# Node Health Checker

The Aptos Node Health Checker (NHC) service can be used to check the health of the following Aptos node types:

• Validator nodes.
• Validator fullnodes, and
• Public fullnodes.

If you are a node operator, use the NHC service to check if your node is running correctly. The NHC service evaluates your node's health by comparing against a baseline node configuration, and outputs the evaluation results.

The Aptos Node Health Checker now also supports fullnodes via a central web service with validator support on the way: https://nodetools.aptosfoundation.org/#/node_checker

This document describes how to run NHC locally when you are operating a node.

## Quickstart​

Before you get into the details of how NHC works, you can run the below steps to start the NHC service and send it a request. This quickstart uses a baseline configuration for a devnet fullnode, i.e., it will evaluate your node against a devnet fullnode that is configured with the baseline configuration YAML.

Important: If your local node is not a devnet fullnode, you must use a different baseline config. See the configuration examples in aptos-core for other such example configs.

### Step 1: Download the baseline configuration YAML​

Download a baseline configuration YAML file for a devnet fullnode. The below command will download the devnet_fullnode.yaml configuration file:

mkdir /tmp/nhccd /tmp/nhcwget https://raw.githubusercontent.com/aptos-labs/aptos-core/main/ecosystem/node-checker/configuration_examples/devnet_fullnode.yaml

### Step 2: Start the NHC service​

Start the NHC service by providing the above-downloaded devnet_fullnode.yaml baseline configuration YAML file:

docker run -v /tmp/nhc:/nhc -p 20121:20121 -t aptoslabs/node-checker:nightly /usr/local/bin/aptos-node-checker server run --baseline-config-paths /nhc/devnet_fullnode.yaml

### Step 3: Send a request to NHC service​

Finally, send a request to the NHC service you started above. The following command runs health checks of your node that is at node_url=http://mynode.mysite.com and compares these results with the node configured in the baseline configuration devnet_fullnode:

curl 'http://localhost:20121/check?node_url=http://mynode.mysite.com&api_port=80&baseline_configuration_id=devnet_fullnode'

You will see output similar to this:

{  "check_results": [    {      "headline": "Chain ID reported by baseline and target match",      "score": 100,      "explanation": "The node under investigation reported the same Chain ID 18 as is reported by the baseline node",      "checker_name": "node_identity",      "links": []    },    {      "headline": "Role Type reported by baseline and target match",      "score": 100,      "explanation": "The node under investigation reported the same Role Type full_node as is reported by the baseline node",      "checker_name": "node_identity",      "links": []    },    {      "headline": "Target node produced valid recent transaction",      "score": 100,      "explanation": "We were able to pull the same transaction (version: 3238616) from both your node and the baseline node. Great! This implies that your node is keeping up with other nodes in the network.",      "checker_name": "transaction_availability",      "links": []    }  ],  "summary_score": 100,  "summary_explanation": "100: Awesome!"}

## How NHC works​

The NHC runs as a service. When you want to run a health check of your node, you send the HTTP requests to this service.

A single NHC instance can be configured to check the health of multiple node configurations, each of different type, for example:

• A public fullnode connected to the Aptos mainnet.
• A validator node connected to the Aptos testnet.
• A node running in a single node testnet.

### Baseline configuration​

In all the above cases, a baseline node is used to compare your node's health. For example, for a public fullnode connected to the Aptos devnet, the baseline node might be a node run by the Aptos team and this node demonstrates optimal performance and participation characteristics.

You will download the baseline configuration YAML before running the NHC service for your node. The baseline node's configuration YAML describes where to find this baseline node (URL + port), what evaluators (e.g. metrics checks, TPS tests, API validations, etc.) the NHC service should run, what parameters the NHC should use for those evaluators, what name the configuration has, and so on. See these example baseline configuration YAML files.

When you send requests to the NHC service, you must include a baseline configuration. For example, a request to NHC to use devnet_fullnode as the baseline configuration will look like this:

curl 'http://nhc.aptoslabs.com/check?node_url=http://myfullnode.mysite.com&baseline_configuration_id=devnet_fullnode'

### Getting baseline configurations ready​

In order to run the NHC service, you must have a baseline configuration that the service can use. You have two options here:

#### Configure a pre-existing YAML​

You can find a few example baseline configuration YAML files that work for each of the above use cases and more.

Next, download these configuration YAML files into the /etc/nhc folder in your host system. For example:

mkdir /tmp/nhccd /tmp/nhcconfigs=(devnet_fullnode testnet_fullnode mainnet_fullnode); for c in ${configs[@]}; do wget https://raw.githubusercontent.com/aptos-labs/aptos-core/main/ecosystem/node-checker/configuration_examples/$c.yaml; done

These configurations are not quite ready to be used as they are. You will need to modify certain fields, such as the baseline node address or evaluator set (evaluators and evaluator_args in the YAML) used. The best way to iterate on this is to run the NHC with a downloaded baseline configuration and see what it says on startup.

### Required files​

For some NHC configurations, you will need accompanying files, e.g. mint.key to use for running a TPS test against a validator. You should make sure these files are also available to NHC, either on disk or mounted into your container. NHC expects them on startup at a path specified in the baseline configuration YAML.

## Running NHC: Docker​

tip

While the Aptos team hosts our own instances of this service, we encourage node operators to run their own instances.

When you are ready with baseline configuration YAML and the required files, you can run the NHC server with a command like this, for example, with Docker:

docker run -v /etc/nhc:/etc/nhc -p 20121:20121 -t aptoslabs/node-checker:nightly /usr/local/bin/aptos-node-checker server run --baseline-config-paths /tmp/nhc/devnet_fullnode.yaml /tmp/nhc/testnet_fullnode.yaml /tmp/nhc/mainnet/fullnode.yaml
tip

You may want to include other environment variables such as RUST_LOG=info. As you can see, by default NHC runs on port 20121. Make sure to publish it from the container, as shown in the above command, and ensure the port is open on your host. You may change the port NHC runs on with --listen-port.

## Running NHC: Source​

First, check out the source:

git clone git@github.com:aptos-labs/aptos-core.gitcd aptos-core

Depending on your setup, you may want to check out a particular branch, to ensure NHC is compatible with your node, e.g. git checkout --track devnet.

Run NHC:

cargo run -p aptos-node-checker --release -- server run --baseline-config-paths /tmp/nhc/devnet_fullnode.yaml

## Generating the OpenAPI specs​

To generate the OpenAPI specs, run the following commands from ecosystem/node-checker:

cargo run -- server generate-openapi -f yaml > doc/spec.yamlcargo run -- server generate-openapi -f json > doc/spec.json

You can also hit the /spec.yaml and /spec.json endpoints of the running service.