Concept project · runs in your browserTypeScript · React.js · Next.js
Job Queue and Background Workers with NestJS and BullMQ Demo
A live simulation of a Redis-backed job queue with background workers. Enqueue email, report and webhook jobs with priorities, delays and idempotency keys. Add or SIGTERM workers, change concurrency, raise the chaos slider and watch failed attempts back off exponentially until they succeed or land in the failed set. Speed up the clock to see it all faster.
Interactive demo
samiullah.tech/lab/job-queue-workers
connecting to queue…
## How it works
queue.ts is a pure state machine. Every 100 ms the UI calls tick(state, dt), which promotes delayed jobs whose time has come, advances active jobs, finishes or fails them, and lets idle worker slots pick the next job by priority, then insertion order.
A failed attempt with attempts left goes back to delayed for base × 2^(attempt−1) ms. When attempts run out, the job moves to the failed set, where you can inspect the reason and retry it by hand. The chaos slider sets how often webhook receivers fail.
The limiter counts job starts in a sliding one-second window across all workers, like BullMQ's limiter: { max, duration }. Sending SIGTERM to a worker stops it taking jobs; it closes only after its active jobs finish, so nothing is lost or run twice.
## View source
The code running in the window above, exactly as deployed.
app/lab/job-queue-workers/queue.ts472 lines
/**
* A tick-based simulation of a BullMQ-style queue with a pool of workers.
* No React here: this module is the "Redis + worker processes" half of the demo. Every function takes the
* current state and returns a new one, so the whole queue is serialisable (it is saved to localStorage).
*
* The rules mirror BullMQ:
* - lower `priority` number runs first; equal priority is FIFO by insertion order
* - `delay` parks a job in the delayed set until its timestamp
* - a failed attempt with attempts left goes back to delayed with exponential backoff: base * 2^(attempt-1)
* - when attempts are exhausted the job moves to the failed set (our dead-letter view)
* - a custom jobId (idempotency key) that already exists is ignored instead of creating a duplicate
* - the limiter allows at most `max` job starts per `duration` ms across all workers
* - pausing the queue stops new jobs from being picked; active jobs finish
* - a worker that receives SIGTERM finishes its active jobs, takes nothing new, then exits
*/
export type JobType = "email" | "report" | "webhook";
export type JobState = "waiting" | "delayed" | "active" | "completed" | "failed";
export type JobEvent = { at: number; text: string };
export type Job = {
id: string;
type: JobType;
name: string;
data: Record<string, string | number>;
priority: number; // 1 = highest
state: JobState;
attemptsMade: number;
maxAttempts: number;
backoffMs: number;
addedAt: number;
order: number; // insertion order, FIFO tie-break
runAt: number; // when a delayed job becomes waiting
startedAt: number | null;
durationMs: number; // simulated work time of the current attempt
willFail: boolean; // decided when the attempt starts (from the seeded RNG)
workerId: string | null;
progress: number; // 0..100
finishedAt: number | null;
failedReason: string | null;
returnValue: string | null;
events: JobEvent[];
};
export type Worker = { id: string; concurrency: number; draining: boolean; processed: number; failed: number };
export type Span = { jobId: string; type: JobType; workerId: string; slot: number; start: number; end: number | null; outcome: "ok" | "fail" | null };
export type Repeatable = { key: string; type: JobType; name: string; everyMs: number; nextAt: number };
export type QueueConfig = {
paused: boolean;
/** Probability that a webhook attempt fails (the receiver times out or answers 5xx). */
chaos: number;
limiter: { max: number; durationMs: number } | null;
/** BullMQ removeOnComplete: keep only the latest N completed jobs. */
keepCompleted: number;
};
export type LogTone = "ok" | "warn" | "err" | "info" | "dim";
export type QueueLog = { id: number; at: number; text: string; tone: LogTone };
export type QueueState = {
now: number; // simulated ms since the queue started
seq: number; // last numeric job id
order: number;
rng: number;
jobs: Job[];
workers: Worker[];
workerSeq: number;
spans: Span[];
starts: number[]; // timestamps of recent job starts (limiter window)
repeatables: Repeatable[];
config: QueueConfig;
log: QueueLog[]; // newest first, consumed by the UI
logSeq: number;
totals: { completed: number; failed: number; retried: number };
};
/* ------------------------------------------------------------------ */
/* Workload profiles */
/* ------------------------------------------------------------------ */
export const PROFILES: Record<JobType, { minMs: number; maxMs: number; failRate: number; errors: string[] }> = {
email: { minMs: 500, maxMs: 1400, failRate: 0.05, errors: ["SMTP 421: service not available", "Template render error: missing {{firstName}}"] },
report: { minMs: 2500, maxMs: 5500, failRate: 0.08, errors: ["Query timeout after 30s", "Storage PUT failed: 503 Slow Down"] },
webhook: { minMs: 300, maxMs: 1100, failRate: 0, errors: ["Receiver answered 503", "ETIMEDOUT after 10000ms", "Receiver answered 500"] },
};
/* ------------------------------------------------------------------ */
/* Helpers */
/* ------------------------------------------------------------------ */
function rand(s: QueueState): number {
// mulberry32, state kept in s.rng so a saved queue replays the same way
