Merge ~mertkirpici/charm-graylog:lp/2003795 into charm-graylog:master

[Mert Kirpici]

Close LP #2003795

layer/graylog/api: dynamic import search path

The file lib/charms/layer/graylog/api.py is both imported by the graylog charm and the nrpe charm. While running in the nrpe context, we need to add the graylog charm's site-packages dir to the search path in order for the import mechanism to work correctly.

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

This merge proposal is being monitored by mergebot. Change the status to Approved to merge.

[🤖 prod-jenkaas-bootstack (prod-jenkaas-bootstack)]

PASSED: Continuous integration, rev:7a2247df7c7dce75445f7b6a4ef5d5bcb9817be3
https://jenkins.canonical.com/bootstack/job/lp-charm-graylog-ci/218/
Executed test runs:
    SUCCESS: https://jenkins.canonical.com/bootstack/job/lp-charm-test-functest/2105/
    None: https://jenkins.canonical.com/bootstack/job/lp-update-mp/1945/

Click here to trigger a rebuild:
https://jenkins.canonical.com/bootstack/job/lp-charm-graylog-ci/218//rebuild

review: Approve (continuous-integration)

[Sudeep Bhandari (sudeephb)]

I tested, and the error has gone away on the first look. Thank you.
Left a small nitpick comment.

review: Approve

[Erhan Sunar (esunar)]

review: Approve

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

Change successfully merged at revision c167a0075da580fd96398ecb2e804ea380164903

[🤖 prod-jenkaas-bootstack (prod-jenkaas-bootstack)]

PASSED: Continuous integration, rev:fac0de5402139254cdcaa71a2d7c0d5bf4edbc9f
https://jenkins.canonical.com/bootstack/job/lp-charm-graylog-ci/219/
Executed test runs:
    SUCCESS: https://jenkins.canonical.com/bootstack/job/lp-charm-test-functest/2107/
    None: https://jenkins.canonical.com/bootstack/job/lp-update-mp/1947/

Click here to trigger a rebuild:
https://jenkins.canonical.com/bootstack/job/lp-charm-graylog-ci/219//rebuild

review: Approve (continuous-integration)

diff --git a/src/lib/charms/layer/graylog/api.py b/src/lib/charms/layer/graylog/api.py
index cdda27b..7445fa6 100644
--- a/src/lib/charms/layer/graylog/api.py
+++ b/src/lib/charms/layer/graylog/api.py
@@ -1,9 +1,14 @@
 """Manage graylog via its API."""
+import importlib.util
 import json
 import os
+import site
 
 import requests
 
+if not importlib.util.find_spec("tenacity"):
+    site.addsitedir("%CHARM_SITEPACKAGES_DIR%")
+
 from tenacity import retry
 from tenacity.retry import retry_if_exception_type
 from tenacity.stop import stop_after_delay
diff --git a/src/reactive/graylog.py b/src/reactive/graylog.py
index f6199f2..640e262 100644
--- a/src/reactive/graylog.py
+++ b/src/reactive/graylog.py
@@ -5,6 +5,7 @@ import os
 import re
 import socket
 import subprocess
+import sys
 import time
 from pathlib import Path
 from urllib.parse import urlparse
@@ -1329,10 +1330,26 @@ def configure_nagios(nagios):
         perms=0o640,
     )
     nagios_plugins = "/usr/local/lib/nagios/plugins/"
+    sitepackages_dir = os.path.realpath(
+        os.path.join(
+            hookenv.charm_dir(),
+            "../.venv/lib/python{major}.{minor}/site-packages".format(
+                major=sys.version_info.major, minor=sys.version_info.minor
+            ),
+        )
+    )
     for f in ("files/check_graylog_health.py", "lib/charms/layer/graylog/api.py"):
-        with open(f, "rb") as content:
+        with open(f, "rb") as raw_content:
             fname = os.path.join(nagios_plugins, os.path.basename(f))
-            host.write_file(fname, content.read(), perms=0o755)
+            # see lib/charms/layer/graylog/api.py
+            # on any other files, this operation is expected to be a no-op.
+            content = (
+                raw_content.read()
+                .decode()
+                .replace("%CHARM_SITEPACKAGES_DIR%", sitepackages_dir)
+                .encode()
+            )
+            host.write_file(fname, content, perms=0o755)
     nrpe_setup.add_check(
         shortname="graylog_health",
         description="Graylog Health check",