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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 | /** * Bulkhead Pattern * * Isolates failures by limiting concurrent executions. * * @module v3/shared/resilience/bulkhead */ import { EventEmitter } from 'events'; /** * Bulkhead options */ export interface BulkheadOptions { /** Name for identification */ name: string; /** Maximum concurrent executions */ maxConcurrent: number; /** Maximum queue size */ maxQueue: number; /** Timeout for queued items in ms */ queueTimeout: number; /** Callback when rejected */ onRejected?: (reason: 'full' | 'timeout') => void; } /** * Bulkhead statistics */ export interface BulkheadStats { active: number; queued: number; maxConcurrent: number; maxQueue: number; completed: number; rejected: number; timedOut: number; } /** * Queued item */ interface QueuedItem<T> { fn: () => Promise<T>; resolve: (value: T) => void; reject: (error: Error) => void; queuedAt: number; timeoutId?: ReturnType<typeof setTimeout>; } /** * Default options */ const DEFAULT_OPTIONS: Omit<BulkheadOptions, 'name'> = { maxConcurrent: 10, maxQueue: 100, queueTimeout: 30000, }; /** * Bulkhead * * Limits concurrent executions to prevent resource exhaustion. * * @example * const bulkhead = new Bulkhead({ * name: 'database', * maxConcurrent: 10, * maxQueue: 50, * }); * * try { * const result = await bulkhead.execute(() => dbQuery()); * } catch (error) { * if (error.message.includes('Bulkhead full')) { * // Handle capacity exceeded * } * } */ export class Bulkhead extends EventEmitter { private readonly options: BulkheadOptions; private active = 0; private readonly queue: Array<QueuedItem<unknown>> = []; private completed = 0; private rejected = 0; private timedOut = 0; constructor(options: BulkheadOptions) { super(); this.options = { ...DEFAULT_OPTIONS, ...options }; } /** * Execute a function within the bulkhead */ async execute<T>(fn: () => Promise<T>): Promise<T> { // If there's room for execution, run immediately if (this.active < this.options.maxConcurrent) { return this.runNow(fn); } // Check if queue is full if (this.queue.length >= this.options.maxQueue) { this.rejected++; this.options.onRejected?.('full'); throw new Error(`Bulkhead '${this.options.name}' is full. Max concurrent: ${this.options.maxConcurrent}, queue: ${this.options.maxQueue}`); } // Add to queue return this.addToQueue(fn); } /** * Get current statistics */ getStats(): BulkheadStats { return { active: this.active, queued: this.queue.length, maxConcurrent: this.options.maxConcurrent, maxQueue: this.options.maxQueue, completed: this.completed, rejected: this.rejected, timedOut: this.timedOut, }; } /** * Check if there's capacity available */ hasCapacity(): boolean { return this.active < this.options.maxConcurrent || this.queue.length < this.options.maxQueue; } /** * Get available capacity (concurrent + queue) */ availableCapacity(): number { const concurrentAvailable = this.options.maxConcurrent - this.active; const queueAvailable = this.options.maxQueue - this.queue.length; return concurrentAvailable + queueAvailable; } /** * Reset statistics */ resetStats(): void { this.completed = 0; this.rejected = 0; this.timedOut = 0; } /** * Run function immediately */ private async runNow<T>(fn: () => Promise<T>): Promise<T> { this.active++; this.emit('acquire'); try { const result = await fn(); this.completed++; return result; } finally { this.active--; this.emit('release'); this.processQueue(); } } /** * Add function to queue */ private addToQueue<T>(fn: () => Promise<T>): Promise<T> { return new Promise((resolve, reject) => { const item: QueuedItem<T> = { fn, resolve, reject, queuedAt: Date.now(), }; // Set timeout for queued item item.timeoutId = setTimeout(() => { const index = this.queue.indexOf(item as QueuedItem<unknown>); if (index !== -1) { this.queue.splice(index, 1); this.timedOut++; this.options.onRejected?.('timeout'); reject(new Error(`Bulkhead '${this.options.name}' queue timeout after ${this.options.queueTimeout}ms`)); } }, this.options.queueTimeout); this.queue.push(item as QueuedItem<unknown>); this.emit('queued', { queueLength: this.queue.length }); }); } /** * Process next item in queue */ private processQueue(): void { if (this.active >= this.options.maxConcurrent) { return; } const item = this.queue.shift(); if (!item) { return; } // Clear timeout if (item.timeoutId) { clearTimeout(item.timeoutId); } // Execute the queued function this.active++; this.emit('acquire'); item.fn() .then((result) => { this.completed++; item.resolve(result); }) .catch((error) => { item.reject(error); }) .finally(() => { this.active--; this.emit('release'); this.processQueue(); }); } } /** * Create a semaphore for limiting concurrent access */ export function createSemaphore(maxConcurrent: number): { acquire: () => Promise<void>; release: () => void; available: () => number; } { let current = 0; const waiting: Array<() => void> = []; return { async acquire(): Promise<void> { if (current < maxConcurrent) { current++; return; } return new Promise<void>((resolve) => { waiting.push(resolve); }); }, release(): void { const next = waiting.shift(); if (next) { next(); } else { current = Math.max(0, current - 1); } }, available(): number { return maxConcurrent - current; }, }; } |