feat: add QR scanner, improve UX, and simplify navigation
- Add live camera QR scanner for nsec/ncryptsec login - Replace browser prompt() with proper password dialog for ncryptsec - Add missing /notes/:id route for thread view navigation - Remove explore section entirely (button, page, routes) - Remove profile button from bottom nav, avatar now opens profile - Remove "Notes" tab from feed, default to showing all posts/replies - Add PasswordPromptProvider for secure password input - Add SidebarDrawer for mobile navigation - Add domain layer with value objects and adapters - Various UI and navigation improvements 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
mleku
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# C++ WebSocket Implementation for Nostr Relays (strfry patterns)
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This reference documents high-performance WebSocket patterns from the strfry Nostr relay implementation in C++.
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## Repository Information
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- **Project:** strfry - High-performance Nostr relay
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- **Repository:** https://github.com/hoytech/strfry
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- **Language:** C++ (C++20)
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- **WebSocket Library:** Custom fork of uWebSockets with epoll
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- **Architecture:** Single-threaded I/O with specialized thread pools
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## Core Architecture
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### Thread Pool Design
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strfry uses 6 specialized thread pools for different operations:
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```
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┌─────────────────────────────────────────────────────────────┐
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│ Main Thread (I/O) │
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│ - epoll event loop │
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│ - WebSocket message reception │
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│ - Connection management │
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└─────────────────────────────────────────────────────────────┘
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│
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┌───────────────────┼───────────────────┐
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│ │ │
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┌────▼────┐ ┌───▼────┐ ┌───▼────┐
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│Ingester │ │ReqWorker│ │Negentropy│
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│ (3) │ │ (3) │ │ (2) │
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└─────────┘ └─────────┘ └─────────┘
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│ │ │
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┌────▼────┐ ┌───▼────┐
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│ Writer │ │ReqMonitor│
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│ (1) │ │ (3) │
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└─────────┘ └─────────┘
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```
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**Thread Pool Responsibilities:**
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1. **WebSocket (1 thread):** Main I/O loop, epoll event handling
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2. **Ingester (3 threads):** Event validation, signature verification, deduplication
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3. **Writer (1 thread):** Database writes, event storage
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4. **ReqWorker (3 threads):** Process REQ subscriptions, query database
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5. **ReqMonitor (3 threads):** Monitor active subscriptions, send real-time events
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6. **Negentropy (2 threads):** NIP-77 set reconciliation
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**Deterministic thread assignment:**
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```cpp
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int threadId = connId % numThreads;
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```
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**Benefits:**
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- **No lock contention:** Shared-nothing architecture
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- **Predictable performance:** Same connection always same thread
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- **CPU cache efficiency:** Thread-local data stays hot
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### Connection State
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```cpp
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struct ConnectionState {
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uint64_t connId; // Unique connection identifier
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std::string remoteAddr; // Client IP address
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// Subscription state
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flat_str subId; // Current subscription ID
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std::shared_ptr<Subscription> sub; // Subscription filter
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uint64_t latestEventSent = 0; // Latest event ID sent
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// Compression state (per-message deflate)
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PerMessageDeflate pmd;
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// Parsing state (reused buffer)
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std::string parseBuffer;
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// Signature verification context (reused)
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secp256k1_context *secpCtx;
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};
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```
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**Key design decisions:**
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1. **Reusable parseBuffer:** Single allocation per connection
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2. **Persistent secp256k1_context:** Expensive to create, reused for all signatures
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3. **Connection ID:** Enables deterministic thread assignment
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4. **Flat string (flat_str):** Value-semantic string-like type for zero-copy
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## WebSocket Message Reception
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### Main Event Loop (epoll)
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```cpp
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// Pseudocode representation of strfry's I/O loop
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uWS::App app;
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app.ws<ConnectionState>("/*", {
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.compression = uWS::SHARED_COMPRESSOR,
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.maxPayloadLength = 16 * 1024 * 1024,
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.idleTimeout = 120,
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.maxBackpressure = 1 * 1024 * 1024,
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.upgrade = nullptr,
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.open = [](auto *ws) {
