Gizmo Microservice Toolkit

This toolkit provides packages to put together server and pubsub daemons with the following features:

Standardized configuration and logging
Health check endpoints with configurable strategies
Configuration for managing pprof endpoints and log levels
Basic interfaces to define expectations and vocabulary
Structured logging containing basic request information
Useful metrics for endpoints
Graceful shutdowns

Packages

`server`

The server package is the bulk of the toolkit and relies on server.Config to manage Server implementations.

It offers 2 server implementations:

SimpleServer, which is capable of handling basic HTTP and JSON requests via 5 of the available Service implementations: SimpleService, JSONService, ContextService, MixedService and a MixedContextService.
RPCServer, which is capable of serving a gRPC server on one port and JSON endpoints on another. This kind of server can only handle the RPCService implementation.

`server/kit`

This is an experimental package in Gizmo!

The rationale behind this package:
- A more opinionated server with fewer choices
- go-kit is used for serving HTTP/JSON & gRPC is used for serving HTTP2/RPC
- Monitoring and metrics are handled by a sidecar (ie. Cloud Endpoints)
- Logs always go to stdout/stderr
- Using Go's 1.8 graceful HTTP shutdown
- Services using this package are meant for deploy to GCP with GKE and Cloud Endpoints.

`auth`

The auth package provides primitives for verifying inbound authentication tokens:

The PublicKeySource interface is meant to provide *rsa.PublicKeys from JSON Web Key Sets.
The Verifier struct composes key source implementations with custom decoders and verifier functions to streamline server side token verification.

`auth/gcp`

The auth/gcp package provides 2 Google Cloud Platform based auth.PublicKeySource and oauth2.TokenSource implementations:

The "Identity" key source and token source rely on GCP's identity JWT mechanism for asserting instance identities. This is the preferred method for asserting instance identity on GCP.
The "IAM" key source and token source rely on GCP's IAM services for signing and verifying JWTs. This method can be used outside of GCP, if needed and can provide a bridge for users transitioning from the 1st generation App Engine (where Identity tokens are not available) runtime to the 2nd.

`config`

The config package contains a handful of useful functions to load to configuration structs from JSON files, JSON blobs in Consul k/v, or environment variables.

There are also many structs for common configuration options and credentials of different Cloud Services and Databases.
The package also has a generic Config type in the config/combined subpackage that contains all of the above types. It's meant to be a 'catch all' convenience struct that many applications should be able to use.

`pubsub`

The pubsub package contains two (publisher and subscriber) generic interfaces for publishing data to queues as well as subscribing and consuming data from those queues.

There are 4 implementations of pubsub interfaces:

For pubsub via Amazon's SNS/SQS, you can use the pubsub/aws package
For pubsub via Google's Pubsub, you can use the pubsub/gcp package
For pubsub via Kafka topics, you can use the pubsub/kafka package
For publishing via HTTP, you can use the pubsub/http package

The pubsub/pubsubtest package contains test implementations of the pubsub.Publisher, pubsub.MultiPublisher, and pubsub.Subscriber interfaces that will allow developers to easily mock out and test their pubsub implementations.

`web`

The web package has a handful of very useful functions for parsing types from request queries and payloads.

Examples

Several reference implementations utilizing server and pubsub are available in the examples subdirectory.
There are also examples within the GoDoc: here

_{If you experience any issues please create an issue and/or reach out on the #gizmo channel in the Gophers Slack Workspace with what you've found.}

_{The Gizmo logo was based on the Go mascot designed by Renée French and copyrighted under the Creative Commons Attribution 3.0 license.}

DavyJ0nes/gizmo