History playback and snapshot retrieval APIs

SignalK / specification

Signal K is a JSON-based format for storing and sharing marine data from different sources (e.g. nmea 0183, 2000, seatalk, etc)

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History playback and snapshot retrieval APIs #510

Closed tkurki closed 5 years ago

tkurki commented 5 years ago

Add query parameters to stream historical data and retrieve historical snapshot values.

tkurki commented 5 years ago

Ping @panaaj

tkurki commented 5 years ago

No longer WIP.

fabdrol commented 5 years ago

@tkurki as in this should be reviewed and merged or as in it's gone stale?

tkurki commented 5 years ago

It was WIP, no longer is and should be reviewed.

rob42 commented 5 years ago

See swagger definition at https://github.com/SignalK/signalk-java/blob/artemis/signalk-static/docs/openapi.json When https://github.com/SignalK/signalk-java/tree/artemis is installed the swaggerUI is available at http://localhost:8080/docs/

sarfata commented 5 years ago

I think an important use-case is grabbing a big chunk of data over time in one swoop, for example to draw a trace on a map or to graph speed over time.

With the current proposal, this would be very hard to do: you would have to either make a lot of HTTP calls to the snapshot retrieval API - or to the websocket API with playbackRate=100000.

Suggestion of changes to the websocket endpoint:

Add optional endTime parameter. If specified, the server will disconnect when replay (or realtime) has reached this point in time.
If playbackRate is not specified, the server will send all the data it has between startTime and endTime (or now if endTime is not specified) as fast as possible.

I think we should also support a way to let clients know what data is available but that could come separately.

tkurki commented 5 years ago

You are talking about history and/or track api. This is only for playback/snapshot retrieval.

https://github.com/SignalK/specification/issues/363 https://github.com/SignalK/specification/issues/89

tkurki commented 5 years ago

So, separate endpoints then?

tkurki commented 5 years ago

Github swallowed the conversations, but a5c4d504aa86b867be730977dae35a97dc2e59f7 and dae3fb2c3ba21af85f12515057765001d7d9ab3e use now separate endpoints.

Timestamp in the query string makes more sense to me in the api/snapshot full model case than inserting it in the path string, restful or not.