Services and APIs

Simplifying (micro-)service development

Encore makes it simple to build applications with one or many services, without needing to manually handle the typical complexity of developing microservices.

Defining a service

With Encore you define a service by defining one or more APIs within a regular Go package. Encore recognizes this as a service, and uses the package name as the service name. When deploying, Encore will automatically provision the required infrastructure for each service.

On disk it might look like this:

/my-app
├── encore.app          // ... and other top-level project files
│
├── hello               // hello service (a Go package)
│   ├── hello.go        // hello service code
│   └── hello_test.go   // tests for hello service
│
└── world               // world service (a Go package)
    └── world.go        // world service code

This means building a microservices architecture is as simple as creating multiple Go packages within your application. See the app structure documentation for more details.

Service Initialization

Under the hood Encore automatically generates a main function that initializes all your infrastructure resources when the application starts up. This means you don't write a main function for your Encore application.

If you want to customize the initialization behavior of your service, you can define a service struct and define custom initialization logic with that. See the service struct docs for more info.

Defining APIs

To define an API, add the //encore:api annotation any regular Go function. This tells Encore that the function is an API endpoint. Encore will then automatically generate the necessary boilerplate at compile-time.

In the example below, we define the API endpoint Ping, in the hello service, which gets exposed as hello.Ping.

package hello // service name

//encore:api public
func Ping(ctx context.Context, params *PingParams) (*PingResponse, error) {
    msg := fmt.Sprintf("Hello, %s!", params.Name)
    return &PingResponse{Message: msg}, nil
}

Request and response schemas

In the example above we defined an API that uses request and response schemas. The request data is of type PingParams and the response data of type PingResponse. That means we need to define them like so:

package hello // service name

// PingParams is the request data for the Ping endpoint.
type PingParams struct {
    Name string
}

// PingResponse is the response data for the Ping endpoint.
type PingResponse struct {
    Message string
}

// Ping is an API endpoint that responds with a simple response.
// This is exposed as "hello.Ping".
//encore:api public
func Ping(ctx context.Context, params *PingParams) (*PingResponse, error) {
    msg := fmt.Sprintf("Hello, %s!", params.Name)
    return &PingResponse{Message: msg}, nil
}

Request and response schemas are both optional in case you don't need them. That means there are four different ways of defining an API:

  • func Foo(ctx context.Context, p *Params) (*Response, error) – when you need both.
  • func Foo(ctx context.Context) (*Response, error) – when you only return a response.
  • func Foo(ctx context.Context, p *Params) error – when you only respond with success/fail.
  • func Foo(ctx context.Context) error – when you need neither request nor response data.

As you can see, two parts are always present: the ctx context.Context parameter and the error return value.

The ctx parameter is used for cancellation. It lets you detect when the caller is no longer interested in the result, and lets you abort the request processing and save resources that nobody needs. Learn more about contexts on the Go blog.

The error return type is always required because APIs can always fail from the caller's perspective. Therefore even though our simple Ping API endpoint above never fails in its implementation, from the perspective of the caller perhaps the service is crashing or the network is down and the service cannot be reached.

This approach is simple but very powerful. It lets Encore use static analysis to understand the request and response schemas of all your APIs, which enables Encore to automatically generate API documentation, type-safe API clients, and much more.

Access controls

When you define an API, you have three options for how it can be accessed:

  • //encore:api public – defines a public API that anybody on the internet can call.
  • //encore:api private – defines a private API that is never accessible to the outside world. It can only be called from other services in your app and via cron jobs.
  • //encore:api auth – defines a public API that anybody can call, but requires valid authentication.

You can optionally send in auth data to public and private APIs, in which case the auth handler will be used. When used for private APIs, they are still not accessible from the outside world.

For more on defining APIs that require authentication, see the authentication guide.

REST APIs

Encore has support for RESTful APIs and lets you easily define resource-oriented API URLs, parse parameters out of them, and more.

To create a REST API, start by defining an endpoint and specify the method and path fields in the //encore:api comment. (Learn more in the API schemas guide.)

