Teacup provides tooling for quickly building microservices that operate in a consistent, managed environment.

To create a new Teacup microservice the normal work flow involves:

1. Create a new git repo.
2. Run go mod init in project root
3. Run go get github.com/betafish-inc/teacup to add the teacup dependency.
4. Create go launcher in _apps/service/main.go - using a standard naming allows tools to automatically build.
5. If using GitHub, add a GitHub Actions Workflow in .github/workflows/teacup.yaml using the template from _apps/tools/teacup/teacup.yaml.
6. Implement your service in service specific go packages in the project.

TODO it would be nice to add a tool as part of the Teacup project to automate the lion's share of these tasks. e.g. teacup init.

Install Go and in the project root run go get -v -t -d ./... to fetch all go dependencies.

Typical Go development process:

• Unit tests: go test
• Run: go run _apps/subscriber/main.go
• Build: go build -o dist/subscriber _apps/subscriber/main.go

A Teacup based microservice operates in a standardized environment. Typically, this environment will run within a Docker Swarm or Kubernetes cluster. However, the same environment can also be run on bare OS's, Nomad clusters, etc.

In particular, Teacup assumes the following services are available:

• NATS.io for control plane and messaging
• Redis for data
• PostgreSQL for SQL data

Configuration for accessing these services will be searched in the following order:

1. Environmental variables.
2. DNS SRV records.
3. Default ports on localhost.

DNS SRV: This is most common in Consul managed environments. DNS SRV records must resolve using the default operating system DNS resolution system for Teacup microservices to lookup the information required.

For local development, run all the services your microservice relies on using default ports. The easiest is to install Docker and create a file named docker-compose.yml containing the following:

version: '3'
services:
  nats:
    image: nats:latest
    ports:
      - "6222:6222"
  redis:
    image: redislabs/redistimeseries
    ports:
      - "6379:6379"

Then run docker-compose up to start the services. Once the docker containers are running go run _apps/subscriber/main.go to run the subscriber microservice example. You'll need to send data to the same subject using go run _apps/publisher/main.go.

Teacup supports NATS.io "core" servers running in an optional cluster and will search for the following configuration options:

1. NATS_ADDR environmental variable. Should contain a comma separated list of host and port pairs e.g. 100.0.1.1:6222,100.0.1.2:6222.
2. nats.service.consul & nats.local DNS SRV entry.
3. localhost:6222 fall back to the most likely default configuration.

Teacup will attempt to connect to Redis using a connection URL:

• REDIS_URL environmental variable. Should be in the following format: redis://[:password@]host:port/db.

If the connection URL environmental variable doesn't exist, Teacup will search the following locations for Redis connection configuration information:

1. REDIS_ADDR environmental variable. Should contain the host and port like localhost:6379.
2. redis.service.consul & redis.local DNS SRV entry.
3. localhost:6379 fall back to the most likely default configuration.

Optionally, set a password and database using:

• REDIS_PASSWORD and REDIS_DATABASE environmental variables.

The default is no password, and database 0.

TBD