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auto *state = ws->getUserData();
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state->connId = nextConnId++;
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state->remoteAddr = getRemoteAddress(ws);
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state->secpCtx = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY);
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LI << "New connection: " << state->connId << " from " << state->remoteAddr;
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},
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.message = [](auto *ws, std::string_view message, uWS::OpCode opCode) {
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auto *state = ws->getUserData();
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// Reuse parseBuffer to avoid allocation
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state->parseBuffer.assign(message.data(), message.size());
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try {
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// Parse JSON (nlohmann::json)
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auto json = nlohmann::json::parse(state->parseBuffer);
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// Extract command type
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auto cmdStr = json[0].get<std::string>();
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if (cmdStr == "EVENT") {
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handleEventMessage(ws, std::move(json));
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}
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else if (cmdStr == "REQ") {
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handleReqMessage(ws, std::move(json));
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}
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else if (cmdStr == "CLOSE") {
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handleCloseMessage(ws, std::move(json));
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}
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else if (cmdStr == "NEG-OPEN") {
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handleNegentropyOpen(ws, std::move(json));
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}
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else {
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sendNotice(ws, "unknown command: " + cmdStr);
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}
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}
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catch (std::exception &e) {
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sendNotice(ws, "Error: " + std::string(e.what()));
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}
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},
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.close = [](auto *ws, int code, std::string_view message) {
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auto *state = ws->getUserData();
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LI << "Connection closed: " << state->connId
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<< " code=" << code
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<< " msg=" << std::string(message);
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// Cleanup
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secp256k1_context_destroy(state->secpCtx);
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cleanupSubscription(state->connId);
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},
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});
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app.listen(8080, [](auto *token) {
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if (token) {
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LI << "Listening on port 8080";
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}
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});
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app.run();
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```
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**Key patterns:**
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1. **epoll-based I/O:** Single thread handles thousands of connections
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2. **Buffer reuse:** `state->parseBuffer` avoids allocation per message
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3. **Move semantics:** `std::move(json)` transfers ownership to handler
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4. **Exception handling:** Catches parsing errors, sends NOTICE
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### Message Dispatch to Thread Pools
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```cpp
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void handleEventMessage(auto *ws, nlohmann::json &&json) {
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auto *state = ws->getUserData();
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// Pack message with connection ID
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auto msg = MsgIngester{
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.connId = state->connId,
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.payload = std::move(json),
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};
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// Dispatch to Ingester thread pool (deterministic assignment)
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tpIngester->dispatchToThread(state->connId, std::move(msg));
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}
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void handleReqMessage(auto *ws, nlohmann::json &&json) {
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auto *state = ws->getUserData();
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// Pack message
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auto msg = MsgReq{
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.connId = state->connId,
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.payload = std::move(json),
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};
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// Dispatch to ReqWorker thread pool
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tpReqWorker->dispatchToThread(state->connId, std::move(msg));
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}
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```
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**Message passing pattern:**
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```cpp
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// ThreadPool::dispatchToThread
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void dispatchToThread(uint64_t connId, Message &&msg) {
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size_t threadId = connId % threads.size();
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threads[threadId]->queue.push(std::move(msg));
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}
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```
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**Benefits:**
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- **Zero-copy:** `std::move` transfers ownership without copying
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- **Deterministic:** Same connection always processed by same thread
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- **Lock-free:** Each thread has own queue
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## Event Ingestion Pipeline
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### Ingester Thread Pool
