[extension/observer] Expose host and port independently in endpoint e…

…nv (open-telemetry#33572)

**Description:** 
The observer extension currently only exposes `endpoint` in its endpoint
environment that is made available to the receiver creator for
dynamically configuring receivers. Some receivers require `host` and
`port` to be configured separately, so `endpoint` containing both is
incompatible with those receivers. Exposing these independently allows
the receiver creator to be compatible with those receivers.

**Link to tracking Issue:**
Resolves open-telemetry#33571

.chloggen/observer_expose_host_port.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# 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. filelogreceiver)
+component: observerextension
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Expose host and port in endpoint's environment
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [33571]
+
+# (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:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

extension/observer/endpoints.go

@@ -6,6 +6,7 @@ package observer // import "github.com/open-telemetry/opentelemetry-collector-co
 import (
 	"errors"
 	"fmt"
+	"net"
 	"reflect"
 )
 
@@ -69,6 +70,27 @@ func (e *Endpoint) Env() (EndpointEnv, error) {
 	env["type"] = string(e.Details.Type())
 	env["id"] = string(e.ID)
 
+	// Exposing the target as a split "host" and "port" enables the receiver creator
+	// to be able to discover receivers that require these options to be configured
+	// separately.
+	const hostKey = "host"
+	const portKey = "port"
+	host, port, err := net.SplitHostPort(e.Target)
+	// An error most likely means there was no port when splitting, so the host
+	// can simply be the target.
+	if err != nil {
+		host = e.Target
+	} else {
+		// Only try to set the port if a valid port was found when splitting the target
+		if _, keyExists := env[portKey]; !keyExists {
+			env[portKey] = port
+		}
+	}
+
+	if _, keyExists := env[hostKey]; !keyExists {
+		env[hostKey] = host
+	}
+
 	return env, nil
 }
 

extension/observer/endpoints_test.go

@@ -46,6 +46,7 @@ func TestEndpointEnv(t *testing.T) {
 				},
 				"uid":       "pod-uid",
 				"namespace": "pod-namespace",
+				"host":      "192.68.73.2",
 			},
 		},
 		{
@@ -88,6 +89,7 @@ func TestEndpointEnv(t *testing.T) {
 					"namespace": "pod-namespace",
 				},
 				"transport": ProtocolTCP,
+				"host":      "192.68.73.2",
 			},
 		},
 		{
@@ -124,6 +126,7 @@ func TestEndpointEnv(t *testing.T) {
 				"namespace":    "service-namespace",
 				"cluster_ip":   "192.68.73.2",
 				"service_type": "LoadBalancer",
+				"host":         "service.namespace",
 			},
 		},
 		{
@@ -148,6 +151,7 @@ func TestEndpointEnv(t *testing.T) {
 				"is_ipv6":      true,
 				"port":         uint16(2379),
 				"transport":    ProtocolUDP,
+				"host":         "127.0.0.1",
 			},
 		},
 		{
@@ -228,6 +232,54 @@ func TestEndpointEnv(t *testing.T) {
 				"labels": map[string]string{
 					"label_key": "label_val",
 				},
+				"host": "127.0.0.1",
+				"port": "1234",
+			},
+		},
+		{
+			// This is an invalid test case, to ensure "port" keeps the original value and
+			// isn't overwritten by a port parsed from the "Target". The two ports shouldn't mismatch
+			// if they're exposed in both places.
+			name: "K8s pod port - conflicting ports",
+			endpoint: Endpoint{
+				ID:     EndpointID("port_id"),
+				Target: "192.68.73.2:4321",
+				Details: &Port{
+					Name: "port_name",
+					Pod: Pod{
+						Name: "pod_name",
+						Labels: map[string]string{
+							"label_key": "label_val",
+						},
+						Annotations: map[string]string{
+							"annotation_1": "value_1",
+						},
+						Namespace: "pod-namespace",
+						UID:       "pod-uid",
+					},
+					Port:      2379,
+					Transport: ProtocolTCP,
+				},
+			},
+			want: EndpointEnv{
+				"type":     "port",
+				"endpoint": "192.68.73.2:4321",
+				"id":       "port_id",
+				"name":     "port_name",
+				"port":     uint16(2379),
+				"pod": EndpointEnv{
+					"name": "pod_name",
+					"labels": map[string]string{
+						"label_key": "label_val",
+					},
+					"annotations": map[string]string{
+						"annotation_1": "value_1",
+					},
+					"uid":       "pod-uid",
+					"namespace": "pod-namespace",
+				},
+				"transport": ProtocolTCP,
+				"host":      "192.68.73.2",
 			},
 		},
 	}

receiver/receivercreator/README.md

@@ -278,6 +278,14 @@ receivers:
         # Set a resource attribute based on endpoint value.
         rule: type == "port" && port == 6379
 
+      sqlserver:
+        rule: type == "port" && pod.name matches "(?i)mssql"
+        config:
+          server: '`host`'
+          port: '`port`'
+          username: sa
+          password: password
+
     resource_attributes:
       # Dynamic configuration values, overwriting default attributes`
       pod: