Update charm tracing libs + add support for exporting traces via HTTPS

lib/charms/tempo_k8s/v1/charm_tracing.py

@@ -126,15 +126,14 @@ def my_tracing_endpoint(self) -> Optional[str]:
 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
 
@@ -147,7 +146,7 @@ def my_tracing_endpoint(self) -> Optional[str]:
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
 
-LIBPATCH = 8
+LIBPATCH = 10
 
 PYDEPS = ["opentelemetry-exporter-otlp-proto-http==1.21.0"]
 
@@ -295,16 +294,17 @@ def wrap_init(self: CharmBase, framework: Framework, *args, **kwargs):
         # self.handle = Handle(None, self.handle_kind, None)
 
         original_event_context = framework._event_context
+        # default service name isn't just app name because it could conflict with the workload service name
+        _service_name = service_name or f"{self.app.name}-charm"
 
-        _service_name = service_name or self.app.name
-
+        unit_name = self.unit.name
         resource = Resource.create(
             attributes={
                 "service.name": _service_name,
                 "compose_service": _service_name,
                 "charm_type": type(self).__name__,
                 # juju topology
-                "juju_unit": self.unit.name,
+                "juju_unit": unit_name,
                 "juju_application": self.app.name,
                 "juju_model": self.model.name,
                 "juju_model_uuid": self.model.uuid,
@@ -342,16 +342,18 @@ def wrap_init(self: CharmBase, framework: Framework, *args, **kwargs):
         _tracer = get_tracer(_service_name)  # type: ignore
         _tracer_token = tracer.set(_tracer)
 
-        dispatch_path = os.getenv("JUJU_DISPATCH_PATH", "")
+        dispatch_path = os.getenv("JUJU_DISPATCH_PATH", "")  # something like hooks/install
+        event_name = dispatch_path.split("/")[1] if "/" in dispatch_path else dispatch_path
+        root_span_name = f"{unit_name}: {event_name} event"
+        span = _tracer.start_span(root_span_name, attributes={"juju.dispatch_path": dispatch_path})
 
         # all these shenanigans are to work around the fact that the opentelemetry tracing API is built
         # on the assumption that spans will be used as contextmanagers.
         # Since we don't (as we need to close the span on framework.commit),
         # we need to manually set the root span as current.
-        span = _tracer.start_span("charm exec", attributes={"juju.dispatch_path": dispatch_path})
         ctx = set_span_in_context(span)
 
-        # log a trace id so we can look it up in tempo.
+        # log a trace id, so we can pick it up from the logs (and jhack) to look it up in tempo.
         root_trace_id = hex(span.get_span_context().trace_id)[2:]  # strip 0x prefix
         logger.debug(f"Starting root trace with id={root_trace_id!r}.")
 

lib/charms/tempo_k8s/v2/tracing.py

@@ -72,6 +72,7 @@ def __init__(self, *args):
 import enum
 import json
 import logging
+from pathlib import Path
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -82,6 +83,7 @@ def __init__(self, *args):
     Optional,
     Sequence,
     Tuple,
+    Union,
     cast,
 )
 
@@ -105,7 +107,7 @@ 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 = 6
+LIBPATCH = 7
 
 PYDEPS = ["pydantic"]
 
@@ -921,3 +923,68 @@ def get_endpoint(
 
             return None
         return endpoint
+
+
+def charm_tracing_config(
+    endpoint_requirer: TracingEndpointRequirer, cert_path: Optional[Union[Path, str]]
+) -> Tuple[Optional[str], Optional[str]]:
+    """Utility function to determine the charm_tracing config you will likely want.
+
+    If no endpoint is provided:
+     disable charm tracing.
+    If https endpoint is provided but cert_path is not found on disk:
+     disable charm tracing.
+    If https endpoint is provided and cert_path is None:
+     ERROR
+    Else:
+     proceed with charm tracing (with or without tls, as appropriate)
+
+    Usage:
+      If you are using charm_tracing >= v1.9:
+    >>> from lib.charms.tempo_k8s.v1.charm_tracing import trace_charm
+    >>> from lib.charms.tempo_k8s.v2.tracing import charm_tracing_config
+    >>> @trace_charm(tracing_endpoint="my_endpoint", cert_path="cert_path")
+    >>> class MyCharm(...):
+    >>>     _cert_path = "/path/to/cert/on/charm/container.crt"
+    >>>     def __init__(self, ...):
+    >>>         self.tracing = TracingEndpointRequirer(...)
+    >>>         self.my_endpoint, self.cert_path = charm_tracing_config(
+    ...             self.tracing, self._cert_path)
+
+      If you are using charm_tracing < v1.9:
+    >>> from lib.charms.tempo_k8s.v1.charm_tracing import trace_charm
+    >>> from lib.charms.tempo_k8s.v2.tracing import charm_tracing_config
+    >>> @trace_charm(tracing_endpoint="my_endpoint", cert_path="cert_path")
+    >>> class MyCharm(...):
+    >>>     _cert_path = "/path/to/cert/on/charm/container.crt"
+    >>>     def __init__(self, ...):
+    >>>         self.tracing = TracingEndpointRequirer(...)
+    >>>         self._my_endpoint, self._cert_path = charm_tracing_config(
+    ...             self.tracing, self._cert_path)
+    >>>     @property
+    >>>     def my_endpoint(self):
+    >>>         return self._my_endpoint
+    >>>     @property
+    >>>     def cert_path(self):
+    >>>         return self._cert_path
+
+    """
+    if not endpoint_requirer.is_ready():
+        return None, None
+
+    endpoint = endpoint_requirer.get_endpoint("otlp_http")
+    if not endpoint:
+        return None, None
+
+    is_https = endpoint.startswith("https://")
+
+    if is_https:
+        if cert_path is None:
+            raise TracingError("Cannot send traces to an https endpoint without a certificate.")
+        elif not Path(cert_path).exists():
+            # if endpoint is https BUT we don't have a server_cert yet:
+            # disable charm tracing until we do to prevent tls errors
+            return None, None
+        return endpoint, str(cert_path)
+    else:
+        return endpoint, None