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import { EventEmitter } from 'eventemitter3';
import { v4 as uuidv4 } from 'uuid';
import { BrowserInstance, BrowserPoolConfig, Logger } from './types';
/**
* @file Implements a pool for managing Playwright browser instances.
* This helps in reusing browser instances to improve performance and control resource usage
* by limiting the maximum number of concurrent browsers.
*/
/**
* Manages a pool of Playwright browser instances.
* This class handles the creation, acquisition, release, and cleanup of browser instances,
* ensuring efficient reuse and adherence to configured limits (e.g., max size, instance age).
* It emits events related to pool operations like 'pool:acquire', 'pool:release', 'pool:cleanup'.
* @extends EventEmitter
*/
export class BrowserPool extends EventEmitter {
private pool: BrowserInstance[] = [];
private config: BrowserPoolConfig;
private logger: Logger;
private cleanupTimer?: ReturnType<typeof setTimeout>;
private isShuttingDown = false;
/**
* Creates an instance of BrowserPool.
* @param config The configuration object for the browser pool. See {@link BrowserPoolConfig}.
* @param logger An instance of a logger conforming to the {@link Logger} interface.
*/
constructor(config: BrowserPoolConfig, logger: Logger) {
super();
this.config = config;
this.logger = logger;
this.startCleanupTimer();
this.logger.info('BrowserPool initialized', { maxSize: config.maxSize, maxAge: config.maxAge });
}
/**
* Acquires a browser instance from the pool.
* If an idle instance is available, it's reused.
* If the pool is not full, a new instance is created.
* If the pool is full and no instances are idle, it waits for one to become available.
* Emits 'pool:acquire' event when an instance is acquired.
* @returns A Promise that resolves to an available {@link BrowserInstance}.
* @throws Error if the pool is shutting down or if waiting for an instance times out.
*/
async acquire(): Promise<BrowserInstance> {
Iif (this.isShuttingDown) {
this.logger.warn('Attempted to acquire browser instance while pool is shutting down.');
throw new Error('Browser pool is shutting down');
}
// Try to find an available instance
const availableInstance = this.pool.find(instance => !instance.inUse);
if (availableInstance) {
this.logger.debug('Reusing browser instance from pool', {
instanceId: availableInstance.id,
});
// Check if page is still valid
Iif (availableInstance.page.isClosed()) {
this.logger.debug('Page closed, creating new page in existing context', {
instanceId: availableInstance.id,
});
availableInstance.page = await availableInstance.context.newPage();
}
availableInstance.inUse = true;
availableInstance.lastUsed = Date.now();
this.emit('pool:acquire', { instanceId: availableInstance.id });
return availableInstance;
}
// Create new instance if pool is not full
if (this.pool.length < this.config.maxSize) {
this.logger.debug('Creating new browser instance', {
poolSize: this.pool.length,
maxSize: this.config.maxSize,
});
const instance = await this.createInstance();
this.pool.push(instance);
this.emit('pool:acquire', { instanceId: instance.id });
return instance;
}
// Wait for an instance to become available
this.logger.debug('Pool full, waiting for available instance');
return this.waitForAvailableInstance();
}
/**
* Releases a previously acquired browser instance back to the pool,
* marking it as available for reuse.
* Emits 'pool:release' event.
* @param instance The {@link BrowserInstance} to release.
*/
release(instance: BrowserInstance): void {
const poolInstance = this.pool.find(i => i.id === instance.id);
if (poolInstance) {
Iif (!poolInstance.inUse) {
this.logger.warn('Attempted to release an instance that was not marked as in-use.', {
instanceId: instance.id,
});
}
poolInstance.inUse = false;
poolInstance.lastUsed = Date.now();
this.logger.debug('Released browser instance to pool', { instanceId: poolInstance.id });
this.emit('pool:release', { instanceId: poolInstance.id });
} else E{
this.logger.warn('Attempted to release an unknown or already destroyed browser instance.', {
instanceId: instance.id,
});
}
}
/**
* Retrieves statistics about the current state of the browser pool.
* @returns An object containing:
* - `total`: The total number of browser instances currently managed by the pool (both active and idle).
* - `inUse`: The number of browser instances currently acquired and in use.
* - `available`: The number of idle browser instances available for immediate acquisition.
* - `maxSize`: The maximum number of browser instances the pool is configured to allow.
*/
getStats(): {
total: number;
inUse: number;
available: number;
maxSize: number;
} {
const inUseCount = this.pool.filter(i => i.inUse).length;
const stats = {
total: this.pool.length,
inUse: inUseCount,
available: this.pool.length - inUseCount,
maxSize: this.config.maxSize,
};
this.logger.debug('Browser pool stats requested.', stats);
return stats;
}
/**
* Periodically cleans up old and unused browser instances from the pool.
* An instance is considered old if it has not been used for a duration exceeding
* `config.maxAge` and is not currently in use.