s.rng = (s.rng + 0x6d2b79f5) | 0;
let t = s.rng;
t = Math.imul(t ^ (t >>> 15), t | 1);
t ^= t + Math.imul(t ^ (t >>> 7), t | 61);
return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
}
function log(s: QueueState, text: string, tone: LogTone = "info") {
s.logSeq = (s.logSeq ?? 0) + 1;
s.log = [{ id: s.logSeq, at: s.now, text, tone }, ...s.log].slice(0, 120);
}
function event(j: Job, at: number, text: string) {
j.events = [...j.events, { at, text }].slice(-20);
}
export const backoffDelay = (baseMs: number, attemptsMade: number) => baseMs * 2 ** Math.max(0, attemptsMade - 1);
export const fmtTime = (ms: number) => {
const s = Math.floor(ms / 1000);
return `${String(Math.floor(s / 60)).padStart(2, "0")}:${String(s % 60).padStart(2, "0")}.${String(Math.floor((ms % 1000) / 100))}`;
};
function clone(s: QueueState): QueueState {
return { ...s, jobs: s.jobs.map((j) => ({ ...j })), workers: s.workers.map((w) => ({ ...w })), spans: s.spans.map((x) => ({ ...x })), repeatables: s.repeatables.map((r) => ({ ...r })), totals: { ...s.totals } };
}
/* ------------------------------------------------------------------ */
/* Producer API (what the NestJS controller calls) */
/* ------------------------------------------------------------------ */
export type AddInput = {
type: JobType;
name?: string;
data?: Record<string, string | number>;
priority?: number;
delayMs?: number;
attempts?: number;
backoffMs?: number;
jobId?: string; // idempotency key
};
export type AddResult = { status: 202; jobId: string; state: JobState } | { status: 200; jobId: string; duplicate: true } | { status: 422; error: string };
export function validateAdd(input: AddInput): string | null {
if (!["email", "report", "webhook"].includes(input.type)) return "type must be email, report or webhook";
if (input.priority !== undefined && (!Number.isInteger(input.priority) || input.priority < 1 || input.priority > 10)) return "priority must be an integer from 1 (highest) to 10";
if (input.delayMs !== undefined && (input.delayMs < 0 || input.delayMs > 60_000)) return "delay must be between 0 and 60000 ms";
if (input.attempts !== undefined && (!Number.isInteger(input.attempts) || input.attempts < 1 || input.attempts > 10)) return "attempts must be 1–10";
if (input.jobId !== undefined && !/^[\w:.-]{3,64}$/.test(input.jobId)) return "jobId: 3–64 letters, digits, : . _ -";
return null;
}
export function addJob(prev: QueueState, input: AddInput): [QueueState, AddResult] {
const err = validateAdd(input);
if (err) return [prev, { status: 422, error: err }];
const s = clone(prev);
if (input.jobId) {
const existing = s.jobs.find((j) => j.id === input.jobId);
if (existing) {
log(s, `queue.add(${input.type}) jobId=${input.jobId} already exists → ignored (idempotent)`, "warn");
return [s, { status: 200, jobId: existing.id, duplicate: true }];
}
}
s.seq += 1;
s.order += 1;
const id = input.jobId ?? String(s.seq);
const delay = input.delayMs ?? 0;
const job: Job = {
id,
type: input.type,
name: input.name ?? defaultName(input.type),
data: input.data ?? {},
priority: input.priority ?? 5,
state: delay > 0 ? "delayed" : "waiting",
attemptsMade: 0,
maxAttempts: input.attempts ?? 3,
backoffMs: input.backoffMs ?? 1000,
addedAt: s.now,
order: s.order,
runAt: s.now + delay,
startedAt: null,
durationMs: 0,
willFail: false,
workerId: null,
progress: 0,
finishedAt: null,
failedReason: null,
returnValue: null,
events: [],
};
event(job, s.now, delay > 0 ? `added, delayed ${delay} ms` : "added to waiting");
s.jobs.push(job);
log(s, `queue.add("${job.name}") → job ${id} [${job.state}] p${job.priority}`, "dim");
return [s, { status: 202, jobId: id, state: job.state }];
}
function defaultName(t: JobType) {
return { email: "send-welcome-email", report: "build-orders-csv", webhook: "deliver-order.paid" }[t];
}
/** Retry a job from the failed set (Bull Board's "retry" button). Resets attempts. */
export function retryJob(prev: QueueState, id: string): QueueState {
const s = clone(prev);
const j = s.jobs.find((x) => x.id === id);
if (!j || j.state !== "failed") return prev;
j.state = "waiting";
j.attemptsMade = 0;
j.failedReason = null;
j.progress = 0;
j.finishedAt = null;
s.order += 1;
j.order = s.order;
event(j, s.now, "manually retried from failed set");
log(s, `job ${id} moved failed → waiting (manual retry)`, "info");
return s;
}
export function removeJob(prev: QueueState, id: string): QueueState {
const s = clone(prev);
const j = s.jobs.find((x) => x.id === id);
if (!j || j.state === "active") return prev; // BullMQ cannot remove a locked (active) job
s.jobs = s.jobs.filter((x) => x.id !== id);
log(s, `job ${id} removed`, "dim");
return s;
}
/** Promote a delayed job now (Bull Board's "promote"). */
export function promoteJob(prev: QueueState, id: string): QueueState {
const s = clone(prev);
const j = s.jobs.find((x) => x.id === id);
if (!j || j.state !== "delayed") return prev;
j.state = "waiting";
j.runAt = s.now;
event(j, s.now, "promoted to waiting");
return s;
}
/* ------------------------------------------------------------------ */
/* Admin */
/* ------------------------------------------------------------------ */
export function setConfig(prev: QueueState, patch: Partial<QueueConfig>): QueueState {
const s = clone(prev);
s.config = { ...s.config, ...patch };
if (patch.paused !== undefined) log(s, patch.paused ? "queue.pause(): workers finish active jobs, pick nothing new" : "queue.resume()", "warn");