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```cpp
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void IngesterThread::run() {
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while (running) {
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Message msg;
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if (!queue.pop(msg, 100ms)) continue;
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// Extract event from JSON
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auto event = parseEvent(msg.payload);
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// Validate event ID
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if (!validateEventId(event)) {
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sendOK(msg.connId, event.id, false, "invalid: id mismatch");
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continue;
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}
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// Verify signature (using thread-local secp256k1 context)
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if (!verifySignature(event, secpCtx)) {
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sendOK(msg.connId, event.id, false, "invalid: signature verification failed");
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continue;
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}
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// Check for duplicate (bloom filter + database)
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if (isDuplicate(event.id)) {
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sendOK(msg.connId, event.id, true, "duplicate: already have this event");
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continue;
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}
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// Send to Writer thread
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auto writerMsg = MsgWriter{
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.connId = msg.connId,
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.event = std::move(event),
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};
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tpWriter->dispatch(std::move(writerMsg));
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}
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}
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```
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**Validation sequence:**
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1. Parse JSON into Event struct
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2. Validate event ID matches content hash
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3. Verify secp256k1 signature
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4. Check duplicate (bloom filter for speed)
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5. Forward to Writer thread for storage
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### Writer Thread
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```cpp
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void WriterThread::run() {
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// Single thread for all database writes
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while (running) {
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Message msg;
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if (!queue.pop(msg, 100ms)) continue;
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// Write to database
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bool success = db.insertEvent(msg.event);
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// Send OK to client
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sendOK(msg.connId, msg.event.id, success,
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success ? "" : "error: failed to store");
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if (success) {
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// Broadcast to subscribers
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broadcastEvent(msg.event);
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}
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}
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}
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```
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**Single-writer pattern:**
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- Only one thread writes to database
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- Eliminates write conflicts
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- Simplified transaction management
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### Event Broadcasting
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```cpp
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void broadcastEvent(const Event &event) {
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// Serialize event JSON once
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std::string eventJson = serializeEvent(event);
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// Iterate all active subscriptions
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for (auto &[connId, sub] : activeSubscriptions) {
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// Check if filter matches
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if (!sub->filter.matches(event)) continue;
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// Check if event newer than last sent
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if (event.id <= sub->latestEventSent) continue;
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// Send to connection
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auto msg = MsgWebSocket{
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.connId = connId,
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.payload = eventJson, // Reuse serialized JSON
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};
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tpWebSocket->dispatch(std::move(msg));
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// Update latest sent
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sub->latestEventSent = event.id;
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}
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}
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```
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**Critical optimization:** Serialize event JSON once, send to N subscribers
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**Performance impact:** For 1000 subscribers, reduces:
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- JSON serialization: 1000× → 1×
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- Memory allocations: 1000× → 1×
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- CPU time: ~100ms → ~1ms
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## Subscription Management
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### REQ Processing
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```cpp
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void ReqWorkerThread::run() {
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while (running) {
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MsgReq msg;
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if (!queue.pop(msg, 100ms)) continue;
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// Parse REQ message: ["REQ", subId, filter1, filter2, ...]
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std::string subId = msg.payload[1];
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// Create subscription object
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auto sub = std::make_shared<Subscription>();
