Understanding Historical Data from Streamflow Listener for Solana
When you set up a listener to monitor stream changes on the Solana blockchain, you often receive historical data as part of the decoded event. In this article, we’ll break down what each field in the decodeData object means and provide insights into why you might want to receive historical data.
Magic Number
The first field to be decoded is the magic number, which is a unique identifier for the Solana blockchain. It is denoted by “
Version
The next field is the version of the Solana blockchain. It is denoted by “
Created
The “createdAt” field contains the timestamp when the event was published. It is represented as an array of timestamps in seconds since the epoch. In the decrypted data, this value appears as “0x…”, indicating that it is a Unix-style timestamp. This allows you to track when specific events occurred on the blockchain.
Other fields (unwrapped)
The decrypted data is an object with several fields:
- “streamflow”: contains information related to the stream
- “events”: an array of event objects, where each event has the following properties:
+ “type”: specifies the type of event (e.g. “onProgramAccountChange”)
+ name: specifies the name of the event
+ “args”: a list of arguments for the event
While these fields provide valuable information about the events you are monitoring, they may not be immediately relevant to your specific use case. Historical data from a streamflow listener typically includes timestamps, event types, and sometimes additional metadata.
Why get historical data?
Historical data is likely generated by a Solana-based service or application that creates and emits stream events at regular intervals. By listening to these events using the onProgramAccountChange listener, you can capture and analyze the data in real time.
Some possible reasons for retrieving historical data from the onProgramAccountChange listener:
- To monitor network performance or latency
- To analyze transaction patterns or traffic data
- To observe specific event types or frequencies
To better understand which events are sent and when, I recommend reviewing the onProgramAccountChange listener configuration and the decoded data that is received. You can also explore additional documentation provided by Solana to better understand their usage and requirements.
Example Code Snippet
Here is an example code snippet that shows how to create a listener that decodes historical traffic data from the onProgramAccountChange event:
“javascript
import { EventListener } from '@solana/web3.js';
import { StreamflowEventDecodedData } from './streamflow-event-decoded-data';
const listener = (context) => {
const decodedData = decodeEvent(context.event);
if (decodedData.streamflow && decodedData.events.length > 0) {
console.log(Streamflow event type: ${decodedData.events[0].type});
console.log(Streamflow event name: ${decodedData.events[0].name});
// Parse the events and print their timestamps
decodedData.events.forEach((event) => {
const timestamp = event.createdAt;
console.log(Event timestamp: ${timestamp}`);
});
}
};
listener.listen(‘streamflow’, (context, decoded data) => {
if (decodedData.streamflow) {
console.log(decodedData.
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