The Event Gateway combines both API Gateway and Pub/Sub functionality into a single event-driven experience. It's dataflow for event-driven, serverless architectures. It routes Events (data) to Functions (serverless compute). Everything it cares about is an event! Even calling a function. It makes it easy to share events across different systems, teams and organizations!
Use the Event Gateway right now, by running the Event Gateway Example Application locally, with the Serverless Framework.
Features:
- Platform agnostic - All your cloud services are now compatible with one another: share cross-cloud functions and events with AWS Lambda, Microsoft Azure, IBM OpenWhisk and Google Cloud Platform.
- Send events from any cloud - Data streams in your application become events. Centralize events from any cloud provider to get a bird’s eye view of all the data flowing through your cloud.
- React to cross-cloud events - You aren’t locked in to events and functions being on the same provider: Any event, on any cloud, can trigger any function. Set events and functions up like dominoes and watch them fall.
- Expose events to your team - Share events and functions to other parts of the application. Your teammates can find them and utilize them in their own services.
- Extendable through middleware - Perform data transforms, authorizations, serializations, and other custom computes straight from the Event Gateway.
The Event Gateway is a L7 proxy and realtime dataflow engine, intended for use with Functions-as-a-Service on AWS, Azure, Google & IBM.
The project is under heavy development. The APIs will continue to change until we release a 1.0.0 version. It's not yet ready for production applications.
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- Quick Start
- Motivation
- Components
- Events API
- Configuration API
- System Events
- Plugin System
- Client Libraries
- Versioning
- Comparison
- Architecture
- Background
The easiest way to get started with the Event Gateway is using the Serverless Framework. The framework is setup to automatically download and install the Event Gateway during development of a serverless service.
Check out Event Gateway Example Application for a walkthrough of using the Event Gateway locally.
If you want to install and develop with the Event Gateway without the Serverless Framework, instructions can be found here.
- It is cumbersome to plug things into each other. This should be easy! Why do I need to set up a queue system to keep track of new user registrations or failed logins?
- Introspection is terrible. There is no performant way to emit logs and metrics from a function. How do I know a new piece of code is actually working? How do I feed metrics to my existing monitoring system? How do I plug this function into to my existing analytics system?
- Using new functions is risky without the ability to incrementally deploy them.
- The AWS API Gateway is frequently cited as a performance and cost-prohibitive factor for using AWS Lambda.
Discover and call serverless functions from anything that can reach the Event Gateway. Function Discovery supports the following function types:
- FaaS functions (AWS Lambda, Google Cloud Functions, Azure Functions, OpenWhisk Actions)
- HTTP endpoints/Webhook (e.g. POST http://example.com/function)
Function Discovery stores information about functions allowing the Event Gateway to call them as a reaction to received event.
curl --request POST \
--url http://localhost:4001/v1/functions \
--header 'content-type: application/json' \
--data '{
"functionId": "hello",
"provider":{
"type": "awslambda",
"arn": "arn:aws:lambda:us-east-1:377024778620:function:bluegreen-dev-hello",
"region": "us-east-1"
}
}'const eventGateway = fdk.eventGateway({ url: 'http://localhost' })
eventGateway.registerFunction({
functionId: "sendEmail"
provider: {
type: "awslambda"
arn: "xxx",
region: "us-west-2",
}
})curl --request POST \
--url http://localhost:4000/ \
--header 'content-type: application/json' \
--header 'event: invoke' \
--header 'function-id: createUser' \
--data '{ "name": "Max" }'const eventGateway = fdk.eventGateway({ url: "http://localhost" });
eventGateway.invoke({
functionId: "createUser",
data: { name: "Max" }
});Lightweight pub/sub system. Allows functions to asynchronously receive custom events. Instead of rewriting your functions every time you want to send data to another place, this can be handled entirely in configuration using the Event Gateway. This completely decouples functions from one another, reducing communication costs across teams, eliminates effort spent redeploying functions, and allows you to easily share events across functions, HTTP services, even different cloud providers. Functions may be registered as subscribers to a custom event. When an event occurs, all subscribers are called asynchronously with the event as its argument.
