Event Driven Communications (EDC) w/ WebSockets
Is a server-clinet pakage that uses websockets to enable EDC.
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 tie together UUIDs. In additions, 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.
Note: Acknowledge has a few nuances and controls if the
sendEvent()resolves instantly or waits for a reply. If
"acknowledge": truethen the promise will reslove after a valid reply, or reject after a timeout | Error Event See this for more on Acknowledge
Event Chain |-----------------------------------------| | shared data | | |event-1|-->|event-2|-->|event-3| | | | | | |-->|event-N| | |-----------------------------------------|
server.onEvent'event-type',server.onAck =server.onError =
Send an Event (Server)
client.onEvent'event-type', sync cause, replyclient.onAck =client.onError =
Send an Event (Client)
new Event() from a
// event.trigger === cause.id// event.shared === cause.shared
To match any event use
'*' as the event type in the
// This will match any event. But the server|client will first try to match the event to a named one.server.onEvent'*',
Table of Contents
- Event Driven Communications (EDC) w/ WebSockets
- EDC-WS Server/Clients
- What is The Event Driven Communications (EDC) Protocol?
- Table of Contents
- Event Driven Communications (EDC) Components
- Acknowledge and Flow
- Generic Events
- Registering Routes
Event Driven Communications (EDC) Components
An Event is a JSON object defined as
Error Event Details
"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.
The version of the EDC protocoll
The type field represent the event type. It can be any string except
"acknowldegement" which are reserved.
The id field is a UUID and MUST be unique for all events
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
new events. An
event is not limited to causing only a linear chain. It is possible for one
cause to trigger multiple
cause --> event1 & event2
If an event is sent with the
"acknowledge": true flag then the recieving system MUST reply with an
acknowledgement with the
trigger field set to the
id of the sent event. Multiple replies of different events is allowed.
A --> B
B --> AAck Event
-- Or --
-- Or --
The details is any JSON object and would hold the details for the OCCURING event. It is not inteded to be used for
shared properties that relate to the chain of events.
The shared property is any JSON object. It is inteded 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
B --> A// Note the shared data is copied
A --> B// Note that the shared.step was increased
Is only used with the
"type": "error" event. It MUST be a string copy of the event that triggered the error
Acknowledge and Flow
The requirement that
"acknowledge": true event MUST have a reply leads to two thrown errors
TimeoutError. In addition,
"acknowledge": false events are asynchronous even if
await is used. This is because the promise will resolve instantly on the
TimeoutError is thrown on
"acknowledge": true if no non-error reply is recived before the after client/server timeout is reached. Since the
"acknowledge": true events expects a reply and it is not possible to wait forever it is logical that there must be a timeout and that it would be a error by the system.
AckedErrorEvent is throw on
"acknowledge": true event if an event of type
"error" is recieved in response to the sent event. The motivation for this is to allow the handling of events that were expected or NEEDED to be successful in order to continue.
Multiple Synchronous Events
Acknowledge is key in sending multiple synchronous events in which the order of recieval matters. If event
A must be before event
B, then event
A should be sent with
"acknowledge": true this would gurantee an acknowledging reply that
A was recieved and that
B could now be sent. This would be true for any length of synchronous dependant events.
[A, B, C, D, ...]
T represents the type that
details is. While the type
K represents the type that the
shared property is.
T for the ErrorEvent represents the type of
In the hopes of staying organized it is possible to register event-routes in seperate files.
Each route file would have to export an
eventType string and a
The file sturcture would look something like bellow:
src/|-- main.ts|----routes/|-- index.ts|-- route-1.ts|-- route-2.ts|-- route-3.ts
register()will add all event routes that are exported in the array that is in the
src/|-- main.ts|-----routes/|-- index.ts|-- route-1.ts|-- route-2.ts|-- route-3.ts|-----sub/|-- index.ts|-- sub-route-1.ts|-- sub-route-2.ts
It is possible to go to extreme depths using this, grouping common events together.