edc-events
v0.1.3
Published
Event Driven Communications Event Objects and Validation
Maintainers
jchavez443Readme
Event Driven Communications (EDC) Objects
This package contains the basic objects of the EDC protocol, the JSON schemas, & a validator.
EDC-WS Server/Clients
Is a server-clinet package that uses websockets to enable EDC and the EDC Objects. See it here on gtihub and npm
Examples:
What is The Event Driven Communications (EDC) Protocol?
Is a JSON based communications protocol that allows for the communication of events while enabling the sharing of common data between a chain of events.
The concept that one event is the cause of a new event is a first class citizen in the EDC protocol. This allows for the logical grouping of events based on the cause-effect chain by tying together UUIDs. In addition, a chain of events logically share data that is common to each event in the chain. This allows the detail of the events to live seperate from the shared chain data.
Event Chain
|-----------------------------------------|
| shared data |
| |event-1|-->|event-2|-->|event-3| |
| | |
| |-->|event-N| |
|-----------------------------------------|Examples
Event with types
type Details = { foo: string; bar: number }
type Shared = { who: string; where: string }
const event = new Event<Details, Shared>('some-event-type', {
acknowledge: true,
details: {
bar: 100,
foo: 'string here'
},
shared: {
where: 'to',
who: 'from'
}
})
// 'event' will inherit the 'Shared' property from 'cause'
const event = cause.caused('new-event', {
details: {
test: 'this',
list: 'of details from generic'
}
})
// 'event' will inherit the 'Shared' property from 'cause'
const event = new Event<Details, Shared>('new-event').inherit(cause)Error Event
const error = new ErrorEvent(event, {
cn: 'common-name',
code: 400,
data: {
foo: 'bar'
},
message: 'simple message of error'
})
const error = event.createError({
cn: 'cn',
code: 1000,
message: 'Simple message',
data: {
fish: 'boat'
}
})Ack Event
const ack = new AckEvent(event)
const ack = event.createAcknowledgment()Table of Contents
- Event Driven Communications (EDC) Objects
Event Driven Communications (EDC) Components
Event
An Event is a JSON object defined as
{
"edc" : string // Version
"type": string, // Event type
"id": string, // UUID for the event,
"trigger":? string, // UUID of the event triggering this event
"acknowledge":? boolean, // A reply is expected (synchronous) if true
"details":? {}, // Details of this event
"shared":? {} // Shared information from the chain of events, (modifiable),
}Acknowledgement Event
{
"edc": "1.0",
"type": "acknowledgement",
"id": "71e92430-77b6-48ad-899c-7a5fc769f328",
"trigger": "af0f0d3e-5c48-4265-9f3e-e37a21ff84c1"
}Error Event
{
"edc": "1.0",
"type": "error",
"id": "71e92430-77b6-48ad-899c-7a5fc769f328",
"trigger": "af0f0d3e-5c48-4265-9f3e-e37a21ff84c1",
"details": {
"code": 4083,
"cn": "common-error",
"message": "Simple message about error",
"failed": "<JSON string of failing payload>"
"data": {}
},
"shared": { shared data from erroring event },
}Error Event Details
The "details" of the error event MUST include
"cn"the common name of the error"code"the number for the error"message"the message to help understand the error"failed"the string form of the failed event"data"this field is allowed for any additional information about the error.
details: {
code: number;
cn: string;
message: string;
failed: string;
data: {} | null
}Fields
edc
The version of the EDC protocol
"edc": "1.0"type
The type field represent the event type. It can be any string except "error" and "acknowledgement" which are reserved.
Examples:
"type": "mouse-moved" "type": "transcripted" "type": "request-action" "type": "initiate-action"id
The id field is a UUID and MUST be unique for all events
trigger
The trigger is set to the event that triggered the new event. new event.trigger = cause.id
The concept is meant to build a chain of events with events becoming the cuase of new events. An event is not limited to causing only a linear chain. It is possible for one cause to trigger multiple events. cause --> event1 & event2
acknowledge
If an event is sent with the "acknowledge": true flag then the recieving system MUST reply with an event, error, or acknowledgement with the trigger field set to the id of the sent event. Multiple replies of different events is allowed.
