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Mini P

Mini P (Berlin slang for mini pizza) is a simple database that can replicate with CouchDB.

This is an experimental project. If you're looking for something to use in production, consider PouchDB.

Build Status

Adapters

Mini P provides two adapters by now:

  • MemoryP - in memory store
  • HttpP - talks to a real CouchDB

both share the same interface.

API

The API is just two methods:

  • read(options)
  • write(docs, options)

(and a reset used for testing)

Options

  • For read you pass { revs: true } and get _revisions included in the documents
  • For write you can pass { new_edits: false } to circumvent optimistic locking

Pull Streams

You can create pull-streams out of an adapter by calling stream.reader(db) or stream.writer(db).

Replication

For replication you just pipe a reader stream into a writer stream:

pull(
  stream.reader(source)({ revs: true }),
  stream.writer(target)({ new_edits: false })
)

The CouchDB replication protocol replicates documents via the changes feed. This replication, though, is based on allDocs by now.

Dependencies

Mini P requires Node v8.
HttpP adapter only works with CouchDB 2 (relies on _bulk_get).
The only npm dependency is request, which is used for the HttpP adapter.

Example

import { HttpP, MemoryP, stream } from 'minip'
import pull from 'pull-stream'
import onEnd from 'pull-stream/sinks/on-end'

const local = new MemoryP()
const remote = new HttpP('http://localhost:5984/mydb')

// write to local database
local.write([{ _id: 'foo', bar: 'baz' }], (error, response) => {
  // replicate local to remote
  pull(
    stream.reader(source)({ revs: true }),
    stream.writer(target)({ new_edits: false }),
    onEnd(() => {
      // once finished, query remote db
      remote.read((error, [doc]) => {
        // {
        //   _id: 'foo',
        //   _rev: '1-b3cec23b98d5f20d20a8279878ddce3d',
        //   bar: 'baz'
        // }
      })
    })
  )
})

State of Mini P

What Works

  • Store and retrieve a bunch of docs
  • Store docs with new_edits: false.
  • Get docs with revs: true
  • Update a doc, increment _rev
  • choose winning rev
  • replicating a whole database
  • merge _revisions tree on new_edits:false

What does not work

Everything else.

No changes feed. No views. Almost no error handling. No deletes. No checkpointing. No revs diff. Hah: no attachments for sure.

Development

The development process is pretty straight forward:

  • Write a test and works with HttpP break MemoryP
  • Fix MemoryP

Tests

Additionaly to npm test a npm run test:perf task provides you with some numbers for throughput.

All tests run against all adapters. Replication is tested across all adapter combinations.

(c) 2018 J. J. Schmidt