[receiver/redis] Command latency metrics. (open-telemetry#26569)

**Description:** Added command latency metric to the redis receiver.

**Link to tracking Issue:**
open-telemetry#6942

**Testing:** Added tests for parsing `latencystats` section of redis
info.

**Documentation:** Metric documentation in metadata.yaml

.chloggen/redisreceiver_cmd_latency.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: Added `redis.cmd.latency` metric.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [6942]
+
+# (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: [user]

receiver/redisreceiver/documentation.md

@@ -292,6 +292,21 @@ Total number of calls for a command
 | ---- | ----------- | ------ |
 | cmd | Redis command name | Any Str |
 
+### redis.cmd.latency
+
+Command execution latency
+
+| Unit | Metric Type | Value Type |
+| ---- | ----------- | ---------- |
+| us | Gauge | Double |
+
+#### Attributes
+
+| Name | Description | Values |
+| ---- | ----------- | ------ |
+| cmd | Redis command name | Any Str |
+| percentile | Percentile | Str: ``p50``, ``p99``, ``p99.9`` |
+
 ### redis.cmd.usec
 
 Total time for all executions of this command

receiver/redisreceiver/internal/metadata/testdata/config.yaml

@@ -11,6 +11,8 @@ all_set:
       enabled: true
     redis.cmd.calls:
       enabled: true
+    redis.cmd.latency:
+      enabled: true
     redis.cmd.usec:
       enabled: true
     redis.commands:
@@ -82,6 +84,8 @@ none_set:
       enabled: false
     redis.cmd.calls:
       enabled: false
+    redis.cmd.latency:
+      enabled: false
     redis.cmd.usec:
       enabled: false
     redis.commands:

receiver/redisreceiver/latencystats.go

@@ -0,0 +1,40 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package redisreceiver // import "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/redisreceiver"
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// Holds percentile latencies, e.g. "p99" -> 1.5.
+type latencies map[string]float64
+
+// parseLatencyStats parses the values part of one entry in Redis latencystats section,
+// e.g. "p50=181.247,p99=309.247,p99.9=1023.999".
+func parseLatencyStats(str string) (latencies, error) {
+	res := make(latencies)
+
+	pairs := strings.Split(strings.TrimSpace(str), ",")
+
+	for _, pairStr := range pairs {
+		pair := strings.Split(pairStr, "=")
+		if len(pair) != 2 {
+			return nil, fmt.Errorf("unexpected latency percentiles pair '%s'", pairStr)
+		}
+
+		key := pair[0]
+		valueStr := pair[1]
+
+		value, err := strconv.ParseFloat(valueStr, 64)
+		if err != nil {
+			return nil, err
+		}
+
+		res[key] = value
+	}
+
+	return res, nil
+}

receiver/redisreceiver/latencystats_test.go

@@ -0,0 +1,34 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package redisreceiver
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestParseLatencyStats(t *testing.T) {
+	ls, err := parseLatencyStats("p50=181.247,p55=182.271,p99=309.247,p99.9=1023.999")
+	require.Nil(t, err)
+	require.Equal(t, ls["p50"], 181.247)
+	require.Equal(t, ls["p55"], 182.271)
+	require.Equal(t, ls["p99"], 309.247)
+	require.Equal(t, ls["p99.9"], 1023.999)
+}
+
+func TestParseMalformedLatencyStats(t *testing.T) {
+	tests := []struct{ name, stats string }{
+		{"missing value", "p50=42.0,p90=50.0,p99.9="},
+		{"missing equals", "p50=42.0,p90=50.0,p99.9"},
+		{"extra comma", "p50=42.0,,p90=50.0"},
+		{"wrong value type", "p50=asdf"},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			_, err := parseLatencyStats(test.stats)
+			require.NotNil(t, err)
+		})
+	}
+}

receiver/redisreceiver/metadata.yaml

@@ -45,6 +45,13 @@ attributes:
   cmd:
     description: Redis command name
     type: string
+  percentile:
+    description: Percentile
+    type: string
+    enum:
+      - p50
+      - p99
+      - p99.9
 
 metrics:
   redis.maxmemory:
@@ -84,6 +91,14 @@ metrics:
       aggregation_temporality: cumulative
     attributes: [cmd]
 
+  redis.cmd.latency:
+    enabled: false
+    description: Command execution latency
+    unit: us
+    gauge:
+      value_type: double
+    attributes: [cmd, percentile]
+
   redis.uptime:
     enabled: true
     description: Number of seconds since Redis server start