Example:
Request
A --> B
{
"edc": "1.0",
"type": "initiate",
"id": "0a385c23-4b65-4d9f-8c78-6b7bf5ad0530",
"acknowledge": true,
}Responses
B --> A
Ack Event
{
"edc": "1.0",
"type": "acknowledgement",
"id": "71e92430-77b6-48ad-899c-7a5fc769f328",
"trigger": "0a385c23-4b65-4d9f-8c78-6b7bf5ad0530"
}-- Or --
Error Event
{
"edc": "1.0",
"type": "error",
"id": "93de2206-9669-4e07-948d-329f4b722ee2",
"trigger": "0a385c23-4b65-4d9f-8c78-6b7bf5ad0530",
"details": {
"cn": "common-error",
"code": 10983,
"message": "Common error caused my silly mistake",
"failed": "{\"type\":\"initiate\",\"id\":\"0a385c23-4b65-4d9f-8c78-6b7bf5ad0530\",\"acknowledge\":\"true\"}",
"data": {}
}
}-- Or --
Responding Event
{
"edc": "1.0",
"type": "next-event",
"id": "a201b948-4282-49e8-ae92-1c146ddd538b",
"trigger": "0a385c23-4b65-4d9f-8c78-6b7bf5ad0530"
}details
The details is any JSON object and would hold the details for the OCCURING event. It is not intended to be used for shared properties that relate to the chain of events.
shared
The shared property is any JSON object. It is intended to be used as a property that a chain of events share in common.
When an event is triggered by a cause then it SHOULD set the trigger to the cause.id and copy the cause.shared data to the new event.shared. The shared data is not immutable and can evolve.
Examples would include a connection-Id that events share incommon, a call-Id for a phone call, a survey-Id, or a start time for a chain of events.
A --> B
{
"edc": "1.0",
"type": "survey-question",
"id": "e680a8a0-ad3e-4f9e-991b-fa0fe752b8d1",
"details": {
"question": "what is your favorite programming language?"
},
"shared": {
"survey": "programming-favorites",
"step": 0
}
}B --> A
// Note the shared data is copied
{
"edc": "1.0",
"type": "survey-answer",
"id": "09d0bc49-29be-4e2e-a347-aee23f9a815b",
"trigger": "e680a8a0-ad3e-4f9e-991b-fa0fe752b8d1",
"details": {
"answer": "I love them all!"
},
"shared": {
"survey": "programming-favorites",
"step": 0
}
}A --> B
// Note that the shared.step was increased
{
"edc": "1.0",
"type": "survey-question",
"id": "9d37afee-9b68-4d8f-ae63-2bc8f9b2d7a7",
"trigger": "09d0bc49-29be-4e2e-a347-aee23f9a815b",
"details": {
"question": "Who is your favorite computer scientist?"
},
"shared": {
"survey": "programming-favorites",
"step": 1
}
}failed
Is only used with the "type": "error" event. It MUST be a string copy of the event that triggered the error
{
"edc": "1.0",
"type": "error",
"id": "93de2206-9669-4e07-948d-329f4b722ee2",
"trigger": "0a385c23-4b65-4d9f-8c78-6b7bf5ad0530",
"details": {
"cn": "common-error",
"code": 10983,
"message": "Common error caused my silly mistake",
"failed": "{\"type\":\"initiate\",\"id\":\"0a385c23-4b65-4d9f-8c78-6b7bf5ad0530\",\"acknowledge\":\"true\"}",
"data": {}
}
}Acknowledge and Flow
The requirement that "acknowledge": true event MUST have a reply leads to two thrown errors AckedErrorEvent and TimeoutError. In addition, "acknowledge": false events are asynchronous even if await is used. This is because the promise will resolve instantly on the sendEvent() as Promise<undefined>.
Multiple Synchronous Events
Acknowledge is key in sending multiple synchronous events in which the order of receival matters. If event A must be before event B, then event A should be sent with "acknowledge": true this would guarantee an acknowledging reply that A was received and that B could now be sent. This would be true for any length of synchronous dependent events. A before B, B before C, C before D, etc.... [A, B, C, D, ...]
Generic Events
Event<T, K>
The type T represents the type that details is. While the type K represents the type that the shared property is.
type T = { foo: string }
type K = { baz: string }
const event = new Event<T, K>('event-type', {
details: {
// type T
foo: 'bar'
},
shared: {
// type K
baz: 'taz'
}
})ErrorEvent
The type T for the ErrorEvent represents the type of error.details.data
type T = { foo: string }
const error = new ErrorEvent<T>({
cn: 'cn',
code: 9999,
message: 'simple message',
failed: failedEventStr,
data: {
// type T
foo: 'bar'
}
})