mc-server-manager/agent/source/app.d

import std.stdio;
import std.algorithm;
import std.array;
import std.json;
import std.datetime;

import requests;

import shared_utils.server_status;

import config;
import server_metadata;
import server_actions;

/**
 * This program will run frequently (maybe every minute or more), and does the following:
 * - Fetches a list of requested servers from the mc-server-manager API, and starts them.
 * - Checks for any servers without any players online, and writes a blank file to track.
 * - For servers with nobody online, and a timestamp file older than N minutes, the server is shut down.
 */
void main() {
	AgentConfig config = readConfig();
	ServerMetaData[] servers = readServerMetaData();
	ServerStatus[] statuses = servers.map!(determineStatus).array;
	try {
		sendServerStatusToWeb(statuses, config);
	} catch (Exception e) {
		stderr.writeln(e.msg);
	}
	checkForEmptyServers(servers, statuses, config);
	try {
		startRequestedServers(servers, config);
	} catch (Exception e) {
		stderr.writeln(e.msg);
	}
}

void sendServerStatusToWeb(in ServerStatus[] statuses, in AgentConfig config) {
	JSONValue jsonPayload = serializeServerStatuses(statuses);
	string payload = jsonPayload.toJSON();
	Request rq = Request();
	rq.addHeaders(["X-Agent-Key": config.agentKey]);
	Response resp = rq.post(config.webUrl ~ "/api/servers", payload, "application/json");
	if (resp.code >= 300) {
		import std.format;
		throw new Exception(
			format!"Failed to post server statuses: Error code %d, Response body: %s"(
				resp.code,
				resp.responseBody
			)
		);
	}
}

void startRequestedServers(ServerMetaData[] servers, AgentConfig config) {
	auto content = getContent(config.webUrl ~ "/api/server-requests");
	JSONValue jsonContent = parseJSON(cast(string) content.data);
	string[] requestedServerNames = jsonContent.array()
		.map!(node => node.str)
		.array;
	foreach (server; servers) {
		if (canFind(requestedServerNames, server.name)) {
			startServer(server, config);
		}
	}
}

void checkForEmptyServers(ServerMetaData[] servers, ServerStatus[] statuses, AgentConfig config) {
	foreach (i, server; servers) {
		ServerStatus status = statuses[i];
		if (status.online && status.playersOnline > 0) {
			removeIdleTrackerFileIfPresent(server);
		} else if (status.online && status.playersOnline == 0) {
			const Duration idleTime = getOrCreateIdleTrackerFileAndGetAge(server);
			if (idleTime.total!"minutes" > config.serverInactivityTimeoutMinutes) {
				stopServer(server, config);
			}
		}
	}
}