[receiver/rabbitmq] Enhancement/rabbitmq Added node level metrics (#38473)

<!-- Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
This PR enhances the RabbitMQ receiver by adding support for node-level
metrics collection. It introduces the ability to individually enable the
collection of specific node metrics, including:

- `rabbitmq.node.disk_free`: Free disk space on the node.
- `rabbitmq.node.fd_used`: The number of file descriptors used on the
node.
- `rabbitmq.node.mem_limit`: The memory limit on the node.
- `rabbitmq.node.mem_used`: The memory used on the node.

This enhancement improves the flexibility and granularity of the metrics
collection for RabbitMQ monitoring by allowing users to configure which
node metrics to collect.

<!-- Issue number (e.g. #1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Fixes #36925

<!--Describe what testing was performed and which tests were added.-->
#### Testing
- Added unit tests to validate the enabling and disabling of individual
node metrics.
- Verified that each node metric is correctly collected when enabled and
omitted when disabled.
- Ran integration tests to ensure the receiver operates without issues
in various configurations.

<!--Describe the documentation added.-->
#### Documentation
- Updated the `README.md` with details about the new per-metric
configuration options for enabling node-level metrics.
- Added examples in `config.yaml` to demonstrate how to configure the
receiver with the new metrics.
- Included explanations for node-specific metrics in `metadata.yaml`.

Author: VenuEmmadi

.chloggen/rabbitmqreceiver_node_metrics_enhancement.yaml

@@ -0,0 +1,11 @@
+# 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: rabbitmqreceiver
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Enhance the RabbitMQ receiver to collect and report node-level metrics (`rabbitmq.node.disk_free`, `rabbitmq.node.fd_used`, `rabbitmq.node.mem_limit`, and `rabbitmq.node.mem_used`). This provides additional observability into the state and resource usage of RabbitMQ nodes."
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [36925]

