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/**
* Very scuffed request queue. OpenAI's GPT-4 keys have a very strict rate limit
* of 40000 generated tokens per minute. We don't actually know how many tokens
* a given key has generated, so our queue will simply retry requests that fail
* with a non-billing related 429 over and over again until they succeed.
*
* Dequeueing can operate in one of two modes:
* - 'fair': requests are dequeued in the order they were enqueued.
* - 'random': requests are dequeued randomly, not really a queue at all.
*
* When a request to a proxied endpoint is received, we create a closure around
* the call to http-proxy-middleware and attach it to the request. This allows
* us to pause the request until we have a key available. Further, if the
* proxied request encounters a retryable error, we can simply put the request
* back in the queue and it will be retried later using the same closure.
*/
import type { Handler, Request } from "express";
import { config, DequeueMode } from "../config";
import { keyPool, SupportedModel } from "../key-management";
import { logger } from "../logger";
import { AGNAI_DOT_CHAT_IP } from "./rate-limit";
import { buildFakeSseMessage } from "./middleware/common";
export type QueuePartition = "claude" | "turbo" | "gpt-4";
const queue: Request[] = [];
const log = logger.child({ module: "request-queue" });
let dequeueMode: DequeueMode = "fair";
/** Maximum number of queue slots for Agnai.chat requests. */
const AGNAI_CONCURRENCY_LIMIT = 15;
/** Maximum number of queue slots for individual users. */
const USER_CONCURRENCY_LIMIT = 1;
const sameIpPredicate = (incoming: Request) => (queued: Request) =>
queued.ip === incoming.ip;
const sameUserPredicate = (incoming: Request) => (queued: Request) => {
const incomingUser = incoming.user ?? { token: incoming.ip };
const queuedUser = queued.user ?? { token: queued.ip };
return queuedUser.token === incomingUser.token;
};
export function enqueue(req: Request) {
let enqueuedRequestCount = 0;
let isGuest = req.user?.token === undefined;
if (isGuest) {
enqueuedRequestCount = queue.filter(sameIpPredicate(req)).length;
} else {
enqueuedRequestCount = queue.filter(sameUserPredicate(req)).length;
}
// All Agnai.chat requests come from the same IP, so we allow them to have
// more spots in the queue. Can't make it unlimited because people will
// intentionally abuse it.
// Authenticated users always get a single spot in the queue.
const maxConcurrentQueuedRequests =
isGuest && req.ip === AGNAI_DOT_CHAT_IP
? AGNAI_CONCURRENCY_LIMIT
: USER_CONCURRENCY_LIMIT;
if (enqueuedRequestCount >= maxConcurrentQueuedRequests) {
if (req.ip === AGNAI_DOT_CHAT_IP) {
// Re-enqueued requests are not counted towards the limit since they
// already made it through the queue once.
if (req.retryCount === 0) {
throw new Error("Too many agnai.chat requests are already queued");
}
} else {
throw new Error("Your IP or token already has a request in the queue");
}
}
queue.push(req);
req.queueOutTime = 0;
// shitty hack to remove hpm's event listeners on retried requests
removeProxyMiddlewareEventListeners(req);
// If the request opted into streaming, we need to register a heartbeat
// handler to keep the connection alive while it waits in the queue. We
// deregister the handler when the request is dequeued.
if (req.body.stream === "true" || req.body.stream === true) {
const res = req.res!;
if (!res.headersSent) {
initStreaming(req);
}
req.heartbeatInterval = setInterval(() => {
if (process.env.NODE_ENV === "production") {
req.res!.write(": queue heartbeat\n\n");
} else {
req.log.info(`Sending heartbeat to request in queue.`);
const partition = getPartitionForRequest(req);
const avgWait = Math.round(getEstimatedWaitTime(partition) / 1000);
const currentDuration = Math.round((Date.now() - req.startTime) / 1000);
const debugMsg = `queue length: ${queue.length}; elapsed time: ${currentDuration}s; avg wait: ${avgWait}s`;
req.res!.write(buildFakeSseMessage("heartbeat", debugMsg, req));
}
}, 10000);
}
// Register a handler to remove the request from the queue if the connection
// is aborted or closed before it is dequeued.
const removeFromQueue = () => {
req.log.info(`Removing aborted request from queue.`);
const index = queue.indexOf(req);
if (index !== -1) {
queue.splice(index, 1);
}
if (req.heartbeatInterval) {
clearInterval(req.heartbeatInterval);
}
};
req.onAborted = removeFromQueue;
req.res!.once("close", removeFromQueue);
if (req.retryCount ?? 0 > 0) {
req.log.info({ retries: req.retryCount }, `Enqueued request for retry.`);
} else {
req.log.info(`Enqueued new request.`);
}
}
function getPartitionForRequest(req: Request): QueuePartition {
// There is a single request queue, but it is partitioned by model and API
// provider.
