Retrieve info from CLUSTER INFO redis cmd (open-telemetry#42406)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

Currently, the redisreceiver fetches only from the INFO command (and is
capable of monitoring individual redis performance).
We need to record from the CLUSTER INFO command too.

<!-- Issue number (e.g. open-telemetry#1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Fixes open-telemetry#38117

<!--Describe what testing was performed and which tests were added.-->
#### Testing

Added tests for the `CLUSTER INFO` command in the
`receiver/redisreceiver/client_test.go` file. However, the
`cluster_info.txt` is yet to be added.

<!--Please delete paragraphs that you did not use before submitting.-->

---------

Signed-off-by: Yaten <[email protected]>

Author: yaten2302

.chloggen/feat_redisreceiver-cluster_info-capability.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: "redisreceiver"
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Add `ClusterInfo` capability to `redisreceiver`"
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [38117]
+
+# (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: []

receiver/redisreceiver/client.go

@@ -13,6 +13,8 @@ import (
 type client interface {
 	// retrieves a string of key/value pairs of redis metadata
 	retrieveInfo() (string, error)
+	// retrieves a string of key/value pairs of redis cluster metadata
+	retrieveClusterInfo() (string, error)
 	// line delimiter
 	// redis lines are delimited by \r\n, files (for testing) by \n
 	delimiter() string
@@ -44,6 +46,11 @@ func (c *redisClient) retrieveInfo() (string, error) {
 	return c.client.Info(context.Background(), "all").Result()
 }
 
+// Retrieve Redis CLUSTER INFO.
+func (c *redisClient) retrieveClusterInfo() (string, error) {
+	return c.client.ClusterInfo(context.Background()).Result()
+}
+
 // close client to release connection pool.
 func (c *redisClient) close() error {
 	return c.client.Close()

receiver/redisreceiver/client_test.go

@@ -33,6 +33,10 @@ func (fakeClient) retrieveInfo() (string, error) {
 	return readFile("info")
 }
 
+func (fakeClient) retrieveClusterInfo() (string, error) {
+	return readFile("cluster_info")
+}
+
 func (fakeClient) close() error {
 	return nil
 }

receiver/redisreceiver/documentation.md

@@ -278,6 +278,108 @@ metrics:
     enabled: true
 ```
 
+### redis.cluster.known_nodes
+
+Number of known nodes in the cluster
+
+| Unit | Metric Type | Value Type | Stability |
+| ---- | ----------- | ---------- | --------- |
+| {node} | Gauge | Int | development |
+
+### redis.cluster.links_buffer_limit_exceeded.count
+
+Total number of times the cluster links buffer limit was exceeded
+
+| Unit | Metric Type | Value Type | Aggregation Temporality | Monotonic | Stability |
+| ---- | ----------- | ---------- | ----------------------- | --------- | --------- |
+| {count} | Sum | Int | Cumulative | true | development |
+
+### redis.cluster.node.count
+
+Number of master nodes in the cluster
+
+| Unit | Metric Type | Value Type | Stability |
+| ---- | ----------- | ---------- | --------- |
+| {node} | Gauge | Int | development |
+
+### redis.cluster.node.uptime
+
+The node's current epoch
+
+| Unit | Metric Type | Value Type | Stability |
+| ---- | ----------- | ---------- | --------- |
+| s | Gauge | Int | development |
+
+### redis.cluster.slots_assigned
+
+Number of slots assigned in the cluster
+
+| Unit | Metric Type | Value Type | Stability |
+| ---- | ----------- | ---------- | --------- |
+| {slot} | Gauge | Int | development |
+
+### redis.cluster.slots_fail
+
+Number of slots in the cluster that are in a failing state
+
+| Unit | Metric Type | Value Type | Stability |
+| ---- | ----------- | ---------- | --------- |
+| {slot} | Gauge | Int | development |
+
+### redis.cluster.slots_ok
+
+Number of slots in the cluster that are ok
+
+| Unit | Metric Type | Value Type | Stability |
+| ---- | ----------- | ---------- | --------- |
+| {slot} | Gauge | Int | development |
+
+### redis.cluster.slots_pfail
+
+Number of slots in the cluster that are in a 'potentially failing' state
+
+| Unit | Metric Type | Value Type | Stability |
+| ---- | ----------- | ---------- | --------- |
+| {slot} | Gauge | Int | development |
+
+### redis.cluster.state
+
+State of the cluster
+
+| Unit | Metric Type | Value Type | Stability |
+| ---- | ----------- | ---------- | --------- |
+| {state} | Gauge | Int | development |
+
+#### Attributes
+
+| Name | Description | Values | Optional |
+| ---- | ----------- | ------ | -------- |
+| cluster_state | State of the cluster | Str: ``ok``, ``fail`` | false |
+
+### redis.cluster.stats_messages_received
+
+Total number of messages received by the cluster
+
+| Unit | Metric Type | Value Type | Aggregation Temporality | Monotonic | Stability |
+| ---- | ----------- | ---------- | ----------------------- | --------- | --------- |
+| {message} | Sum | Int | Cumulative | true | development |
+
+### redis.cluster.stats_messages_sent
+
+Total number of messages sent by the cluster
+
+| Unit | Metric Type | Value Type | Aggregation Temporality | Monotonic | Stability |
+| ---- | ----------- | ---------- | ----------------------- | --------- | --------- |
+| {message} | Sum | Int | Cumulative | true | development |
+
+### redis.cluster.uptime
+
+Current epoch of the cluster
+
+| Unit | Metric Type | Value Type | Stability |
+| ---- | ----------- | ---------- | --------- |
+| s | Gauge | Int | development |
+
 ### redis.cmd.calls
 
 Total number of calls for a command