path: root/kazoo/handlers/utils.py

"""Kazoo handler helpers"""

from collections import defaultdict
import errno
import functools
import select
import selectors
import ssl
import socket
import time

HAS_FNCTL = True
try:
    import fcntl
except ImportError:  # pragma: nocover
    HAS_FNCTL = False

# sentinel objects
_NONE = object()


class AsyncResult(object):
    """A one-time event that stores a value or an exception"""

    def __init__(self, handler, condition_factory, timeout_factory):
        self._handler = handler
        self._exception = _NONE
        self._condition = condition_factory()
        self._callbacks = []
        self._timeout_factory = timeout_factory
        self.value = None

    def ready(self):
        """Return true if and only if it holds a value or an
        exception"""
        return self._exception is not _NONE

    def successful(self):
        """Return true if and only if it is ready and holds a value"""
        return self._exception is None

    @property
    def exception(self):
        if self._exception is not _NONE:
            return self._exception

    def set(self, value=None):
        """Store the value. Wake up the waiters."""
        with self._condition:
            self.value = value
            self._exception = None
            self._do_callbacks()
            self._condition.notify_all()

    def set_exception(self, exception):
        """Store the exception. Wake up the waiters."""
        with self._condition:
            self._exception = exception
            self._do_callbacks()
            self._condition.notify_all()

    def get(self, block=True, timeout=None):
        """Return the stored value or raise the exception.

        If there is no value raises TimeoutError.

        """
        with self._condition:
            if self._exception is not _NONE:
                if self._exception is None:
                    return self.value
                raise self._exception
            elif block:
                self._condition.wait(timeout)
                if self._exception is not _NONE:
                    if self._exception is None:
                        return self.value
                    raise self._exception

            # if we get to this point we timeout
            raise self._timeout_factory()

    def get_nowait(self):
        """Return the value or raise the exception without blocking.

        If nothing is available, raises TimeoutError

        """
        return self.get(block=False)

    def wait(self, timeout=None):
        """Block until the instance is ready."""
        with self._condition:
            if not self.ready():
                self._condition.wait(timeout)
        return self._exception is not _NONE

    def rawlink(self, callback):
        """Register a callback to call when a value or an exception is
        set"""
        with self._condition:
            if callback not in self._callbacks:
                self._callbacks.append(callback)

            # Are we already set? Dispatch it now
            if self.ready():
                self._do_callbacks()

    def unlink(self, callback):
        """Remove the callback set by :meth:`rawlink`"""
        with self._condition:
            if self.ready():
                # Already triggered, ignore
                return

            if callback in self._callbacks:
                self._callbacks.remove(callback)

    def _do_callbacks(self):
        """Execute the callbacks that were registered by :meth:`rawlink`.
        If the handler is in running state this method only schedules
        the calls to be performed by the handler. If it's stopped,
        the callbacks are called right away."""

        for callback in self._callbacks:
            if self._handler.running:
                self._handler.completion_queue.put(
                    functools.partial(callback, self)
                )
            else:
                functools.partial(callback, self)()


def _set_fd_cloexec(fd):
    flags = fcntl.fcntl(fd, fcntl.F_GETFD)
    fcntl.fcntl(fd, fcntl.F_SETFD, flags | fcntl.FD_CLOEXEC)


def _set_default_tcpsock_options(module, sock):
    sock.setsockopt(module.IPPROTO_TCP, module.TCP_NODELAY, 1)
    if HAS_FNCTL:
        _set_fd_cloexec(sock)
    return sock


def create_socket_pair(module, port=0):
    """Create socket pair.

    If socket.socketpair isn't available, we emulate it.
    """
    # See if socketpair() is available.
    have_socketpair = hasattr(module, "socketpair")
    if have_socketpair:
        client_sock, srv_sock = module.socketpair()
        return client_sock, srv_sock

    # Create a non-blocking temporary server socket
    temp_srv_sock = module.socket()
    temp_srv_sock.setblocking(False)
    temp_srv_sock.bind(("", port))
    port = temp_srv_sock.getsockname()[1]
    temp_srv_sock.listen(1)

    # Create non-blocking client socket
    client_sock = module.socket()
    client_sock.setblocking(False)
    try:
        client_sock.connect(("localhost", port))
    except module.error as err:
        # EWOULDBLOCK is not an error, as the socket is non-blocking
        if err.errno != errno.EWOULDBLOCK:
            raise

    # Use select to wait for connect() to succeed.
    timeout = 1
    readable = select.select([temp_srv_sock], [], [], timeout)[0]
    if temp_srv_sock not in readable:
        raise Exception(
            "Client socket not connected in %s" " second(s)" % (timeout)
        )
    srv_sock, _ = temp_srv_sock.accept()
    return client_sock, srv_sock


def create_tcp_socket(module):
    """Create a TCP socket with the CLOEXEC flag set."""
    type_ = module.SOCK_STREAM
    if hasattr(module, "SOCK_CLOEXEC"):  # pragma: nocover
        # if available, set cloexec flag during socket creation
        type_ |= module.SOCK_CLOEXEC
    sock = module.socket(module.AF_INET, type_)
    _set_default_tcpsock_options(module, sock)
    return sock


