btcproxy.py

""" A bitcoind proxy that allows instrumentation and canned responses
"""
from flask import Flask, request
from bitcoin.rpc import JSONRPCError
from bitcoin.rpc import RawProxy as BitcoinProxy
from utils import BitcoinD
from cheroot.wsgi import Server
from cheroot.wsgi import PathInfoDispatcher

import decimal
import flask
import json
import logging
import os
import threading


class DecimalEncoder(json.JSONEncoder):
    """By default json.dumps does not handle Decimals correctly, so we override it's handling
    """
    def default(self, o):
        if isinstance(o, decimal.Decimal):
            return float(o)
        return super(DecimalEncoder, self).default(o)


class ProxiedBitcoinD(BitcoinD):
    def __init__(self, bitcoin_dir, proxyport=0):
        BitcoinD.__init__(self, bitcoin_dir, rpcport=None)
        self.app = Flask("BitcoindProxy")
        self.app.add_url_rule("/", "API entrypoint", self.proxy, methods=['POST'])
        self.proxyport = proxyport
        self.mocks = {}

    def _handle_request(self, r):
        conf_file = os.path.join(self.bitcoin_dir, 'bitcoin.conf')
        brpc = BitcoinProxy(btc_conf_file=conf_file)
        method = r['method']

        # If we have set a mock for this method reply with that instead of
        # forwarding the request.
        if method in self.mocks and type(method) == dict:
            return self.mocks[method]
        elif method in self.mocks and callable(self.mocks[method]):
            return self.mocks[method](r)

        try:
            reply = {
                "result": brpc._call(r['method'], *r['params']),
                "error": None,
                "id": r['id']
            }
        except JSONRPCError as e:
            reply = {
                "error": e.error,
                "id": r['id']
            }
        return reply

    def proxy(self):
        r = json.loads(request.data.decode('ASCII'))

        if isinstance(r, list):
            reply = [self._handle_request(subreq) for subreq in r]
        else:
            reply = self._handle_request(r)

        reply = json.dumps(reply, cls=DecimalEncoder)
        logging.debug("Replying to %r with %r", r, reply)

        response = flask.Response(reply)
        response.headers['Content-Type'] = 'application/json'
        return response

    def start(self):
        d = PathInfoDispatcher({'/': self.app})
        self.server = Server(('0.0.0.0', self.proxyport), d)
        self.proxy_thread = threading.Thread(target=self.server.start)
        self.proxy_thread.daemon = True
        self.proxy_thread.start()
        BitcoinD.start(self)

        # Now that bitcoind is running on the real rpcport, let's tell all
        # future callers to talk to the proxyport. We use the bind_addr as a
        # signal that the port is bound and accepting connections.
        while self.server.bind_addr[1] == 0:
            pass
        self.proxiedport = self.rpcport
        self.rpcport = self.server.bind_addr[1]
        logging.debug("bitcoind reverse proxy listening on {}, forwarding to {}".format(
            self.rpcport, self.proxiedport
        ))

    def stop(self):
        BitcoinD.stop(self)
        self.server.stop()
        self.proxy_thread.join()

    def mock_rpc(self, method, response=None):
        """Mock the response to a future RPC call of @method

        The response can either be a dict with the full JSON-RPC response, or a
        function that returns such a response. If the response is None the mock
        is removed and future calls will be passed through to bitcoind again.

        """
        if response is not None:
            self.mocks[method] = response
        elif method in self.mocks:
            del self.mocks[method]


# The main entrypoint is mainly used to test the proxy. It is not used during
# lightningd testing.
if __name__ == "__main__":
    p = ProxiedBitcoinD(bitcoin_dir='/tmp/bitcoind-test/', proxyport=5000)
    p.start()
    p.proxy_thread.join()