rpchost.py

#! /usr/bin/env python3
"""Originally written for the ACME project as part of the script blocknotifybase.py.

(c) Graham Higgins, The Slimcoin Developers
License: MIT
"""

try:
    import simplejson as json # needed for Decimal conversions, test if it breaks something
except ImportError:
    import json

import requests
import time

class RPCHost(object):
    """Class defining a 'host' for remote procedure calls."""
    def __init__(self, url):
        self._session = requests.Session()
        self._url = url
        self._headers = {'content-type': 'application/json'}

    def call(self, rpcMethod, *params):
        """RPC call using the Bitcoin JSON RPC API."""
        payload = json.dumps({"method": rpcMethod, "params": list(params), "jsonrpc": "2.0"})
        tries = 10
        hadConnectionFailures = False
        while True:
            # print("{url} {headers} {data}".format(url=self._url, headers=self._headers, data=payload))
            try:
                response = self._session.get(self._url, headers=self._headers, data=payload)
            except requests.exceptions.ConnectionError:
                tries -= 1
                if tries == 0:
                    raise Exception('Failed to connect for remote procedure call.')
                hadConnectionFailures = True
                print("Couldn't connect for remote procedure call, will sleep for ten seconds and then try again ({} more tries)".format(tries))
                time.sleep(10)
            else:
                if hadConnectionFailures:
                    print('Connected for remote procedure call after retry.')
                break
        if response.status_code not in (200, 500):
            raise Exception('RPC connection failure: ' + str(response.status_code) + ' ' + response.reason)
        responseJSON = response.json()
        if 'error' in responseJSON and responseJSON['error'] is not None:
            raise Exception('Error in RPC call: ' + str(responseJSON['error']))
        return responseJSON['result']