Add AsyncTransport

Author: sethmlarson

elasticsearch/__init__.py

@@ -72,7 +72,8 @@
         raise ImportError
 
     from ._async.http_aiohttp import AIOHttpConnection
+    from ._async.transport import AsyncTransport
 
-    __all__ += ["AIOHttpConnection"]
+    __all__ += ["AIOHttpConnection", "AsyncTransport"]
 except (ImportError, SyntaxError):
     pass

elasticsearch/_async/transport.py

@@ -0,0 +1,327 @@
+# Licensed to Elasticsearch B.V under one or more agreements.
+# Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+# See the LICENSE file in the project root for more information
+
+import asyncio
+import logging
+from itertools import chain
+
+from .compat import get_running_loop
+from .http_aiohttp import AIOHttpConnection
+from ..transport import Transport
+from ..exceptions import (
+    TransportError,
+    ConnectionTimeout,
+    ConnectionError,
+    SerializationError,
+)
+
+
+logger = logging.getLogger("elasticsearch")
+
+
+class AsyncTransport(Transport):
+    """
+    Encapsulation of transport-related to logic. Handles instantiation of the
+    individual connections as well as creating a connection pool to hold them.
+
+    Main interface is the `perform_request` method.
+    """
+
+    DEFAULT_CONNECTION_CLASS = AIOHttpConnection
+
+    def __init__(self, hosts, *args, sniff_on_start=False, **kwargs):
+        """
+        :arg hosts: list of dictionaries, each containing keyword arguments to
+            create a `connection_class` instance
+        :arg connection_class: subclass of :class:`~elasticsearch.Connection` to use
+        :arg connection_pool_class: subclass of :class:`~elasticsearch.ConnectionPool` to use
+        :arg host_info_callback: callback responsible for taking the node information from
+            `/_cluster/nodes`, along with already extracted information, and
+            producing a list of arguments (same as `hosts` parameter)
+        :arg sniff_on_start: flag indicating whether to obtain a list of nodes
+            from the cluster at startup time
+        :arg sniffer_timeout: number of seconds between automatic sniffs
+        :arg sniff_on_connection_fail: flag controlling if connection failure triggers a sniff
+        :arg sniff_timeout: timeout used for the sniff request - it should be a
+            fast api call and we are talking potentially to more nodes so we want
+            to fail quickly. Not used during initial sniffing (if
+            ``sniff_on_start`` is on) when the connection still isn't
+            initialized.
+        :arg serializer: serializer instance
+        :arg serializers: optional dict of serializer instances that will be
+            used for deserializing data coming from the server. (key is the mimetype)
+        :arg default_mimetype: when no mimetype is specified by the server
+            response assume this mimetype, defaults to `'application/json'`
+        :arg max_retries: maximum number of retries before an exception is propagated
+        :arg retry_on_status: set of HTTP status codes on which we should retry
+            on a different node. defaults to ``(502, 503, 504)``
+        :arg retry_on_timeout: should timeout trigger a retry on different
+            node? (default `False`)
+        :arg send_get_body_as: for GET requests with body this option allows
+            you to specify an alternate way of execution for environments that
+            don't support passing bodies with GET requests. If you set this to
+            'POST' a POST method will be used instead, if to 'source' then the body
+            will be serialized and passed as a query parameter `source`.
+
+        Any extra keyword arguments will be passed to the `connection_class`
+        when creating and instance unless overridden by that connection's
+        options provided as part of the hosts parameter.
+        """
+        self.sniffing_task = None
+        self.loop = None
+        self._async_init_called = False
+
+        super(AsyncTransport, self).__init__(
+            *args, hosts=[], sniff_on_start=False, **kwargs
+        )
+
+        # Don't enable sniffing on Cloud instances.
+        if kwargs.get("cloud_id", False):
+            sniff_on_start = False
+
+        # Since we defer connections / sniffing to not occur
+        # within the constructor we never want to signal to
+        # our parent to 'sniff_on_start' or non-empty 'hosts'.
+        self.hosts = hosts
+        self.sniff_on_start = sniff_on_start
+
+    async def _async_init(self):
+        """This is our stand-in for an async constructor. Everything
+        that was deferred within __init__() should be done here now.
+
+        This method will only be called once per AsyncTransport instance
+        and is called from one of AsyncElasticsearch.__aenter__(),
+        AsyncTransport.perform_request() or AsyncTransport.get_connection()
+        """
+        # Detect the async loop we're running in and set it
+        # on all already created HTTP connections.
+        self.loop = get_running_loop()
