Environment Variables

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Overview

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Environment Variable Summary

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Service-Specific Variables

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Backend Router Service

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SERVER_ADDR

• Description: Server bind address and port for the backend router API
• Type: String (format: host:port)
• Source: Secret (exchange-router-secret)
• Required: Yes
• Example: 0.0.0.0:8080
• Usage: Defines where the HTTP server listens for incoming requests

env:
  - name: SERVER_ADDR
    valueFrom:
      secretKeyRef:
        name: exchange-router-secret
        key: server_addr

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DATABASE_URL

• Description: PostgreSQL database connection string
• Type: String (PostgreSQL URL format)
• Source: Secret (exchange-router-secret)
• Required: Yes
• Example: postgres://root:[email protected]:80/exchange-db
• Usage: Establishes connection to the PostgreSQL database

env:
  - name: DATABASE_URL
    valueFrom:
      secretKeyRef:
        name: exchange-router-secret
        key: database_url

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REDIS_URL

• Description: Redis connection string for caching and pub/sub
• Type: String (Redis URL format)
• Source: Secret (exchange-router-secret)
• Required: Yes
• Example: redis://exchange-redis-service.default.svc.cluster.local:80
• Usage: Connects to Redis for session management, caching, and message queuing

env:
  - name: REDIS_URL
    valueFrom:
      secretKeyRef:
        name: exchange-router-secret
        key: redis_url

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PostgreSQL Database Service

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POSTGRES_USER

• Description: PostgreSQL database superuser name
• Type: String
• Source: ConfigMap (exchange-postgres-config)
• Required: Yes
• Default: root
• Usage: Initial database user created during PostgreSQL initialization

env:
  - name: POSTGRES_USER
    valueFrom:
      configMapKeyRef:
        name: exchange-postgres-config
        key: POSTGRES_USER

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POSTGRES_PASSWORD

• Description: Password for the PostgreSQL superuser
• Type: String
• Source: ConfigMap (exchange-postgres-config)
• Required: Yes
• Default: root
• Usage: Authenticates the database superuser

env:
  - name: POSTGRES_PASSWORD
    valueFrom:
      configMapKeyRef:
        name: exchange-postgres-config
        key: POSTGRES_PASSWORD

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POSTGRES_DB

• Description: Name of the default database to create
• Type: String
• Source: ConfigMap (exchange-postgres-config)
• Required: Yes
• Default: exchange-db
• Usage: Database created automatically on first startup

env:
  - name: POSTGRES_DB
    valueFrom:
      configMapKeyRef:
        name: exchange-postgres-config
        key: POSTGRES_DB

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Engine Service

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DATABASE_URL

• Description: PostgreSQL connection string for the matching engine
• Type: String (PostgreSQL URL format)
• Source: ConfigMap (exchange-engine-config)
• Required: Yes
• Example: postgres://root:[email protected]:80/exchange-db
• Usage: Connects engine to database for order management and trade execution

env:
  - name: DATABASE_URL
    valueFrom:
      configMapKeyRef:
        name: exchange-engine-config
        key: database_url

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REDIS_URL

• Description: Redis connection for order book caching and pub/sub
• Type: String (Redis URL format)
• Source: ConfigMap (exchange-engine-config)
• Required: Yes
• Example: redis://exchange-redis-service.default.svc.cluster.local:80
• Usage: Publishes trade events and maintains in-memory order book state

env:
  - name: REDIS_URL
    valueFrom:
      configMapKeyRef:
        name: exchange-engine-config
        key: redis_url

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Database Processor Service

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DATABASE_URL

• Description: PostgreSQL connection for background processing
• Type: String (PostgreSQL URL format)
• Source: ConfigMap (exchange-db-processor-config)
• Required: Yes
• Example: postgres://root:[email protected]:80/exchange-db
• Usage: Processes database operations asynchronously

env:
  - name: DATABASE_URL
    valueFrom:
      configMapKeyRef:
        name: exchange-db-processor-config
        key: database_url

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REDIS_URL

• Description: Redis connection for job queue processing
• Type: String (Redis URL format)
• Source: ConfigMap (exchange-db-processor-config)
• Required: Yes
• Example: redis://exchange-redis-service.default.svc.cluster.local:80
• Usage: Consumes jobs from Redis queues for batch processing

env:
  - name: REDIS_URL
    valueFrom:
      configMapKeyRef:
        name: exchange-db-processor-config
        key: redis_url

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WebSocket Service

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WS_STREAM_URL

• Description: WebSocket server bind address and port
• Type: String (format: host:port)
• Source: ConfigMap (exchange-ws-stream-config)
• Required: Yes
• Default: 0.0.0.0:4000
• Usage: Defines where the WebSocket server listens for client connections

env:
  - name: WS_STREAM_URL
    valueFrom:
      configMapKeyRef:
        name: exchange-ws-stream-config
        key: ws_stream_url

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REDIS_URL

• Description: Redis connection for subscribing to real-time events
• Type: String (Redis URL format)
• Source: ConfigMap (exchange-ws-stream-config)
• Required: Yes
• Example: redis://exchange-redis-service.default.svc.cluster.local:80
• Usage: Subscribes to Redis pub/sub channels for streaming trade updates to WebSocket clients

env:
  - name: REDIS_URL
    valueFrom:
      configMapKeyRef:
        name: exchange-ws-stream-config
        key: redis_url

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Redis Service

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Configuration Patterns

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URL Formats

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PostgreSQL Connection String

postgres://[username]:[password]@[host]:[port]/[database]

postgres://root:[email protected]:80/exchange-db

• username: Database user (default: root)
• password: User password (default: root)
• host: Service hostname using Kubernetes DNS
• port: Service port (PostgreSQL service exposes port 80, maps to container port 5432)
• database: Target database name (default: exchange-db)