if (patch.limiter !== undefined) log(s, patch.limiter ? `limiter: max ${patch.limiter.max} jobs / ${patch.limiter.durationMs} ms` : "limiter: off", "info");
return s;
}
export function addWorker(prev: QueueState, concurrency: number): QueueState {
const s = clone(prev);
s.workerSeq += 1;
const id = `worker-${s.workerSeq}`;
s.workers.push({ id, concurrency, draining: false, processed: 0, failed: 0 });
log(s, `${id} connected (concurrency ${concurrency})`, "ok");
return s;
}
/** SIGTERM: stop taking jobs, finish what is active, then disconnect (graceful shutdown). */
export function stopWorker(prev: QueueState, id: string): QueueState {
const s = clone(prev);
const w = s.workers.find((x) => x.id === id);
if (!w || w.draining) return prev;
w.draining = true;
const active = s.jobs.filter((j) => j.state === "active" && j.workerId === id).length;
log(s, `${id} got SIGTERM: draining ${active} active job(s)`, "warn");
if (active === 0) {
s.workers = s.workers.filter((x) => x.id !== id);
log(s, `${id} closed cleanly`, "dim");
}
return s;
}
export function setConcurrency(prev: QueueState, id: string, concurrency: number): QueueState {
const s = clone(prev);
const w = s.workers.find((x) => x.id === id);
if (!w) return prev;
w.concurrency = Math.max(1, Math.min(4, concurrency));
return s;
}
/* ------------------------------------------------------------------ */
/* The tick: one step of the event loop */
/* ------------------------------------------------------------------ */
export function tick(prev: QueueState, dtMs: number): QueueState {
const s = clone(prev);
s.now += dtMs;
// 1. Repeatable jobs (cron-like scheduler)
const due: AddInput[] = [];
for (const r of s.repeatables) {
while (r.nextAt <= s.now) {
due.push({ type: r.type, name: r.name, jobId: `repeat:${r.key}:${r.nextAt}`, priority: 8, attempts: 1 });
r.nextAt += r.everyMs;
}
}
for (const input of due) {
const [next] = addJob(s, input);
Object.assign(s, next);
log(s, `scheduler: repeat job "${input.name}" fired (every ${s.repeatables[0]?.everyMs ?? 0} ms)`, "info");
}
// 2. Delayed -> waiting
for (const j of s.jobs) {
if (j.state === "delayed" && j.runAt <= s.now) {
j.state = "waiting";
event(j, s.now, j.attemptsMade > 0 ? `backoff over, retry #${j.attemptsMade}` : "delay over → waiting");
}
}
// 3. Progress active jobs; finish the ones whose time is up
for (const j of s.jobs) {
if (j.state !== "active" || j.startedAt === null) continue;
const elapsed = s.now - j.startedAt;
j.progress = Math.min(100, Math.round((elapsed / j.durationMs) * 100));
// failing attempts fail part-way through, like a real timeout or 5xx
const failAt = j.durationMs * 0.6;
if (j.willFail && elapsed >= failAt) finishAttempt(s, j, false);
else if (!j.willFail && elapsed >= j.durationMs) finishAttempt(s, j, true);
}
// 4. Remove drained workers with nothing active
for (const w of [...s.workers]) {
if (w.draining && !s.jobs.some((j) => j.state === "active" && j.workerId === w.id)) {
s.workers = s.workers.filter((x) => x.id !== w.id);
log(s, `${w.id} closed cleanly (no job lost)`, "dim");
}
}
// 5. Pick new jobs
if (!s.config.paused) pickJobs(s);
// 6. Housekeeping: removeOnComplete, old spans, limiter window
const completed = s.jobs.filter((j) => j.state === "completed").sort((a, b) => (b.finishedAt ?? 0) - (a.finishedAt ?? 0));
if (completed.length > s.config.keepCompleted) {
const drop = new Set(completed.slice(s.config.keepCompleted).map((j) => j.id));
s.jobs = s.jobs.filter((j) => !drop.has(j.id));
}
s.spans = s.spans.filter((x) => x.end === null || x.end > s.now - TIMELINE_MS);
const windowMs = s.config.limiter?.durationMs ?? 0;
s.starts = s.starts.filter((t) => t > s.now - windowMs);
return s;
}
export const TIMELINE_MS = 20_000;
function finishAttempt(s: QueueState, j: Job, ok: boolean) {
const w = s.workers.find((x) => x.id === j.workerId);
const span = s.spans.find((x) => x.jobId === j.id && x.end === null);
if (span) {
span.end = s.now;
span.outcome = ok ? "ok" : "fail";
}
j.attemptsMade += 1;
if (ok) {
j.state = "completed";
j.progress = 100;
j.finishedAt = s.now;
j.returnValue = returnValueFor(j);
event(j, s.now, `completed on ${j.workerId} (attempt ${j.attemptsMade})`);
log(s, `✓ job ${j.id} ${j.name} completed in ${j.durationMs} ms (${j.workerId})`, "ok");
if (w) w.processed += 1;
s.totals.completed += 1;
} else {
const errors = PROFILES[j.type].errors;
const reason = errors[Math.floor(rand(s) * errors.length)] ?? "Unknown error";
j.failedReason = reason;
if (w) w.failed += 1;
if (j.attemptsMade < j.maxAttempts) {
const delay = backoffDelay(j.backoffMs, j.attemptsMade);
j.state = "delayed";
j.runAt = s.now + delay;
j.progress = 0;
event(j, s.now, `attempt ${j.attemptsMade} failed: ${reason}; retry in ${delay} ms`);
log(s, `✗ job ${j.id} attempt ${j.attemptsMade}/${j.maxAttempts} failed (${reason}) → backoff ${delay} ms`, "warn");
s.totals.retried += 1;
} else {
j.state = "failed";
j.finishedAt = s.now;
event(j, s.now, `attempt ${j.attemptsMade} failed: ${reason}; no attempts left → failed set`);
log(s, `✗ job ${j.id} exhausted ${j.maxAttempts} attempts → failed (dead letter)`, "err");
s.totals.failed += 1;
}
}
j.workerId = null;
j.startedAt = null;
}
function returnValueFor(j: Job) {
if (j.type === "email") return `{"messageId":"<${j.id}@mail.acme.test>"}`;
if (j.type === "report") return `{"file":"reports/orders-${j.id}.csv","rows":${1200 + (Number(j.id.replace(/\D/g, "")) % 9) * 311}}`;
return `{"status":200,"receiver":"hooks.acme-crm.test"}`;
}
function pickJobs(s: QueueState) {
const waiting = s.jobs.filter((j) => j.state === "waiting").sort((a, b) => a.priority - b.priority || a.order - b.order);
