Update metric instrumentation docs

doc/development/service_ping/metrics_instrumentation.md

@@ -11,7 +11,7 @@ This guide describes how to develop Service Ping metrics using metrics instrumen
 ## Nomenclature
 
 - **Instrumentation class**:
-  - Inherits one of the metric classes: `DatabaseMetric`, `RedisHLLMetric` or `GenericMetric`.
+  - Inherits one of the metric classes: `DatabaseMetric`, `RedisMetric`, `RedisHLLMetric` or `GenericMetric`.
   - Implements the logic that calculates the value for a Service Ping metric.
 
 - **Metric definition**
@@ -24,7 +24,7 @@ This guide describes how to develop Service Ping metrics using metrics instrumen
 
 A metric definition has the [`instrumentation_class`](metrics_dictionary.md) field, which can be set to a class.
 
-The defined instrumentation class should have one of the existing metric classes: `DatabaseMetric`, `RedisHLLMetric`, or `GenericMetric`.
+The defined instrumentation class should have one of the existing metric classes: `DatabaseMetric`, `RedisMetric`, `RedisHLLMetric`, or `GenericMetric`.
 
 Using the instrumentation classes ensures that metrics can fail safe individually, without breaking the entire
  process of Service Ping generation.
@@ -50,6 +50,20 @@ module Gitlab
   end
 end
 ```
+## Redis metrics
+
+[Example of a merge request that adds a `Redis` metric](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/66582).
+
+Count unique values for `source_code_pushes` event.
+
+```yaml
+time_frame: all
+data_source: redis
+instrumentation_class: 'RedisMetric'
+options:
+  event: pushes
+  counter_class: SourceCodeCounter
+```
 
 ## Redis HyperLogLog metrics
 
@@ -60,7 +74,7 @@ Count unique values for `i_quickactions_approve` event.
 ```yaml
 time_frame: 28d
 data_source: redis_hll
-instrumentation_class: 'Gitlab::Usage::Metrics::Instrumentations::RedisHLLMetric'
+instrumentation_class: 'RedisHLLMetric'
 options:
   events:
     - i_quickactions_approve
@@ -91,13 +105,13 @@ end
 There is support for:
 
 - `count`, `distinct_count` for [database metrics](#database-metrics).
+- [Redis metrics](#redis-metrics).
 - [Redis HLL metrics](#redis-hyperloglog-metrics).
 - [Generic metrics](#generic-metrics), which are metrics based on settings or configurations.
 
 Currently, there is no support for:
 
 - `add`, `sum`, `histogram`, `estimate_batch_distinct_count` for database metrics.
-- Regular Redis counters.
 
 You can [track the progress to support these](https://gitlab.com/groups/gitlab-org/-/epics/6118).
 
@@ -107,7 +121,7 @@ To create a stub instrumentation for a Service Ping metric, you can use a dedica
 
 The generator takes the class name as an argument and the following options:
 
-- `--type=TYPE` Required. Indicates the metric type. It must be one of: `database`, `generic`.
+- `--type=TYPE` Required. Indicates the metric type. It must be one of: `database`, `generic`, `redis`.
 - `--operation` Required for `database` type. It must be one of: `count`, `distinct_count`.
 - `--ee` Indicates if the metric is for EE.