+        self.kwargs["loop"] = self.loop
+
+        # Now that we have a loop we can create all our HTTP connections
+        self.set_connections(self.hosts)
+        self.seed_connections = list(self.connection_pool.connections[:])
+
+        # ... and we can start sniffing in the background.
+        if self.sniffing_task is None and self.sniff_on_start:
+            self.last_sniff = self.loop.time()
+            self.create_sniff_task(initial=True)
+
+    async def _async_call(self):
+        """This method is called within any async method of AsyncTransport
+        where the transport is not closing. This will check to see if we should
+        call our _async_init() or create a new sniffing task
+        """
+        if not self._async_init_called:
+            self._async_init_called = True
+            await self._async_init()
+
+        if self.sniffer_timeout:
+            if self.loop.time() >= self.last_sniff + self.sniff_timeout:
+                self.create_sniff_task()
+
+    async def _get_node_info(self, conn, initial):
+        try:
+            # use small timeout for the sniffing request, should be a fast api call
+            _, headers, node_info = await conn.perform_request(
+                "GET",
+                "/_nodes/_all/http",
+                timeout=self.sniff_timeout if not initial else None,
+            )
+            return self.deserializer.loads(node_info, headers.get("content-type"))
+        except Exception:
+            pass
+        return None
+
+    async def _get_sniff_data(self, initial=False):
+        previous_sniff = self.last_sniff
+
+        # reset last_sniff timestamp
+        self.last_sniff = self.loop.time()
+
+        # use small timeout for the sniffing request, should be a fast api call
+        timeout = self.sniff_timeout if not initial else None
+
+        def _sniff_request(conn):
+            return self.loop.create_task(
+                conn.perform_request("GET", "/_nodes/_all/http", timeout=timeout)
+            )
+
+        # Go through all current connections as well as the
+        # seed_connections for good measure
+        tasks = []
+        for conn in self.connection_pool.connections:
+            tasks.append(_sniff_request(conn))
+        for conn in self.seed_connections:
+            # Ensure that we don't have any duplication within seed_connections.
+            if conn in self.connection_pool.connections:
+                continue
+            tasks.append(_sniff_request(conn))
+
+        done = ()
+        try:
+            while tasks:
+                # execute sniff requests in parallel, wait for first to return
+                done, tasks = await asyncio.wait(
+                    tasks, return_when=asyncio.FIRST_COMPLETED, loop=self.loop
+                )
+                # go through all the finished tasks
+                for t in done:
+                    try:
+                        _, headers, node_info = t.result()
+                        node_info = self.deserializer.loads(
+                            node_info, headers.get("content-type")
+                        )
+                    except (ConnectionError, SerializationError):
+                        continue
+                    node_info = list(node_info["nodes"].values())
+                    return node_info
+            else:
+                # no task has finished completely
+                raise TransportError("N/A", "Unable to sniff hosts.")
+        except Exception:
+            # keep the previous value on error
+            self.last_sniff = previous_sniff
+            raise
+        finally:
+            # Cancel all the pending tasks
+            for task in chain(done, tasks):
+                task.cancel()
+
+    async def sniff_hosts(self, initial=False):
+        """Either spawns a sniffing_task which does regular sniffing
+        over time or does a single sniffing session and awaits the results.
+        """
+        # Without a loop we can't do anything.
+        if not self.loop:
+            return
+
+        node_info = await self._get_sniff_data(initial)
+        hosts = list(filter(None, (self._get_host_info(n) for n in node_info)))
+
+        # we weren't able to get any nodes, maybe using an incompatible
+        # transport_schema or host_info_callback blocked all - raise error.
+        if not hosts:
+            raise TransportError(
+                "N/A", "Unable to sniff hosts - no viable hosts found."
+            )
+
+        # remember current live connections
+        orig_connections = self.connection_pool.connections[:]
+        self.set_connections(hosts)
+        # close those connections that are not in use any more
+        for c in orig_connections:
+            if c not in self.connection_pool.connections:
+                await c.close()
+
+    def create_sniff_task(self, initial=False):
+        """
+        Initiate a sniffing task. Make sure we only have one sniff request
+        running at any given time. If a finished sniffing request is around,
+        collect its result (which can raise its exception).
