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flaky-server.js
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flaky-server.js
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// This is a flaky webserver that introduces random weirdness and errors.
// It randomly pauses and resumes.
// It also writes out data in random-sized bursts with random delays.
var clientIdCounter = 0;
// Generate a 128k random data buffer
var buf = new Buffer(128 * 1024),
from = 'abcdefghijklmnopqrstuvwxyz ';
for (var i = 0; i < buf.length; i++) {
buf[i] = from.charCodeAt(Math.floor(Math.random() * from.length));
}
// Create the server
require('net').createServer(handleConnection).listen(8000);
function handleConnection(socket) {
var clientId = ++clientIdCounter,
sendTimeout = null,
receiveTimeout = null,
errorTimeout = null,
disconnectTimeout = null,
paused = true,
received = 0,
sentMin = 0,
sentMax = 0;
console.log("#%d: New connection from %s:%d.",
clientId,
socket.remoteAddress,
socket.remotePort);
// Start in paused state
socket.pause();
// Attach listeners.
socket.on('data', function(buf) {
received += buf.length;
});
socket.on('error', function(err) {
console.log('#%d: %s.', clientId, err);
cancelReceive();
cancelSend();
cancelDisconnect();
});
socket.on('end', function() {
console.log('#%d: Received FIN packet.', clientId);
cancelReceive();
});
socket.on('close', function() {
if (sentMin != sentMax) {
console.log('#%d: Connection closed. Received: %d bytes. Sent: between %d and %d bytes.',
clientId,
received,
sentMin,
sentMax);
} else {
console.log('#%d: Connection closed. Received: %d bytes. Sent: %d bytes.',
clientId,
received,
sentMax);
}
cancelReceive();
cancelSend();
cancelDisconnect();
});
// Schedule flakyness
scheduleSend();
scheduleReceive();
scheduleDisconnect();
function scheduleSend() {
var delay = Math.pow(2000, Math.random()) - 1;
sendTimeout = setTimeout(sendBurst, delay);
}
function scheduleReceive() {
var delay = Math.pow(2000, Math.random()) - 1;
receiveTimeout = setTimeout(flipPausedState, delay);
}
function scheduleDisconnect() {
var delay = 60000; // Math.round(Math.pow(5 * 60 * 1000, Math.random())) - 1;
console.log("#%d: Will disconnect after %d seconds.", clientId, delay / 1000);
disconnectTimeout = setTimeout(disconnect, delay);
}
function cancelReceive() {
if (receiveTimeout) {
clearTimeout(receiveTimeout);
receiveTimeout = null;
}
}
function cancelSend() {
if (sendTimeout) {
clearTimeout(sendTimeout);
sendTimeout = null;
}
}
function cancelDisconnect() {
if (disconnectTimeout) {
clearTimeout(disconnectTimeout);
disconnectTimeout = null;
}
}
function flipPausedState() {
if (paused) {
paused = false;
socket.resume();
} else {
paused = true;
socket.pause();
}
scheduleReceive();
}
function sendBurst() {
var size = Math.floor(Math.pow(buf.length, Math.random())) - 1,
offset = Math.floor(Math.random() * (buf.length - size)),
burst = buf.slice(offset, offset + size);
socket.write(burst, function(err) {
if (err) {
return;
}
sentMin += size;
if (socket.writable)
scheduleSend();
});
sentMax += size;
sendTimeout = null;
}
function disconnect() {
var graceful = socket.writable && (Math.random() >= .5);
if (graceful) {
console.log('#%d: Sending FIN packet.', clientId);
socket.end();
cancelSend();
} else {
console.log('#%d: Initiating hard close.', clientId);
socket.destroy();
cancelSend();
cancelReceive();
}
disconnectTimeout = null;
}
}