Files
stats/packages/db/src/buffers/event-buffer.ts
Carl-Gerhard Lindesvärd 664f1abe0a perf: optimize event buffer
2026-03-11 21:33:08 +01:00

643 lines
19 KiB
TypeScript

import { getSafeJson } from '@openpanel/json';
import {
type Redis,
getRedisCache,
getRedisPub,
publishEvent,
} from '@openpanel/redis';
import { ch } from '../clickhouse/client';
import {
type IClickhouseEvent,
type IServiceEvent,
transformEvent,
} from '../services/event.service';
import { BaseBuffer } from './base-buffer';
/**
* Simplified Event Buffer
*
* Rules:
* 1. All events go into a single list buffer (event_buffer:queue)
* 2. screen_view events are handled specially:
* - Store current screen_view as "last" for the session
* - When a new screen_view arrives, flush the previous one with calculated duration
* 3. session_end events:
* - Retrieve the last screen_view (don't modify it)
* - Push both screen_view and session_end to buffer
* 4. Flush: Simply process all events from the list buffer
*
* Optimizations:
* - Micro-batching: Events are buffered locally and flushed every 10ms to reduce Redis round-trips
* - Batched publishes: All PUBLISH commands are included in the multi pipeline
* - Simplified active visitor tracking: Only uses ZADD (removed redundant heartbeat SET)
*/
// Pending event for local buffer
interface PendingEvent {
event: IClickhouseEvent;
eventJson: string;
eventWithTimestamp?: string;
type: 'regular' | 'screen_view' | 'session_end';
}
export class EventBuffer extends BaseBuffer {
// Configurable limits
private batchSize = process.env.EVENT_BUFFER_BATCH_SIZE
? Number.parseInt(process.env.EVENT_BUFFER_BATCH_SIZE, 10)
: 4000;
private chunkSize = process.env.EVENT_BUFFER_CHUNK_SIZE
? Number.parseInt(process.env.EVENT_BUFFER_CHUNK_SIZE, 10)
: 1000;
// Micro-batching configuration
private microBatchIntervalMs = process.env.EVENT_BUFFER_MICRO_BATCH_MS
? Number.parseInt(process.env.EVENT_BUFFER_MICRO_BATCH_MS, 10)
: 10; // Flush every 10ms by default
private microBatchMaxSize = process.env.EVENT_BUFFER_MICRO_BATCH_SIZE
? Number.parseInt(process.env.EVENT_BUFFER_MICRO_BATCH_SIZE, 10)
: 100; // Or when we hit 100 events
// Local event buffer for micro-batching
private pendingEvents: PendingEvent[] = [];
private flushTimer: ReturnType<typeof setTimeout> | null = null;
private isFlushing = false;
// Throttled publish configuration
private publishThrottleMs = process.env.EVENT_BUFFER_PUBLISH_THROTTLE_MS
? Number.parseInt(process.env.EVENT_BUFFER_PUBLISH_THROTTLE_MS, 10)
: 1000; // Publish at most once per second
private lastPublishTime = 0;
private pendingPublishEvent: IClickhouseEvent | null = null;
private publishTimer: ReturnType<typeof setTimeout> | null = null;
private activeVisitorsExpiration = 60 * 5; // 5 minutes
// LIST - Stores all events ready to be flushed
private queueKey = 'event_buffer:queue';
// STRING - Tracks total buffer size incrementally
protected bufferCounterKey = 'event_buffer:total_count';
// Script SHAs for loaded Lua scripts
private scriptShas: {
addScreenView?: string;
addSessionEnd?: string;
} = {};
// Hash key for storing last screen_view per session
private getLastScreenViewKeyBySession(sessionId: string) {
return `event_buffer:last_screen_view:session:${sessionId}`;
}
// Hash key for storing last screen_view per profile
private getLastScreenViewKeyByProfile(projectId: string, profileId: string) {
return `event_buffer:last_screen_view:profile:${projectId}:${profileId}`;
}
/**
* Lua script for handling screen_view addition - RACE-CONDITION SAFE without GroupMQ
*
* Strategy: Use Redis GETDEL (atomic get-and-delete) to ensure only ONE thread
* can process the "last" screen_view at a time.
