[DPE-4173] Stabilize exporter tests by using listen-port to avoid ephemeral ports (#277)

## Issue
We are finding connections in `TIME_WAIT` between router exporter and
mysql (still investigating what is happening here). Due to pebble's
`on-failure: restart`, the exporter service eventually is able to start
up when the connection in `TIME_WAIT` terminates after 60s - however,
our retry in the test is 3 mins sometimes does not provide enough time
for pebble's exponential backoff to work

## Solution
Extend the timeout to 7 mins

Author: shayancanonical

metadata.yaml

@@ -57,6 +57,6 @@ resources:
   mysql-router-image:
     type: oci-image
     description: OCI image for mysql-router
-    upstream-source: ghcr.io/canonical/charmed-mysql@sha256:4a605458a09dc53feed91a0d81310dca267b2ac273ed7e1798bc4cb50c14fe68
+    upstream-source: ghcr.io/canonical/charmed-mysql@sha256:89b8305613f6ce94f78a7c9b4baedef78f2816fd6bc74c00f6607bc5e57bd8e6
 assumes:
   - k8s-api

src/relations/cos.py

@@ -29,12 +29,13 @@ class ExporterConfig:
     url: str
     username: str
     password: str
+    listen_port: str
 
 
 class COSRelation:
     """Relation with the cos bundle."""
 
-    _EXPORTER_PORT = "49152"
+    _EXPORTER_PORT = "9152"
     HTTP_SERVER_PORT = "8443"
     _METRICS_RELATION_NAME = "metrics-endpoint"
     _LOGGING_RELATION_NAME = "logging"
@@ -86,6 +87,7 @@ def exporter_user_config(self) -> ExporterConfig:
             url=f"https://127.0.0.1:{self.HTTP_SERVER_PORT}",
             username=self.MONITORING_USERNAME,
             password=self.get_monitoring_password(),
+            listen_port=self._EXPORTER_PORT,
         )
 
     @property

src/rock.py

@@ -161,6 +161,7 @@ def update_mysql_router_exporter_service(
             startup = ops.pebble.ServiceStartup.ENABLED.value
 
             environment = {
+                "MYSQLROUTER_EXPORTER_LISTEN_PORT": config.listen_port,
                 "MYSQLROUTER_EXPORTER_USER": config.username,
                 "MYSQLROUTER_EXPORTER_PASS": config.password,
                 "MYSQLROUTER_EXPORTER_URL": config.url,

tests/integration/test_exporter.py

@@ -112,7 +112,7 @@ async def test_exporter_endpoint(ops_test: OpsTest) -> None:
     unit_address = await get_unit_address(ops_test, unit.name)
 
     try:
-        requests.get(f"http://{unit_address}:49152/metrics", stream=False)
+        requests.get(f"http://{unit_address}:9152/metrics", stream=False)
     except requests.exceptions.ConnectionError as e:
         assert "[Errno 111] Connection refused" in str(e), "❌ expected connection refused error"
     else:
@@ -137,7 +137,7 @@ async def test_exporter_endpoint(ops_test: OpsTest) -> None:
         wait=tenacity.wait_fixed(10),
     ):
         with attempt:
-            response = requests.get(f"http://{unit_address}:49152/metrics", stream=False)
+            response = requests.get(f"http://{unit_address}:9152/metrics", stream=False)
             response.raise_for_status()
             assert (
                 "mysqlrouter_route_health" in response.text
@@ -156,7 +156,7 @@ async def test_exporter_endpoint(ops_test: OpsTest) -> None:
     ):
         with attempt:
             try:
-                requests.get(f"http://{unit_address}:49152/metrics", stream=False)
+                requests.get(f"http://{unit_address}:9152/metrics", stream=False)
             except requests.exceptions.ConnectionError as e:
                 assert "[Errno 111] Connection refused" in str(
                     e

tests/integration/test_exporter_with_tls.py

@@ -161,7 +161,7 @@ async def test_exporter_endpoint(ops_test: OpsTest) -> None:
     ):
         with attempt:
             try:
-                requests.get(f"http://{unit_address}:49152/metrics", stream=False)
+                requests.get(f"http://{unit_address}:9152/metrics", stream=False)
             except requests.exceptions.ConnectionError as e:
                 assert "[Errno 111] Connection refused" in str(
                     e
@@ -187,7 +187,7 @@ async def test_exporter_endpoint(ops_test: OpsTest) -> None:
         wait=tenacity.wait_fixed(10),
     ):
         with attempt:
-            response = requests.get(f"http://{unit_address}:49152/metrics", stream=False)
+            response = requests.get(f"http://{unit_address}:9152/metrics", stream=False)
             response.raise_for_status()
             assert (
                 "mysqlrouter_route_health" in response.text
@@ -222,7 +222,7 @@ async def test_exporter_endpoint(ops_test: OpsTest) -> None:
     ):
         with attempt:
             try:
-                requests.get(f"http://{unit_address}:49152/metrics", stream=False)
+                requests.get(f"http://{unit_address}:9152/metrics", stream=False)
             except requests.exceptions.ConnectionError as e:
                 assert "[Errno 111] Connection refused" in str(
                     e