Creating a subscription requires providing ID of registered function, an event type and a path (/ by default). The
path property indicated URL path which Events API will be listening on.
curl --request POST \
--url http://localhost:4001/v1/subscriptions \
--header 'content-type: application/json' \
--data '{
"functionId": "sendEmail",
"event": "user.created",
"path": "/myteam"
}'const eventGateway = fdk.eventGateway({ url: "http://localhost" });
eventGateway.subscribe({
event: "user.created",
functionId: "sendEmail",
path: "/myteam"
});sendEmail function will be invoked for every user.created event to <Events API>/myteam endpoint.
curl --request POST \
--url http://localhost:4000/ \
--header 'content-type: application/json' \
--header 'event: user.created' \
--data '{ "name": "Max" }'const eventGateway = fdk.eventGateway({ url: "http://localhost" });
eventGateway.emit({
event: "user.created",
data: { name: "Max" }
});Custom event subscriptions are asynchronous. There is a special http event type for creating synchronous
subscriptions. http event is an HTTP request received to specified path and for specified HTTP method. There can be
only one http subscription for the same method and path pair.
curl --request POST \
--url http://localhost:4001/v1/subscriptions \
--header 'content-type: application/json' \
--data '{
"functionId": "listUsers",
"event": "http",
"method": "GET",
"path": "/users"
}'const eventGateway = fdk.eventGateway({ url: "http://localhost" });
eventGateway.subscribe({
functionId: "listUsers",
event: "http",
method: "GET",
path: "/users"
});listUsers function will be invoked for every HTTP GET request to <Events API>/users endpoint.
The Event Gateway exposes an API for emitting events. Events API can be used for emitting custom event, HTTP events and
for invoking function. By default Events API runs on :4000 port.
All data that passes through the Event Gateway is formatted as an Event, based on our default Event schema:
event-string- the event nameid-string- the event's instance universally unique ID (provided by the event gateway)receivedAt-number- the time (milliseconds) when the Event was received by the Event Gateway (provided by the event gateway)data- type depends ondataType- the event payloaddataType-string- the mime type ofdatapayload
Example:
{
"event": "myapp.user.created",
"id": "66dfc31d-6844-42fd-b1a7-a489a49f65f3",
"receivedAt": 1500897327098,
"data": { "foo": "bar" },
"dataType": "application/json"
}When an event occurs, all subscribers are called with the event in above schema as its argument.
The MIME type of the data block can be specified using the Content-Type header (by default it's
application/octet-stream). This allows the event gateway to understand how to deserialize the data block if it needs
to. In case of application/json type the event gateway passes JSON payload to the target functions. In any other case
the data block is base64 encoded.
http event is a built-in type of event occurring for HTTP requests on paths defined in HTTP subscriptions. The
data field of an http event has the following structure:
path-string- request pathmethod-string- request methodheaders-object- request headershost-string- request hostquery-object- query parametersparams-object- matched path parametersbody- depends onContent-Typeheader - request payload
invoke is a built-in event type allowing synchronous invocations. Function will react to this event only if there is a
subscription created beforehand.
Creating a subscription requires path property (by default it's "/"). path indicates path under which you can push.
Endpoint
POST <Events API URL>/<Subscription Path>
Request Headers
Event-string- required, event nameContent-Type-MIME type string- payload type
Request
arbitrary payload, subscribed function receives an event in Event schema
Response
Status code:
202 Accepted
Creating HTTP subscription requires method and path properties. Those properties are used to listen for HTTP events.
Endpoint
<method> <Events API URL>/<path>
Request
arbitrary payload, subscribed function receives an event in HTTP Event schema.
Response
Status code:
200 OKwith payload with function response
By default cross-origin resource sharing (CORS) is disabled for http subscriptions. It can be enabled and configured
per-subscription basis.
Event Gateway handles preflight OPTIONS requests for you. You don't need to setup subscription for OPTIONS method
because the Event Gateway will respond with all appropriate headers.
The Event Gateway allows creating HTTP subscription with parameterized paths. Every path segment prefixed with : is
treated as a parameter, e.g. /users/:id.
The Event Gateway prevents from creating subscriptions in following conflicting situations:
- registering static path when there is parameterized path registered already (
/users/:idvs./users/foo) - registering parameterized path with different parameter name (
/users/:idvs./users/:name)
Key and value of matched parameters are passed to a function in an HTTP Event under params field.