+        """
+        if self.sniffing_task and self.sniffing_task.done():
+            try:
+                if self.sniffing_task is not None:
+                    self.sniffing_task.result()
+            finally:
+                self.sniffing_task = None
+
+        if self.sniffing_task is None:
+            self.sniffing_task = self.loop.create_task(self.sniff_hosts(initial))
+
+    def mark_dead(self, connection):
+        """
+        Mark a connection as dead (failed) in the connection pool. If sniffing
+        on failure is enabled this will initiate the sniffing process.
+
+        :arg connection: instance of :class:`~elasticsearch.Connection` that failed
+        """
+        self.connection_pool.mark_dead(connection)
+        if self.sniff_on_connection_fail:
+            self.create_sniff_task()
+
+    def get_connection(self):
+        return self.connection_pool.get_connection()
+
+    async def perform_request(self, method, url, headers=None, params=None, body=None):
+        """
+        Perform the actual request. Retrieve a connection from the connection
+        pool, pass all the information to it's perform_request method and
+        return the data.
+
+        If an exception was raised, mark the connection as failed and retry (up
+        to `max_retries` times).
+
+        If the operation was successful and the connection used was previously
+        marked as dead, mark it as live, resetting it's failure count.
+
+        :arg method: HTTP method to use
+        :arg url: absolute url (without host) to target
+        :arg headers: dictionary of headers, will be handed over to the
+            underlying :class:`~elasticsearch.Connection` class
+        :arg params: dictionary of query parameters, will be handed over to the
+            underlying :class:`~elasticsearch.Connection` class for serialization
+        :arg body: body of the request, will be serialized using serializer and
+            passed to the connection
+        """
+        await self._async_call()
+
+        method, params, body, ignore, timeout = self._resolve_request_args(
+            method, params, body
+        )
+
+        for attempt in range(self.max_retries + 1):
+            connection = self.get_connection()
+
+            try:
+                status, headers, data = await connection.perform_request(
+                    method,
+                    url,
+                    params,
+                    body,
+                    headers=headers,
+                    ignore=ignore,
+                    timeout=timeout,
+                )
+            except TransportError as e:
+                if method == "HEAD" and e.status_code == 404:
+                    return False
+
+                retry = False
+                if isinstance(e, ConnectionTimeout):
+                    retry = self.retry_on_timeout
+                elif isinstance(e, ConnectionError):
+                    retry = True
+                elif e.status_code in self.retry_on_status:
+                    retry = True
+
+                if retry:
+                    # only mark as dead if we are retrying
+                    self.mark_dead(connection)
+                    # raise exception on last retry
+                    if attempt == self.max_retries:
+                        raise
+                else:
+                    raise
+
+            else:
+                if method == "HEAD":
+                    return 200 <= status < 300
+
+                # connection didn't fail, confirm it's live status
+                self.connection_pool.mark_live(connection)
+                if data:
+                    data = self.deserializer.loads(data, headers.get("content-type"))
+                return data
+
+    async def close(self):
+        """
+        Explicitly closes connections
+        """
+        if self.sniffing_task:
+            self.sniffing_task.cancel()
+            self.sniffing_task = None
+        for connection in self.connection_pool.connections:
+            await connection.close()

elasticsearch/connection_pool.py

@@ -256,9 +256,12 @@ def close(self):
         """
         Explicitly closes connections
         """
-        for conn in self.orig_connections:
+        for conn in self.connections:
             conn.close()
 
+    def __repr__(self):
+        return "<%s: %r>" % (type(self).__name__, self.connections)
+
 
 class DummyConnectionPool(ConnectionPool):
     def __init__(self, connections, **kwargs):
@@ -284,3 +287,19 @@ def _noop(self, *args, **kwargs):
         pass
 
     mark_dead = mark_live = resurrect = _noop
+
+
+class EmptyConnectionPool(ConnectionPool):
+    """A connection pool that is empty. Errors out if used."""
+
+    def __init__(self, *_, **__):
+        self.connections = []
+        self.connection_opts = []
+
+    def get_connection(self):
+        raise ImproperlyConfigured("No connections were configured")
+
+    def _noop(self, *args, **kwargs):
+        pass
+
+    close = mark_dead = mark_live = resurrect = _noop