w3aio

This is the beginning of an asyncio version of the Ethereum Web3 libraries. This system has been written in Python3.6.

More usage and explanations of code coming soon!

Why This Library was Written

At Mimir, we have been building systems that work with the Ethereum blockchain for some time. What we found was that Python is an amazing language but, at some level of complexity things can get... messy. See below:

As an aside, you can see more amazing comics at xkcd.

The Hard Lessons

Duck Typing is Both Wonderful and Terrible

What we found was that although duck typing is great, mixing duck typing with strong typing has it's downsides. It often left our code feeling brittle and uncoordinated. Things like

some_hex_string.replace('0x','').lower() == some_other_hex_string.replace('0x','').lower()

started to litter our code. Refactors cleaned this up, but there was always some edge case that worked its way back into the code. This got us thinking... what if all solidity types were objects, that knew how to add, compare, iterate, and encode themselves? Then, all of that mess could be contained in one place and not spread like a terrible virus. So we built a psuedo-strong typing system.

Stateful Filtering on the Node is a Bad Idea

When PubSub was added to the JSONRPC spec of Ethereum, we were like giddy children. Such a great new toy! Imagine the possibilities! What we found was that, when you mix websockets, load balancers, stateful server side filters, and production code... you get a nightmare. So all filtering is done using client side polling of the server. We also found some clients left the proc filesystem a little messy... almost memory leaky. This is also scary. So we said,

No more server side filters!
From thence day forth, all block filtering shall be done
on the client side, using a long poll and callbacks!

... and life has been better since.

Connection Objects Should Eat from a Queue

You know, graceful reconnection, backpressure, and what not.

Async

Async code is hard, but powerful. Writing server side systems that play well with the blockchain means async or parrellel. Parrellel is better left to things like rust, but Python does async well (at least since 3.5). In order to make synchronous code async via threading, you have to get all mutex-y. Although it can be done, when dealing with dining philosophers it is easy to have one starve or at least have one start an argument. So we decided to go async all the way.

Multiplexing

Writing a multiplexor is fun! In Python, it also is easy to make a huge memory hog. So rather than build a complex multiplexor, use only call response commands and never PubSub. Then you can call your transport object like this:

async def call(self,msg):
  await self.ws.write(msg)
  response = await self.ws.read()
  return response

and no multiplexor is needed.

Usage

Usage goes here!