*
* KEYS[1] = last screen_view key (by session) - stores both event and timestamp as JSON
* KEYS[2] = last screen_view key (by profile, may be empty)
* KEYS[3] = queue key
* KEYS[4] = buffer counter key
* ARGV[1] = new event with timestamp as JSON: {"event": {...}, "ts": 123456}
* ARGV[2] = TTL for last screen_view (1 hour)
*/
private readonly addScreenViewScript = `
local sessionKey = KEYS[1]
local profileKey = KEYS[2]
local queueKey = KEYS[3]
local counterKey = KEYS[4]
local newEventData = ARGV[1]
local ttl = tonumber(ARGV[2])
-- GETDEL is atomic: get previous and delete in one operation
-- This ensures only ONE thread gets the previous event
local previousEventData = redis.call("GETDEL", sessionKey)
-- Store new screen_view as last for session
redis.call("SET", sessionKey, newEventData, "EX", ttl)
-- Store new screen_view as last for profile (if key provided)
if profileKey and profileKey ~= "" then
redis.call("SET", profileKey, newEventData, "EX", ttl)
end
-- If there was a previous screen_view, add it to queue with calculated duration
if previousEventData then
local prev = cjson.decode(previousEventData)
local curr = cjson.decode(newEventData)
-- Calculate duration (ensure non-negative to handle clock skew)
if prev.ts and curr.ts then
prev.event.duration = math.max(0, curr.ts - prev.ts)
end
redis.call("RPUSH", queueKey, cjson.encode(prev.event))
redis.call("INCR", counterKey)
return 1
end
return 0
`;
/**
* Lua script for handling session_end - RACE-CONDITION SAFE
*
* Uses GETDEL to atomically retrieve and delete the last screen_view
*
* KEYS[1] = last screen_view key (by session)
* KEYS[2] = last screen_view key (by profile, may be empty)
* KEYS[3] = queue key
* KEYS[4] = buffer counter key
* ARGV[1] = session_end event JSON
*/
private readonly addSessionEndScript = `
local sessionKey = KEYS[1]
local profileKey = KEYS[2]
local queueKey = KEYS[3]
local counterKey = KEYS[4]
local sessionEndJson = ARGV[1]
-- GETDEL is atomic: only ONE thread gets the last screen_view
local previousEventData = redis.call("GETDEL", sessionKey)
local added = 0
-- If there was a previous screen_view, add it to queue
if previousEventData then
local prev = cjson.decode(previousEventData)
redis.call("RPUSH", queueKey, cjson.encode(prev.event))
redis.call("INCR", counterKey)
added = added + 1
end
-- Add session_end to queue
redis.call("RPUSH", queueKey, sessionEndJson)
redis.call("INCR", counterKey)
added = added + 1
-- Delete profile key
if profileKey and profileKey ~= "" then
redis.call("DEL", profileKey)
end
return added
`;
constructor() {
super({
name: 'event',
onFlush: async () => {
await this.processBuffer();
},
});
// Load Lua scripts into Redis on startup
this.loadScripts();
}
/**
* Load Lua scripts into Redis and cache their SHAs.
* This avoids sending the entire script on every call.
*/
private async loadScripts() {
try {
const redis = getRedisCache();
const [screenViewSha, sessionEndSha] = await Promise.all([
redis.script('LOAD', this.addScreenViewScript),
redis.script('LOAD', this.addSessionEndScript),
]);
this.scriptShas.addScreenView = screenViewSha as string;
this.scriptShas.addSessionEnd = sessionEndSha as string;
this.logger.info('Loaded Lua scripts into Redis', {
addScreenView: this.scriptShas.addScreenView,
addSessionEnd: this.scriptShas.addSessionEnd,
});
} catch (error) {
this.logger.error('Failed to load Lua scripts', { error });
}
}
bulkAdd(events: IClickhouseEvent[]) {
// Add all events to local buffer - they will be flushed together
for (const event of events) {
this.add(event);
}
}
/**
* Add an event into the local buffer for micro-batching.
*
* Events are buffered locally and flushed to Redis every microBatchIntervalMs
* or when microBatchMaxSize is reached. This dramatically reduces Redis round-trips.
*
* Logic:
* - screen_view: Store as "last" for session, flush previous if exists
* - session_end: Flush last screen_view + session_end
* - Other events: Add directly to queue
*/
add(event: IClickhouseEvent, _multi?: ReturnType<Redis['multi']>) {
const eventJson = JSON.stringify(event);
// Determine event type and prepare data
let type: PendingEvent['type'] = 'regular';
let eventWithTimestamp: string | undefined;
if (event.session_id && event.name === 'screen_view') {
type = 'screen_view';
const timestamp = new Date(event.created_at || Date.now()).getTime();
eventWithTimestamp = JSON.stringify({
event: event,
ts: timestamp,
});
} else if (event.session_id && event.name === 'session_end') {
type = 'session_end';
}
const pendingEvent: PendingEvent = {
event,
eventJson,
eventWithTimestamp,
type,
};
// If a multi was provided (legacy bulkAdd pattern), add directly without batching
if (_multi) {
this.addToMulti(_multi, pendingEvent);
return;
}
// Add to local buffer for micro-batching
this.pendingEvents.push(pendingEvent);
// Check if we should flush immediately due to size
if (this.pendingEvents.length >= this.microBatchMaxSize) {
this.flushLocalBuffer();
return;
}
// Schedule flush if not already scheduled
if (!this.flushTimer) {
this.flushTimer = setTimeout(() => {
this.flushTimer = null;
this.flushLocalBuffer();
}, this.microBatchIntervalMs);
}
}
/**
* Add a single pending event to a multi pipeline.
