Add support rule evaluation via query frontend docs

Signed-off-by: SungJin1212 <[email protected]>

docs/guides/rule-evaluations-via-query-frontend.md

@@ -0,0 +1,67 @@
+---
+title: "Rule evaluations via query frontend"
+linkTitle: "Rule evaluations via query frontend"
+weight: 10
+slug: rule-evalutions-via-query-frontend
+---
+
+This guide explains how to configure the Ruler to evaluate rules via Query Frontends instead of the Ingesters and pros and cons of the rule evaluation via Query Frontend.
+
+## How to enable
+
+By default, the Ruler query to the Ingesters for evaluating rules (alerting rules or recording rules). If you have set `-ruler.frontend-address` then the Ruler query to the Query Frontend for evaluation rules.
+The address should be the gRPC listen address in host:port format.
+
+You can configure via args:
+```
+-ruler.frontend-address=query-frontend.svc.cluster.local:9095
+```
+And via yaml:
+```yaml
+ruler:
+  ...
+  frontend_address: query-frontend.svc.cluster.local:9095
+  ...
+```
+
+In addition, you can configure gRPC client (Ruler -> Query Frontend) config via args:
+```
+-ruler.frontendClient.grpc-max-recv-msg-size=104857600
+-ruler.frontendClient.grpc-max-send-msg-size=16777216
+-ruler.frontendClient.grpc-compression=""
+-ruler.frontendClient.grpc-client-rate-limit=0
+-ruler.frontendClient.grpc-client-rate-limit-burst=0
+-ruler.frontendClient.backoff-on-ratelimits=false
+-ruler.frontendClient.backoff-min-period=100ms
+-ruler.frontendClient.backoff-max-period=10s
+-ruler.frontendClient.backoff-retries=10
+```
+
+And via yaml:
+
+```yaml
+ruler:
+  ...
+  frontend_client:
+    max_recv_msg_size: 104857600
+    max_send_msg_size: 16777216
+    grpc_compression: ""
+    rate_limit: 0
+    rate_limit_burst: <int> | default = 0
+    backoff_on_ratelimits: <boolean> | default = false
+    backoff_config:
+      min_period: 100ms
+      max_period: 10s
+      max_retries: 10
+  ...
+```
+
+## Pros and Cons
+
+### Pros
+The rule evaluation performance is improved as we can use Query Frontend features like the vertical query sharding.
+The ruler can use fewer resources as it doesn't need to initialize the querier anymore.
+
+### Cons
+Currently, the only support format of the query response of the Query Frontend is the JSON format. The JSON format only contains partial information of the native histogram.
+So, if your rules use the natvie histogram, it is not allowed yet.