Merge ~dparv/charm-telegraf:fix_1891943 into charm-telegraf:master

[Diko Parvanov]

Fixes for bug 1891943

- prometheus_datasource now defaults to ""
- relation prometheus-client is used to parse the related application
name for prometheus from the related unit name
- prometheus_datasource will override this setting
- fixed lint/black

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

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

FAILED: Continuous integration, rev:295b888239451808d3bd801216f3772f0138066c
https://jenkins.canonical.com/bootstack/job/lp-charm-telegraf-ci/92/
Executed test runs:
    FAILURE: https://jenkins.canonical.com/bootstack/job/lp-charm-test-functest/233/
    None: https://jenkins.canonical.com/bootstack/job/lp-update-mp/680/

Click here to trigger a rebuild:
https://jenkins.canonical.com/bootstack/job/lp-charm-telegraf-ci/92//rebuild

review: Needs Fixing (continuous-integration)

[Xav Paice (xavpaice)]

CI failed on charm build due to the move of the nrpe-external-master interface. I've retriggered the CI run.

Other than CI, change LGTM.

Unmerged commits

295b888... by Diko Parvanov on 2021-12-01

Fixes for bug 1891943

- prometheus_datasource now defaults to ""
- relation prometheus-client is used to parse the related application
name for prometheus from the related unit name
- prometheus_datasource will override this setting
- fixed lint/black

diff --git a/src/config.yaml b/src/config.yaml
index 6bc4da8..591d434 100644
--- a/src/config.yaml
+++ b/src/config.yaml
@@ -197,11 +197,13 @@ options:
     description: >
       Comma separated list of nagios servicegroups for the telegraf check
   prometheus_datasource:
-    default: "prometheus"
+    default: ""
     type: string
     description: >
         Specifies the datasource for Grafana dashboards. This usually corresponds
-        to the application name of the related Prometheus. Defaults to "prometheus".
+        to the application name of the related Prometheus. Defaults to "" to
+        use the prometheus-client relation to parse the application name. If set
+        it will override the relation data.
 
         Note: The complete datasource inserted into dashboard will be
         "$prometheus_datasource - Juju generated source"
diff --git a/src/reactive/telegraf.py b/src/reactive/telegraf.py
index ba2e170..2cf3a47 100644
--- a/src/reactive/telegraf.py
+++ b/src/reactive/telegraf.py
@@ -1362,7 +1362,7 @@ def redis_input(redis):
 @when("endpoint.postfix.joined")
 @when_not("apt.installed.acl")
 def install_acl_package():
-    apt.queue_install(['acl'])
+    apt.queue_install(["acl"])
 
 
 @when("endpoint.postfix.joined")
@@ -1390,9 +1390,9 @@ def postfix_input(postfix, spool="/var/spool/postfix"):
             host.write_file(config_path, input_config.encode("utf-8"))
 
             # https://github.com/influxdata/telegraf/blob/master/plugins/inputs/postfix/README.md#permissions
-            cmd = ['setfacl', '-Rm', 'g:{}:rX'.format(get_telegraf_group()), spool]
+            cmd = ["setfacl", "-Rm", "g:{}:rX".format(get_telegraf_group()), spool]
             subprocess.call(cmd)
-            cmd = ['setfacl', '-dm', 'g:{}:rX'.format(get_telegraf_group()), spool]
+            cmd = ["setfacl", "-dm", "g:{}:rX".format(get_telegraf_group()), spool]
             subprocess.call(cmd)
 
             set_flag("plugins.postfix.configured")
@@ -1794,9 +1794,18 @@ def register_grafana_dashboard():
 
 
 def _load_grafana_dashboard(dashboard_data):
-    prometheus_datasource = "{} - Juju generated source".format(
-        hookenv.config().get("prometheus_datasource", "prometheus")
-    )
+
+    related_prometheus_app = None
+    for relation_id in hookenv.relation_ids("prometheus-client"):
+        for unit in hookenv.related_units(relation_id):
+            related_prometheus_app = unit[0 : unit.find("/")]  # noqa W203
+
+    if related_prometheus_app:
+        prometheus_app = related_prometheus_app
+    else:
+        prometheus_app = hookenv.config().get("prometheus_datasource", "prometheus")
+
+    prometheus_datasource = "{} - Juju generated source".format(prometheus_app)
     dashboard_context = dict(datasource=prometheus_datasource)
     dashboard_context.update(dashboard_data.get("context_vars", {}))
     return render_custom(
diff --git a/src/tests/unit/test_telegraf.py b/src/tests/unit/test_telegraf.py
index e9dc1f1..e4d3b54 100644
--- a/src/tests/unit/test_telegraf.py
+++ b/src/tests/unit/test_telegraf.py
@@ -957,8 +957,8 @@ def test_postfix_input_no_relations(monkeypatch):
     monkeypatch.setattr(telegraf.hookenv, "relations_of_type", lambda n: [])
     telegraf.postfix_input("test")
     assert not configs_dir().join("postfix.conf").exists()
-    with open(configs_dir().join("postfix.conf"), 'w') as f:
-        f.write('blah blah')
+    with open(configs_dir().join("postfix.conf"), "w") as f:
+        f.write("blah blah")
     telegraf.postfix_input("test", spool="/tmp")
     assert not configs_dir().join("postfix.conf").exists()