if (!waiting.length) return;
for (const w of s.workers) {
if (w.draining) continue;
const busySlots = new Set(s.spans.filter((x) => x.workerId === w.id && x.end === null).map((x) => x.slot));
for (let slot = 0; slot < w.concurrency; slot++) {
if (busySlots.has(slot)) continue;
const next = waiting[0];
if (!next) return;
const lim = s.config.limiter;
if (lim && s.starts.filter((t) => t > s.now - lim.durationMs).length >= lim.max) {
if (!s.log[0]?.text.startsWith("limiter")) log(s, `limiter: ${lim.max}/${lim.durationMs} ms reached, ${waiting.length} job(s) wait`, "dim");
return;
}
waiting.shift();
startAttempt(s, next, w, slot);
busySlots.add(slot);
}
}
}
function startAttempt(s: QueueState, j: Job, w: Worker, slot: number) {
const p = PROFILES[j.type];
const failRate = j.type === "webhook" ? s.config.chaos : p.failRate;
j.state = "active";
j.workerId = w.id;
j.startedAt = s.now;
j.durationMs = Math.round(p.minMs + rand(s) * (p.maxMs - p.minMs));
j.willFail = rand(s) < failRate;
j.progress = 0;
s.starts.push(s.now);
s.spans.push({ jobId: j.id, type: j.type, workerId: w.id, slot, start: s.now, end: null, outcome: null });
event(j, s.now, `picked by ${w.id} (attempt ${j.attemptsMade + 1}/${j.maxAttempts})`);
log(s, `→ ${w.id}#${slot} took job ${j.id} ${j.name}`, "info");
}
/* ------------------------------------------------------------------ */
/* Seed */
/* ------------------------------------------------------------------ */
export function initialState(): QueueState {
let s: QueueState = {
now: 0,
seq: 1040,
order: 0,
rng: 1042,
jobs: [],
workers: [],
workerSeq: 0,
spans: [],
starts: [],
repeatables: [{ key: "cleanup", type: "report", name: "nightly-cleanup", everyMs: 30_000, nextAt: 30_000 }],
config: { paused: false, chaos: 0.3, limiter: { max: 4, durationMs: 1000 }, keepCompleted: 30 },
log: [],
logSeq: 0,
totals: { completed: 0, failed: 0, retried: 0 },
};
s = addWorker(s, 2);
s = addWorker(s, 2);
const seed: AddInput[] = [
{ type: "email", name: "send-welcome-email", data: { to: "maria@acme-dental.test", template: "welcome" } },
{ type: "report", name: "build-orders-csv", data: { range: "2026-10", orders: 1042 }, priority: 7 },
{ type: "webhook", name: "deliver-order.paid", data: { orderId: 1042, url: "https://hooks.acme-crm.test/orders" }, attempts: 5 },
{ type: "webhook", name: "deliver-order.shipped", data: { orderId: 1039, url: "https://hooks.acme-crm.test/orders" }, attempts: 5 },
{ type: "email", name: "send-invoice", data: { to: "billing@northwind-clinic.test", invoice: "INV-2207" }, priority: 2 },
{ type: "email", name: "send-reminder", data: { to: "sam@harbor-gym.test" }, delayMs: 6000 },
];
for (const a of seed) [s] = addJob(s, a);
s.log = [{ id: 0, at: 0, text: "queue \"default\" ready on redis://localhost:6379 (simulated)", tone: "ok" }, ...s.log];
return s;
}
export function isQueueState(v: unknown): boolean {
const x = v as QueueState | null;
return !!x && typeof x.now === "number" && typeof x.logSeq === "number" && Array.isArray(x.jobs) && Array.isArray(x.workers) && typeof x.config === "object";
}app/lab/job-queue-workers/Demo.tsx528 lines
"use client";
import { useCallback, useEffect, useMemo, useState } from "react";
import { PanelTitle, Pill, TerminalLog, btn, btnDanger, btnPrimary, input, label, useInterval, useStoredState, type LogLine } from "@/components/lab/systems/ui";
import {
TIMELINE_MS,
addJob,
addWorker,
fmtTime,
initialState,
isQueueState,
promoteJob,
removeJob,
retryJob,
setConcurrency,
setConfig,
stopWorker,
tick,
type AddInput,
type AddResult,
type Job,
type JobState,
type JobType,
type QueueState,
} from "./queue";
const KEY = "lab:job-queue-workers:v1";
const TICK_MS = 100;
const COLUMNS: { state: JobState; title: string }[] = [
{ state: "waiting", title: "waiting" },
{ state: "delayed", title: "delayed" },
{ state: "active", title: "active" },
{ state: "completed", title: "completed" },
{ state: "failed", title: "failed (DLQ)" },
];
const TYPE_COLOUR: Record<JobType, string> = { email: "var(--accent-2)", report: "var(--accent-3)", webhook: "var(--accent)" };
const TYPE_DOT: Record<JobType, string> = { email: "bg-accent-2", report: "bg-accent-3", webhook: "bg-accent" };
const SAMPLE_DATA: Record<JobType, Record<string, string | number>> = {
email: { to: "frontdesk@acme-dental.test", template: "appointment-reminder" },
report: { range: "2026-11", format: "csv" },
webhook: { orderId: 1043, url: "https://hooks.acme-crm.test/orders", event: "order.paid" },
};
type Form = { type: JobType; name: string; priority: string; delay: string; attempts: string; backoff: string; jobId: string };
const EMPTY_FORM: Form = { type: "webhook", name: "", priority: "5", delay: "0", attempts: "3", backoff: "1000", jobId: "" };
export default function Demo() {
const [q, setQ, resetQ] = useStoredState<QueueState>(KEY, initialState, isQueueState);
const [running, setRunning] = useState(true);
const [speed, setSpeed] = useState(1);
const [form, setForm] = useState<Form>(EMPTY_FORM);
const [response, setResponse] = useState<{ req: string; res: AddResult } | null>(null);
const [selected, setSelected] = useState<string | null>(null);
const [newConcurrency, setNewConcurrency] = useState(2);
useInterval(
() => setQ((s) => (s ? tick(s, TICK_MS * speed) : s)),
running && q ? TICK_MS : null,
);
const update = useCallback((fn: (s: QueueState) => QueueState) => setQ((s) => (s ? fn(s) : s)), [setQ]);
// Space toggles the clock; "n" enqueues the form job (when focus is not in a field).