To specify a placeholder variable, use :name and add a function parameter with the same name to the function signature. Encore parses the incoming request URL and makes sure it matches the type of the parameter.

For example, if you want to have a GetBlogPost endpoint that takes a numeric id as a parameter:

// GetBlogPost retrieves a blog post by id.
//encore:api public method=GET path=/blog/:id
func GetBlogPost(ctx context.Context, id int) (*BlogPost, error) {
    // Use id to query database...
}

You can also combine path parameters with body payloads. For example, if you want to have an UpdateBlogPost endpoint:

// UpdateBlogPost updates an existing blog post by id.
//encore:api public method=PUT path=/blog/:id
func UpdateBlogPost(ctx context.Context, id int, post *BlogPost) error {
    // Use `post` to update the blog post with the given id.
}
Take care

You cannot define paths that conflict with each other, including paths where the static part can be mistaken for a parameter, e.g both /blog and /blog/:id would conflict with /:username.

As a rule of thumb, try to place path parameters at the end of the path and prefix them with the service name, e.g:

GET /blog/posts
GET /blog/posts/:id
GET /user/profile/:username
GET /user/me

Query parameters

When fetching data with GET endpoints, it's common to receive additional parameters for optional behavior, like filtering a list or changing the sort order.

When you use a struct type as the last argument in the function signature, Encore automatically parses these fields from the HTTP query string (for the GET, HEAD, and DELETE methods).

For example, if you want to have a ListBlogPosts endpoint:

type ListParams struct {
    Limit uint // number of blog posts to return
    Offset uint // number of blog posts to skip, for pagination
}

type ListResponse struct {
    Posts []*BlogPost
}

//encore:api public method=GET path=/blog
func ListBlogPosts(ctx context.Context, opts *ListParams) (*ListResponse, error) {
    // Use limit and offset to query database...
}

This could then be queried as /blog?limit=10&offset=20.

Query parameters are more limited than structured JSON data, and can only consist of basic types (string, bool, integer and floating point numbers), Encore's UUID types, and slices of those types.

Raw endpoints

In case you need to operate at a lower abstraction level, Encore supports defining raw endpoints that let you access the underlying HTTP request. This is often useful for things like accepting webhooks.

To define a raw endpoint, change the //encore:api annotation and function signature like so:

package service

import "net/http"

// Webhook receives incoming webhooks from Some Service That Sends Webhooks.
//encore:api public raw
func Webhook(w http.ResponseWriter, req *http.Request) {
    // ... operate on the raw HTTP request ...
}

Like any other Encore API endpoint, once deployed this will be exposed at the URL:
https://<env>-<app-id>.encr.app/service.Webhook. Just like regular endpoints, raw endpoints support the use of :id and *wildcard segments.

Experienced Go developers will have already noted this is just a regular Go HTTP handler. (See the net/http documentation for how Go HTTP handlers work.)

Learn more about receiving webhooks and using WebSockets in the receiving regular HTTP requests guide.

Calling APIs

Calling an API endpoint looks like a regular function call with Encore. Import the service package as a regular Go package using import "encore.app/package-name" and then call the API endpoint like a regular function. Encore will then automatically generate the necessary boilerplate at compile-time.

In the example below, we import the service package hello and call the Ping endpoint using a function call to hello.Ping.

import "encore.app/hello" // import service

//encore:api public
func MyOtherAPI(ctx context.Context) error {
    resp, err := hello.Ping(ctx, &hello.PingParams{Name: "World"})
    if err == nil {
        log.Println(resp.Message) // "Hello, World!"
    }
    return err
}

This means your development workflow is as simple as building a monolith, even if you use multiple services. You get all the benefits of function calls, like compile-time checking of all the parameters and auto-completion in your editor, while still allowing the division of code into logical components, services, and systems.

Then when building your application, Encore uses static analysis to parse all API calls and compiles them to proper API calls.

Current Request

By using Encore's current request API you can get meta-information about the current request. Including the type of request, the time the request started, the service and endpoint called and the path which was called on the service.

For more information, see the metadata documentation.

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