Goerli Testnet

This is a tutorial on how to set up your Goerli Testnet node.

Goerli

• Official Docs

• Github Repository

Recommended Hardware Specifications

AWS:

• m5a.large or any equivalent instance type

Bare Metal:

• 8GB RAM

• 2 vCPUs

• At least 300 GB of storage - make sure it's extendable

Assumptions

We're going to assume you are already logged into your Virtual Machine as a privileged user or as the root user.

Setup

You can use the method described below which uses the Official Optimism Github Repository or follow the instructions here: https://github.com/smartcontracts/simple-optimism-node - this is a pretty well-written guide which will also take care of the monitoring part for you.

For running an Optimism Goerli node, we recommend going with the docker-compose stack (https://github.com/ethereum-optimism/optimism/tree/develop/infra/op-replica/docker-compose) as it is pretty easy to set up.

In order to do this, we will need to install Docker and Docker-compose, both of these processes are described in the Official Documentation, but I will post the links here again:

Install Docker (Ubuntu): https://docs.docker.com/engine/install/ubuntu/
Install Docker-Compose: https://docs.docker.com/compose/install/

Now that we've got both binaries installed, we can start by cloning the actual repo that holds all the files needed for installing and configuring an Optimism Goerli RPC node (please make sure you have git installed), move to the required directory and start setting up the environment:

git clone https://github.com/ethereum-optimism/optimism.git
cd optimism/infra/op-replica/docker-compose
cp default-goerli.env .env

Now that we have the .env file ready, we will just need to replace some placeholders with actual corresponding values.

Since Optimism is a Layer 2 network, you will need to provide a Layer 1 Endpoint (DATA_TRANSPORT_LAYER__L1_RPC_ENDPOINT in the documentation) and a Layer 2 Endpoint(DATA_TRANSPORT_LAYER__L2_RPC_ENDPOINT in the documentation). You can get an L1 Ethereum Endpoint for this for free via https://blastapi.io, while for theDATA_TRANSPORT_LAYER__L2_RPC_ENDPOINT we recommend using https://goerli.optimism.io

We are now ready to start the Docker Compose stack - please make sure you are in the optimism/infra/op-replica/docker-compose directory before running the command below:

docker-compose up -d

At the end of the process, there should be 3 containers running: l2geth, data-transport-layer and replica-healthcheck.

We can check the logs for each individually by running docker logs -f <container_id>.

That's pretty much it. Your Optimism Goerli node is now up and running. All you need to do now is wait for it to sync. You can check if the node is synced by running the API Call listed below from inside your environment. You are going to need to have the curl and jq packages installed for this, so make sure to install them beforehand.

Usually, we can use eth_syncing to check if a geth-based node (as Optimism L2Geth component is) is synced, but in this case, the call is going to return "false" whether the node is synced or not.

In this case, we're just going to use the method below:

curl -H "Content-Type: application/json" -d '{"id":1, "jsonrpc":"2.0", "method": "eth_blockNumber","params": []}' localhost:9991

The result should be a hex number (i.e 0x10c5815). If you convert it to a decimal number, you can compare it to the latest block listed on the Optimism Goerli explorer.

The usual RPC port for Optimism Chain using this docker-compose setup is 9991 and the WS port is 9992.

In order to test the WS endpoint, we will need to install a package called node-ws.

An example WS call would look like this:

wscat --connect ws://localhost:9992
> {"id":1, "jsonrpc":"2.0", "method": "eth_blockNumber","params": []}

Monitoring Guidelines

In order to maintain a healthy node that passes the Integrity Protocol's checks, you should have a monitoring system in place. Blockchain nodes usually offer metrics regarding the node's behaviour and health - a popular way to offer these metrics is Prometheus-like metrics. The most popular monitoring stack, which is also open source, consists of:

• Prometheus - scrapes and stores metrics as time series data (blockchain nodes cand send the metrics to it);

• Grafana - allows querying, visualization and alerting based on metrics (can use Prometheus as a data source);

• Alertmanager - handles alerting (can use Prometheus metrics as data for creating alerts);

• Node Exporter - exposes hardware and kernel-related metrics (can send the metrics to Prometheus).

We will assume that Prometheus/Grafana/Alertmanager are already installed (we will provide a detailed guide of how to set up monitoring and alerting with the Prometheus + Grafana stack at a later time; for now, if you do not have the stack already installed, please follow this official basic guide here).

We recommend installing the Node Exporter utility since it offers valuable information regarding CPU, RAM & storage. This way, you will be able to monitor possible hardware bottlenecks, or to check if your node is underutilized - you could use these valuable insights to make decisions regarding scaling up/down the allocated hardware resources.

Below, you can find a script that installs Node Exporter as a systemd service.