receiver/rabbitmqreceiver/README.md

@@ -45,11 +45,19 @@ receivers:
     username: otelu
     password: ${env:RABBITMQ_PASSWORD}
     collection_interval: 10s
+     metrics:  # Enable node metrics by explicitly setting them to true
+      rabbitmq.node.disk_free:
+        enabled: true
+      rabbitmq.node.fd_used:
+        enabled: true
+      rabbitmq.node.mem_limit:
+        enabled: true
+      rabbitmq.node.mem_used:
+        enabled: true
 ```
 
 The full list of settings exposed for this receiver are documented in [config.go](./config.go) with detailed sample configurations in [testdata/config.yaml](./testdata/config.yaml). TLS config is documented further under the [opentelemetry collector's configtls package](https://github.com/open-telemetry/opentelemetry-collector/blob/main/config/configtls/README.md).
 
 ## Metrics
 
-Details about the metrics produced by this receiver can be found in [metadata.yaml](./metadata.yaml)
-
+Details about the metrics produced by this receiver can be found in [metadata.yaml](./metadata.yaml)

receiver/rabbitmqreceiver/client.go

@@ -16,12 +16,19 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/rabbitmqreceiver/internal/models"
 )
 
-// queuePath is the path to queues endpoint
-const queuePath = "/api/queues"
+const (
+	// queuePath is the endpoint for RabbitMQ queues.
+	queuePath = "/api/queues"
+
+	// nodePath is the endpoint for RabbitMQ nodes.
+	nodePath = "/api/nodes"
+)
 
 type client interface {
 	// GetQueues calls "/api/queues" endpoint to get list of queues for the target node
 	GetQueues(ctx context.Context) ([]*models.Queue, error)
+	// GetNodes calls "/api/nodes" endpoint to get list of nodes for the target node
+	GetNodes(ctx context.Context) ([]*models.Node, error)
 }
 
 var _ client = (*rabbitmqClient)(nil)
@@ -66,6 +73,17 @@ func (c *rabbitmqClient) GetQueues(ctx context.Context) ([]*models.Queue, error)
 	return queues, nil
 }
 
+func (c *rabbitmqClient) GetNodes(ctx context.Context) ([]*models.Node, error) {
+	var nodes []*models.Node
+
+	if err := c.get(ctx, nodePath, &nodes); err != nil {
+		c.logger.Debug("Failed to retrieve nodes", zap.Error(err))
+		return nil, err
+	}
+
+	return nodes, nil
+}
+
 func (c *rabbitmqClient) get(ctx context.Context, path string, respObj any) error {
 	// Construct endpoint and create request
 	url := c.hostEndpoint + path

receiver/rabbitmqreceiver/client_test.go

@@ -26,6 +26,7 @@ import (
 
 const (
 	queuesAPIResponseFile = "get_queues_response.json"
+	nodesAPIResponseFile  = "get_nodes_response.json"
 )
 
 func TestNewClient(t *testing.T) {
@@ -161,6 +162,75 @@ func TestGetQueuesDetails(t *testing.T) {
 	}
 }
 
+func TestGetNodesDetails(t *testing.T) {
+	testCases := []struct {
+		desc     string
+		testFunc func(*testing.T)
+	}{
+		{
+			desc: "Non-200 Response for GetNodes",
+			testFunc: func(t *testing.T) {
+				// Setup test server
+				ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+					w.WriteHeader(http.StatusForbidden)
+				}))
+				defer ts.Close()
+
+				tc := createTestClient(t, ts.URL)
+
+				nodes, err := tc.GetNodes(context.Background())
+				require.Nil(t, nodes)
+				require.EqualError(t, err, "non 200 code returned 403")
+			},
+		},
+		{
+			desc: "Bad payload returned for GetNodes",
+			testFunc: func(t *testing.T) {
+				// Setup test server
+				ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+					_, err := w.Write([]byte("{invalid-json}"))
+					assert.NoError(t, err)
+				}))
+				defer ts.Close()
+
+				tc := createTestClient(t, ts.URL)
+
+				nodes, err := tc.GetNodes(context.Background())
+				require.Nil(t, nodes)
+				require.ErrorContains(t, err, "failed to decode response payload")
+			},
+		},
+		{
+			desc: "Successful GetNodes call",
+			testFunc: func(t *testing.T) {
+				data := loadAPIResponseData(t, nodesAPIResponseFile)
+
+				// Setup test server
+				ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+					_, err := w.Write(data)
+					assert.NoError(t, err)
+				}))
+				defer ts.Close()
+
+				tc := createTestClient(t, ts.URL)
+
+				// Load the valid data into a struct to compare
+				var expected []*models.Node
+				err := json.Unmarshal(data, &expected)
+				require.NoError(t, err)
+
+				nodes, err := tc.GetNodes(context.Background())
+				require.NoError(t, err)
+				require.Equal(t, expected, nodes)
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.desc, tc.testFunc)
+	}
+}
+
 func createTestClient(t *testing.T, baseEndpoint string) client {
 	t.Helper()
 	cfg := createDefaultConfig().(*Config)

receiver/rabbitmqreceiver/documentation.md

@@ -66,6 +66,48 @@ The number of messages published to a queue.
 | ---- | ----------- | ---------- | ----------------------- | --------- |
 | {messages} | Sum | Int | Cumulative | true |
 
+## Optional Metrics
+
+The following metrics are not emitted by default. Each of them can be enabled by applying the following configuration:
+
+```yaml
+metrics:
+  <metric_name>:
+    enabled: true
+```
+
+### rabbitmq.node.disk_free
+
+Free disk space on the node.
+
+| Unit | Metric Type | Value Type | Aggregation Temporality | Monotonic |
+| ---- | ----------- | ---------- | ----------------------- | --------- |
+| {bytes} | Sum | Int | Cumulative | false |
+
+### rabbitmq.node.fd_used
+
+The number of file descriptors used on the node.
+
+| Unit | Metric Type | Value Type | Aggregation Temporality | Monotonic |
+| ---- | ----------- | ---------- | ----------------------- | --------- |
+| {fd} | Sum | Int | Cumulative | false |
+
+### rabbitmq.node.mem_limit
+
+The memory limit on the node.
+
+| Unit | Metric Type | Value Type | Aggregation Temporality | Monotonic |
+| ---- | ----------- | ---------- | ----------------------- | --------- |
+| {bytes} | Sum | Int | Cumulative | false |
+
+### rabbitmq.node.mem_used
+
+The memory used on the node.
+
+| Unit | Metric Type | Value Type | Aggregation Temporality | Monotonic |
+| ---- | ----------- | ---------- | ----------------------- | --------- |
+| {bytes} | Sum | Int | Cumulative | false |
+
 ## Resource Attributes
 
 | Name | Description | Values | Enabled |