Sepolia Testnet

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

Recommended Hardware Specifications

AWS:

m6g.xlarge or any equivalent instance type(ARM based instance)

Bare Metal:

16GB RAM
4 vCPUs
At least 250 GB SSD of storage - make sure it's extendable

Setup

As this is a major update for the Ethereum network and for the entire crypto world more exactly moving from PoW to PoS, please refer to this announcement in order to get a detailed overview.

As per document above, there are two important steps:

Configure an execution node using an execution-layer client.
Configure a beacon node using Prysm, a consensus-layer client.

The first step is already detailed in the previous alignments, and for the second one there is a documentation you can follow: https://docs.prylabs.network/docs/install/install-with-script.

We recommend using the following startup command:

Geth Node

/usr/local/bin/geth --sepolia --syncmode full --override.terminaltotaldifficulty 17000000000000000 --metrics --metrics.addr=<metrics_port> --http --http.api net,eth,personal,web3,engine,admin --authrpc.vhosts=localhost --authrpc.jwtsecret=/path/to/jwt.hex --http.addr 0.0.0.0 --http.port 8545 --http.vhosts * --http.corsdomain * --ws --ws.addr 0.0.0.0 --ws.port 8546 --ws.api net,eth,personal,web3 --ws.origins * --datadir /path/to/database --authrpc.jwtsecret=/path/to/jwt.hex

2. Beacon Node

./prysm.sh --accept-terms-of-use --sepolia --http-web3provider=http://localhost:8551 --genesis-state=/path/to/genesis.ssz --jwt-secret=/path/to/jwt.hex --datadir=/path/to/database --terminal-total-difficulty-override 17000000000000000

That's pretty much it. You now have a running Ethereum Sepolia RPC node. 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 package installed for this, so make sure to install them beforehand.

curl -H "Content-Type: application/json" -d '{"id":1, "jsonrpc":"2.0", "method": "eth_syncing"}' --silent localhost:8545

If the above call result will be false it means your node is synced.

You now have a running Ethereum Sepolia RPC node. 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.

curl -H "Content-Type: application/json" -d '{"id":1, "jsonrpc":"2.0", "method": "eth_syncing","params": []}' localhost:8545

If the result is false, it means that your node is fully synced.

Another way to check which block the node is at would be running:

curl -H "Content-Type: application/json" -d '{"id":1, "jsonrpc":"2.0", "method": "eth_blockNumber","params": []}' localhost:8545

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 Ethereum Sepolia explorer: https://sepolia.etherscan.io/

The Ethereum node exports both RPC on port 8545 and WS on port 8546.

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:8546
> {"id":1, "jsonrpc":"2.0", "method": "eth_blockNumber","params": []}

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.

The Merge

As you may know Ethereum has been moving to proof-of-stake!. The transition, known as The Merge, must first be activated on the Beacon Chain with the Bellatrix upgrade. After this, the proof-of-work chain will migrate to proof-of-stake upon hitting a specific Total Difficulty value.

The Terminal Total Difficulty value that triggered The Merge is 58750000000000000000000.

So an Ethereum node will consist in two components:

Execution Layer which will be referred as EL, and is basically the geth that is explained in the first part of this documentation page;
Consensus Layer which will be referred as CL and could be started via multiple alternatives like Lighthouse, Prysm, Lodestar, Teku. Our decision was to go with Prysm as they have very nice documentation about The Merge, which you can find here.

Running prysm node

Below you will find the prysm flags that you should use to make sure your node will pass onboarding and integrity checks:

--accept-terms-of-use
--sepolia
--http-web3provider defaults to http://localhost:8551
--genesis-state=/path/to/genesis.ssz
--jwt-secret=/path/to/jwt.hex
--datadir=/path/to/datastore
--terminal-total-difficulty-override=17000000000000000

In order to check if EL communicates with CL , you can have a look into the logs that should state the blocks are being generated and that there are no [ERROR] logs. Also, you can check the chain functionality by calling a JSON-RPC method like eth_chainId.

Sync from a checkpoint

Official Docs: https://docs.prylabs.network/docs/prysm-usage/checkpoint-sync

Checkpoint sync is a feature that significantly speeds up the initial sync between your beacon node and the Beacon Chain. With checkpoint sync configured, your beacon node will begin syncing from a recently finalized checkpoint instead of syncing from genesis. This can make installations, validator migrations, recoveries, and testnet deployments way faster.

To sync from a checkpoint, your Prysm beacon node needs three pieces of information: the latest finalized BeaconState, the SignedBeaconBlock, and (if you're on a testnet) the genesis state for the network you're using. Together, the BeaconState and SignedBeaconBlock represent a single checkpoint state.

The following added flag starts a beacon node with checkpoint sync configured to pull checkpoint state from another local beacon node's RPC endpoint using port 3500:

--checkpoint-sync-url=http://localhost:3500

You can also refer to https://eth-clients.github.io/checkpoint-sync-endpoints/ in order to find public Ethereum Beacon Chain checkpoint sync endpoints.

Note that this is entirely optional. The beacon node requesting the checkpoint state from a prysm node started from scratch doesn't need this flag.

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 6060 - for monitoring the ethereum node).

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:

scrape_configs:
  - job_name: 'sepolia-node'
    scrape_interval: 10s
    metrics_path: /debug/metrics/prometheus
    static_configs:
      - targets:
        - '<NODE0_IP>:6060'
        - '<NODE1_IP>:6060' # you can add any number of nodes as targets
  - job_name: 'sepolia-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="sepolia-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="sepolia-node-exporter"} - node_memory_MemAvailable_bytes{job="sepolia-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="sepolia-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="sepolia-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 expressions:
- up{job="sepolia-node"}, 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);
chain_head_block - metrics exposed by the ethereum node - for monitoring purposes, you could use the following expressions:
- increase(chain_head_block{job="sepolia-node"}[1m]), which means how many blocks ethereum has been producing in the last 1 minute - this can be used to get an alert whenever the node has fallen behind by comparing with a certain threshold (you should start worrying if the difference is greater than 2-3 for the last 5 minutes);
p2p_peers - metrics exposed by the ethereum node - for monitoring purposes, you could use the following expressions:
- p2p_peers{job="sepolia-node"}, which means the number of peers connected to the node on the ethereum side - this can be used to get an alert whenever there are less peers than a certain threshold for a certain period of time (i.e. less than 3 peers for 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.

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Last updated 10 months ago