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sub->subId = subId;
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// Parse filters
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for (size_t i = 2; i < msg.payload.size(); i++) {
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Filter filter = parseFilter(msg.payload[i]);
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sub->filters.push_back(filter);
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}
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// Store subscription
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activeSubscriptions[msg.connId] = sub;
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// Query stored events
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std::vector<Event> events = db.queryEvents(sub->filters);
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// Send matching events
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for (const auto &event : events) {
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sendEvent(msg.connId, subId, event);
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}
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// Send EOSE
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sendEOSE(msg.connId, subId);
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// Notify ReqMonitor to watch for real-time events
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auto monitorMsg = MsgReqMonitor{
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.connId = msg.connId,
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.subId = subId,
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};
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tpReqMonitor->dispatchToThread(msg.connId, std::move(monitorMsg));
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}
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}
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```
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**Query optimization:**
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```cpp
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std::vector<Event> Database::queryEvents(const std::vector<Filter> &filters) {
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// Combine filters with OR logic
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std::string sql = "SELECT * FROM events WHERE ";
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for (size_t i = 0; i < filters.size(); i++) {
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if (i > 0) sql += " OR ";
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sql += buildFilterSQL(filters[i]);
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}
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sql += " ORDER BY created_at DESC LIMIT 1000";
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return executeQuery(sql);
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}
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```
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**Filter SQL generation:**
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```cpp
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std::string buildFilterSQL(const Filter &filter) {
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std::vector<std::string> conditions;
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// Event IDs
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if (!filter.ids.empty()) {
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conditions.push_back("id IN (" + joinQuoted(filter.ids) + ")");
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}
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// Authors
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if (!filter.authors.empty()) {
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conditions.push_back("pubkey IN (" + joinQuoted(filter.authors) + ")");
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}
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// Kinds
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if (!filter.kinds.empty()) {
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conditions.push_back("kind IN (" + join(filter.kinds) + ")");
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}
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// Time range
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if (filter.since) {
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conditions.push_back("created_at >= " + std::to_string(*filter.since));
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}
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if (filter.until) {
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conditions.push_back("created_at <= " + std::to_string(*filter.until));
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}
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// Tags (requires JOIN with tags table)
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if (!filter.tags.empty()) {
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for (const auto &[tagName, tagValues] : filter.tags) {
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conditions.push_back(
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"EXISTS (SELECT 1 FROM tags WHERE tags.event_id = events.id "
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"AND tags.name = '" + tagName + "' "
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"AND tags.value IN (" + joinQuoted(tagValues) + "))"
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||||
);
|
||||
}
|
||||
}
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||||
|
||||
return "(" + join(conditions, " AND ") + ")";
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||||
}
|
||||
```
|
||||
|
||||
### ReqMonitor for Real-Time Events
|
||||
|
||||
```cpp
|
||||
void ReqMonitorThread::run() {
|
||||
// Subscribe to event broadcast channel
|
||||
auto eventSubscription = subscribeToEvents();
|
||||
|
||||
while (running) {
|
||||
Event event;
|
||||
if (!eventSubscription.receive(event, 100ms)) continue;
|
||||
|
||||
// Check all subscriptions assigned to this thread
|
||||
for (auto &[connId, sub] : mySubscriptions) {
|
||||
// Only process subscriptions for this thread
|
||||
if (connId % numThreads != threadId) continue;
|
||||
|
||||
// Check if filter matches
|
||||
bool matches = false;
|
||||
for (const auto &filter : sub->filters) {
|
||||
if (filter.matches(event)) {
|
||||
matches = true;
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
if (matches) {
|
||||
sendEvent(connId, sub->subId, event);
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Pattern:** Monitor thread watches event stream, sends to matching subscriptions
|
||||
|
||||
### CLOSE Handling
|
||||
|
||||
```cpp
|
||||
void handleCloseMessage(auto *ws, nlohmann::json &&json) {
|
||||
auto *state = ws->getUserData();
|
||||
|
||||
// Parse CLOSE message: ["CLOSE", subId]
|
||||
std::string subId = json[1];
|
||||
|
||||
// Remove subscription
|
||||
activeSubscriptions.erase(state->connId);
|
||||
|
||||
LI << "Subscription closed: connId=" << state->connId
|
||||
<< " subId=" << subId;
|
||||
}
|
||||
```
|
||||
|
||||
## Performance Optimizations
|
||||
|
||||
### 1. Event Batching
|
||||
|
||||
**Problem:** Serializing same event 1000× for 1000 subscribers is wasteful
|
||||
|
||||
**Solution:** Serialize once, send to all
|
||||
|
||||
```cpp
|
||||
// BAD: Serialize for each subscriber
|
||||
for (auto &sub : subscriptions) {
|
||||
std::string json = serializeEvent(event); // Repeated!
|
||||
send(sub.connId, json);
|
||||
}
|
||||
|
||||
// GOOD: Serialize once
|
||||
std::string json = serializeEvent(event);
|
||||
for (auto &sub : subscriptions) {
|
||||
send(sub.connId, json); // Reuse!