* This method is typically called by an internal timer.
* Emits 'pool:cleanup' event with the number of removed instances.
* @returns A Promise that resolves when the cleanup operation is complete.
*/
async cleanupOldInstances(): Promise<void> {
Iif (this.isShuttingDown) {
this.logger.debug('Cleanup skipped as pool is shutting down.');
return;
}
const now = Date.now();
const instancesToRemove: BrowserInstance[] = [];
for (const instance of this.pool) {
if (!instance.inUse && now - instance.lastUsed > this.config.maxAge) {
instancesToRemove.push(instance);
}
}
if (instancesToRemove.length > 0) {
this.logger.debug('Cleaning up old browser instances', {
count: instancesToRemove.length,
});
for (const instance of instancesToRemove) {
await this.destroyInstance(instance);
const index = this.pool.indexOf(instance);
if (index > -1) {
this.pool.splice(index, 1);
}
}
this.emit('pool:cleanup', { removedInstances: instancesToRemove.length });
}
}
/**
* Shuts down the browser pool.
* This process involves stopping the cleanup timer and closing all active browser instances
* managed by the pool. No new instances can be acquired after shutdown is initiated.
* @returns A Promise that resolves when all browser instances have been closed and resources are freed.
*/
async shutdown(): Promise<void> {
this.logger.info('Shutting down browser pool...');
this.isShuttingDown = true;
if (this.cleanupTimer) {
clearInterval(this.cleanupTimer);
}
const closePromises = this.pool.map(instance => this.destroyInstance(instance));
await Promise.all(closePromises);
this.pool = [];
this.logger.info('Browser pool shutdown complete');
}
/**
* Create a new browser instance
*/
private async createInstance(): Promise<BrowserInstance> {
const launchOptions: LaunchOptions = {
headless: this.config.launchOptions.headless,
args: this.config.launchOptions.args,
timeout: this.config.launchOptions.timeout,
};
const browser = await chromium.launch(launchOptions);
const context = await browser.newContext({
viewport: { width: 1920, height: 1080 },
userAgent:
'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36',
});
const page = await context.newPage();
const id = uuidv4();
const instance: BrowserInstance = {
id,
browser,
context,
page,
lastUsed: Date.now(),
inUse: true,
createdAt: Date.now(),
};
this.logger.debug('Created new browser instance', { instanceId: id });
return instance;
}
/**
* Destroy a browser instance
*/
private async destroyInstance(instance: BrowserInstance): Promise<void> {
try {
await instance.browser.close();
this.logger.debug('Destroyed browser instance', { instanceId: instance.id });
} catch (error) {
this.logger.error('Error destroying browser instance', {
instanceId: instance.id,
error: error instanceof Error ? error.message : String(error),
});
}
}
/**
* Wait for an available instance
*/
private async waitForAvailableInstance(): Promise<BrowserInstance> {
return new Promise((resolve, reject) => {
const timeout = setTimeout(() => {
reject(new Error('Timeout waiting for available browser instance'));
}, 30000);
const checkInterval = setInterval(() => {
const availableInstance = this.pool.find(instance => !instance.inUse);
Iif (availableInstance) {
clearInterval(checkInterval);
clearTimeout(timeout);
availableInstance.inUse = true;
availableInstance.lastUsed = Date.now();
// Check if page is still valid
if (availableInstance.page.isClosed()) {
availableInstance.context
.newPage()
.then((page: Page) => {
availableInstance.page = page;
resolve(availableInstance);
})
.catch(reject);
} else {
resolve(availableInstance);
}
}
}, 200);
});
}
/**
* Start the cleanup timer
*/
private startCleanupTimer(): void {
this.cleanupTimer = setInterval(() => {
this.cleanupOldInstances().catch(error => {
this.logger.error('Error during scheduled cleanup', {
error: error instanceof Error ? error.message : String(error),
});
});
}, this.config.cleanupInterval);
}
}
/**
* Provides a default configuration for the {@link BrowserPool}.
* This configuration can be used as a base and customized as needed.
* Key defaults include:
* - `maxSize`: 5 browser instances.
* - `maxAge`: 30 minutes for an instance before it's recycled.
* - `headless`: True (or as per `BROWSER_HEADLESS` env var).
* - `cleanupInterval`: 5 minutes.
*/
export const defaultBrowserPoolConfig: BrowserPoolConfig = {
maxSize: 5,
maxAge: 30 * 60 * 1000, // 30 minutes
launchOptions: {
headless: process.env.BROWSER_HEADLESS !== 'false',
args: [
'--no-sandbox',
'--disable-setuid-sandbox',
'--disable-dev-shm-usage',
'--disable-accelerated-2d-canvas',
'--no-first-run',
'--no-zygote',
'--disable-gpu',
],
timeout: 30000,
},
cleanupInterval: 5 * 60 * 1000, // 5 minutes
};
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