@@ -0,0 +1,280 @@
+"""
+Implementation details of the analytics event delivery component.
+"""
+
+import asyncio
+import gzip
+import json
+import queue
+import time
+import uuid
+from collections import namedtuple
+from random import Random
+from typing import Callable, Optional, Union
+
+from ldclient.async_config import AsyncConfig
+from ldclient.impl.aio.concurrency import (
+    AsyncEvent,
+    AsyncLock,
+    AsyncQueue,
+    AsyncRepeatingTask,
+    AsyncTaskRunner,
+    AsyncWorkerPool
+)
+from ldclient.impl.aio.transport import AsyncHTTPTransport
+from ldclient.impl.events.diagnostics import create_diagnostic_init
+from ldclient.impl.events.event_processor_common import (
+    EventBuffer,
+    EventDispatcherBase,
+    EventOutputFormatter
+)
+from ldclient.impl.events.types import EventInput
+from ldclient.impl.lru_cache import SimpleLRUCache
+from ldclient.impl.sampler import Sampler
+from ldclient.impl.util import (
+    _headers,
+    check_if_error_is_recoverable_and_log,
+    log
+)
+from ldclient.interfaces import EventProcessor
+
+__MAX_FLUSH_THREADS__ = 5
+__CURRENT_EVENT_SCHEMA__ = 4
+
+
+EventProcessorMessage = namedtuple('EventProcessorMessage', ['type', 'param'])
+
+
+class EventPayloadSendTask:
+    def __init__(self, http: AsyncHTTPTransport, config: AsyncConfig, formatter: EventOutputFormatter, payload, response_fn: Callable):
+        self._http = http
+        self._config = config
+        self._formatter = formatter
+        self._payload = payload
+        self._response_fn = response_fn
+
+    async def run(self):
+        try:
+            output_events = self._formatter.make_output_events(self._payload.events, self._payload.summary)
+            await self._do_send(output_events)
+        except Exception:
+            log.warning('Unhandled exception in event processor. Analytics events were not processed.', exc_info=True)
+
+    async def _do_send(self, output_events):
+        # noinspection PyBroadException
+        try:
+            json_body = json.dumps(output_events, separators=(',', ':'))
+            log.debug('Sending events payload: ' + json_body)
+            payload_id = str(uuid.uuid4())
+            r = await _post_events_with_retry(self._http, self._config, self._config.events_uri, payload_id, json_body, "%d events" % len(output_events))
+            if r:
+                self._response_fn(r)
+            return r
+        except Exception as e:
+            log.warning('Unhandled exception in event processor. Analytics events were not processed. [%s]', e)
+
+
+class DiagnosticEventSendTask:
+    def __init__(self, http: AsyncHTTPTransport, config: AsyncConfig, event_body: dict):
+        self._http = http
+        self._config = config
+        self._event_body = event_body
+
+    async def run(self):
+        # noinspection PyBroadException
+        try:
+            json_body = json.dumps(self._event_body)
+            log.debug('Sending diagnostic event: ' + json_body)
+            await _post_events_with_retry(self._http, self._config, self._config.events_base_uri + '/diagnostic', None, json_body, "diagnostic event")
+        except Exception as e:
+            log.warning('Unhandled exception in event processor. Diagnostic event was not sent. [%s]', e)
+
+
+class EventDispatcher(EventDispatcherBase):
+    def __init__(self, inbox: AsyncQueue, config: AsyncConfig, http_client, diagnostic_accumulator=None):
+        self._inbox = inbox
+        self._config = config
+        # When no client is injected, the transport creates one targeting the
+        # events URI and owns it (closing it on shutdown); an injected client
+        # remains owned by the caller.