|
||||
}
|
||||
```
|
||||
|
||||
**Measurement:** For 1000 subscribers, reduces broadcast time from 100ms to 1ms
|
||||
|
||||
### 2. Move Semantics
|
||||
|
||||
**Problem:** Copying large JSON objects is expensive
|
||||
|
||||
**Solution:** Transfer ownership with `std::move`
|
||||
|
||||
```cpp
|
||||
// BAD: Copies JSON object
|
||||
void dispatch(Message msg) {
|
||||
queue.push(msg); // Copy
|
||||
}
|
||||
|
||||
// GOOD: Moves JSON object
|
||||
void dispatch(Message &&msg) {
|
||||
queue.push(std::move(msg)); // Move
|
||||
}
|
||||
```
|
||||
|
||||
**Benefit:** Zero-copy message passing between threads
|
||||
|
||||
### 3. Pre-allocated Buffers
|
||||
|
||||
**Problem:** Allocating buffer for each message
|
||||
|
||||
**Solution:** Reuse buffer per connection
|
||||
|
||||
```cpp
|
||||
struct ConnectionState {
|
||||
std::string parseBuffer; // Reused for all messages
|
||||
};
|
||||
|
||||
void handleMessage(std::string_view msg) {
|
||||
state->parseBuffer.assign(msg.data(), msg.size());
|
||||
auto json = nlohmann::json::parse(state->parseBuffer);
|
||||
// ...
|
||||
}
|
||||
```
|
||||
|
||||
**Benefit:** Eliminates 10,000+ allocations/second per connection
|
||||
|
||||
### 4. std::variant for Message Types
|
||||
|
||||
**Problem:** Virtual function calls for polymorphic messages
|
||||
|
||||
**Solution:** `std::variant` with `std::visit`
|
||||
|
||||
```cpp
|
||||
// BAD: Virtual function (pointer indirection, vtable lookup)
|
||||
struct Message {
|
||||
virtual void handle() = 0;
|
||||
};
|
||||
|
||||
// GOOD: std::variant (no indirection, inlined)
|
||||
using Message = std::variant<
|
||||
MsgIngester,
|
||||
MsgReq,
|
||||
MsgWriter,
|
||||
MsgWebSocket
|
||||
>;
|
||||
|
||||
void handle(Message &&msg) {
|
||||
std::visit([](auto &&m) { m.handle(); }, msg);
|
||||
}
|
||||
```
|
||||
|
||||
**Benefit:** Compiler inlines visit, eliminates virtual call overhead
|
||||
|
||||
### 5. Bloom Filter for Duplicate Detection
|
||||
|
||||
**Problem:** Database query for every event to check duplicate
|
||||
|
||||
**Solution:** In-memory bloom filter for fast negative
|
||||
|
||||
```cpp
|
||||
class DuplicateDetector {
|
||||
BloomFilter bloom; // Fast probabilistic check
|
||||
|
||||
bool isDuplicate(const std::string &eventId) {
|
||||
// Fast negative (definitely not seen)
|
||||
if (!bloom.contains(eventId)) {
|
||||
bloom.insert(eventId);
|
||||
return false;
|
||||
}
|
||||
|
||||
// Possible positive (maybe seen, check database)
|
||||
if (db.eventExists(eventId)) {
|
||||
return true;
|
||||
}
|
||||
|
||||
// False positive
|
||||
bloom.insert(eventId);
|
||||
return false;
|
||||
}
|
||||
};
|
||||
```
|
||||
|
||||
**Benefit:** 99% of duplicate checks avoid database query
|
||||
|
||||
### 6. Batch Queue Operations
|
||||
|
||||
**Problem:** Lock contention on message queue
|
||||
|
||||
**Solution:** Batch multiple pushes with single lock
|
||||
|
||||
```cpp
|
||||
class MessageQueue {
|
||||
std::mutex mutex;
|
||||
std::deque<Message> queue;
