dnsexperiment

#!/usr/bin/env python3
"""Experimental DNS resolving STEEM API-NODE monitor.

As soon as the problem with "python3 setup.py bdist" + "twine upload dist/*.tar.gz" is resolved
and no longer results in "Could not find a version that satisfies the requirement txjsonrpcqueue",
this script should move to its own repo.

FIXME
"""
import logging
from twisted.python import log
from twisted.names import dns, error, server
from twisted.internet import reactor, defer
from txjsonrpcqueue.steem import EmbeddedHealthHostInjector

class FastestNodeResolver(object):
    """DNS resolver class that only responds with the currently fastest JSON-RPC STEEM API node"""
    def __init__(self, start_node):
        self.injector = EmbeddedHealthHostInjector(start_node)
        self.injector.register_forwarder(self)
        self.fastest_node = start_node
    def inject_host_url(self, url):
        """Entry point for EmbeddedHealthHostInjector events"""
        self.fastest_node = url
        log.msg("Updating response string to " + url)
    def query(self, query, timeout=None):
        """DNS Query resolver that only resolves TXT queries"""
        #pylint: disable=unused-argument
        if query.type == dns.TXT:
            log.msg("Responding to TXT query")
            response = self.fastest_node
            payload = dns.Record_TXT(response.encode("utf8"), ttl=90)
            answer = dns.RRHeader(query.name.name,
                                  type=dns.TXT,
                                  cls=dns.IN,
                                  ttl=90,
                                  payload=payload)
            return [answer], [], []
        log.msg("Unexpected query of type " + str(query.type))
        return defer.fail(error.DomainError())


#Set up some basic logging
log.PythonLoggingObserver().start()
logging.basicConfig(filename="dns-experiment.log", level=logging.DEBUG)

#Instantiate DNS resolving and monitoring classes.
FACTORY = server.DNSServerFactory(
    clients=[FastestNodeResolver(["https://api.steemit.com",
                                  "https://rpc.steemviz.com",
                                  "https://appbasetest.timcliff.com"])])

#Make DNS resolver work on a non standard port so it doesn't need to run as root.
#Will need to set up NAT, either in rooter, or using Docker port mapping.
PROTOCOL = dns.DNSDatagramProtocol(controller=FACTORY)
#pylint: disable=no-member
reactor.listenUDP(9053, PROTOCOL)
#Start the reactor
reactor.run()