// - claude: requests for the Anthropic API, regardless of model
// - gpt-4: requests for the OpenAI API, specifically for GPT-4 models
// - turbo: effectively, all other requests
const provider = req.outboundApi;
const model = (req.body.model as SupportedModel) ?? "gpt-3.5-turbo";
if (provider === "anthropic") {
return "claude";
}
if (provider === "openai" && model.startsWith("gpt-4")) {
return "gpt-4";
}
return "turbo";
}
function getQueueForPartition(partition: QueuePartition): Request[] {
return queue.filter((req) => getPartitionForRequest(req) === partition);
}
export function dequeue(partition: QueuePartition): Request | undefined {
const modelQueue = getQueueForPartition(partition);
if (modelQueue.length === 0) {
return undefined;
}
let req: Request;
if (dequeueMode === "fair") {
// Dequeue the request that has been waiting the longest
req = modelQueue.reduce((prev, curr) =>
prev.startTime < curr.startTime ? prev : curr
);
} else {
// Dequeue a random request
const index = Math.floor(Math.random() * modelQueue.length);
req = modelQueue[index];
}
queue.splice(queue.indexOf(req), 1);
if (req.onAborted) {
req.res!.off("close", req.onAborted);
req.onAborted = undefined;
}
if (req.heartbeatInterval) {
clearInterval(req.heartbeatInterval);
}
// Track the time leaving the queue now, but don't add it to the wait times
// yet because we don't know if the request will succeed or fail. We track
// the time now and not after the request succeeds because we don't want to
// include the model processing time.
req.queueOutTime = Date.now();
return req;
}
/**
* Naive way to keep the queue moving by continuously dequeuing requests. Not
* ideal because it limits throughput but we probably won't have enough traffic
* or keys for this to be a problem. If it does we can dequeue multiple
* per tick.
**/
function processQueue() {
// This isn't completely correct, because a key can service multiple models.
// Currently if a key is locked out on one model it will also stop servicing
// the others, because we only track one rate limit per key.
const gpt4Lockout = keyPool.getLockoutPeriod("gpt-4");
const turboLockout = keyPool.getLockoutPeriod("gpt-3.5-turbo");
const claudeLockout = keyPool.getLockoutPeriod("claude-v1");
const reqs: (Request | undefined)[] = [];
if (gpt4Lockout === 0) {
reqs.push(dequeue("gpt-4"));
}
if (turboLockout === 0) {
reqs.push(dequeue("turbo"));
}
if (claudeLockout === 0) {
reqs.push(dequeue("claude"));
}
reqs.filter(Boolean).forEach((req) => {
if (req?.proceed) {
req.log.info({ retries: req.retryCount }, `Dequeuing request.`);
req.proceed();
}
});
setTimeout(processQueue, 50);
}
/**
* Kill stalled requests after 5 minutes, and remove tracked wait times after 2
* minutes.
