Otel distributions cleanup

Author: dragomirp

src/charm.py

@@ -4,6 +4,63 @@
 
 """Charmed Machine Operator for the PostgreSQL database."""
 
+
+def _remove_stale_otel_sdk_packages():
+    """Hack to remove stale opentelemetry sdk packages from the charm's python venv.
+
+    See https://github.com/canonical/grafana-agent-operator/issues/146 and
+    https://bugs.launchpad.net/juju/+bug/2058335 for more context. This patch can be removed after
+    this juju issue is resolved and sufficient time has passed to expect most users of this library
+    have migrated to the patched version of juju.  When this patch is removed, un-ignore rule E402 for this file in the pyproject.toml (see setting
+    [tool.ruff.lint.per-file-ignores] in pyproject.toml).
+
+    This only has an effect if executed on an upgrade-charm event.
+    """
+    # all imports are local to keep this function standalone, side-effect-free, and easy to revert later
+    import os
+
+    if os.getenv("JUJU_DISPATCH_PATH") != "hooks/upgrade-charm":
+        return
+
+    import logging
+    import shutil
+    from collections import defaultdict
+
+    from importlib_metadata import distributions
+
+    otel_logger = logging.getLogger("charm_tracing_otel_patcher")
+    otel_logger.debug("Applying _remove_stale_otel_sdk_packages patch on charm upgrade")
+    # group by name all distributions starting with "opentelemetry_"
+    otel_distributions = defaultdict(list)
+    for distribution in distributions():
+        name = distribution._normalized_name
+        if name.startswith("opentelemetry_"):
+            otel_distributions[name].append(distribution)
+
+    otel_logger.debug(f"Found {len(otel_distributions)} opentelemetry distributions")
+
+    # If we have multiple distributions with the same name, remove any that have 0 associated files
+    for name, distributions_ in otel_distributions.items():
+        if len(distributions_) <= 1:
+            continue
+
+        otel_logger.debug(f"Package {name} has multiple ({len(distributions_)}) distributions.")
+        for distribution in distributions_:
+            if not distribution.files:  # Not None or empty list
+                path = distribution._path
+                otel_logger.info(f"Removing empty distribution of {name} at {path}.")
+                shutil.rmtree(path)
+
+    otel_logger.debug("Successfully applied _remove_stale_otel_sdk_packages patch. ")
+
+
+# apply hacky patch to remove stale opentelemetry sdk packages on upgrade-charm.
+# it could be trouble if someone ever decides to implement their own tracer parallel to
+# ours and before the charm has inited. We assume they won't.
+# !!IMPORTANT!! keep all otlp imports UNDER this call.
+_remove_stale_otel_sdk_packages()
+
+# ruff: disable[E402]
 import json
 import logging
 import os
@@ -122,6 +179,8 @@
 from upgrade import PostgreSQLUpgrade, get_postgresql_dependencies_model
 from utils import new_password, snap_refreshed
 
+# ruff: enable[E402]
+
 logger = logging.getLogger(__name__)
 logging.getLogger("httpx").setLevel(logging.WARNING)
 logging.getLogger("httpcore").setLevel(logging.WARNING)