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| # The Icepeak Multiple-Subcription-Single-Connection Protocol | ||
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| This protocol was developed atop the existing protocol to allow the client to subscribe to multiple "paths"/"topics" using a single websocket connection. | ||
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| Whereas the original existing protocol required a new websocket connection for each path the client wanted to subscribe to. | ||
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| # Initial Connection | ||
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| A client can connect to a multiple-subscription protocol connection with a URL such as: | ||
| `ws://yourdomain.com/?method=reusable` | ||
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| The URL path: | ||
| - points to the root of your icepeak service | ||
| - has the query parameter `method` set to `reusable` | ||
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| The authorisation mechanism is a "subscription deadline timout": Initial websocket connection does not need authorisation, but if the client does not subscribe to a client before the server-configured timeout, then the connection will be closed un-politely, i.e the server will not send a WS close control message. | ||
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| Timeout is set by the `--first-subscription-deadline-timeout` flag, the input is in terms of microseconds, the default value is `1000000` (1 second). | ||
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| # Subscribing, Unsubscribing & Updates | ||
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| In summary: | ||
| - The client can request to subscribe to an array of paths. | ||
| - The client, on the single connection, can cumulatively keep subscribing and unsubscribing to paths by sending corresponding payloads. | ||
| - The server also sends back a response about the status, and some data of the corresponding subscription or unsubscription request. | ||
| - The server will send the client the new value/update at the subscribed path whenever there is a change at that path. | ||
| - Both, subscription and unsubscription requests are idempotent, in terms of the effect on the state of the server, actual response received from client varies depending on the state of the server. | ||
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| ## Update | ||
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| `JSON Schema` declaration of the update the server will send to the client upon subscribed path change: | ||
| ```javascript | ||
| { | ||
| "$schema": "https://json-schema.org/draft/2020-12/schema", | ||
| "$id": "wss://updates.channable.com", | ||
| "title": "Path changes", | ||
| "description": "Indicates changes occurred at the subscribed paths", | ||
| "type": "object", | ||
| "properties": { | ||
| "type": { "const": "update" }, | ||
| "path": { "type": "string" }, | ||
| "value": {} | ||
| } | ||
| } | ||
| ``` | ||
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| Example: | ||
| ```javascript | ||
| { | ||
| "type": "update", | ||
| "path": "path/to/value", | ||
| "value": <any-type> | ||
| } | ||
| ``` | ||
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| ## Subscribe | ||
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| In summary: | ||
| - The client can send a payload that contains an array of paths to subscribe to. | ||
| - The client has to send a JWT that authorises all the paths. | ||
| - The client can expect a response from the server that contains the status/acknowledgement of the request. | ||
| - Upon a successful request, the client can expect the payload to also contain the current value of the paths requested. | ||
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| ### Client Subscribe Request | ||
| Each subscription is checked against a JWT to see if the user is authorised to access the path(s). | ||
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| `JSON Schema` declaration of the subscribe client request: | ||
| ```javascript | ||
| { | ||
| "$schema": "https://json-schema.org/draft/2020-12/schema", | ||
| "$id": "wss://updates.channable.com/", | ||
| "title": "Add subscription", | ||
| "description": "Adding an additional subscription", | ||
| "type": "object", | ||
| "properties": { | ||
| "type": { "const": "subscribe" }, | ||
| "paths": { "type": "array", "items": { "type": "string" } }, | ||
| "token": { "type": "string" } | ||
| } | ||
| } | ||
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| ``` | ||
| Example: | ||
| ```javascript | ||
| { | ||
| "type": "subscribe", | ||
| "paths": [ "path/one", "path/two", "otherpath" ], | ||
| "token": "eyJ..." | ||
| } | ||
| ``` | ||
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| ### Server Subscribe Response | ||
| The server sends back a payload to the client. The payload will always contain a status code: | ||
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| | Status code | When | | ||