+        self._http = AsyncHTTPTransport(config, client=http_client)
+        self._disabled = False
+        self._outbox = EventBuffer(config.events_max_pending)
+        self._context_keys = SimpleLRUCache(config.context_keys_capacity)
+        self._formatter = EventOutputFormatter(config)
+        self._last_known_past_time = 0
+        self._deduplicated_contexts = 0
+        self._diagnostic_accumulator = None if config.diagnostic_opt_out else diagnostic_accumulator
+        self._sampler = Sampler(Random())
+        self._omit_anonymous_contexts = config.omit_anonymous_contexts
+
+        self._flush_workers = AsyncWorkerPool(__MAX_FLUSH_THREADS__, "ldclient.flush")
+        self._diagnostic_flush_workers: Optional[AsyncWorkerPool] = None
+        if self._diagnostic_accumulator is not None:
+            self._diagnostic_flush_workers = AsyncWorkerPool(1, "ldclient.events.diag_flush")
+            init_event = create_diagnostic_init(self._diagnostic_accumulator.data_since_date, self._diagnostic_accumulator.diagnostic_id, config)
+            task = DiagnosticEventSendTask(self._http, self._config, init_event)
+            self._diagnostic_flush_workers.execute(task.run)
+
+        self._runner = AsyncTaskRunner()
+        self._runner.spawn("ldclient.events.processor", self._run_main_loop)
+
+    async def _run_main_loop(self):
+        log.info("Starting event processor")
+        while True:
+            try:
+                message = await self._inbox.get()
+                if message.type == 'event':
+                    self._process_event(message.param)
+                elif message.type == 'flush':
+                    self._trigger_flush()
+                elif message.type == 'flush_contexts':
+                    self._context_keys.clear()
+                elif message.type == 'diagnostic':
+                    self._send_and_reset_diagnostics()
+                elif message.type == 'test_sync':
+                    await self._flush_workers.wait()
+                    if self._diagnostic_flush_workers is not None:
+                        await self._diagnostic_flush_workers.wait()
+                    message.param.set()
+                elif message.type == 'stop':
+                    await self._do_shutdown()
+                    message.param.set()
+                    return
+            except Exception:
+                log.error('Unhandled exception in event processor', exc_info=True)
+
+    def _trigger_flush(self):
+        if self._disabled:
+            return
+        payload = self._outbox.get_payload()
+        if self._diagnostic_accumulator:
+            self._diagnostic_accumulator.record_events_in_batch(len(payload.events))
+        if len(payload.events) > 0 or not payload.summary.is_empty():
+            task = EventPayloadSendTask(self._http, self._config, self._formatter, payload, self._handle_response)
+            if self._flush_workers.execute(task.run):
+                # The events have been handed off to a flush worker; clear them from our buffer.
+                self._outbox.clear()
+            else:
+                # We're already at our limit of concurrent flushes; leave the events in the buffer.
+                pass
+
+    def _send_and_reset_diagnostics(self):
+        if self._diagnostic_accumulator is not None and self._diagnostic_flush_workers is not None:
+            dropped_event_count = self._outbox.get_and_clear_dropped_count()
+            stats_event = self._diagnostic_accumulator.create_event_and_reset(dropped_event_count, self._deduplicated_contexts)
+            self._deduplicated_contexts = 0
+            task = DiagnosticEventSendTask(self._http, self._config, stats_event)
+            self._diagnostic_flush_workers.execute(task.run)
+
+    async def _do_shutdown(self):
+        self._flush_workers.stop()
+        await self._flush_workers.wait()
+
+        if self._diagnostic_flush_workers is not None:
+            self._diagnostic_flush_workers.stop()
+            await self._diagnostic_flush_workers.wait()
+
+        await self._http.close()
+
+
+class AsyncEventProcessor(EventProcessor):
+    def __init__(self, config: AsyncConfig, http=None, dispatcher_class=None, diagnostic_accumulator=None):
+        self._inbox = AsyncQueue(config.events_max_pending)
+        self._inbox_full = False