useEffect(() => {
const onKey = (e: KeyboardEvent) => {
const t = e.target instanceof HTMLElement ? e.target : document.body;
if (t.closest("input, select, textarea, button")) return;
if (e.key === " ") {
e.preventDefault();
setRunning((r) => !r);
}
};
window.addEventListener("keydown", onKey);
return () => window.removeEventListener("keydown", onKey);
}, []);
function enqueue(e: React.FormEvent) {
e.preventDefault();
const body: AddInput = {
type: form.type,
name: form.name.trim() || undefined,
data: SAMPLE_DATA[form.type],
priority: Number(form.priority),
delayMs: Number(form.delay),
attempts: Number(form.attempts),
backoffMs: Number(form.backoff),
jobId: form.jobId.trim() || undefined,
};
if (!q) return;
const [next, res] = addJob(q, body);
setQ(next);
setResponse({ req: JSON.stringify(body, null, 2), res });
if (res.status === 202) setSelected(res.jobId);
}
function burst() {
update((s) => {
let n = s;
const types: JobType[] = ["email", "webhook", "report", "webhook", "email", "webhook", "email", "webhook", "report", "email"];
types.forEach((type, i) => {
[n] = addJob(n, { type, data: SAMPLE_DATA[type], priority: i % 4 === 0 ? 2 : 5, attempts: type === "webhook" ? 5 : 3 });
});
return n;
});
}
function reset() {
resetQ();
setSelected(null);
setResponse(null);
setForm(EMPTY_FORM);
setRunning(true);
setSpeed(1);
}
const byState = useMemo(() => {
const m: Record<JobState, Job[]> = { waiting: [], delayed: [], active: [], completed: [], failed: [] };
for (const j of q?.jobs ?? []) m[j.state].push(j);
m.waiting.sort((a, b) => a.priority - b.priority || a.order - b.order);
m.delayed.sort((a, b) => a.runAt - b.runAt);
m.completed.sort((a, b) => (b.finishedAt ?? 0) - (a.finishedAt ?? 0));
m.failed.sort((a, b) => (b.finishedAt ?? 0) - (a.finishedAt ?? 0));
return m;
}, [q?.jobs]);
const logLines: LogLine[] = useMemo(
() =>
(q?.log ?? []).slice(0, 60).map((l) => ({
id: l.id,
text: `[${fmtTime(l.at)}] ${l.text}`,
tone: l.tone,
})),
[q?.log],
);
if (!q) {
return <div className="p-6 font-mono text-sm text-fg-muted">connecting to queue…</div>;
}
const job = q.jobs.find((j) => j.id === selected) ?? null;
const limiterOn = q.config.limiter !== null;
return (
<div className="space-y-5 p-4 sm:p-6">
{/* Toolbar */}
<div className="flex flex-wrap items-center gap-3 rounded-md border border-border bg-bg-elev p-3">
<button type="button" className={btn} onClick={() => setRunning((r) => !r)} aria-pressed={running}>
{running ? "❚❚ pause clock" : "▶ run clock"}
</button>
<label className="flex items-center gap-2 font-mono text-xs">
speed
<input type="range" min={0.5} max={8} step={0.5} value={speed} onChange={(e) => setSpeed(Number(e.target.value))} className="w-24 accent-[var(--accent)]" />
<span className="w-8">{speed}×</span>
</label>
<span className="font-mono text-xs text-fg-muted" aria-label="simulated time">
t={fmtTime(q.now)}
</span>
<span className="mx-1 hidden h-5 w-px bg-border sm:block" aria-hidden="true" />
<button type="button" className={btn} onClick={() => update((s) => setConfig(s, { paused: !s.config.paused }))} aria-pressed={q.config.paused}>
{q.config.paused ? "queue.resume()" : "queue.pause()"}
</button>
{q.config.paused && <Pill tone="warn">queue paused</Pill>}
<button type="button" className={`${btn} ml-auto`} onClick={reset}>
reset demo
</button>
</div>
<div className="grid gap-5 lg:grid-cols-[22rem_1fr]">
{/* Producer + settings */}
<div className="space-y-5">
<form onSubmit={enqueue} className="space-y-3 rounded-md border border-border p-3" noValidate>
<PanelTitle>
<span className="text-accent">POST</span> /jobs
</PanelTitle>
<div className="grid grid-cols-2 gap-2">
<label className={label}>
type
<select className={`${input} mt-1`} value={form.type} onChange={(e) => setForm({ ...form, type: e.target.value as JobType })}>
<option value="email">email</option>
<option value="report">report</option>
<option value="webhook">webhook</option>
</select>
</label>
<label className={label}>
priority (1 = high)
<input className={`${input} mt-1`} type="number" min={1} max={10} value={form.priority} onChange={(e) => setForm({ ...form, priority: e.target.value })} />
</label>
<label className={label}>
delay (ms)
<input className={`${input} mt-1`} type="number" min={0} step={500} value={form.delay} onChange={(e) => setForm({ ...form, delay: e.target.value })} />
</label>
<label className={label}>
attempts
<input className={`${input} mt-1`} type="number" min={1} max={10} value={form.attempts} onChange={(e) => setForm({ ...form, attempts: e.target.value })} />
</label>
<label className={label}>
backoff base (ms)
<input className={`${input} mt-1`} type="number" min={100} step={100} value={form.backoff} onChange={(e) => setForm({ ...form, backoff: e.target.value })} />
</label>
<label className={label}>
name
<input className={`${input} mt-1`} placeholder="optional" value={form.name} onChange={(e) => setForm({ ...form, name: e.target.value })} />
</label>
</div>
<label className={label}>
Idempotency-Key → jobId (optional)
<input className={`${input} mt-1 font-mono`} placeholder="order-1043-paid" value={form.jobId} onChange={(e) => setForm({ ...form, jobId: e.target.value })} />
</label>
<div className="flex flex-wrap gap-2">
<button type="submit" className={btnPrimary}>
Enqueue job
</button>
<button type="button" className={btn} onClick={burst}>
+10 mixed jobs
</button>
</div>
<div aria-live="polite">
{response && (
