMismatchError(LokiPushApiError):
     """Raised if the relation with the given name has a different interface."""
 
     def __init__(
@@ -607,7 +630,7 @@ def __init__(
         super().__init__(self.message)
 
 
-class RelationRoleMismatchError(Exception):
+class RelationRoleMismatchError(LokiPushApiError):
     """Raised if the relation with the given name has a different direction."""
 
     def __init__(
@@ -2555,7 +2578,7 @@ def _on_pebble_ready(self, event: PebbleReadyEvent):
 
         self._update_endpoints(event.workload, loki_endpoints)
 
-    def _update_logging(self, _):
+    def _update_logging(self, event: RelationEvent):
         """Update the log forwarding to match the active Loki endpoints."""
         if not (loki_endpoints := self._retrieve_endpoints_from_relation()):
             logger.warning("No Loki endpoints available")
@@ -2566,6 +2589,8 @@ def _update_logging(self, _):
                 self._update_endpoints(container, loki_endpoints)
             # else: `_update_endpoints` will be called on pebble-ready anyway.
 
+        self._handle_alert_rules(event.relation)
+
     def _retrieve_endpoints_from_relation(self) -> dict:
         loki_endpoints = {}
 
@@ -2750,3 +2775,49 @@ def _exec(self, cmd) -> str:
         result = subprocess.run(cmd, check=True, stdout=subprocess.PIPE)
         output = result.stdout.decode("utf-8").strip()
         return output
+
+
+def charm_logging_config(
+    endpoint_requirer: LokiPushApiConsumer, cert_path: Optional[Union[Path, str]]
+) -> Tuple[Optional[List[str]], Optional[str]]:
+    """Utility function to determine the charm_logging config you will likely want.
+
+    If no endpoint is provided:
+     disable charm logging.
+    If https endpoint is provided but cert_path is not found on disk:
+     disable charm logging.
+    If https endpoint is provided and cert_path is None:
+     ERROR
+    Else:
+     proceed with charm logging (with or without tls, as appropriate)
+
+    Args:
+        endpoint_requirer: an instance of LokiPushApiConsumer.
+        cert_path: a path where a cert is stored.
+
+    Returns:
+        A tuple with (optionally) the values of the endpoints and the certificate path.
+
+    Raises:
+         LokiPushApiError: if some endpoint are http and others https.
+    """
+    endpoints = [ep["url"] for ep in endpoint_requirer.loki_endpoints]
+    if not endpoints:
+        return None, None
+
+    https = tuple(endpoint.startswith("https://") for endpoint in endpoints)
+
+    if all(https):  # all endpoints are https
+        if cert_path is None:
+            raise LokiPushApiError("Cannot send logs to https endpoints without a certificate.")
+        if not Path(cert_path).exists():
+            # if endpoints is https BUT we don't have a server_cert yet:
+            # disable charm logging until we do to prevent tls errors
+            return None, None
+        return endpoints, str(cert_path)
+
+    if all(not x for x in https):  # all endpoints are http
+        return endpoints, None
+
+    # if there's a disagreement, that's very weird:
+    raise LokiPushApiError("Some endpoints are http, some others are https. That's not good.")

lib/charms/tempo_k8s/v1/charm_tracing.py renamed to lib/charms/tempo_coordinator_k8s/v0/charm_tracing.py

@@ -12,15 +12,15 @@
 # Quickstart
 Fetch the following charm libs (and ensure the minimum version/revision numbers are satisfied):
 
-    charmcraft fetch-lib charms.tempo_k8s.v2.tracing  # >= 1.10
-    charmcraft fetch-lib charms.tempo_k8s.v1.charm_tracing  # >= 2.7
+    charmcraft fetch-lib charms.tempo_coordinator_k8s.v0.tracing  # >= 1.10
+    charmcraft fetch-lib charms.tempo_coordinator_k8s.v0.charm_tracing  # >= 2.7
 