| | ---- | -------------------------------------------- | | ||
| | 200 | Subscription was successfully processed | | ||
| | 400 | Request payload was malformed | | ||
| | 401 | No authorization token provided | | ||
| | 403 | Authorization token was rejected / malformed | | ||
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| If the status code is `200` and **whether or not the client is already subscribed**, the client can expect a payload from server that contains: | ||
| - The status code. | ||
| - Path(s) of the subscription requested. | ||
| - The current value(s) of that path(s). | ||
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| `JSON Schema` declaration of the server response: | ||
| ```javascript | ||
| { | ||
| "$schema": "https://json-schema.org/draft/2020-12/schema", | ||
| "$id": "wss://updates.channable.com", | ||
| "title": "Subscription status", | ||
| "description": "Indicates whether the subscription was successful", | ||
| "type": "object", | ||
| "properties": { | ||
| "type": { "const": "subscribe" }, | ||
| "paths": { | ||
| "type": "array", | ||
| "path": { | ||
| "type": "object", | ||
| "properties": { | ||
| "path": { "type": "string" }, | ||
| "value": {} | ||
| } | ||
| } | ||
| }, | ||
| "code": { "type": "number" }, | ||
| "message": { "type": "string" }, | ||
| "extra": {} | ||
| } | ||
| } | ||
| ``` | ||
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| Example success: | ||
| ```javascript | ||
| { | ||
| "type": "subscribe", | ||
| "paths": [ | ||
| { "path": "path/one", "value": val }, | ||
| { "path": "path/two", "value": val2 }, | ||
| { "path": "otherpath", "value": val3 }, | ||
| ], | ||
| "code": 200, | ||
| "message": "You've been successfully subscribed to the paths", | ||
| "extra": {} | ||
| } | ||
| ``` | ||
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| ## Unsubscribe | ||
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| In summary: | ||
| - The client can send a payload that contains paths to unsubscribe from. | ||
| - The client can expect a response from the server that contains the status/acknowledgement of the request, and paths unsubscribed from. | ||
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| ### Client Unsubscribe Request | ||
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| `JSON Schema` declaration of the unsubscribe client request: | ||
| ```javascript | ||
| { | ||
| "$schema": "https://json-schema.org/draft/2020-12/schema", | ||
| "$id": "wss://updates.channable.com", | ||
| "title": "Remove Subscription", | ||
| "description": "Remove an existing subscription", | ||
| "type": "object", | ||
| "properties": { | ||
| "type": { "const": "unsubscribe" }, | ||
| "paths": { "type": "array", "items": { "type": "string" } } | ||
| } | ||
| } | ||
| ``` | ||
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| Example unsubscribe request: | ||
| ```javascript | ||
| { | ||
| "type": "unsubscribe", | ||
| "paths": [ "path/one", "path/two", "path/three" ], | ||
| } | ||
| ``` | ||
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| ### Server Unsubscribe Response | ||
| The server sends back a payload to the client. The payload will always contain a status code: | ||
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| | Status code | When | | ||
| | ------------- | -------------------------------- | | ||
| | 200 | Unsubscription was successfully processed | | ||
| | 400 | Request payload was malformed | | ||
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| If the status code is `200`, the client can expect a payload from server that contains: | ||
| - the list of paths that the client had been meaningfully unsubscribe from, i.e only the paths that the client had subscribed to. | ||
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| `JSON Schema` declaration of the unsubscribe client request: | ||
| ```javascript | ||
| { | ||
| "$schema": "https://json-schema.org/draft/2020-12/schema", | ||
| "$id": "wss://updates.channable.com", | ||
| "title": "Unsubscription status", | ||
| "description": "Indicates whether the unsubscription was successful", | ||
| "type": "object", | ||
| "properties": { | ||
| "type": { "const": "unsubscribe" }, | ||
| "paths": { "type": "array", "items": { "type": "string" } }, | ||
| "code": { "type": "number" }, | ||
| "message": { "type": "string" }, | ||
| "extra": {} | ||
| } | ||
| } | ||
| ``` | ||
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| Example succesful unsubscribe response: | ||
| ```javascript | ||
| { | ||
| "type": "unsubscribe", | ||
| "paths": [ "path/one", "path/two" ], | ||
| "code": 200, | ||
| "message": "You've been successfully unsubscribed from the paths", | ||
| "extra": {} | ||
| } | ||
| ``` | ||
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| # Invalid Client Message | ||
| The server will close the websocket connection with an informative message if the client payload is not recognised. |
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