Expose the Prometheus exporter port when specified in the config

.chloggen/1689-expose-prometheusexporter-pod-when-enabled.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. operator, target allocator, github action)
+component: operator
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Expose the Prometheus exporter port in the OpenTelemetry Collector container when it is used in the configuration.
+
+# One or more tracking issues related to the change
+issues: [1689]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

pkg/collector/container.go

@@ -186,6 +186,18 @@ func getConfigContainerPorts(logger logr.Logger, cfg string) map[string]corev1.C
 		ContainerPort: metricsPort,
 		Protocol:      corev1.ProtocolTCP,
 	}
+
+	promExporterPort, err := getPrometheusExporterPort(c)
+	if err != nil {
+		logger.V(2).Info("prometheus exporter port not detected")
+	} else {
+		ports["promexporter"] = corev1.ContainerPort{
+			Name:          "promexporter",
+			ContainerPort: promExporterPort,
+			Protocol:      corev1.ProtocolTCP,
+		}
+	}
+
 	return ports
 }
 
@@ -223,6 +235,36 @@ func getMetricsPort(c map[interface{}]interface{}) (int32, error) {
 	return int32(i64), nil
 }
 
+func getPrometheusExporterPort(c map[interface{}]interface{}) (int32, error) {
+	// we don't need to unmarshal the whole config, just follow the keys down to
+	// the prometheus endpoint.
+	type prometheusCfg struct {
+		Endpoint string
+	}
+	type exportersCfg struct {
+		Prometheus prometheusCfg
+	}
+	type cfg struct {
+		Exporters exportersCfg
+	}
+	var cOut cfg
+	err := mapstructure.Decode(c, &cOut)
+	if err != nil {
+		return 0, nil
+	}
+
+	_, port, err := net.SplitHostPort(cOut.Exporters.Prometheus.Endpoint)
+	if err != nil {
+		return 0, err
+	}
+	i64, err := strconv.ParseInt(port, 10, 32)
+	if err != nil {
+		return 0, err
+	}
+
+	return int32(i64), nil
+}
+
 func portMapToList(portMap map[string]corev1.ContainerPort) []corev1.ContainerPort {
 	ports := make([]corev1.ContainerPort, 0, len(portMap))
 	for _, p := range portMap {

pkg/collector/container_test.go

@@ -177,6 +177,21 @@ service:
 				},
 			},
 		},
+		{
+			description: "prometheus exporter ",
+			specConfig: `exporters:
+    prometheus:
+        endpoint: "0.0.0.0:9090"`,
+			specPorts: []corev1.ServicePort{},
+			expectedPorts: []corev1.ContainerPort{
+				metricContainerPort,
+				{
+					Name:          "promexporter",
+					ContainerPort: 9090,
+					Protocol:      corev1.ProtocolTCP,
+				},
+			},
+		},
 	}
 
 	for _, testCase := range tests {