Real time resources for agencies

[DylanVanAssche]

This PR adds the :agency/events resource to the Linked Connections Server.
If a client connects to the resource, the server will check if the client is:

• A SSE client: add it to the listeners and pushes all the missing information since the last time the client synced with server. By watching the files directory of the events storage (generated by the EventsManager), the clients receive pushes from the server.
• A HTTP client: serves the events page related to the last time the client synced with the server. The client can follow the hydra:next properties to get the next page of events to get in sync with the server. The lastSyncTime is used to lookup the required page and add the hydra metadata to it.

Besides this resource, this PR also adds the possibility to cancel a complete trip based on its tripURI. If you supply a startingConnection the trip can be cancelled from that connection until the end. If you don't supply this argument to cancelTrip(tripURI, agency, dataset, startingConnection=null), the whole trip will be cancelled from the beginning until the end.

TO DO list finished:

• Binary search to lookup the events pages.
• Ignore big sync requests, the client can asks to sync with the server with a time range of almost infinity. This might lock up the server when too many clients are doing this.
• Fix the skeleton of SSE, we don't need any hydra metadata in there.

[DylanVanAssche]

@julianrojas87 I think I have fixed your last remarks, review?

[julianrojas87]

Given the last updates made to the code base, I will manually extract the contributions made on this PR and adapt them accordingly

[DylanVanAssche]

Given the last updates made to the code base, I will manually extract the contributions made on this PR and adapt them accordingly

Fine for me!

[pietercolpaert]

Small update on this one: we are thinking more thoroughly about the hypermedia design, and including a possibility for a new Linked Data Event Streams resource on top of the existing collections

[DylanVanAssche]

@pietercolpaert Linked Data Event Streams would make a nice fit here I think 👍

[pietercolpaert]

@DylanVanAssche While this pull request and the work behind your master thesis was instrumental to get to the LC2.0 specification, I think we will close this pull request in favour of #79, in which we implement a full-history polling interface for the connections with hypermedia descriptions that follow the LDES/TREE specifications. Would you be available to review the code they have so far?

[DylanVanAssche]

@DylanVanAssche While this pull request and the work behind your master thesis was instrumental to get to the LC2.0 specification, I think we will close this pull request in favour of #26, in which we implement a full-history polling interface for the connections with hypermedia descriptions that follow the LDES/TREE specifications. Would you be available to review the code they have so far?

Sure! I think you mean #79 ? right?

[pietercolpaert]

Yes! Edited ↑