const logger = require('logger-sharelatex') module.exports = { startDrainTimeWindow(io, minsToDrain, callback) { const drainPerMin = io.sockets.clients().length / minsToDrain // enforce minimum drain rate this.startDrain(io, Math.max(drainPerMin / 60, 4), callback) }, startDrain(io, rate, callback) { // Clear out any old interval clearInterval(this.interval) logger.log({ rate }, 'starting drain') if (rate === 0) { return } let pollingInterval if (rate < 1) { // allow lower drain rates // e.g. rate=0.1 will drain one client every 10 seconds pollingInterval = 1000 / rate rate = 1 } else { pollingInterval = 1000 } this.interval = setInterval(() => { const requestedAllClientsToReconnect = this.reconnectNClients(io, rate) if (requestedAllClientsToReconnect && callback) { callback() callback = undefined } }, pollingInterval) }, RECONNECTED_CLIENTS: {}, reconnectNClients(io, N) { let drainedCount = 0 for (const client of io.sockets.clients()) { if (!this.RECONNECTED_CLIENTS[client.id]) { this.RECONNECTED_CLIENTS[client.id] = true logger.log( { client_id: client.id }, 'Asking client to reconnect gracefully' ) client.emit('reconnectGracefully') drainedCount++ } const haveDrainedNClients = drainedCount === N if (haveDrainedNClients) { break } } if (drainedCount < N) { logger.log('All clients have been told to reconnectGracefully') return true } return false }, }