def create_tcp_connection(
    module,
    address,
    timeout=None,
    use_ssl=False,
    ca=None,
    certfile=None,
    keyfile=None,
    keyfile_password=None,
    verify_certs=True,
    options=None,
    ciphers=None,
):
    end = None
    if timeout is None:
        # thanks to create_connection() developers for
        # this ugliness...
        timeout = module.getdefaulttimeout()
    if timeout is not None:
        end = time.time() + timeout
    sock = None

    while True:
        timeout_at = end if end is None else end - time.time()
        # The condition is not '< 0' here because socket.settimeout treats 0 as
        # a special case to put the socket in non-blocking mode.
        if timeout_at is not None and timeout_at <= 0:
            break

        if use_ssl:
            # Disallow use of SSLv2 and V3 (meaning we require TLSv1.0+)
            context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)

            if options is not None:
                context.options = options
            else:
                context.options |= ssl.OP_NO_SSLv2
                context.options |= ssl.OP_NO_SSLv3

            if ciphers:
                context.set_ciphers(ciphers)

            # Load default CA certs
            context.load_default_certs(ssl.Purpose.SERVER_AUTH)
            # We must set check_hostname to False prior to setting
            # verify_mode to CERT_NONE.
            # TODO: Make hostname verification configurable as some users may
            # elect to use it.
            context.check_hostname = False
            context.verify_mode = (
                ssl.CERT_REQUIRED if verify_certs else ssl.CERT_NONE
            )
            if ca:
                context.load_verify_locations(ca)
            if certfile and keyfile:
                context.load_cert_chain(
                    certfile=certfile,
                    keyfile=keyfile,
                    password=keyfile_password,
                )
            try:
                # Query the address to get back it's address family
                addrs = socket.getaddrinfo(
                    address[0], address[1], 0, socket.SOCK_STREAM
                )
                conn = context.wrap_socket(module.socket(addrs[0][0]))
                conn.settimeout(timeout_at)
                conn.connect(address)
                sock = conn
                break
            except ssl.SSLError:
                raise
        else:
            try:
                # if we got a timeout, lets ensure that we decrement the time
                # otherwise there is no timeout set and we'll call it as such
                sock = module.create_connection(address, timeout_at)
                break
            except Exception as ex:
                errnum = ex.errno if isinstance(ex, OSError) else ex[0]
                if errnum == errno.EINTR:
                    continue
                raise

    if sock is None:
        raise module.error

    _set_default_tcpsock_options(module, sock)
    return sock


def capture_exceptions(async_result):
    """Return a new decorated function that propagates the exceptions of the
    wrapped function to an async_result.

    :param async_result: An async result implementing :class:`IAsyncResult`

    """

    def capture(function):
        @functools.wraps(function)
        def captured_function(*args, **kwargs):
            try:
                return function(*args, **kwargs)
            except Exception as exc:
                async_result.set_exception(exc)

        return captured_function

    return capture


def wrap(async_result):
    """Return a new decorated function that propagates the return value or
    exception of wrapped function to an async_result.  NOTE: Only propagates a
    non-None return value.

    :param async_result: An async result implementing :class:`IAsyncResult`

    """

    def capture(function):
        @capture_exceptions(async_result)
        def captured_function(*args, **kwargs):
            value = function(*args, **kwargs)
            if value is not None:
                async_result.set(value)
            return value

        return captured_function

    return capture


def fileobj_to_fd(fileobj):
    """Return a file descriptor from a file object.

    Parameters:
    fileobj -- file object or file descriptor

    Returns:
    corresponding file descriptor

    Raises:
    TypeError if the object is invalid
    """
    if isinstance(fileobj, int):
        fd = fileobj
    else:
        try:
            fd = int(fileobj.fileno())
        except (AttributeError, TypeError, ValueError):
            raise TypeError("Invalid file object: " "{!r}".format(fileobj))
    if fd < 0:
        raise TypeError("Invalid file descriptor: {}".format(fd))
    return fd


def selector_select(
    rlist, wlist, xlist, timeout=None, selectors_module=selectors
):
    """Selector-based drop-in replacement for select to overcome select
    limitation on a maximum filehandle value.
    """
    if timeout is not None:
        if not isinstance(timeout, (int, float)):
            raise TypeError("timeout must be a number")
        if timeout < 0:
            raise ValueError("timeout must be non-negative")

    events_mapping = {
        selectors_module.EVENT_READ: rlist,
        selectors_module.EVENT_WRITE: wlist,
    }
    fd_events = defaultdict(int)
    fd_fileobjs = defaultdict(list)

    for event, fileobjs in events_mapping.items():
        for fileobj in fileobjs:
            fd = fileobj_to_fd(fileobj)
            fd_events[fd] |= event
            fd_fileobjs[fd].append(fileobj)

    selector = selectors_module.DefaultSelector()
    for fd, events in fd_events.items():
        try:
            selector.register(fd, events)
        except (ValueError, OSError) as e:
            # gevent can raise OSError
            raise ValueError("Invalid event mask or fd") from e

    revents, wevents, xevents = [], [], []
    try:
        ready = selector.select(timeout)
    finally:
        selector.close()

    for info in ready:
        k, events = info
        if events & selectors_module.EVENT_READ:
            revents.extend(fd_fileobjs[k.fd])
        elif events & selectors_module.EVENT_WRITE:
            wevents.extend(fd_fileobjs[k.fd])

    return revents, wevents, xevents