124 lines
3.8 KiB
JavaScript
124 lines
3.8 KiB
JavaScript
"use strict";
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import { once, EventEmitter } from 'events';
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import log from './io/NamespacedLog.mjs'; const l = log("systemquery");
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import Agent from './agent/Agent.mjs';
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import InfoBroker from './core/InfoBroker.mjs';
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import HttpSubsystem from './agent/subsystems/http/HttpSubsystem.mjs';
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import ItemQueue from './async/ItemQueue.mjs';
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class SystemQuery extends EventEmitter {
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constructor(config, mode = "agent") {
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super();
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// The operating mode. Possible values: agent [default], query_client
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// TODO: Is this the best way of doing this? Maybe we should have a separate class for this? I'm not sure.
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this.mode = mode;
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this.config = config;
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this.info = new InfoBroker();
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this.http = new HttpSubsystem(this);
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}
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async init() {
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///
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// 1: Create agent
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///
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this.agent = new Agent(this.config);
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this.http.init(
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this.config.net.http.port,
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this.config.net.http.bind_address
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);
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///
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// 2: Attach listeners
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///
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this.agent.on("message-query", this.handle_query.bind(this));
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this.agent.on("message-query-response", this.handle_query_response.bind(this));
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///
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// 3: Start agent
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///
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await this.agent.init();
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}
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async handle_query(peer, msg) {
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// 1: Validate input
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if(typeof msg.name !== "string"
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|| !this.info.is_valid_table(msg.name)) return;
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// 2: Fetch system info
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let table = await this.info.fetch_table(msg.name);
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if(table === null) return;
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// 3: Return to requester
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await peer.send("query-response", { name: msg.name, table });
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}
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async handle_query_response(peer, msg) {
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l.log(`query-response from ${peer.id_short}`, msg);
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}
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async capture_query_response(event_name, ac) {
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return await once(this.agent, `message-${event_name}`, { signal: ac });
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}
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async *fetch_table(name) {
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// If it isn't valid for us, it ain't gonna be valid for anyone else....
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if(!this.info.is_valid_table(name)) return null;
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l.log(`fetch table ${name} start`)
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const queue = new ItemQueue();
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const handle_response = (peer, msg) => {
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// TODO: Validate response. Is it the right table? Is it even a table? Note that multiple fetch_table calls may be running in parallel, so we should not make too much of a fuss if we get the wrong table by accident.
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// TODO: It would be seriously cool to have fetch_table() be an async generator that yields pairs of peer ids and tables as they come in.
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if(typeof msg !== "object"
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|| typeof msg.table !== "object"
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|| typeof msg.name !== "string") {
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l.debug(`Discarding invalid table from peer ${peer.id_short}`);
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return;
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}
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// If it's not the right table, ignore it
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if(msg.name !== name) return;
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queue.enqueue({ peer, table: msg.table });
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};
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this.agent.on("message-query-response", handle_response);
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// Only *after* we have our listeners in place do we then broadcast the
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// query. Note that despite not having entered the below while loop yet,
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// we do not drop any messages due to the use of the ItemQueue.
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this.agent.broadcast(`query`, { name });
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let peers_seen = [];
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while(peers_seen.length < this.agent.connected_peers.length) {
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l.info(`peers_seen:`, peers_seen, `connected peers:`, this.agent.connected_peers.length);
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let next = await queue.dequeue(this.config.net.table_timeout * 1000);
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if(typeof next === "undefined") // We timed out
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break;
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l.log(`fetch table DEBUG`, next);
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if(!peers_seen.includes(next.peer.id))
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peers_seen.push(next.peer.id);
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yield next;
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}
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this.agent.off("message-query-response", handle_response);
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l.log(`fetch table END`);
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// FUTURE: Add a cache here? Note that we also do not listen for query responses unless we've asked for a table.
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}
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}
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SystemQuery.Create = async function(config) {
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let result = new SystemQuery(config);
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await result.init();
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return result;
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}
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export default SystemQuery;
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