<pre className="max-h-40 overflow-auto rounded-md bg-[#0b0b0d] p-2 font-mono text-[11px] text-[#a1a1aa]">
<span className={response.res.status === 202 ? "text-[#4ade80]" : response.res.status === 200 ? "text-[#fbbf24]" : "text-[#f87171]"}>
{response.res.status} {response.res.status === 202 ? "Accepted" : response.res.status === 200 ? "OK (duplicate)" : "Unprocessable Entity"}
</span>
{"\n"}
{JSON.stringify(response.res, null, 2)}
</pre>
)}
</div>
</form>
<section className="space-y-3 rounded-md border border-border p-3" aria-label="Queue settings">
<PanelTitle>settings</PanelTitle>
<label className="block text-xs">
<span className="flex justify-between font-medium text-fg-muted">
chaos: webhook failure rate <span className="font-mono text-fg">{Math.round(q.config.chaos * 100)}%</span>
</span>
<input type="range" min={0} max={1} step={0.05} value={q.config.chaos} onChange={(e) => update((s) => setConfig(s, { chaos: Number(e.target.value) }))} className="mt-1 w-full accent-[var(--accent)]" />
</label>
<div className="flex flex-wrap items-center gap-2 text-xs">
<label className="flex items-center gap-2">
<input type="checkbox" checked={limiterOn} onChange={(e) => update((s) => setConfig(s, { limiter: e.target.checked ? { max: 4, durationMs: 1000 } : null }))} />
rate limiter
</label>
{q.config.limiter && (
<label className="flex items-center gap-1 font-mono">
max
<input
type="number"
min={1}
max={20}
value={q.config.limiter.max}
onChange={(e) => update((s) => setConfig(s, { limiter: { max: Math.max(1, Number(e.target.value) || 1), durationMs: 1000 } }))}
className="w-14 rounded border border-border bg-bg-elev px-1 py-0.5"
aria-label="Limiter: max job starts per second"
/>
/ 1000 ms
</label>
)}
</div>
<div>
<p className="text-xs font-medium text-fg-muted">workers</p>
<ul className="mt-1 space-y-1">
{q.workers.map((w) => {
const active = byState.active.filter((j) => j.workerId === w.id).length;
return (
<li key={w.id} className="flex flex-wrap items-center gap-2 rounded border border-border px-2 py-1 font-mono text-xs">
<span className={`size-2 rounded-full ${w.draining ? "bg-warn-fg" : active ? "bg-accent" : "bg-fg-muted/50"}`} aria-hidden="true" />
<span>{w.id}</span>
<span className="text-fg-muted">
{active}/{w.concurrency} · ✓{w.processed} ✗{w.failed}
</span>
{w.draining ? (
<Pill tone="warn">draining</Pill>
) : (
<span className="ml-auto flex gap-1">
<select
aria-label={`Concurrency for ${w.id}`}
value={w.concurrency}
onChange={(e) => update((s) => setConcurrency(s, w.id, Number(e.target.value)))}
className="rounded border border-border bg-bg-elev px-1"
>
{[1, 2, 3, 4].map((n) => (
<option key={n} value={n}>
×{n}
</option>
))}
</select>
<button type="button" className={btnDanger} onClick={() => update((s) => stopWorker(s, w.id))} aria-label={`Send SIGTERM to ${w.id}`}>
SIGTERM
</button>
</span>
)}
</li>
);
})}
{q.workers.length === 0 && <li className="text-xs text-warn-fg">No workers: jobs pile up in waiting.</li>}
</ul>
<div className="mt-2 flex items-center gap-2">
<button type="button" className={btn} onClick={() => update((s) => addWorker(s, newConcurrency))} disabled={q.workers.length >= 4}>
+ add worker
</button>
<label className="flex items-center gap-1 font-mono text-xs text-fg-muted">
concurrency
<select value={newConcurrency} onChange={(e) => setNewConcurrency(Number(e.target.value))} className="rounded border border-border bg-bg-elev px-1">
{[1, 2, 3, 4].map((n) => (
<option key={n} value={n}>
{n}
</option>
))}
</select>
</label>
</div>
</div>
</section>
</div>
{/* Board + timeline */}
<div className="min-w-0 space-y-5">
<dl className="grid grid-cols-3 gap-2 font-mono text-xs sm:grid-cols-6">
{[
["completed", q.totals.completed, "text-accent"],
["retried", q.totals.retried, "text-warn-fg"],
["dead", q.totals.failed, "text-danger"],
["waiting", byState.waiting.length, ""],
["delayed", byState.delayed.length, ""],
["active", byState.active.length, "text-accent-2"],
].map(([k, v, c]) => (
<div key={k as string} className="rounded border border-border px-2 py-1.5">
<dt className="text-fg-muted">{k}</dt>
<dd className={`text-lg ${c as string}`}>{v}</dd>
</div>
))}
</dl>
<div className="grid grid-cols-2 gap-2 sm:grid-cols-3 xl:grid-cols-5">
{COLUMNS.map((c) => (
<section key={c.state} aria-label={`${c.title} jobs`} className="min-w-0 rounded-md border border-border bg-bg-elev">
<h4 className="flex items-center justify-between border-b border-border px-2 py-1.5 font-mono text-xs">
{c.title}
<span className="text-fg-muted">{byState[c.state].length}</span>
</h4>
<ul className="max-h-60 space-y-1 overflow-y-auto p-1.5">
{byState[c.state].slice(0, 25).map((j) => (
<li key={j.id}>
<button
type="button"
onClick={() => setSelected(j.id)}
aria-pressed={selected === j.id}
className={`w-full rounded border px-1.5 py-1 text-left font-mono text-[11px] hover:border-accent ${selected === j.id ? "border-accent bg-accent-soft/60" : "border-border bg-bg"}`}
>
<span className="flex items-center gap-1">
<span className={`size-1.5 shrink-0 rounded-full ${TYPE_DOT[j.type]}`} aria-hidden="true" />
<span className="truncate">#{j.id}</span>
{j.priority < 5 && <span className="ml-auto text-warn-fg">p{j.priority}</span>}
</span>
<span className="block truncate text-fg-muted">{j.name}</span>
{j.state === "active" && (
<span className="mt-1 block h-1 overflow-hidden rounded bg-bg-muted">
<span className="block h-full bg-accent-2" style={{ width: `${j.progress}%` }} />
</span>
)}