**/
function cleanQueue() {
const now = Date.now();
const oldRequests = queue.filter(
(req) => now - (req.startTime ?? now) > 5 * 60 * 1000
);
oldRequests.forEach((req) => {
req.log.info(`Removing request from queue after 5 minutes.`);
killQueuedRequest(req);
});
const index = waitTimes.findIndex(
(waitTime) => now - waitTime.end > 300 * 1000
);
const removed = waitTimes.splice(0, index + 1);
log.trace(
{ stalledRequests: oldRequests.length, prunedWaitTimes: removed.length },
`Cleaning up request queue.`
);
setTimeout(cleanQueue, 20 * 1000);
}
export function start() {
processQueue();
cleanQueue();
log.info(`Started request queue.`);
}
let waitTimes: { partition: QueuePartition; start: number; end: number }[] = [];
/** Adds a successful request to the list of wait times. */
export function trackWaitTime(req: Request) {
waitTimes.push({
partition: getPartitionForRequest(req),
start: req.startTime!,
end: req.queueOutTime ?? Date.now(),
});
}
/** Returns average wait time in milliseconds. */
export function getEstimatedWaitTime(partition: QueuePartition) {
const now = Date.now();
const recentWaits = waitTimes.filter(
(wt) => wt.partition === partition && now - wt.end < 300 * 1000
);
if (recentWaits.length === 0) {
return 0;
}
return (
recentWaits.reduce((sum, wt) => sum + wt.end - wt.start, 0) /
recentWaits.length
);
}
export function getQueueLength(partition: QueuePartition | "all" = "all") {
if (partition === "all") {
return queue.length;
}
const modelQueue = getQueueForPartition(partition);
return modelQueue.length;
}
export function createQueueMiddleware(proxyMiddleware: Handler): Handler {
return (req, res, next) => {
if (config.queueMode === "none") {
return proxyMiddleware(req, res, next);
}
req.proceed = () => {
proxyMiddleware(req, res, next);
};
try {
enqueue(req);
} catch (err: any) {
req.res!.status(429).json({
type: "proxy_error",
message: err.message,
stack: err.stack,
proxy_note: `Only one request can be queued at a time. If you don't have another request queued, your IP or user token might be in use by another request.`,
});
}
};
}
function killQueuedRequest(req: Request) {
if (!req.res || req.res.writableEnded) {
req.log.warn(`Attempted to terminate request that has already ended.`);
return;
}
const res = req.res;
try {
const message = `Your request has been terminated by the proxy because it has been in the queue for more than 5 minutes. The queue is currently ${queue.length} requests long.`;
if (res.headersSent) {
const fakeErrorEvent = buildFakeSseMessage(
"proxy queue error",
message,
req
);
res.write(fakeErrorEvent);
res.end();
} else {
res.status(500).json({ error: message });
}
} catch (e) {
req.log.error(e, `Error killing stalled request.`);
}
}
function initStreaming(req: Request) {
req.log.info(`Initiating streaming for new queued request.`);
const res = req.res!;
res.statusCode = 200;
res.setHeader("Content-Type", "text/event-stream");
res.setHeader("Cache-Control", "no-cache");
res.setHeader("Connection", "keep-alive");
res.setHeader("X-Accel-Buffering", "no"); // nginx-specific fix
res.flushHeaders();
res.write("\n");
res.write(": joining queue\n\n");
}
/**
* http-proxy-middleware attaches a bunch of event listeners to the req and
* res objects which causes problems with our approach to re-enqueuing failed
* proxied requests. This function removes those event listeners.
* We don't have references to the original event listeners, so we have to
* look through the list and remove HPM's listeners by looking for particular
* strings in the listener functions. This is an astoundingly shitty way to do
* this, but it's the best I can come up with.
*/
function removeProxyMiddlewareEventListeners(req: Request) {
// node_modules/http-proxy-middleware/dist/plugins/default/debug-proxy-errors-plugin.js:29
// res.listeners('close')
const RES_ONCLOSE = `Destroying proxyRes in proxyRes close event`;
// node_modules/http-proxy-middleware/dist/plugins/default/debug-proxy-errors-plugin.js:19
// res.listeners('error')
const RES_ONERROR = `Socket error in proxyReq event`;
// node_modules/http-proxy/lib/http-proxy/passes/web-incoming.js:146
// req.listeners('aborted')
const REQ_ONABORTED = `proxyReq.abort()`;
// node_modules/http-proxy/lib/http-proxy/passes/web-incoming.js:156
// req.listeners('error')
const REQ_ONERROR = `if (req.socket.destroyed`;
const res = req.res!;
const resOnClose = res
.listeners("close")
.find((listener) => listener.toString().includes(RES_ONCLOSE));
if (resOnClose) {
res.removeListener("close", resOnClose as any);
}
const resOnError = res
.listeners("error")
.find((listener) => listener.toString().includes(RES_ONERROR));
if (resOnError) {
res.removeListener("error", resOnError as any);
}
const reqOnAborted = req
.listeners("aborted")
.find((listener) => listener.toString().includes(REQ_ONABORTED));
if (reqOnAborted) {
req.removeListener("aborted", reqOnAborted as any);
}
const reqOnError = req
.listeners("error")
.find((listener) => listener.toString().includes(REQ_ONERROR));
if (reqOnError) {
req.removeListener("error", reqOnError as any);
}
}
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