* Used both for legacy _multi pattern and during batch flush.
*/
private addToMulti(multi: ReturnType<Redis['multi']>, pending: PendingEvent) {
const { event, eventJson, eventWithTimestamp, type } = pending;
if (type === 'screen_view' && event.session_id) {
const sessionKey = this.getLastScreenViewKeyBySession(event.session_id);
const profileKey = event.profile_id
? this.getLastScreenViewKeyByProfile(event.project_id, event.profile_id)
: '';
this.evalScript(
multi,
'addScreenView',
this.addScreenViewScript,
4,
sessionKey,
profileKey,
this.queueKey,
this.bufferCounterKey,
eventWithTimestamp!,
'3600',
);
} else if (type === 'session_end' && event.session_id) {
const sessionKey = this.getLastScreenViewKeyBySession(event.session_id);
const profileKey = event.profile_id
? this.getLastScreenViewKeyByProfile(event.project_id, event.profile_id)
: '';
this.evalScript(
multi,
'addSessionEnd',
this.addSessionEndScript,
4,
sessionKey,
profileKey,
this.queueKey,
this.bufferCounterKey,
eventJson,
);
} else {
// Regular events go directly to queue
multi.rpush(this.queueKey, eventJson).incr(this.bufferCounterKey);
}
// Active visitor tracking (simplified - only ZADD, no redundant SET)
if (event.profile_id) {
this.incrementActiveVisitorCount(
multi,
event.project_id,
event.profile_id,
);
}
}
/**
* Force flush all pending events from local buffer to Redis immediately.
* Useful for testing or when you need to ensure all events are persisted.
*/
public async flush() {
// Clear any pending timer
if (this.flushTimer) {
clearTimeout(this.flushTimer);
this.flushTimer = null;
}
await this.flushLocalBuffer();
}
/**
* Flush all pending events from local buffer to Redis in a single pipeline.
* This is the core optimization - batching many events into one round-trip.
*/
private async flushLocalBuffer() {
if (this.isFlushing || this.pendingEvents.length === 0) {
return;
}
this.isFlushing = true;
// Grab current pending events and clear buffer
const eventsToFlush = this.pendingEvents;
this.pendingEvents = [];
try {
const redis = getRedisCache();
const multi = redis.multi();
// Add all events to the pipeline
for (const pending of eventsToFlush) {
this.addToMulti(multi, pending);
}
await multi.exec();
// Throttled publish - just signal that events were received
// Store the last event for publishing (we only need one to signal activity)
const lastEvent = eventsToFlush[eventsToFlush.length - 1];
if (lastEvent) {
this.scheduleThrottledPublish(lastEvent.event);
}
} catch (error) {
this.logger.error('Failed to flush local buffer to Redis', {
error,
eventCount: eventsToFlush.length,
});
} finally {
this.isFlushing = false;
}
}
/**
* Throttled publish - publishes at most once per publishThrottleMs.
* Instead of publishing every event, we just signal that events were received.
* This reduces pub/sub load from 3000/s to 1/s.
*/
private scheduleThrottledPublish(event: IClickhouseEvent) {
// Always keep the latest event
this.pendingPublishEvent = event;
const now = Date.now();
const timeSinceLastPublish = now - this.lastPublishTime;
// If enough time has passed, publish immediately
if (timeSinceLastPublish >= this.publishThrottleMs) {
this.executeThrottledPublish();
return;
}
// Otherwise, schedule a publish if not already scheduled
if (!this.publishTimer) {
const delay = this.publishThrottleMs - timeSinceLastPublish;
this.publishTimer = setTimeout(() => {
this.publishTimer = null;
this.executeThrottledPublish();
}, delay);
}
}
/**
* Execute the throttled publish with the latest pending event.
*/
private executeThrottledPublish() {
if (!this.pendingPublishEvent) {
return;
}
const event = this.pendingPublishEvent;
this.pendingPublishEvent = null;
this.lastPublishTime = Date.now();
// Fire-and-forget publish (no multi = returns Promise)
const result = publishEvent('events', 'received', transformEvent(event));
if (result instanceof Promise) {
result.catch(() => {});
}
}
/**
* Execute a Lua script using EVALSHA (cached) or fallback to EVAL.
* This avoids sending the entire script on every call.
