stategate

A pluggable "Application State Gateway" that enforces the Event Sourcing Pattern for securely persisting & broadcasting application state changes

What is Event Sourcing?

Event sourcing persists the state of a business entity such an Order or a Customer as a sequence of state-changing events. Whenever the state of a business entity changes, a new event is appended to the list of events. Since saving an event is a single operation, it is inherently atomic. The application reconstructs an entity’s current state by replaying the events.

Applications persist events in an event store, which is a database of events. The store has an API for adding and retrieving an entity’s events. The event store also behaves like a message broker. It provides an API that enables services to subscribe to events. When a service saves an event in the event store, it is delivered to all interested subscribers.

API Documentation

Features

Goals

Create a simple API interface for storing state and subscribing to state changes(events) using pluggable channel & storage providers
Capture all changes to an application's state as a sequence of events.
Safe to swap backend providers without changing client-side code
Type-safe client's generated in many languages
Safe to expose to the public internet due to fine-grained authentication/authorization model.
Different combinations of Channel & Storage Providers are interoperable.
Capture a persistant, immutable historical record of all state changes using a pluggable storage provider
Store identity(jwt.claims) & timestamp in event logs to capture who is changing what & when
Easy deployment model - fully configureable via environmental variables

Concepts

Storage Provider: A stategate storage provider is a pluggable, 3rd party database storage service. Storage providers provide persistance for all objects & events and should be scaled independently of stategate instances.
Channel Provider: A stategate channel provider is a pluggable, 3rd party message-queue/channel service. Channel providers provide a way for stategate to broadcast events to itself while scaling horizontally. Channel providers should be scaled independently of stategate instances.

Environmental Variables

# port to serve on (optional). defaults to 8080
STATEGATE_PORT=8080
# enable debug logs (optional)
STATEGATE_DEBUG=true
# disable all authentication & authorization(jwks, request policies, response policies) (optional)
STATEGATE_AUTH_DISABLED=false
# tls cert file (optional)
STATEGATE_TLS_CERT_FILE=/tmp/certs/stategate.cert
# tls key file (optional)
STATEGATE_TLS_KEY_FILE=/tmp/certs/stategate.key

# JSON Web Key Set remote URI used for fetching jwt signing keys for verification/validation (optional)
STATEGATE_JWKS_URI=https://www.googleapis.com/oauth2/v3/certs

# base64 encoded OPA rego policy executed on inbound requests from clients (optional)
STATEGATE_REQUEST_POLICY=cGFja2FnZSBzdGF0ZWdhdGUuYXV0aHoKCmRlZmF1bHQgYWxsb3cgPSB0cnVl
# base64 encoded OPA rego policy executed on responses sent to clients (optional)
STATEGATE_RESPONSE_POLICY=cGFja2FnZSBzdGF0ZWdhdGUuYXV0aHoKCmRlZmF1bHQgYWxsb3cgPSB0cnVl
# channel provider configuration(JSON) options: [inmem, redis, nats, stan, kafka] REQUIRED
STATEGATE_CHANNEL_PROVIDER={ "name": "redis", "addr": "localhost:6379" }
# STATEGATE_CHANNEL_PROVIDER={ "name": "nats", "addr": "localhost:4222" }
# STATEGATE_CHANNEL_PROVIDER={ "name": "stan", "addr": "localhost:4222" }
# STATEGATE_CHANNEL_PROVIDER={ "name": "inmem" }

# storage provider configuration(JSON) options: [mongo] REQUIRED
STATEGATE_STORAGE_PROVIDER={ "name": "mongo", "database": "testing", "addr": "mongodb://localhost:27017/testing" }