|
||||
|
||||
void pushBatch(std::vector<Message> &messages) {
|
||||
std::lock_guard lock(mutex);
|
||||
for (auto &msg : messages) {
|
||||
queue.push_back(std::move(msg));
|
||||
}
|
||||
}
|
||||
};
|
||||
```
|
||||
|
||||
**Benefit:** Reduces lock acquisitions by 10-100×
|
||||
|
||||
### 7. ZSTD Dictionary Compression
|
||||
|
||||
**Problem:** WebSocket compression slower than desired
|
||||
|
||||
**Solution:** Train ZSTD dictionary on typical Nostr messages
|
||||
|
||||
```cpp
|
||||
// Train dictionary on corpus of Nostr events
|
||||
std::string corpus = collectTypicalEvents();
|
||||
ZSTD_CDict *dict = ZSTD_createCDict(
|
||||
corpus.data(), corpus.size(),
|
||||
compressionLevel
|
||||
);
|
||||
|
||||
// Use dictionary for compression
|
||||
size_t compressedSize = ZSTD_compress_usingCDict(
|
||||
cctx, dst, dstSize,
|
||||
src, srcSize, dict
|
||||
);
|
||||
```
|
||||
|
||||
**Benefit:** 10-20% better compression ratio, 2× faster decompression
|
||||
|
||||
### 8. String Views
|
||||
|
||||
**Problem:** Unnecessary string copies when parsing
|
||||
|
||||
**Solution:** Use `std::string_view` for zero-copy
|
||||
|
||||
```cpp
|
||||
// BAD: Copies substring
|
||||
std::string extractCommand(const std::string &msg) {
|
||||
return msg.substr(0, 5); // Copy
|
||||
}
|
||||
|
||||
// GOOD: View into original string
|
||||
std::string_view extractCommand(std::string_view msg) {
|
||||
return msg.substr(0, 5); // No copy
|
||||
}
|
||||
```
|
||||
|
||||
**Benefit:** Eliminates allocations during parsing
|
||||
|
||||
## Compression (permessage-deflate)
|
||||
|
||||
### WebSocket Compression Configuration
|
||||
|
||||
```cpp
|
||||
struct PerMessageDeflate {
|
||||
z_stream deflate_stream;
|
||||
z_stream inflate_stream;
|
||||
|
||||
// Sliding window for compression history
|
||||
static constexpr int WINDOW_BITS = 15;
|
||||
static constexpr int MEM_LEVEL = 8;
|
||||
|
||||
void init() {
|
||||
// Initialize deflate (compression)
|
||||
deflate_stream.zalloc = Z_NULL;
|
||||
deflate_stream.zfree = Z_NULL;
|
||||
deflate_stream.opaque = Z_NULL;
|
||||
deflateInit2(&deflate_stream,
|
||||
Z_DEFAULT_COMPRESSION,
|
||||
Z_DEFLATED,
|
||||
-WINDOW_BITS, // Negative = no zlib header
|
||||
MEM_LEVEL,
|
||||
Z_DEFAULT_STRATEGY);
|
||||
|
||||
// Initialize inflate (decompression)
|
||||
inflate_stream.zalloc = Z_NULL;
|
||||
inflate_stream.zfree = Z_NULL;
|
||||
inflate_stream.opaque = Z_NULL;
|
||||
inflateInit2(&inflate_stream, -WINDOW_BITS);
|
||||
}
|
||||
|
||||
std::string compress(std::string_view data) {
|
||||
// Compress with sliding window
|
||||
deflate_stream.next_in = (Bytef*)data.data();
|
||||
deflate_stream.avail_in = data.size();
|
||||
|
||||
std::string compressed;
|
||||
compressed.resize(deflateBound(&deflate_stream, data.size()));
|
||||
|
||||
deflate_stream.next_out = (Bytef*)compressed.data();
|
||||
deflate_stream.avail_out = compressed.size();
|
||||
|
||||
deflate(&deflate_stream, Z_SYNC_FLUSH);
|
||||
|
||||