{j.state === "delayed" && <span className="block text-warn-fg">in {Math.max(0, j.runAt - q.now)} ms{j.attemptsMade ? ` · retry ${j.attemptsMade}` : ""}</span>}
</button>
</li>
))}
{byState[c.state].length === 0 && <li className="px-1 py-2 text-center text-[11px] text-fg-muted">empty</li>}
</ul>
</section>
))}
</div>
<Timeline q={q} onSelect={setSelected} />
<div className="grid gap-5 xl:grid-cols-2">
<section aria-label="Job details" className="rounded-md border border-border p-3">
<PanelTitle
right={
job && (
<span className="flex gap-1">
{job.state === "failed" && (
<button type="button" className={btn} onClick={() => update((s) => retryJob(s, job.id))}>
retry
</button>
)}
{job.state === "delayed" && (
<button type="button" className={btn} onClick={() => update((s) => promoteJob(s, job.id))}>
promote
</button>
)}
{job.state !== "active" && (
<button
type="button"
className={btnDanger}
onClick={() => {
update((s) => removeJob(s, job.id));
setSelected(null);
}}
>
remove
</button>
)}
</span>
)
}
>
job {job ? <span className="text-accent">#{job.id}</span> : null}
</PanelTitle>
{job ? (
<div className="space-y-2 text-xs">
<p className="flex flex-wrap gap-1">
<Pill tone={job.state === "completed" ? "ok" : job.state === "failed" ? "err" : job.state === "delayed" ? "warn" : job.state === "active" ? "info" : "muted"}>{job.state}</Pill>
<Pill tone="muted">{job.type}</Pill>
<Pill tone="muted">priority {job.priority}</Pill>
<Pill tone="muted">
attempts {job.attemptsMade}/{job.maxAttempts}
</Pill>
</p>
<pre className="overflow-x-auto rounded bg-bg-muted p-2 font-mono text-[11px]">{JSON.stringify({ name: job.name, data: job.data, opts: { backoff: { type: "exponential", delay: job.backoffMs } } }, null, 2)}</pre>
{job.failedReason && <p className="text-danger">failedReason: {job.failedReason}</p>}
{job.returnValue && <p className="font-mono text-accent">returnvalue: {job.returnValue}</p>}
<ol className="space-y-0.5 border-l border-border pl-3 font-mono text-[11px] text-fg-muted">
{job.events.map((e, i) => (
<li key={i}>
<span className="text-fg">{fmtTime(e.at)}</span> {e.text}
</li>
))}
</ol>
</div>
) : (
<p className="text-xs text-fg-muted">Select a job card or timeline bar to inspect its payload, attempts and history.</p>
)}
</section>
<section aria-label="Worker log">
<PanelTitle>worker log</PanelTitle>
<TerminalLog lines={logLines} label="Queue and worker events" className="h-72" />
</section>
</div>
</div>
</div>
<p className="text-xs text-fg-muted">
Shortcut: <kbd className="rounded border border-border px-1 font-mono">Space</kbd> pauses or runs the clock. State is saved in your browser.
</p>
</div>
);
}
/** Swimlane per worker slot showing the last 20 simulated seconds. */
function Timeline({ q, onSelect }: { q: QueueState; onSelect: (id: string) => void }) {
const lanes = useMemo(() => {
const keys = new Set<string>();
for (const w of q.workers) for (let i = 0; i < w.concurrency; i++) keys.add(`${w.id}#${i}`);
for (const s of q.spans) keys.add(`${s.workerId}#${s.slot}`);
return [...keys].sort();
}, [q.workers, q.spans]);
const W = 600;
const laneH = 18;
const top = 4;
const H = top + lanes.length * laneH + 16;
const from = q.now - TIMELINE_MS;
const x = (t: number) => Math.max(0, ((t - from) / TIMELINE_MS) * W);
return (
<section aria-label="Timeline of the last 20 seconds" className="rounded-md border border-border p-3">
<PanelTitle
right={
<span className="flex gap-3 font-mono text-[11px] text-fg-muted">
{(["email", "report", "webhook"] as JobType[]).map((t) => (
<span key={t} className="flex items-center gap-1">
<span className={`size-2 rounded-sm ${TYPE_DOT[t]}`} aria-hidden="true" />
{t}
</span>
))}
<span className="flex items-center gap-1">
<span className="size-2 rounded-sm border-2 border-danger" aria-hidden="true" />
failed attempt
</span>
</span>
}
>
timeline (last 20 s)
</PanelTitle>
<div className="flex gap-2">
<ul className="shrink-0 font-mono text-[10px] text-fg-muted" style={{ paddingTop: top }}>
{lanes.map((l) => (
<li key={l} style={{ height: laneH, lineHeight: `${laneH}px` }}>
{l.replace("worker-", "w")}
</li>
))}
</ul>
<svg viewBox={`0 0 ${W} ${H}`} className="w-full" style={{ height: H }} preserveAspectRatio="none" role="img" aria-label={`${q.spans.length} job attempts in the last 20 seconds across ${lanes.length} worker slots`}>
{lanes.map((l, i) => (
<line key={l} x1={0} x2={W} y1={top + i * laneH + laneH - 1} y2={top + i * laneH + laneH - 1} stroke="var(--border)" strokeWidth={1} />
))}
{[0, 5, 10, 15, 20].map((s) => (
<text key={s} x={Math.min(W - 14, (s / 20) * W)} y={H - 3} fontSize={9} fill="var(--fg-muted)" fontFamily="monospace">
-{20 - s}s
</text>
))}
{q.spans.map((s) => {
const lane = lanes.indexOf(`${s.workerId}#${s.slot}`);
if (lane < 0) return null;
const x1 = x(s.start);
const x2 = x(s.end ?? q.now);
return (
<rect
key={`${s.jobId}-${s.start}`}
x={x1}
y={top + lane * laneH + 2}
width={Math.max(2, x2 - x1)}
height={laneH - 6}
rx={2}
fill={TYPE_COLOUR[s.type]}
fillOpacity={s.end === null ? 0.9 : 0.55}
stroke={s.outcome === "fail" ? "var(--danger)" : "none"}
strokeWidth={2}
className="cursor-pointer"
onClick={() => onSelect(s.jobId)}
>
<title>{`job ${s.jobId} (${s.type}) ${s.outcome ?? "running"}`}</title>
</rect>
);
})}
</svg>
</div>
</section>
);
}components/lab/systems/ui.tsx175 lines
"use client";
/**
* Small shared pieces for the systems/backend lab demos (job queue, webhook relay, uploads, chat).