Special type of path parameter is wildcard parameter. It's a path segment prefixed with *. Wildcard parameter can only
be specified at the end of the path and will match every character till the end of the path. For examples
parameter /users/*userpath for request path /users/group1/user1 will match group1/user1 as a userpath parameter.
To respond to an HTTP event a function needs to return object with following fields:
statusCode-int- response status code, default: 200headers-object- response headersbody-string- response body
Currently, the event gateway supports only string responses.
Endpoint
POST <Events API URL>/
Request Headers
Event-string-"invoke"Function-ID-string- ID of a function to call
Request
arbitrary payload, invoked function receives an event in above schema, where request payload is passed as data field
Response
Status code:
200 OKwith payload with function response
Events API supports CORS requests which means that any origin can emit a custom event. In case of http events CORS is
configured per-subscription basis.
The Event Gateway exposes a RESTful JSON configuration API. By default Configuration API runs on :4001 port.
Endpoint
POST <Configuration API URL>/v1/functions
Request
JSON object:
functionId-string- required, function nameprovider-object- required, provider specific information about a function, depends on type:- for AWS Lambda:
type-string- required, provider type:awslambdaarn-string- required, AWS ARN identifierregion-string- required, region nameawsAccessKeyId-string- optional, AWS API key ID. By default credentials from the environment are used.awsSecretAccessKey-string- optional, AWS API access key. By default credentials from the environment are used.awsSessionToken-string- optional, AWS session token
- for HTTP function:
type-string- required, provider type:httpurl-string- required, the URL of an http or https remote endpoint
- for AWS Lambda:
Response
Status code:
200 OKon success400 Bad Requeston validation error
JSON object:
functionId-string- function nameprovider-object- provider specific information about a function
Endpoint
PUT <Configuration API URL>/v1/functions/<function id>
Request
JSON object:
provider-object- required, provider specific information about a function, depends on type:- for AWS Lambda:
type-string- required, provider type:awslambdaarn-string- required, AWS ARN identifierregion-string- required, region nameawsAccessKeyId-string- optional, AWS API key IDawsSecretAccessKey-string- optional, AWS API keyawsSessionToken-string- optional, AWS session token
- for HTTP function:
type-string- required, provider type:httpurl-string- required, the URL of an http or https remote endpoint
- for AWS Lambda:
Response
Status code:
200 OKon success400 Bad Requeston validation error404 Not Foundif function doesn't exists
JSON object:
functionId-string- function nameprovider-object- provider specific information about a function
Delete all types of functions. This operation fails if the function is currently in-use by a subscription.
Endpoint
DELETE <Configuration API URL>/v1/functions/<function id>
Response
Status code:
204 No Contenton success404 Not Foundif function doesn't exists
Endpoint
GET <Configuration API URL>/v1/functions
Response
Status code:
200 OKon success
JSON object:
functions-arrayofobject- functions:functionId-string- function nameprovider-object- provider specific information about a function
Endpoint
POST <Configuration API URL>/v1/subscriptions
Request
event-string- event namefunctionId-string- ID of function to receive eventsmethod-string- optional, in case ofhttpevent, HTTP method that accepts requestspath-string- optional, in case ofhttpevent, path that accepts requests, it starts with "/"cors-object- optional, in case ofhttpevent, By default CORS is disabled. When set to empty object CORS configuration will use default values for all fields below. Available fields:origins-arrayofstring- list of allowed origins. An origin may contain a wildcard (*) to replace 0 or more characters (i.e.: http://*.domain.com), default:*methods-arrayofstring- list of allowed methods, default:HEAD,GET,POSTheaders-arrayofstring- list of allowed headers, default:Origin,Accept,Content-TypeallowCredentials-bool- default: false
Response
Status code:
200 OKon success400 Bad Requeston validation error
JSON object:
subscriptionId-string- subscription IDevent-string- event namefunctionId- ID of functionmethod-string- optional, in case ofhttpevent, HTTP method that accepts requestspath-string- optional, in case ofhttpevent, path that accepts requests, starts with/cors-object- optional, in case ofhttpevent, CORS configuration
Endpoint
DELETE <Configuration API URL>/v1/subscriptions/<subscription id>
Response
Status code:
204 No Contenton success404 Not Foundif subscription doesn't exists
Endpoint
GET <Configuration API URL>/v1/subscriptions
Response
Status code:
200 OKon success
JSON object:
subscriptions-arrayofobject- subscriptionssubscriptionId-string- subscription IDevent-string- event namefunctionId- ID of functionmethod-string- optional, in case ofhttpevent, HTTP method that accepts requestspath-string- optional, in case ofhttpevent, path that accepts requestscors-object- optional, in case ofhttpevent, CORS configuration
Dummy endpoint (always returning 200 OK status code) for checking if the event gateway instance is running.
