httpinterface.py

#
# Copyright (C) 2011,2012,2014,2016,2018  Kipp Cannon
#
# This program is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the
# Free Software Foundation; either version 2 of the License, or (at your
# option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
# Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
#


"""
Stuff to help add an http control and query interface to a program.
"""


#
# =============================================================================
#
#                                   Preamble
#
# =============================================================================
#


import socket
import sys
import threading
import time


from . import bottle
from . import servicediscovery


#
# =============================================================================
#
#                            HTTP Interface Helpers
#
# =============================================================================
#


class HTTPDServer(object):
    def __init__(self, host, port, bottle_app, verbose = False):
        self.host = host
        self.port = port
        self.bottle_app = bottle_app
        self.verbose = verbose

    def __enter__(self):
        self.httpd = bottle.WSGIRefServer(host = self.host, port = self.port)
        self.httpd_thread = threading.Thread(target = self.httpd.run, args = (self.bottle_app,))
        self.httpd_thread.daemon = True
        self.httpd_thread.start()
        if self.verbose:
            print >>sys.stderr, "waiting for http server to start ..."
        while self.httpd.port == 0:
            time.sleep(0.25)
        self.host = self.httpd.host
        self.port = self.httpd.port
        if self.verbose:
            print >>sys.stderr, "started http server on http://%s:%d" % (self.httpd.host, self.httpd.port)
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        if self.verbose:
            print >>sys.stderr, "stopping http server on http://%s:%d ..." % (self.httpd.host, self.httpd.port),
        try:
            self.httpd.shutdown()
        except Exception as e:
            result = "failed: %s" % str(e)
        else:
            result = "done"
        if self.verbose:
            print >>sys.stderr, result
            print >>sys.stderr, "killing http server thread ...",
        # wait 10 seconds, then give up
        self.httpd_thread.join(10.0)
        if self.verbose:
            print >>sys.stderr, "timeout" if self.httpd_thread.is_alive() else "done"


class HTTPServers(list):
    """
    Utility to start, advertise, track and shutdown http servers on all
    interfaces.  De-advertise and shutdown the servers by deleting this
    object.  Do not allow the object to be garbage collected until you
    wish the servers to be shutdown.

    Example:

    >>> # save return value in a variable to prevent garbage collection
    >>> servers = HTTPServers(port = 12345)
    >>> pass    # blah
    >>> pass    # blah
    >>> pass    # blah
    >>> # shutdown servers by deleting object
    >>> del servers

    If port = 0 (the default) a port will be assigned randomly.
    bottle_app should be a Bottle instance.  If bottle_app is None (the
    default) then the current default Bottle application is used.
    """
    def __init__(self, port = 0, bottle_app = None, service_name = "www", service_domain = None, service_properties = None, verbose = False):
        if bottle_app is None:
            bottle_app = bottle.default_app()
        self.verbose = verbose
        self.service_publisher = servicediscovery.Publisher().__enter__()
        for (ignored, ignored, ignored, ignored, (host, port)) in socket.getaddrinfo(None, port, socket.AF_INET, socket.SOCK_STREAM, 0, socket.AI_NUMERICHOST | socket.AI_PASSIVE):
            httpd = HTTPDServer(host, port, bottle_app, verbose = verbose).__enter__()
            if verbose:
                print >>sys.stderr, "advertising http server \"%s\" on http://%s:%d ..." % (service_name, httpd.host, httpd.port),
            service = self.service_publisher.add_service(
                sname = service_name,
                sdomain = service_domain,
                port = httpd.port,
                properties = service_properties,
                commit = False
            )
            if verbose:
                print >>sys.stderr, "done (%s)" % ".".join((service.sname, service.sdomain))
            self.append((httpd, service))
        if not self:
            raise ValueError("unable to start servers%s" % (" on port %d" % port if port != 0 else ""))
        self.service_publisher.commit()

    def __del__(self):
        if self.verbose:
            print >>sys.stderr, "de-advertising http server(s) ...",
        try:
            self.service_publisher.__exit__(None, None, None)
        except Exception as e:
            if self.verbose:
                print >>sys.stderr, "failed: %s" % str(e)
        else:
            if self.verbose:
                print >>sys.stderr, "done"
        while self:
            try:
                self.pop()[0].__exit__(None, None, None)
            except Exception as e:
                if self.verbose:
                    print >>sys.stderr, "failed: %s" % str(e)