Multilevel Support

[mcollina]

It's time to add multilevel support into LevelGraph, so we can query a remote database from the web and/or other sources.

As far as I get it, we should just add:

db.methods = {
  graph: {
    type: 'object', 
    methods: {
      get: {type: 'async'},
      getStream: {type: 'readable'}
      //... all LevelGraph methods
    }
  }
}

And everything should 'just work': it's standard multilevel + level-manifest.

[tgvashworth]

👍 (sorry, not much more to contribute!)

[mcollina]

We are blocked by juliangruber/multilevel#41 as multilevel has not yet nested object support, but it is in a separate branch.

[mcollina]

I've added support for partial multilevel support for put, get and search. Stream are not working.

Everything is based on juliangruber/multilevel#41.

[juliangruber]

i'll release as soon as we fix this

[juliangruber]

how exactly is the stream not working? debugging via multilevel.server(db).on('data', console.log.bind(null, 'S ->')) etc helps a lot

[mcollina]

Here is the error:

  1) a multileveled triple store should put a triple with a stream:
     Uncaught Error: stream is not writable: b4d8d8fa9495684c
      at Error (<anonymous>)
      at Stream.<anonymous> (/Users/matteo/Repositories/levelgraph/node_modules/multilevel/node_modules/mux-demux/inject.js:93:19)
      at Stream.stream.write (/Users/matteo/Repositories/levelgraph/node_modules/multilevel/node_modules/mux-demux/node_modules/through/index.js:26:11)
      at write (/Users/matteo/Repositories/levelgraph/node_modules/readable-stream/lib/_stream_readable.js:586:24)
      at Array.forEach (native)
      at flow (/Users/matteo/Repositories/levelgraph/node_modules/readable-stream/lib/_stream_readable.js:597:19)
      at /Users/matteo/Repositories/levelgraph/node_modules/readable-stream/lib/_stream_readable.js:563:7
      at process._tickCallback (node.js:415:13)

It seems multilevel does not recognize that the stream is writable.
Also, put() in the nested object works even if I do not put the definition in the manifest.

Here is the output you asked for:

S -> ["b2521de8ca94c32b","close"]

S -> ["c2e379d1a4e44882","close"]

Not really useful :(.

[juliangruber]

put is there because it's part of the default levelup methods, as are get, createKeyStream etc. If you don't want these, pass false as the 2nd argument to level-manifest (https://github.com/dominictarr/level-manifest/blob/master/index.js#L33).

I'll try to look into the stream issue soon.

[mcollina]

put is not in the manifest for the nested object, but only for the
'main' db, yet it's exposed to remote calls: I'll open up a separate issue
on multilevel for this.
Nested objects are not sublevels and may not share levelup API.

[transcranial]

@mcollina we're trying to use levelgraph with multilevel in the way you reference here, by forwarding leveldb with multilevel and then initializing levelgraph on that. Attempts have been unsuccessful unfortunately. Would you have any tips to point us in the right direction, given interval changes in packages, api, etc.? Thanks!

[transcranial]

I think the above pull request should do the trick!

[mcollina]

Thanks!! :)