The Node's Event Stream

Each Casper node streams events through the SSE (Server Sent Event) server via an /events endpoint and the port specified as the event_stream_server.address in the node's config.toml. This port is by default 9999 for nodes on Testnet and Mainnet.

Monitoring a Node's Event Stream

As an operator, you can use cURL to monitor the event stream on a node.

curl -s http://HOST:PORT/events/

• HOST - The IP address of a node on the network.
• PORT - The port specified as the event_stream_server.address in the node's config.toml.

Another helpful tool is the Casper Sidecar, which provides the recommended way to monitor events on a node. Visit the Casper Sidecar Usage Guide for a detailed list of events and REST queries you can use to monitor the node and the state of the network.

Replaying the Event Stream

This command will replay the event stream from an old event onward. If the ID is 0 or if you specify an event ID already purged from the cache, the server will replay all the cached events. Replace the HOST, PORT, and ID fields with the needed values.

curl -sN http://HOST:PORT/events?start_from=ID

Example:

curl -sN http://65.21.235.219:9999/events?start_from=29267508

note

The node stores only a limited number of events in its cache, which can be configured using the event_stream_buffer_length in the config.toml. The intended use case is to allow the Sidecar consuming the event stream to reconnect (if it loses its connection) and catch up with the events emitted while it was disconnected.

The Casper Sidecar may store additional events depending on how it was configured.