*/
private evalScript(
multi: ReturnType<Redis['multi']>,
scriptName: keyof typeof this.scriptShas,
scriptContent: string,
numKeys: number,
...args: (string | number)[]
) {
const sha = this.scriptShas[scriptName];
if (sha) {
// Use EVALSHA with cached SHA
multi.evalsha(sha, numKeys, ...args);
} else {
// Fallback to EVAL and try to reload script
multi.eval(scriptContent, numKeys, ...args);
this.logger.warn(`Script ${scriptName} not loaded, using EVAL fallback`);
// Attempt to reload scripts in background
this.loadScripts();
}
}
/**
* Process the Redis buffer - simplified version.
*
* Simply:
* 1. Fetch events from the queue (up to batchSize)
* 2. Parse and sort them
* 3. Insert into ClickHouse in chunks
* 4. Publish saved events
* 5. Clean up processed events from queue
*/
async processBuffer() {
const redis = getRedisCache();
try {
// Fetch events from queue
const queueEvents = await redis.lrange(
this.queueKey,
0,
this.batchSize - 1,
);
if (queueEvents.length === 0) {
this.logger.debug('No events to process');
return;
}
// Parse events
const eventsToClickhouse: IClickhouseEvent[] = [];
for (const eventStr of queueEvents) {
const event = getSafeJson<IClickhouseEvent>(eventStr);
if (event) {
eventsToClickhouse.push(event);
}
}
if (eventsToClickhouse.length === 0) {
this.logger.debug('No valid events to process');
return;
}
// Sort events by creation time
eventsToClickhouse.sort(
(a, b) =>
new Date(a.created_at || 0).getTime() -
new Date(b.created_at || 0).getTime(),
);
// Insert events into ClickHouse in chunks
this.logger.info('Inserting events into ClickHouse', {
totalEvents: eventsToClickhouse.length,
chunks: Math.ceil(eventsToClickhouse.length / this.chunkSize),
});
for (const chunk of this.chunks(eventsToClickhouse, this.chunkSize)) {
await ch.insert({
table: 'events',
values: chunk,
format: 'JSONEachRow',
});
}
// Publish "saved" events
const pubMulti = getRedisPub().multi();
for (const event of eventsToClickhouse) {
await publishEvent('events', 'saved', transformEvent(event), pubMulti);
}
await pubMulti.exec();
// Clean up processed events from queue
await redis
.multi()
.ltrim(this.queueKey, queueEvents.length, -1)
.decrby(this.bufferCounterKey, queueEvents.length)
.exec();
this.logger.info('Processed events from Redis buffer', {
batchSize: this.batchSize,
eventsProcessed: eventsToClickhouse.length,
});
} catch (error) {
this.logger.error('Error processing Redis buffer', { error });
}
}
/**
* Retrieve the latest screen_view event for a given session or profile
*/
public async getLastScreenView(
params:
| {
sessionId: string;
}
| {
projectId: string;
profileId: string;
},
): Promise<IServiceEvent | null> {
const redis = getRedisCache();
let lastScreenViewKey: string;
if ('sessionId' in params) {
lastScreenViewKey = this.getLastScreenViewKeyBySession(params.sessionId);
} else {
lastScreenViewKey = this.getLastScreenViewKeyByProfile(
params.projectId,
params.profileId,
);
}
const eventDataStr = await redis.get(lastScreenViewKey);
if (eventDataStr) {
const eventData = getSafeJson<{ event: IClickhouseEvent; ts: number }>(
eventDataStr,
);
if (eventData?.event) {
return transformEvent(eventData.event);
}
}
return null;
}
public async getBufferSize() {
return this.getBufferSizeWithCounter(async () => {
const redis = getRedisCache();
return await redis.llen(this.queueKey);
});
}
/**
* Track active visitors using ZADD only.
*
* Optimization: Removed redundant heartbeat SET key.
* The ZADD score (timestamp) already tracks when a visitor was last seen.
* We use ZRANGEBYSCORE in getActiveVisitorCount to filter active visitors.
*/
private incrementActiveVisitorCount(
multi: ReturnType<Redis['multi']>,
projectId: string,
profileId: string,
) {
const now = Date.now();
const zsetKey = `live:visitors:${projectId}`;
// Only ZADD - the score is the timestamp, no need for separate heartbeat key
return multi.zadd(zsetKey, now, profileId);
}
public async getActiveVisitorCount(projectId: string): Promise<number> {
const redis = getRedisCache();
const zsetKey = `live:visitors:${projectId}`;
const cutoff = Date.now() - this.activeVisitorsExpiration * 1000;
const multi = redis.multi();
multi
.zremrangebyscore(zsetKey, '-inf', cutoff)
.zcount(zsetKey, cutoff, '+inf');
const [, count] = (await multi.exec()) as [
[Error | null, any],
[Error | null, number],
];
return count[1] || 0;
}
}