 Then edit your charm code to include:
 
 ```python
 # import the necessary charm libs
-from charms.tempo_k8s.v2.tracing import TracingEndpointRequirer, charm_tracing_config
-from charms.tempo_k8s.v1.charm_tracing import charm_tracing
+from charms.tempo_coordinator_k8s.v0.tracing import TracingEndpointRequirer, charm_tracing_config
+from charms.tempo_coordinator_k8s.v0.charm_tracing import charm_tracing
 
 # decorate your charm class with charm_tracing:
 @charm_tracing(
@@ -51,7 +51,7 @@ def __init__(self, ...):
 
 2) add to your charm a "my_tracing_endpoint" (you can name this attribute whatever you like)
 **property**, **method** or **instance attribute** that returns an otlp http/https endpoint url.
-If you are using the ``charms.tempo_k8s.v2.tracing.TracingEndpointRequirer`` as
+If you are using the ``charms.tempo_coordinator_k8s.v0.tracing.TracingEndpointRequirer`` as
 ``self.tracing = TracingEndpointRequirer(self)``, the implementation could be:
 
 ```
@@ -80,7 +80,7 @@ def my_tracing_endpoint(self) -> Optional[str]:
 
 For example:
 ```
-from charms.tempo_k8s.v1.charm_tracing import trace_charm
+from charms.tempo_coordinator_k8s.v0.charm_tracing import trace_charm
 @trace_charm(
     tracing_endpoint="my_tracing_endpoint",
     server_cert="_server_cert"
@@ -129,7 +129,7 @@ def get_tracer(self) -> opentelemetry.trace.Tracer:
 For example:
 
 ```
-    from charms.tempo_k8s.v0.charm_tracing import trace_charm
+    from charms.tempo_coordinator_k8s.v0.charm_tracing import trace_charm
 
     @trace_charm(
         tracing_endpoint="my_tracing_endpoint",
@@ -150,7 +150,7 @@ def my_tracing_endpoint(self) -> Optional[str]:
 needs to be replaced with:
 
 ```
-    from charms.tempo_k8s.v1.charm_tracing import trace_charm
+    from charms.tempo_coordinator_k8s.v0.charm_tracing import trace_charm
 
     @trace_charm(
         tracing_endpoint="my_tracing_endpoint",
@@ -249,28 +249,27 @@ def _remove_stale_otel_sdk_packages():
 from opentelemetry.sdk.resources import Resource
 from opentelemetry.sdk.trace import Span, TracerProvider
 from opentelemetry.sdk.trace.export import BatchSpanProcessor
+from opentelemetry.trace import INVALID_SPAN, Tracer
+from opentelemetry.trace import get_current_span as otlp_get_current_span
 from opentelemetry.trace import (
-    INVALID_SPAN,
-    Tracer,
     get_tracer,
     get_tracer_provider,
     set_span_in_context,
     set_tracer_provider,
 )
-from opentelemetry.trace import get_current_span as otlp_get_current_span
 from ops.charm import CharmBase
 from ops.framework import Framework
 
 # The unique Charmhub library identifier, never change it
-LIBID = "cb1705dcd1a14ca09b2e60187d1215c7"
+LIBID = "01780f1e588c42c3976d26780fdf9b89"
 
 # Increment this major API version when introducing breaking changes
-LIBAPI = 1
+LIBAPI = 0
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
 
-LIBPATCH = 15
+LIBPATCH = 1
 
 PYDEPS = ["opentelemetry-exporter-otlp-proto-http==1.21.0"]
 
@@ -332,7 +331,7 @@ def _get_tracer() -> Optional[Tracer]:
         return tracer.get()
     except LookupError:
         # fallback: this course-corrects for a user error where charm_tracing symbols are imported
-        # from different paths (typically charms.tempo_k8s... and lib.charms.tempo_k8s...)
+        # from different paths (typically charms.tempo_coordinator_k8s... and lib.charms.tempo_coordinator_k8s...)
         try:
             ctx: Context = copy_context()
             if context_tracer := _get_tracer_from_context(ctx):
@@ -562,8 +561,8 @@ def trace_charm(
     method calls on instances of this class.
 
     Usage:
-    >>> from charms.tempo_k8s.v1.charm_tracing import trace_charm
-    >>> from charms.tempo_k8s.v1.tracing import TracingEndpointRequirer
+    >>> from charms.tempo_coordinator_k8s.v0.charm_tracing import trace_charm
+    >>> from charms.tempo_coordinator_k8s.v0.tracing import TracingEndpointRequirer
     >>> from ops import CharmBase
     >>>
     >>> @trace_charm(
@@ -626,7 +625,7 @@ def _autoinstrument(
 
     Usage:
 
-    >>> from charms.tempo_k8s.v1.charm_tracing import _autoinstrument
+    >>> from charms.tempo_coordinator_k8s.v0.charm_tracing import _autoinstrument
     >>> from ops.main import main
     >>> _autoinstrument(
     >>>         MyCharm,