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#

#

# Copyright (C) 2007, 2008, 2010 Google Inc.

#

# 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.

"""HTTP client module.

"""

import logging

import pycurl

from cStringIO import StringIO

from ganeti import http

from ganeti import compat

class HttpClientRequest(object):

  def __init__(self, host, port, method, path, headers=None, post_data=None,

               read_timeout=None, curl_config_fn=None):

    """Describes an HTTP request.

    @type host: string

    @param host: Hostname

    @type port: int

    @param port: Port

    @type method: string

    @param method: Method name

    @type path: string

    @param path: Request path

    @type headers: list or None

    @param headers: Additional headers to send, list of strings

    @type post_data: string or None

    @param post_data: Additional data to send

    @type read_timeout: int

    @param read_timeout: if passed, it will be used as the read

        timeout while reading the response from the server

    @type curl_config_fn: callable

    @param curl_config_fn: Function to configure cURL object before request

                           (Note: if the function configures the connection in

                           a way where it wouldn't be efficient to reuse them,

                           a "identity" property should be defined, see

                           L{HttpClientRequest.identity})

    """

    assert path.startswith("/"), "Path must start with slash (/)"

    assert curl_config_fn is None or callable(curl_config_fn)

    # Request attributes

    self.host = host

    self.port = port

    self.method = method

    self.path = path

    self.read_timeout = read_timeout

    self.curl_config_fn = curl_config_fn

    if post_data is None:

      self.post_data = ""

    else:

      self.post_data = post_data

    if headers is None:

      self.headers = []

    elif isinstance(headers, dict):

      # Support for old interface

      self.headers = ["%s: %s" % (name, value)

                      for name, value in headers.items()]

    else:

      self.headers = headers

    # Response status

    self.success = None

    self.error = None

    # Response attributes

    self.resp_status_code = None

    self.resp_body = None

  def __repr__(self):

    status = ["%s.%s" % (self.__class__.__module__, self.__class__.__name__),

              "%s:%s" % (self.host, self.port),

              self.method,

              self.path]

    return "<%s at %#x>" % (" ".join(status), id(self))

  @property

  def url(self):

    """Returns the full URL for this requests.

    """

    # TODO: Support for non-SSL requests

    return "https://%s:%s%s" % (self.host, self.port, self.path)

  @property

  def identity(self):

    """Returns identifier for retrieving a pooled connection for this request.

    This allows cURL client objects to be re-used and to cache information

    (e.g. SSL session IDs or connections).

    """

    parts = [self.host, self.port]

    if self.curl_config_fn:

      try:

        parts.append(self.curl_config_fn.identity)

      except AttributeError:

        pass

    return "/".join(str(i) for i in parts)

class _HttpClient(object):

  def __init__(self, curl_config_fn):

    """Initializes this class.

    @type curl_config_fn: callable

    @param curl_config_fn: Function to configure cURL object after

                           initialization

    """

    self._req = None

    curl = self._CreateCurlHandle()

    curl.setopt(pycurl.VERBOSE, False)

    curl.setopt(pycurl.NOSIGNAL, True)

    curl.setopt(pycurl.USERAGENT, http.HTTP_GANETI_VERSION)

    curl.setopt(pycurl.PROXY, "")

    # Pass cURL object to external config function

    if curl_config_fn:

      curl_config_fn(curl)

    self._curl = curl

  @staticmethod

  def _CreateCurlHandle():

    """Returns a new cURL object.

    """

    return pycurl.Curl()

  def GetCurlHandle(self):

    """Returns the cURL object.

    """

    return self._curl

  def GetCurrentRequest(self):

    """Returns the current request.

    @rtype: L{HttpClientRequest} or None

    """

    return self._req

  def StartRequest(self, req):

    """Starts a request on this client.

    @type req: L{HttpClientRequest}

    @param req: HTTP request

    """

    assert not self._req, "Another request is already started"

    self._req = req

    self._resp_buffer = StringIO()

    url = req.url

    method = req.method

    post_data = req.post_data

    headers = req.headers

    # PycURL requires strings to be non-unicode

    assert isinstance(method, str)

    assert isinstance(url, str)

    assert isinstance(post_data, str)

    assert compat.all(isinstance(i, str) for i in headers)

    # Configure cURL object for request

    curl = self._curl

    curl.setopt(pycurl.CUSTOMREQUEST, str(method))

    curl.setopt(pycurl.URL, url)

    curl.setopt(pycurl.POSTFIELDS, post_data)

    curl.setopt(pycurl.WRITEFUNCTION, self._resp_buffer.write)

    curl.setopt(pycurl.HTTPHEADER, headers)

    if req.read_timeout is None:

      curl.setopt(pycurl.TIMEOUT, 0)

    else:

      curl.setopt(pycurl.TIMEOUT, int(req.read_timeout))

    # Pass cURL object to external config function

    if req.curl_config_fn:

      req.curl_config_fn(curl)

  def Done(self, errmsg):

    """Finishes a request.

    @type errmsg: string or None

    @param errmsg: Error message if request failed

    """

    req = self._req

    assert req, "No request"

    logging.debug("Request %s finished, errmsg=%s", req, errmsg)

    curl = self._curl

    req.success = not bool(errmsg)

    req.error = errmsg

    # Get HTTP response code

    req.resp_status_code = curl.getinfo(pycurl.RESPONSE_CODE)

    req.resp_body = self._resp_buffer.getvalue()

    # Reset client object

    self._req = None

    self._resp_buffer = None

    # Ensure no potentially large variables are referenced

    curl.setopt(pycurl.POSTFIELDS, "")

    curl.setopt(pycurl.WRITEFUNCTION, lambda _: None)

class _PooledHttpClient:

  """Data structure for HTTP client pool.