Endpoint
GET <Configuration API URL>/v1/status
System Events are special type of events emitted by the Event Gateway instance. They are emitted on each stage of event processing flow starting from receiving event to function invocation end. Those events are:
gateway.event.received- the event is emitted when an event was received by Events API. Data fields:event- event payloadpath- Events API pathheaders- HTTP request headers
gateway.function.invoking- the event emitted before invoking a function. Data fields:event- event payloadfunctionId- registered function ID
gateway.function.invoked- the event emitted after successful function invocation. Data fields:event- event payloadfunctionId- registered function IDresult- function response
gateway.function.invocationFailed- the event emitted after failed function invocation. Data fields:event- event payloadfunctionId- registered function IDerror- invocation error
The Event Gateway is built with extensibility in mind. Built-in plugin system allows reacting on system events and manipulate how an event is processed through the Event Gateway.
Current implementation supports plugins written only in Golang. We plan to support other languages in the future.
Plugin system is based on go-plugin. A plugin needs to implement the following interface:
type Reacter interface {
Subscriptions() []Subscription
React(event event.Event) error
}Subscription model indicates the event that plugin subscribes to and the subscription type. A subscription can be either
sync or async. Sync (blocking) subscription means that in case of error returned from React method the event won't be
further processed by the Event Gateway.
React method is called for every system event that plugin subscribed to.
For more details, see the example plugin.
This project uses Semantic Versioning 2.0.0. We are in initial development phase right now (v0.X.Y). The public APIs should not be considered stable. Every breaking change will be listed in the release changelog.
- it's not a replacement for message queues (no message ordering, currently weak durability guarantees only)
- it's not a replacement for streaming platforms (no processing capability and consumers group)
- it's not a replacement for existing service discovery solutions from the microservices world
The Event Gateway is NOT a FaaS platform. It integrates with existing FaaS providers (AWS Lambda, Google Cloud Functions, Azure Functions, OpenWhisk Actions). The Event Gateway enables building large serverless architectures in a unified way across different providers.
┌──────────────┐
│ │
│ Client │
│ │
└──────────────┘
▲
│
Event
│
▼
┌───────────────────────────────────────────────────────────┐
│ │
│ Event Gateway Cluster │
│ │
└───────────────────────────────────────────────────────────┘
▲
│
│
┌─────────────────────────────┼─────────────────────────────┐
│ │ │
│ │ │
▼ ▼ ▼
┌───────────────┐ ┌───────────────┐ ┌───────────────┐
│ AWS Lambda │ │ Google Cloud │ │Azure Function │
│ Function │ │ Function │ │ │
│ │ │ │ │ Region: │
│ Region: │ │ Region: │ │ West US │
│ us-east-1 │ │ us-central1 │ │ │
└───────────────┘ └───────────────┘ └───────────────┘
The Event Gateway instances use a strongly consistent, subscribable DB (initially etcd, with support for Consul, and Zookeeper planned) to store and broadcast configuration. The instances locally cache configuration used to drive low-latency event routing. The instance local cache is built asynchronously based on events from backing DB.
The Event Gateway is a horizontally scalable system. It can be scaled by adding instances to the cluster. A cluster is a group of instances sharing the same database. A cluster can be created in one cloud region, across multiple regions, across multiple cloud provider or even in both cloud and on-premise data centers.
The Event Gateway is a stateless service and there is no direct communication between different instances. All configuration data is shared using backing DB. If the instance from region 1 needs to call a function from region 2 the invocation is not routed through the instance in region 2. The instance from region 1 invokes the function from region 2 directly.