+        self._flush_timer = AsyncRepeatingTask("ldclient.events.flush", config.flush_interval, config.flush_interval, self.flush)
+        self._contexts_flush_timer = AsyncRepeatingTask("ldclient.events.context-flush", config.context_keys_flush_interval, config.context_keys_flush_interval, self._flush_contexts)
+        self._flush_timer.start()
+        self._contexts_flush_timer.start()
+        self._diagnostic_event_timer: Optional[AsyncRepeatingTask]
+        if diagnostic_accumulator is not None:
+            self._diagnostic_event_timer = AsyncRepeatingTask("ldclient.events.send-diagnostic", config.diagnostic_recording_interval, config.diagnostic_recording_interval, self._send_diagnostic)
+            self._diagnostic_event_timer.start()
+        else:
+            self._diagnostic_event_timer = None
+
+        self._close_lock = AsyncLock()
+        self._closed = False
+
+        (dispatcher_class or EventDispatcher)(self._inbox, config, http, diagnostic_accumulator)
+
+    def send_event(self, event: EventInput):
+        self._post_to_inbox(EventProcessorMessage('event', event))
+
+    def flush(self):
+        self._post_to_inbox(EventProcessorMessage('flush', None))
+
+    async def stop(self):
+        async with self._close_lock:
+            if self._closed:
+                return
+            self._closed = True
+        self._flush_timer.stop()
+        self._contexts_flush_timer.stop()
+        if self._diagnostic_event_timer:
+            self._diagnostic_event_timer.stop()
+        self.flush()
+        # Note that here we are not calling _post_to_inbox, because we *do* want to wait if the inbox
+        # is full; an orderly shutdown can't happen unless these messages are received.
+        await self._post_message_and_wait('stop')
+
+    def _post_to_inbox(self, message: EventProcessorMessage):
+        try:
+            self._inbox.put_nowait(message)
+        except queue.Full:
+            if not self._inbox_full:
+                # possible race condition here, but it's of no real consequence - we'd just get an extra log line
+                self._inbox_full = True
+                log.warning("Events are being produced faster than they can be processed; some events will be dropped")
+
+    async def _flush_contexts(self):
+        await self._inbox.put(EventProcessorMessage('flush_contexts', None))
+
+    async def _send_diagnostic(self):
+        await self._inbox.put(EventProcessorMessage('diagnostic', None))
+
+    # Used only in tests
+    async def _wait_until_inactive(self):
+        await self._post_message_and_wait('test_sync')
+
+    async def _post_message_and_wait(self, type):
+        reply = AsyncEvent()
+        await self._inbox.put(EventProcessorMessage(type, reply))
+        await reply.wait()
+
+    # These magic methods allow use of the "with" block in tests
+    async def __aenter__(self):
+        return self
+
+    async def __aexit__(self, type, value, traceback):
+        await self.stop()
+
+
+async def _post_events_with_retry(http_client: AsyncHTTPTransport, config: AsyncConfig, uri: str, payload_id: Optional[str], body: str, events_description: str):
+    hdrs = _headers(config)
+    hdrs['Content-Type'] = 'application/json'
+    if config.enable_event_compression:
+        hdrs['Content-Encoding'] = 'gzip'
+
+    if payload_id:
+        hdrs['X-LaunchDarkly-Event-Schema'] = str(__CURRENT_EVENT_SCHEMA__)
+        hdrs['X-LaunchDarkly-Payload-ID'] = payload_id
+    can_retry = True
+    context = "posting %s" % events_description
+    data: Union[bytes, str] = gzip.compress(bytes(body, 'utf-8')) if config.enable_event_compression else body
+    while True:
+        next_action_message = "will retry" if can_retry else "some events were dropped"
+        try:
+            r = await http_client.request('POST', uri, headers=hdrs, body=data)
+            if r.status < 300:
+                return r
+            recoverable = check_if_error_is_recoverable_and_log(context, r.status, None, next_action_message)
+            if not recoverable:
+                return r
+        except Exception as e:
+            check_if_error_is_recoverable_and_log(context, None, str(e), next_action_message)
+        if not can_retry:
+            return None
+        can_retry = False
+        # fixed delay of 1 second for event retries
+        await asyncio.sleep(1)