  """

  def __init__(self, identity, client):

    """Initializes this class.

    @type identity: string

    @param identity: Client identifier for pool

    @type client: L{_HttpClient}

    @param client: HTTP client

    """

    self.identity = identity

    self.client = client

    self.lastused = 0

  def __repr__(self):

    status = ["%s.%s" % (self.__class__.__module__, self.__class__.__name__),

              "id=%s" % self.identity,

              "lastuse=%s" % self.lastused,

              repr(self.client)]

    return "<%s at %#x>" % (" ".join(status), id(self))

class HttpClientPool:

  """A simple HTTP client pool.

  Supports one pooled connection per identity (see

  L{HttpClientRequest.identity}).

  """

  #: After how many generations to drop unused clients

  _MAX_GENERATIONS_DROP = 25

  def __init__(self, curl_config_fn):

    """Initializes this class.

    @type curl_config_fn: callable

    @param curl_config_fn: Function to configure cURL object after

                           initialization

    """

    self._curl_config_fn = curl_config_fn

    self._generation = 0

    self._pool = {}

  @staticmethod

  def _GetHttpClientCreator():

    """Returns callable to create HTTP client.

    """

    return _HttpClient

  def _Get(self, identity):

    """Gets an HTTP client from the pool.

    @type identity: string

    @param identity: Client identifier

    """

    try:

      pclient  = self._pool.pop(identity)

    except KeyError:

      # Need to create new client

      client = self._GetHttpClientCreator()(self._curl_config_fn)

      pclient = _PooledHttpClient(identity, client)

      logging.debug("Created new client %s", pclient)

    else:

      logging.debug("Reusing client %s", pclient)

    assert pclient.identity == identity

    return pclient

  def _StartRequest(self, req):

    """Starts a request.

    @type req: L{HttpClientRequest}

    @param req: HTTP request

    """

    logging.debug("Starting request %r", req)

    pclient = self._Get(req.identity)

    assert req.identity not in self._pool

    pclient.client.StartRequest(req)

    pclient.lastused = self._generation

    return pclient

  def _Return(self, pclients):

    """Returns HTTP clients to the pool.

    """

    for pc in pclients:

      logging.debug("Returning client %s to pool", pc)

      assert pc.identity not in self._pool

      assert pc not in self._pool.values()

      self._pool[pc.identity] = pc

    # Check for unused clients

    for pc in self._pool.values():

      if (pc.lastused + self._MAX_GENERATIONS_DROP) < self._generation:

        logging.debug("Removing client %s which hasn't been used"

                      " for %s generations",

                      pc, self._MAX_GENERATIONS_DROP)

        self._pool.pop(pc.identity, None)

    assert compat.all(pc.lastused >= (self._generation -

                                      self._MAX_GENERATIONS_DROP)

                      for pc in self._pool.values())

  @staticmethod

  def _CreateCurlMultiHandle():

    """Creates new cURL multi handle.

    """

    return pycurl.CurlMulti()

  def ProcessRequests(self, requests):

    """Processes any number of HTTP client requests using pooled objects.

    @type requests: list of L{HttpClientRequest}

    @param requests: List of all requests

    """

    multi = self._CreateCurlMultiHandle()

    # For client cleanup

    self._generation += 1

    assert compat.all((req.error is None and

                       req.success is None and

                       req.resp_status_code is None and

                       req.resp_body is None)

                      for req in requests)

    curl_to_pclient = {}

    for req in requests:

      pclient = self._StartRequest(req)

      curl = pclient.client.GetCurlHandle()

      curl_to_pclient[curl] = pclient

      multi.add_handle(curl)

      assert pclient.client.GetCurrentRequest() == req

      assert pclient.lastused >= 0

    assert len(curl_to_pclient) == len(requests)

    done_count = 0

    while True:

      (ret, _) = multi.perform()

      assert ret in (pycurl.E_MULTI_OK, pycurl.E_CALL_MULTI_PERFORM)

      if ret == pycurl.E_CALL_MULTI_PERFORM:

        # cURL wants to be called again

        continue

      while True:

        (remaining_messages, successful, failed) = multi.info_read()

        for curl in successful:

          multi.remove_handle(curl)

          done_count += 1

          pclient = curl_to_pclient[curl]

          req = pclient.client.GetCurrentRequest()

          pclient.client.Done(None)

          assert req.success

          assert not pclient.client.GetCurrentRequest()

        for curl, errnum, errmsg in failed:

          multi.remove_handle(curl)

          done_count += 1

          pclient = curl_to_pclient[curl]

          req = pclient.client.GetCurrentRequest()

          pclient.client.Done("Error %s: %s" % (errnum, errmsg))

          assert req.error

          assert not pclient.client.GetCurrentRequest()

        if remaining_messages == 0:

          break

      assert done_count <= len(requests)

      if done_count == len(requests):

        break

      # Wait for I/O. The I/O timeout shouldn't be too long so that HTTP

      # timeouts, which are only evaluated in multi.perform, aren't

      # unnecessarily delayed.

      multi.select(1.0)

    assert compat.all(pclient.client.GetCurrentRequest() is None

                      for pclient in curl_to_pclient.values())

    # Return clients to pool

    self._Return(curl_to_pclient.values())

    assert done_count == len(requests)

    assert compat.all(req.error is not None or

                      (req.success and

                       req.resp_status_code is not None and

                       req.resp_body is not None)

                      for req in requests)