leader discovery fix and code cleaning
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Pierre
@@ -0,0 +1,223 @@
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/**
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* LeaderClient - Client for reading leader info from meta-core
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*
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* This replaces the old LeaderDiscovery.ts by delegating leader election
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* to meta-core (Go sidecar) and just reading the results.
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*
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* Features:
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* - Reads kv-leader.info file for leader URLs
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* - Calls meta-core /urls API for current leader URLs
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* - Watches for leader changes via file system watcher
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*/
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import { promises as fs } from 'fs';
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import { watch, FSWatcher } from 'fs';
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import { dirname } from 'path';
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import { Logger } from 'tslog';
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import type { LeaderLockInfo } from './IKVClient.js';
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const logger = new Logger({ name: 'LeaderClient' });
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export interface LeaderClientConfig {
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/** Path to META_CORE_VOLUME (e.g., /meta-core) */
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metaCorePath: string;
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/** meta-core API URL (e.g., http://meta-core:9000 or http://localhost:9000) */
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metaCoreUrl?: string;
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}
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export interface URLsResponse {
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hostname: string;
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baseUrl: string;
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apiUrl: string;
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redisUrl: string;
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webdavUrl: string;
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isLeader: boolean;
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}
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export class LeaderClient {
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private config: LeaderClientConfig;
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private infoFilePath: string;
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private leaderInfo: LeaderLockInfo | null = null;
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private watcher: FSWatcher | null = null;
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private onChangeCallbacks: (() => void)[] = [];
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constructor(config: LeaderClientConfig) {
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this.config = config;
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this.infoFilePath = `${config.metaCorePath}/locks/kv-leader.info`;
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}
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/**
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* Read leader info from the info file
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*/
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async getLeaderInfo(): Promise<LeaderLockInfo | null> {
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try {
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const content = await fs.readFile(this.infoFilePath, 'utf-8');
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this.leaderInfo = JSON.parse(content) as LeaderLockInfo;
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return this.leaderInfo;
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} catch (error: any) {
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logger.error(`Failed to read leader info: ${error.message}`);
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return null;
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}
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}
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/**
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* Get Redis URL from leader info
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*/
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async getRedisUrl(): Promise<string | null> {
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const info = await this.getLeaderInfo();
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return info?.redisUrl ?? null;
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}
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/**
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* Get WebDAV URL from leader info
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*/
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async getWebdavUrl(): Promise<string | null> {
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const info = await this.getLeaderInfo();
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return info?.webdavUrl ?? null;
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}
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/**
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* Get meta-core API URL from leader info
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*/
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async getApiUrl(): Promise<string | null> {
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const info = await this.getLeaderInfo();
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return info?.apiUrl ?? null;
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}
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/**
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* Call meta-core /urls API to get current URLs
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* Useful for getting URLs when you don't want to read the file directly
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*/
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async getUrls(): Promise<URLsResponse | null> {
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// First try using configured metaCoreUrl
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let apiUrl = this.config.metaCoreUrl;
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// Fall back to reading from leader info
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if (!apiUrl) {
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const info = await this.getLeaderInfo();
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apiUrl = info?.apiUrl;
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}
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if (!apiUrl) {
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logger.error('No meta-core API URL available');
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return null;
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}
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try {
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const response = await fetch(`${apiUrl}/urls`, {
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method: 'GET',
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headers: { 'Accept': 'application/json' },
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signal: AbortSignal.timeout(5000)
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});
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if (!response.ok) {
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logger.error(`Failed to get URLs: ${response.status} ${response.statusText}`);
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return null;
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}
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return await response.json() as URLsResponse;
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} catch (error: any) {
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logger.error(`Error calling /urls API: ${error.message}`);
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return null;
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}
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}
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/**
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* Wait for leader info to be available
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*/
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async waitForLeader(timeoutMs: number = 30000): Promise<LeaderLockInfo> {
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const startTime = Date.now();
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const pollInterval = 500;
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while (Date.now() - startTime < timeoutMs) {
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const info = await this.getLeaderInfo();
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if (info) {
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logger.info(`Leader found: ${info.hostname} at ${info.redisUrl}`);
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return info;
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}
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logger.debug('Waiting for leader...');
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await new Promise(resolve => setTimeout(resolve, pollInterval));
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}
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throw new Error(`No leader found within ${timeoutMs}ms`);
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}
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/**
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* Start watching for leader changes
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*/
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startWatching(): void {
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if (this.watcher) {
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return; // Already watching
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}
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const lockDir = dirname(this.infoFilePath);
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try {
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this.watcher = watch(lockDir, (eventType, filename) => {
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if (filename === 'kv-leader.info') {
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logger.debug(`Lock file ${eventType}, checking for leader...`);
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this.getLeaderInfo().then(() => {
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this.notifyChange();
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}).catch((err) => logger.error(`Error reloading leader info: ${err.message}`));
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}
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});
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this.watcher.on('error', (error: any) => {
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logger.warn(`File watcher error: ${error.message}`);
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});
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logger.info(`Watching for leader changes in ${lockDir}`);
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} catch (error: any) {
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logger.error(`Failed to start watching: ${error.message}`);
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}
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}
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/**
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* Stop watching for leader changes
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*/
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stopWatching(): void {
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if (this.watcher) {
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this.watcher.close();
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this.watcher = null;
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logger.debug('Stopped watching for leader changes');
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}
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}
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/**
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* Register callback for leader changes
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*/
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onChange(callback: () => void): this {
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this.onChangeCallbacks.push(callback);
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return this;
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}
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/**
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* Notify all change callbacks
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*/
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private notifyChange(): void {
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for (const callback of this.onChangeCallbacks) {
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try {
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callback();
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} catch (error: any) {
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logger.error(`Error in change callback: ${error.message}`);
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}
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}
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}
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/**
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* Get cached leader info (without re-reading file)
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*/
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getCachedLeaderInfo(): LeaderLockInfo | null {
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return this.leaderInfo;
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}
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/**
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* Clean up resources
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*/
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close(): void {
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this.stopWatching();
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this.onChangeCallbacks = [];
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}
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}
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