#!/bin/bash

# set the latest version
VERSION=1.3.1

# download and untar the binary
wget https://github.com/prometheus/node_exporter/releases/download/v${VERSION}/node_exporter-${VERSION}.linux-amd64.tar.gz
tar xvf node_exporter-*.tar.gz
sudo cp ./node_exporter-${VERSION}.linux-amd64/node_exporter /usr/local/bin/

# create system user
sudo useradd --no-create-home --shell /usr/sbin/nologin node_exporter

# change ownership of node exporter binary
sudo chown node_exporter:node_exporter /usr/local/bin/node_exporter

# remove temporary files
rm -rf ./node_exporter*

# create systemd service file
cat > /etc/systemd/system/node_exporter.service <<EOF
[Unit]
Description=Node Exporter
Wants=network-online.target
After=network-online.target
[Service]
User=node_exporter
Group=node_exporter
Type=simple
ExecStart=/usr/local/bin/node_exporter
[Install]
WantedBy=multi-user.target
EOF

# enable the node exporter service and start it
sudo systemctl daemon-reload
sudo systemctl enable node_exporter.service
sudo systemctl start node_exporter.service

As a reminder, Node Exporter uses port 9100 by default, so be sure to expose this port to the machine which holds the Prometheus server. The same should be done for the metrics port(s) of the blockchain node (in this case, we should expose port 7878).

Having installed Node Exporter and having already exposed the node's metrics, these should be added as targets under the scrape_configs section in your Prometheus configuration file (i.e. /etc/prometheus/prometheus.yml), before reloading the new config (either by restarting or reloading the config - please check the official documentation). This should look similar to this:

Unfortunately, the L2Geth component of Optimism does not expose metrics in Prometheus format. The only way to monitor its stats is to host an InfluxDB and write all the metrics into it and then configure Grafana to use that InfluxDB Instance as a Datasource. We will only cover the DTL Monitoring in this section for now.

scrape_configs:
  - job_name: 'optimism-node-dtl'
    scrape_interval: 10s
    metrics_path: /metrics
    static_configs:
      - targets:
        - '<NODE0_IP>:7878'
        - '<NODE1_IP>:7878' # you can add any number of nodes as targets
  - job_name: 'optimism-node-exporter'
    scrape_interval: 10s
    metrics_path: /metrics
    static_configs:
      - targets:
        - '<NODE0_IP>:9100'
        - '<NODE1_IP>:9100' # you can add any number of nodes as targets

In the configuration file above, please replace:

• <NODE0_IP> - node 0's IP

• <NODE1_IP> - node 1's IP (you can add any number of nodes as targets)

• ...

• <NODEN_IP> - node N's IP (you can add any number of nodes as targets)

That being said, the most important metrics that should be checked are:

• node_cpu_seconds_total - CPU metrics exposed by Node Exporter - for monitoring purposes, you could use the following expression:

  • 100 - (avg by (instance) (rate(node_cpu_seconds_total{job="optimism-node-exporter",mode="idle"}[5m])) * 100), which means the average percentage of CPU usage over the last 5 minutes;

• node_memory_MemTotal_bytes/node_memory_MemAvailable_bytes - RAM metrics exposed by Node Exporter - for monitoring purposes, you could use the following expression:

  • (node_memory_MemTotal_bytes{job="optimism-node-exporter"} - node_memory_MemAvailable_bytes{job="optimism-node-exporter"}) / 1073741824, which means the amount of RAM (in GB) used, excluding cache/buffers;

• node_network_receive_bytes_total - network traffic metrics exposed by Node Exporter - for monitoring purposes, you could use the following expression:

  • rate(node_network_receive_bytes_total{job="optimism-node-exporter"}[1m]), which means the average network traffic received, per second, over the last minute (in bytes);

• node_filesystem_avail_bytes - FS metrics exposed by Node Exporter - for monitoring purposes, you could use the following expression:

  • node_filesystem_avail_bytes{job="optimism-node-exporter",device="<DEVICE>"} / 1073741824, which means the filesystem space available to non-root users (in GB) for a certain device <DEVICE> (i.e. /dev/sda or wherever the blockchain data is stored) - this can be used to get an alert whenever the available space left is below a certain threshold (please be careful how you choose this threshold: if you have storage that can easily be increased - for example, EBS storage from AWS, you can set a lower threshold, but if you run your node on a bare metal machine which is not easily upgradable, you should set a higher threshold just to be sure you are able to find a solution before it fills up);

• up - Prometheus automatically generated metrics - for monitoring purposes, you could use the following expression:

  • up{job="optimism-node-dtl"}, which has 2 possible values: 1, if the node is up, or 0, if the node is down - this can be used to get an alert whenever the node goes down (i.e. it can be triggered at each restart of the node);

• data_transport_layer_highest_synced_l2_block - this is a metric that can be used in order to check if the node is currently syncing with the network - for monitoring purposes, you could use the following expression:

  • increase(data_transport_layer_highest_synced_l2_block{job="optimism-node"}[1m]), which is going to show the latest block that has been received by the node - this can be used to get an alert whenever the node is not syncing blocks anymore (i.e less than 5 blocks in the past 5 minutes);

You can use the above metrics to create both Grafana dashboards and Alertmanager alerts.

Please make sure to also check the Official Documentation and the Github Repository posted above in order to make sure you are keeping your node up to date.