Saga Purchase

Purchase service of my saga pattern implementation.

Features:

• Realtime event-driven subscription using Redis Stream and server-sent events (SSE)
• Prometheus metrics
• Distributed tracing with OpenTelemetry
  • HTTP server
  • gPRC client
• Comprehensive application struture with domain-driven design (DDD), decoupling service implementations from configurations and transports
• Compile-time dependecy injection using wire
• Graceful shutdown
• Unit testing and continuous integration using Drone CI

Usage

Setup githooks:

git config core.hooksPath githooks

Build from source:

go mod tidy
make build

Start the service:

REDIS_ADDRS=redis-node1:7000,redis-node2:7001 \
REDIS_PASSWORD=pass.123 \
NATS_URL=nats://nats-streaming:4222 \
NATS_CLUSTER_ID=test-cluster \
RPC_AUTH_SVC_HOST=saga-account:8000 \
RPC_PRODUCT_SVC_HOST=saga-product:8000 \
JAEGER_URL=http://jaeger:14268/api/traces \
./server

Test locally:

make test

• REDIS_ADDRS: list of Redis addresses
• REDIS_PASSWORD: Redis password
• NATS_URL: NATS Streaming server URL.
• NATS_CLUSTER_ID: NATS Cluster ID
• RPC_AUTH_SVC_HOST: gRPC account service host
• RPC_PRODUCT_SVC_HOST: gRPC product service host
• JAEGER_URL: Jaeger collector URL

Running in Docker

See docker-compose example for details.

Exported Metrics

Metric	Description	Labels
purchase_pubsub_subscriber_messages_received_total	A Prometheus Counter. Counts the number of messages obtained by the subscriber.	acked ("acked" or "nacked"), handler_name, subscriber_name
purchase_pubsub_publish_time_seconds (purchase_pubsub_publish_time_seconds_count, purchase_pubsub_publish_time_seconds_bucket, purchase_pubsub_publish_time_seconds_sum)	A Prometheus Histogram. Registers the time of execution of the Publish function of the decorated publisher.	handler_name, success ("true" or "false"), publisher_name
purchase_http_request_duration_seconds (purchase_http_request_duration_seconds_count, purchase_http_request_duration_seconds_bucket, purchase_http_request_duration_sum)	A Prometheus histogram. Records the latency of the HTTP requests.	code, handler, method
purchase_http_requests_inflight	A Prometheus gauge. Records the number of inflight requests being handled at the same time.	code, handler, method
purchase_http_response_size_bytes (purchase_http_response_size_bytes_count, purchase_http_response_size_bytes_bucket, purchase_http_response_size_bytes_sum)	A Prometheus histogram. Records the size of the HTTP responses.	handler