* Theme-aware controls use tokens; terminal panels are always dark and use fixed colours.
*/
import { useCallback, useEffect, useRef, useState, type ReactNode } from "react";
export const btn =
"inline-flex items-center justify-center gap-1.5 rounded-md border border-border px-2.5 py-1 font-mono text-xs hover:border-accent hover:text-accent disabled:cursor-not-allowed disabled:opacity-50 disabled:hover:border-border disabled:hover:text-inherit";
export const btnPrimary =
"inline-flex items-center justify-center gap-1.5 rounded-md bg-accent px-3 py-1.5 text-sm font-medium text-accent-fg hover:opacity-90 disabled:cursor-not-allowed disabled:opacity-50";
export const btnDanger =
"inline-flex items-center justify-center gap-1.5 rounded-md border border-border px-2.5 py-1 font-mono text-xs hover:border-danger hover:text-danger disabled:opacity-50";
export const input =
"w-full rounded-md border border-border bg-bg-elev px-2.5 py-1.5 text-sm outline-none focus:border-accent";
export const label = "block text-xs font-medium text-fg-muted";
export type Tone = "ok" | "warn" | "err" | "info" | "dim" | "accent";
export type LogLine = { id: number; text: string; tone: Tone };
export const TONE: Record<Tone, string> = {
ok: "text-[#4ade80]",
warn: "text-[#fbbf24]",
err: "text-[#f87171]",
info: "text-[#a1a1aa]",
dim: "text-[#71717a]",
accent: "text-[#60a5fa]",
};
/** Always-dark request/event log. Newest line first. */
export function TerminalLog({
lines,
label: name,
empty = "$ waiting for events…",
className = "h-56",
}: {
lines: LogLine[];
label: string;
empty?: string;
className?: string;
}) {
return (
<ol
role="log"
aria-live="polite"
aria-label={name}
className={`overflow-y-auto rounded-md border border-border bg-[#0b0b0d] p-3 font-mono text-[12px] leading-relaxed ${className}`}
>
{lines.length === 0 && <li className="text-[#71717a]">{empty}</li>}
{lines.map((l) => (
<li key={l.id} className={`break-words ${TONE[l.tone]}`}>
{l.text}
</li>
))}
</ol>
);
}
/** Log buffer with stable ids (no Date.now in render). */
export function useLog(max = 80) {
const [lines, setLines] = useState<LogLine[]>([]);
const seq = useRef(0);
const push = useCallback(
(text: string, tone: Tone = "info") => {
seq.current += 1;
const id = seq.current;
setLines((l) => [{ id, text, tone }, ...l].slice(0, max));
},
[max],
);
const clear = useCallback(() => setLines([]), []);
return { lines, push, clear };
}
/**
* State persisted to localStorage under `key`. The initial render uses `null` (server and first client
* render match); the stored value or the seed is loaded in an effect, so it is hydration-safe.
*/
export function useStoredState<T>(key: string, seed: () => T, isValid: (v: unknown) => boolean = () => true) {
const [state, setState] = useState<T | null>(null);
const seedRef = useRef(seed);
const validRef = useRef(isValid);
useEffect(() => {
let loaded: T | null = null;
try {
const raw = localStorage.getItem(key);
if (raw) {
const parsed: unknown = JSON.parse(raw);
if (validRef.current(parsed)) loaded = parsed as T;
}
} catch {
/* storage blocked or corrupted: fall back to the seed */
}
setState(loaded ?? seedRef.current());
}, [key]);
// Throttled save (at most every 750 ms) so a fast simulation does not write on every tick,
// but a simulation that changes state constantly still gets saved.
const latest = useRef<T | null>(null);
const timer = useRef<number | null>(null);
useEffect(() => {
latest.current = state;
if (state === null || timer.current !== null) return;
timer.current = window.setTimeout(() => {
timer.current = null;
try {
localStorage.setItem(key, JSON.stringify(latest.current));
} catch {
/* quota exceeded or storage blocked: the demo still works in memory */
}
}, 750);
}, [key, state]);
useEffect(
() => () => {
if (timer.current !== null) window.clearTimeout(timer.current);
},
[],
);
const reset = useCallback(() => {
try {
localStorage.removeItem(key);
} catch {
/* ignore */
}
setState(seedRef.current());
}, [key]);
return [state, setState, reset] as const;
}
/** setInterval that always calls the latest callback. `ms = null` stops it. */
export function useInterval(cb: () => void, ms: number | null) {
const ref = useRef(cb);
useEffect(() => {
ref.current = cb;
}, [cb]);
useEffect(() => {
if (ms === null) return;
const id = window.setInterval(() => ref.current(), ms);
return () => window.clearInterval(id);
}, [ms]);
}
/** Section heading used inside demos. */
export function PanelTitle({ children, right }: { children: ReactNode; right?: ReactNode }) {
return (
<div className="mb-2 flex flex-wrap items-center justify-between gap-2">
<h3 className="font-mono text-sm font-semibold">{children}</h3>
{right}
</div>
);
}
/** Small status pill with token colours. */
export function Pill({ tone, children }: { tone: "ok" | "warn" | "err" | "muted" | "info"; children: ReactNode }) {
const cls = {
ok: "border-accent/40 bg-accent-soft text-accent",
warn: "border-warn-fg/40 bg-warn-bg text-warn-fg",
err: "border-danger/40 text-danger",
muted: "border-border text-fg-muted",
info: "border-accent-2/40 text-accent-2",
}[tone];
return <span className={`inline-flex items-center rounded-full border px-2 py-0.5 font-mono text-[11px] ${cls}`}>{children}</span>;
}
export function formatBytes(n: number) {
if (n < 1024) return `${n} B`;
if (n < 1024 * 1024) return `${(n / 1024).toFixed(1)} KB`;
return `${(n / 1024 / 1024).toFixed(2)} MB`;
}