Merge pull request OffchainLabs#2663 from OffchainLabs/add-checklist-to-valnode

add monitoring to the valnode docs

Author: pete-vielhaber

docs/run-arbitrum-node/more-types/04-run-split-validator-node.mdx

@@ -45,9 +45,12 @@ docker run --rm -it \
   --auth.origins 0.0.0.0 \
   --auth.jwtsecret /tmp/nitro-val.jwt \
   --auth.port 5200
+  --metrics \
+  --metrics-server.addr=0.0.0.0 \
+  --metrics-server.port=6070
 ```
 
-The validation node will listen on port 5200.
+The validation node will listen on port 5200, which will also enable the metrics server on port 6070.
 
 #### Step 2: Set up the staker node
 
@@ -150,3 +153,14 @@ docker run --rm -it --entrypoint nitro-val  @@latestNitroNodeImage=offchainlabs/
 ### Additional configurations for helm charts
 
 For more advanced helm chart configurations, please refer to the Arbitrum community Helm Chart [README](https://github.com/OffchainLabs/community-helm-charts/blob/main/charts/nitro/README.md)
+
+### Monitoring
+
+To check if your validation node is running correctly, you can check the `rpc_duration_validation_validate_success_count` metric in your metrics server.
+
+This metric is a counter of the number of successful validation calls; if it is increasing, it means your validation node is running correctly.
+
+You can also check where this log (`validation node started`) appears:
+
+- If this log appears on the validation node, it means your validation node is running correctly.
+- If this log appears on the staker node (validator node), it means your staker node is still validating itself. It indicates that your staker node is not connecting to the validation node correctly; you need to double-check your configuration.