Prysm Beacon API Health Checks & Readiness Probes

by SLV Team 50 views
Prysm Beacon API Health Checks & Readiness Probes

Hey guys! Let's dive into how we're making sure our Prysm beacon node is super healthy and ready to roll. This is all about adding health checks and readiness probes to our system. We want to make sure the beacon node is not just running, but actually ready to serve requests before we give it the green light.

The Lowdown

So, what's the deal? Right now, we've got this waitForBeaconAPI() function, and it's basically just sitting there, waiting for the beacon API to become available. No actual checks, just a timeout. Not ideal, right? This issue is all about fixing that. We're going to implement proper health checks. These checks will make sure the beacon node is ready to go. This involves verifying that it's synced and operational. This is super important so that we can start our validator safely. We'll also add a timeout mechanism with clear error messages. We want a metrics endpoint available for monitoring. Lastly, we need some solid unit tests to back up our logic.

Why is this important?

Because we want our system to be reliable and not just hope everything is working. We need a way to ensure our beacon node is healthy. This is a critical step for the whole system, so we can detect any problems early. If the beacon node isn't ready, then our whole setup is useless. By implementing health checks and readiness probes, we're building a system that's more resilient and provides a better user experience. It's about ensuring everything works as expected, and we know if there are issues.

Deep Dive into the Code

Let's get into the nitty-gritty of the code. We're going to replace the existing waitForBeaconAPI() function with something that actually checks if the API is ready. We'll use the beacon API endpoints to achieve that.

Implementing waitForBeaconAPI()

First, we replace the waitForBeaconAPI() with the implementation described in the original document. We set up a client with a timeout, and then we start checking the beacon API. This function is the heart of the readiness check. We use a ticker to check the beacon API's health at regular intervals. It also has a timeout to prevent it from waiting forever.

Adding checkBeaconHealth()

Next, we'll add a helper function called checkBeaconHealth(). This function will make a request to the /eth/v1/node/health endpoint. The response code tells us if the node is ready. We have a set of status codes to verify. We're looking for http.StatusOK (200), which indicates the node is ready. We also need to check the sync status to verify the node is fully operational.

Adding checkSyncStatus()

We need to add a function called checkSyncStatus() to confirm that our beacon node is synchronized with the network. This will make a request to the /eth/v1/node/syncing endpoint. It returns true if it's synced. This ensures the beacon node has caught up with the chain. In a local development environment, we can accept syncing nodes because we start from genesis. In production, we'd wait for full sync.

Adding Metrics Query Methods

Next, let's add methods to query beacon node metrics. We'll implement GetSyncStatus() and GetPeerCount(). We use these methods to get information about the node's sync status and peer connections. These are useful for monitoring and debugging. The GetSyncStatus() method checks the /eth/v1/node/syncing endpoint to get the current sync status. The GetPeerCount() method checks the /eth/v1/node/peer_count endpoint to get the number of connected peers.

Adding Status Types

We define some new types: SyncStatus and HealthStatus. These will help us organize the data we get from the beacon API. The SyncStatus struct holds information about the node's sync status, such as the head slot, sync distance, and whether it's syncing. The HealthStatus struct contains the overall health status of the client. It includes whether the client is ready, if the beacon and validator are online, the peer count, and the sync status.

Adding GetHealthStatus() Method

Now, let's create a function called GetHealthStatus(). This method provides an aggregated view of the health of the beacon node. This returns a HealthStatus struct, which gives us a complete overview of the client's health. It checks the beacon node's state, and combines the peer count and sync status. This function consolidates all health-related information.

Updating Imports

We need to add the required imports to client.go, which includes encoding/json, net/http, and strconv. These imports are required for making HTTP requests and parsing the JSON responses from the beacon API.

Technicalities & Considerations

Let's talk about some technical details we need to keep in mind.

Beacon API Endpoints

We're going to use a few Beacon API endpoints:

  • /eth/v1/node/health: For health checks.
  • /eth/v1/node/syncing: To check sync status.
  • /eth/v1/node/peer_count: To get the number of peers.
  • /eth/v1/node/version: To get node version information.

Readiness vs. Liveness

  • Liveness: Is the process running? (basic health check)
  • Readiness: Is it ready to serve traffic? (sync status, peer connections)

We're checking both before marking the client as ready. This is a critical distinction.

Local Network Sync

When we're on a local network, things are a bit different. Since we start from genesis, the sync distance should be zero or very small. For testing purposes, we can accept