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Redis Connection String

redis://[host]:[port]

redis://exchange-redis-service.default.svc.cluster.local:80

• host: Service hostname using Kubernetes DNS
• port: Service port (Redis service exposes port 80, maps to container port 6379)

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Service Discovery

<service-name>.<namespace>.svc.cluster.local:<port>

• exchange-postgres-service.default.svc.cluster.local:80
• exchange-redis-service.default.svc.cluster.local:80

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Port Mapping

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Configuration Examples

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Local Development

# Backend Router
export SERVER_ADDR="localhost:8080"
export DATABASE_URL="postgres://root:root@localhost:5432/exchange-db"
export REDIS_URL="redis://localhost:6379"

# Engine
export DATABASE_URL="postgres://root:root@localhost:5432/exchange-db"
export REDIS_URL="redis://localhost:6379"

# WebSocket
export WS_STREAM_URL="0.0.0.0:4000"
export REDIS_URL="redis://localhost:6379"

# PostgreSQL (if running manually)
export POSTGRES_USER="root"
export POSTGRES_PASSWORD="root"
export POSTGRES_DB="exchange-db"

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Docker Compose

services:
  backend:
    environment:
      SERVER_ADDR: "0.0.0.0:8080"
      DATABASE_URL: "postgres://root:root@postgres:5432/exchange-db"
      REDIS_URL: "redis://redis:6379"

  engine:
    environment:
      DATABASE_URL: "postgres://root:root@postgres:5432/exchange-db"
      REDIS_URL: "redis://redis:6379"

  websocket:
    environment:
      WS_STREAM_URL: "0.0.0.0:4000"
      REDIS_URL: "redis://redis:6379"

  postgres:
    environment:
      POSTGRES_USER: "root"
      POSTGRES_PASSWORD: "root"
      POSTGRES_DB: "exchange-db"

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Production Overrides

env:
  # From Secret
  - name: DATABASE_URL
    valueFrom:
      secretKeyRef:
        name: exchange-production-secret
        key: database_url
  
  # From ConfigMap (non-sensitive)
  - name: WS_STREAM_URL
    valueFrom:
      configMapKeyRef:
        name: exchange-production-config
        key: ws_stream_url

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Required vs Optional Variables

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Required Variables

• SERVER_ADDR
• DATABASE_URL
• REDIS_URL

• POSTGRES_USER
• POSTGRES_PASSWORD
• POSTGRES_DB

• DATABASE_URL
• REDIS_URL

• DATABASE_URL
• REDIS_URL

• WS_STREAM_URL
• REDIS_URL

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Optional Variables

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Best Practices

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Security

1. Use Secrets for Credentials
   # Good: Using Secret
   - name: DATABASE_URL
     valueFrom:
       secretKeyRef:
         name: exchange-secret
         key: database_url
   
   # Bad: Hardcoded value
   - name: DATABASE_URL
     value: "postgres://root:root@..."
   
2. Separate Sensitive from Non-Sensitive
   • Store passwords, tokens, and connection strings with credentials in Secrets
   • Store non-sensitive config like URLs without credentials in ConfigMaps
3. Avoid Hardcoding
   • Never hardcode values directly in deployment YAML
   • Always use ConfigMaps or Secrets

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Naming Conventions

1. Use SCREAMING_SNAKE_CASE
   • DATABASE_URL ✓
   • database_url ✗
2. Be Descriptive
   • WS_STREAM_URL ✓ (clear abbreviation)
   • URL ✗ (too vague)
3. Follow Application Conventions
   • Match variable names expected by the application code
   • Document any transformations (e.g., database_url in ConfigMap → DATABASE_URL in container)

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Documentation

1. Document All Variables
   • Purpose and usage
   • Expected format and examples
   • Source (ConfigMap or Secret)
   • Whether required or optional
2. Version Control
   • Track variable changes in Git
   • Use meaningful commit messages when updating configurations
3. Environment Parity
   • Keep development, staging, and production configurations consistent
   • Use the same variable names across environments

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Troubleshooting

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Variable Not Set

# Get pod name
kubectl get pods -l app=exchange-router

# Check all environment variables
kubectl exec <pod-name> -- env

# Check specific variable
kubectl exec <pod-name> -- env | grep DATABASE_URL

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ConfigMap or Secret Missing

# Check ConfigMaps
kubectl get configmap exchange-engine-config

# Check Secrets
kubectl get secret exchange-router-secret

# View ConfigMap data
kubectl describe configmap exchange-engine-config

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Connection Issues

# Test PostgreSQL connection
kubectl exec <pod-name> -- psql $DATABASE_URL -c "SELECT 1"

# Test Redis connection
kubectl exec <pod-name> -- redis-cli -u $REDIS_URL ping

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Service Discovery Problems

# Check if service exists
kubectl get service exchange-postgres-service

# Test DNS from pod
kubectl exec <pod-name> -- nslookup exchange-postgres-service.default.svc.cluster.local

# Test connectivity
kubectl exec <pod-name> -- nc -zv exchange-postgres-service 80

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Restart Pods After Config Changes

# Restart deployment
kubectl rollout restart deployment exchange-router-deployment

# Or delete pods to force recreation
kubectl delete pod -l app=exchange-router

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Related Resources

• ConfigMaps - Detailed ConfigMap documentation
• Secrets - Secret management guide
• Kubernetes Environment Variables
• Kubernetes ConfigMap Reference
• Kubernetes Secret Reference