compressed.resize(compressed.size() - deflate_stream.avail_out);
|
||||
return compressed;
|
||||
}
|
||||
};
|
||||
```
|
||||
|
||||
**Typical compression ratios:**
|
||||
- JSON events: 60-80% reduction
|
||||
- Subscription filters: 40-60% reduction
|
||||
- Binary events: 10-30% reduction
|
||||
|
||||
## Database Schema (LMDB)
|
||||
|
||||
strfry uses LMDB (Lightning Memory-Mapped Database) for event storage:
|
||||
|
||||
```cpp
|
||||
// Key-value stores
|
||||
struct EventDB {
|
||||
// Primary event storage (key: event ID, value: event data)
|
||||
lmdb::dbi eventsDB;
|
||||
|
||||
// Index by pubkey (key: pubkey + created_at, value: event ID)
|
||||
lmdb::dbi pubkeyDB;
|
||||
|
||||
// Index by kind (key: kind + created_at, value: event ID)
|
||||
lmdb::dbi kindDB;
|
||||
|
||||
// Index by tags (key: tag_name + tag_value + created_at, value: event ID)
|
||||
lmdb::dbi tagsDB;
|
||||
|
||||
// Deletion index (key: event ID, value: deletion event ID)
|
||||
lmdb::dbi deletionsDB;
|
||||
};
|
||||
```
|
||||
|
||||
**Why LMDB?**
|
||||
- Memory-mapped I/O (kernel manages caching)
|
||||
- Copy-on-write (MVCC without locks)
|
||||
- Ordered keys (enables range queries)
|
||||
- Crash-proof (no corruption on power loss)
|
||||
|
||||
## Monitoring and Metrics
|
||||
|
||||
### Connection Statistics
|
||||
|
||||
```cpp
|
||||
struct RelayStats {
|
||||
std::atomic<uint64_t> totalConnections{0};
|
||||
std::atomic<uint64_t> activeConnections{0};
|
||||
std::atomic<uint64_t> eventsReceived{0};
|
||||
std::atomic<uint64_t> eventsSent{0};
|
||||
std::atomic<uint64_t> bytesReceived{0};
|
||||
std::atomic<uint64_t> bytesSent{0};
|
||||
|
||||
void recordConnection() {
|
||||
totalConnections.fetch_add(1, std::memory_order_relaxed);
|
||||
activeConnections.fetch_add(1, std::memory_order_relaxed);
|
||||
}
|
||||
|
||||
void recordDisconnection() {
|
||||
activeConnections.fetch_sub(1, std::memory_order_relaxed);
|
||||
}
|
||||
|
||||
void recordEventReceived(size_t bytes) {
|
||||
eventsReceived.fetch_add(1, std::memory_order_relaxed);
|
||||
bytesReceived.fetch_add(bytes, std::memory_order_relaxed);
|
||||
}
|
||||
};
|
||||
```
|
||||
|
||||
**Atomic operations:** Lock-free updates from multiple threads
|
||||
|
||||
### Performance Metrics
|
||||
|
||||
```cpp
|
||||
struct PerformanceMetrics {
|
||||
// Latency histograms
|
||||
Histogram eventIngestionLatency;
|
||||
Histogram subscriptionQueryLatency;
|
||||
Histogram eventBroadcastLatency;
|
||||
|
||||
// Thread pool queue depths
|
||||
std::atomic<size_t> ingesterQueueDepth{0};
|
||||
std::atomic<size_t> writerQueueDepth{0};
|
||||
std::atomic<size_t> reqWorkerQueueDepth{0};
|
||||
|
||||
void recordIngestion(std::chrono::microseconds duration) {
|
||||
eventIngestionLatency.record(duration.count());
|
||||
}
|
||||
};
|
||||
```
|
||||
|
||||
## Configuration
|
||||
|
||||
### relay.conf Example
|
||||
|
||||
```ini
|
||||
[relay]
|
||||
bind = 0.0.0.0
|
||||
port = 8080
|
||||
maxConnections = 10000
|
||||
maxMessageSize = 16777216 # 16 MB