┌─────────────────────────────────────────────Event Gateway Cluster──────────────────────────────────────────────┐
│ │
│ │
│ Cloud Region 1───────┐ │
│ │ │ │
│ │ ┌─────────────┐ │ │
│ │ │ │ │ │
│ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─│─ ▶│etcd cluster │◀ ┼ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ │
│ │ │ │ │ │ │
│ │ │ └─────────────┘ │ │
│ │ ▲ │ │ │
│ │ │ │ │
│ Cloud Region 2───────┐ │ │ │ Cloud Regio│ 3───────┐ │
│ │ │ │ │ │ │ │ │
│ │ ▼ │ │ ▼ │ │ ▼ │ │
│ │ ┌───────────────┐ │ │ ┌──────────────┐ │ │ ┌──────────────┐ │ │
│ │ │ │ │ │ │ │ │ │ │ │ │ │
│ │ │ Event Gateway │ │ │ │Event Gateway │ │ │ │Event Gateway │ │ │
│ │ │ instance │◀┼──────────┐ │ │ instance │◀─┼──────────┐ │ │ instance │ │ │
│ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │
│ │ └───────────────┘ │ │ │ └──────────────┘ │ │ │ └──────────────┘ │ │
│ │ ▲ │ │ │ ▲ │ │ │ ▲ │ │
│ │ │ │ │ │ │ │ │ │ │ │ │
│ │ │ │ │ │ │ │ │ │ │ │ │
│ │ ▼ │ │ │ ▼ │ │ │ ▼ │ │
│ │ ┌───┐ │ │ │ ┌───┐ │ │ │ ┌───┐ │ │
│ │ │ λ ├┐ │ └───┼───────▶│ λ ├┐ │ └────┼───────▶│ λ ├┐ │ │
│ │ └┬──┘│ │ │ └┬──┘│ │ │ └┬──┘│ │ │
│ │ └───┘ │ │ └───┘ │ │ └───┘ │ │
│ └────────────────────┘ └────────────────────┘ └────────────────────┘ │
│ │
│ │
└────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
SOA came along with a new set of challenges. In monolithic architectures, it was simple to call a built-in library or rarely-changing external service. In SOA it involves much more network communication which is not reliable. The main problems to solve include:
- Where is the service deployed? How many instances are there? Which instance is the closest to me? (service discovery)
- Requests to the service should be balanced between all service instances (load balancing)
- If a remote service call failed I want to retry it (retries)
- If the service instance failed I want to stop sending requests there (circuit breaking)
- Services are written in multiple languages, I want to communicate between them using the best language for the particular task (sidecar)
- Calling remote service should not require setting up new connection every time as it increases request time (persistent connections)
The following systems are solutions those problems:
The main goal of those tools is to manage the inconveniences of network communication.
The greatest benefit of serverless/FaaS is that it solves almost all of above problems:
- service discovery: I don't care! I have a function name, that's all I need.
- load balancing: I don't care! I know that there will be a function to handle my request (blue/green deployments still an issue though)
- retries: It's highly unusual that my request will not proceed as function instances are ephemeral and failing function is immediately replaced with a new instance. If it happens I can easily send another request. In case of failure, it's easy to understand what is the cause.
- circuit breaking: Functions are ephemeral and auto-scaled, low possibility of flooding/DoS & cascading failures.
- sidecar: calling function is as simple as calling method from cloud provider fdk.
- in FaaS setting up persistent connection between two functions defeats the purpose as functions instances are ephemeral.
Tools like Envoy/Linkerd solve different domain of technical problems that doesn't occur in serverless space. They have a lot of features that are unnecessary in the context of serverless computing.
Service discovery problems may be relevant to serverless architectures, especially when we have a multi-cloud setup or we want to call a serverless function from a legacy system (microservices, etc...). There is a need for some proxy that will know where the function is actually deployed and have retry logic built-in. Mapping from function name to serverless function calling metadata is a different problem from tracking the availability of a changing number of service instances. That's why there is a room for new tools that solves function discovery problem rather than the service discovery problem. Those problems are fundamentally different.