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      • Disclaimer
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      • Overview
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        • AWS
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        • EU Hosting Companies
        • Other platforms
      • Instance settings
      • Environment variables
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      • Monitoring with Grafana
      • Running behind a proxy
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      • Helm chart configuration
      • Deploying ClickHouse using Altinity.Cloud
      • Configuring Slack
      • Overview
        • Overview
        • Upgrade notes
        • Overview
        • 0001-events-sample-by
        • 0002_events_sample_by
        • 0003_fill_person_distinct_id2
        • ClickHouse
          • Backup
          • Debug hanging / freezing process
          • Horizontal scaling (Sharding & replication)
          • Kafka Engine
          • Resize disk
          • Restore
          • Vertical scaling
        • Kafka
          • Resize disk
          • Log retention
        • PostgreSQL
          • Resize disk
          • Troubleshooting long-running migrations
        • Plugin server
          • Overview
          • Ingestion lag
          • Jobs not executing
          • Scheduled tasks not executing
        • MinIO
        • Redis
        • Zookeeper
      • Disaster recovery
    • Troubleshooting and FAQs
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    • Migrate from Amplitude
    • Migrate to PostHog Cloud EU
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      • Dashboards
      • Funnels
      • Group Analytics
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      • Path analysis
      • Retention
      • Stickiness
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      • Heatmaps
      • Session Recording
      • Correlation Analysis
      • Experimentation
      • Feature Flags
      • Actions
      • Annotations
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      • Events
      • Persons
      • Sessions
      • UTM segmentation
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      • Toolbar
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    • Overview
      • Amazon Kinesis Import
      • BitBucket Release Tracker
      • Event Replicator
      • GitHub Release Tracker
      • GitHub Star Sync
      • GitLab Release Tracker
      • Heartbeat
      • Ingestion Alert
      • Email Scoring
      • n8n Connector
      • Orbit Connector
      • Redshift Import
      • Rudderstack Import
      • Segment Connector
      • Shopify Connector
      • Stripe Connector
      • Twitter Followers Tracker
      • Zendesk Connector
      • Airbyte Exporter
      • Amazon S3 Export
      • Avo Inspector
      • BigQuery Export
      • Customer.io Connector
      • Databricks Export
      • Engage Connector
      • GCP Pub/Sub Connector
      • Google Cloud Storage Export
      • Hubspot Connector
      • Intercom Connector
      • PagerDuty Connector
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      • Redshift Export
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      • Sendgrid Connector
      • Sentry Connector
      • Snowflake Export
      • Twilio Connector
      • Variance Connector
      • Pace Integration
      • Zapier Connector
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      • Event Sequence Timer
      • First Time Event Tracker
      • Property Filter
      • Property Flattener
      • Schema Enforcer
      • Taxonomy Standardizer
      • Unduplicator
      • Advanced GeoIP Enricher
      • Automatic Cohort Creator
      • Currency Normalizer
      • GeoIP Enricher
      • Timestamp Parser
      • URL Normalizer
      • User Agent Populator
      • Pineapple Mode
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Architecture

Last updated: Jan 18, 2023

On this page

  • Zooming right out
  • Zooming closer
  • Zoomed right in

The following pages in this section cover Data model, Ingestion pipeline, ClickHouse and Querying data. This document gives an overview of the general architecture. How our cloud or a deployed PostHog Helm chart works on Kubernetes.

Zooming right out

There are only a few systems to consider. A Website and API is presented for users. An API for Client Apps. A plugin service for processing events on ingestion. And a worker service for processing events in response to triggers (e.g. timers)

User
Client Apps/SDKs
Export Sink
Web/API
plugin/worker service
Celery
Data stores

Zooming closer

Starts to reveal the flow between parts of the system

plugin/worker service
Web/API
views insights and more
send events
read
write events
onEvent
save events
onTimer
export events
e.g. read flags
read events
start task
on schedule
Ingestion
Async
timer
Web
Capture API
Decide API
cron
Celery
User
Client Apps/SDKs
Export Sink
Data stores

Zoomed right in

K8s PostHog namespace
K8s Services
K8s Services
Other traffic
Events endpoint
Write path
Read path
Optional Utilization telemetry
Ingress
Postgres Stateful service
Kafka Stateful Service
Kafka Stateful Service
Redis SS
Service Load Balancer
Service Load Balancer
K8s Services
PGBouncer
ClickHouse Cluster (Operator Managed)
Replica 1 Shard 1
Replica 1 Shard 2
Replica 2 Shard 1
Replica 2 Shard 2
K8s ZooKeeper cluster
ZK1
ZK2
ZK3
Plugin Service
Worker Service
Events Service
Web Service
Client Apps
Posthog License Telemetry service

No communication is needed into or out of this namespace other than the ingress controller for app and collecting data.

Note that the specifics of this may vary:

  • ClickHouse, Kafka, PostgreSQL and Redis services may be hosted outside of the namespace or configured differently.
  • The ClickHouse cluster is managed by clickhouse-operator and the exact number of pods vary according to sharding settings.

Questions?

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Data model

This document provides a high-level overview of the various objects and primitives that make up the PostHog data model. For more information on exactly how data is stored in our database, check out the ClickHouse overview . The two most-basic entities in PostHog are the Event and Person objects, and represent the core of our analytics functionalities. Event An event is the most important object in PostHog, and represents a single action that a user performed at a specific point in time…

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Authors

  • Paul D'Ambra
    Paul D'Ambra
  • Paul Hultgren
    Paul Hultgren
  • kuberaspeaking
    kuberaspeaking

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