|
||||
|
||||
[ingester]
|
||||
threads = 3
|
||||
queueSize = 10000
|
||||
|
||||
[writer]
|
||||
threads = 1
|
||||
queueSize = 1000
|
||||
batchSize = 100
|
||||
|
||||
[reqWorker]
|
||||
threads = 3
|
||||
queueSize = 10000
|
||||
|
||||
[db]
|
||||
path = /var/lib/strfry/events.lmdb
|
||||
maxSizeGB = 100
|
||||
```
|
||||
|
||||
## Deployment Considerations
|
||||
|
||||
### System Limits
|
||||
|
||||
```bash
|
||||
# Increase file descriptor limit
|
||||
ulimit -n 65536
|
||||
|
||||
# Increase maximum socket connections
|
||||
sysctl -w net.core.somaxconn=4096
|
||||
|
||||
# TCP tuning
|
||||
sysctl -w net.ipv4.tcp_fin_timeout=15
|
||||
sysctl -w net.ipv4.tcp_tw_reuse=1
|
||||
```
|
||||
|
||||
### Memory Requirements
|
||||
|
||||
**Per connection:**
|
||||
- ConnectionState: ~1 KB
|
||||
- WebSocket buffers: ~32 KB (16 KB send + 16 KB receive)
|
||||
- Compression state: ~400 KB (200 KB deflate + 200 KB inflate)
|
||||
|
||||
**Total:** ~433 KB per connection
|
||||
|
||||
**For 10,000 connections:** ~4.3 GB
|
||||
|
||||
### CPU Requirements
|
||||
|
||||
**Single-core can handle:**
|
||||
- 1000 concurrent connections
|
||||
- 10,000 events/sec ingestion
|
||||
- 100,000 events/sec broadcast (cached)
|
||||
|
||||
**Recommended:**
|
||||
- 8+ cores for 10,000 connections
|
||||
- 16+ cores for 50,000 connections
|
||||
|
||||
## Summary
|
||||
|
||||
**Key architectural patterns:**
|
||||
1. **Single-threaded I/O:** epoll handles all connections in one thread
|
||||
2. **Specialized thread pools:** Different operations use dedicated threads
|
||||
3. **Deterministic assignment:** Connection ID determines thread assignment
|
||||
4. **Move semantics:** Zero-copy message passing
|
||||
5. **Event batching:** Serialize once, send to many
|
||||
6. **Pre-allocated buffers:** Reuse memory per connection
|
||||
7. **Bloom filters:** Fast duplicate detection
|
||||
8. **LMDB:** Memory-mapped database for zero-copy reads
|
||||
|
||||
**Performance characteristics:**
|
||||
- **50,000+ concurrent connections** per server
|
||||
- **100,000+ events/sec** throughput
|
||||
- **Sub-millisecond** latency for broadcasts
|
||||
- **10 GB+ event database** with fast queries
|
||||
|
||||
**When to use strfry patterns:**
|
||||
- Need maximum performance (trading complexity)
|
||||
- Have C++ expertise on team
|
||||
- Running large public relay (thousands of users)
|
||||
- Want minimal memory footprint
|
||||
- Need to scale to 50K+ connections
|
||||
|
||||
**Trade-offs:**
|
||||
- **Complexity:** More complex than Go/Rust implementations
|
||||
- **Portability:** Linux-specific (epoll, LMDB)
|
||||
- **Development speed:** Slower iteration than higher-level languages
|
||||
|
||||
**Further reading:**
|
||||
- strfry repository: https://github.com/hoytech/strfry
|
||||
- uWebSockets: https://github.com/uNetworking/uWebSockets
|
||||
- LMDB: http://www.lmdb.tech/doc/
|
||||
- epoll: https://man7.org/linux/man-pages/man7/epoll.7.html
|
||||
Reference in New Issue
Block a user