async def test_restart_from_historical():
"""
If we ask the conversation to start again while we're reading historical events
we should re-send the most recent page request.
In this scenario, we start reading the stream at event 10, we receive a
page with 2 events, we request the next page starting at 12.
When we restart the conversation, we should again request the page starting at 12.
"""
conversation_id = uuid.uuid4()
output = TeeQueue()
convo = CatchupSubscription("my-stream",
start_from=10,
conversation_id=conversation_id)
await convo.start(output)
await reply_to(
convo,
(ReadStreamEventsResponseBuilder(stream="stream-123").with_event(
event_number=10).with_event(
event_number=11).with_next_event_number(12).build()),
output,
)
await convo.start(output)
[first_page, second_page, second_page_again
] = [read_as(proto.ReadStreamEvents, m) for m in output.items]
assert second_page.from_event_number == second_page_again.from_event_number
async def test_should_perform_a_catchup_when_subscription_is_confirmed():
"""
When we have read all the events in the stream, we should send a
request to subscribe for new events.
We should start reading catchup events from the `next_event_number` returned
by the historical event read.
"""
convo = CatchupSubscription("my-stream")
output = TeeQueue()
await convo.start(output)
await reply_to(
convo,
ReadStreamEventsResponseBuilder().with_next_event_number(
17).at_end_of_stream().build(),
output,
)
await confirm_subscription(convo, output, event_number=42, commit_pos=40)
[read_historial, subscribe, catch_up] = await output.next_event(3)
assert read_historial.command == msg.TcpCommand.ReadStreamEventsForward
assert subscribe.command == msg.TcpCommand.SubscribeToStream
assert catch_up.command == msg.TcpCommand.ReadStreamEventsForward
payload = proto.ReadStreamEvents()
payload.ParseFromString(catch_up.payload)
assert payload.event_stream_id == "my-stream"
assert payload.from_event_number == 17
async def test_subscribe_with_context_manager():
conversation_id = uuid.uuid4()
output = TeeQueue()
convo = CatchupSubscription("my-stream", conversation_id=conversation_id)
await convo.start(output)
# Create a subscription with three events in it
await reply_to(convo, EMPTY_STREAM_PAGE, output)
await confirm_subscription(convo, output, event_number=10, commit_pos=10)
await reply_to(convo, EMPTY_STREAM_PAGE, output)
for i in range(0, 3):
await reply_to(convo,
event_appeared(event_id=uuid.uuid4(), event_number=i),
output)
async with (await convo.result) as subscription:
events_seen = 0
async for _ in subscription.events:
events_seen += 1
if events_seen == 3:
break
# Having exited the context manager it should send
# an unsubscribe message
[read_historical, subscribe, catch_up, unsubscribe] = output.items
assert unsubscribe.command == msg.TcpCommand.UnsubscribeFromStream
assert unsubscribe.conversation_id == conversation_id
async def test_start_read_phase():
"""
A "catchup" subscription starts by iterating the events in the stream until
it reaches the most recent event.
This is the "Read" phase.
"""
output = TeeQueue()
conversation_id = uuid.uuid4()
convo = CatchupSubscription("my-stream",
start_from=0,
conversation_id=conversation_id)
await convo.start(output)
[request] = output.items
body = proto.ReadStreamEvents()
body.ParseFromString(request.payload)
assert request.command is msg.TcpCommand.ReadStreamEventsForward
assert body.event_stream_id == "my-stream"
assert body.from_event_number == 0
assert body.resolve_link_tos is True
assert body.require_master is False
assert body.max_count == 100
async def test_subscription_dropped_mid_stream():
convo = CatchupSubscription("my-stream")
output = TeeQueue()
empty_page = (ReadStreamEventsResponseBuilder(
stream="stream-123").at_end_of_stream().build())
await reply_to(convo, empty_page, output)
await confirm_subscription(convo, output, event_number=10, commit_pos=10)
await reply_to(convo, empty_page, output)
subscription = convo.result.result()
await reply_to(convo, event_appeared(), output)
await drop_subscription(convo, output)
events = [e async for e in subscription.events]
assert len(events) == 1
async def test_restart_from_catchup():
"""
If the connection drops during the catchup phase, we need to unsubscribe
from the stream and then go back to reading historical events starting from
the last page.
=> Request historical events
<= Receive 1 event, next_event = 1
=> Subscribe
<= Confirmed
=> Catch up from 1
** Restart **
=> Unsubscribe
<= Confirmed
=> Read historical from 1
<= Empty page
=> Subscribe
"""
conversation_id = uuid.uuid4()
output = TeeQueue()
convo = CatchupSubscription("my-stream", conversation_id=conversation_id)
await convo.start(output)
await output.get()
page_one = (ReadStreamEventsResponseBuilder().with_event(
event_number=1).with_next_event_number(1).at_end_of_stream().build())
await reply_to(convo, page_one, output)
await output.get()
await confirm_subscription(convo, output, event_number=10, commit_pos=10)
first_catch_up = read_as(proto.ReadStreamEvents, await output.get())
await reply_to(convo, page_one, output)
# Restart
await convo.start(output)
unsubscribe = await output.get()
assert first_catch_up.from_event_number == 1
assert unsubscribe.command == msg.TcpCommand.UnsubscribeFromStream
await drop_subscription(convo, output)
second_catchup = read_as(proto.ReadStreamEvents, await output.get())
assert second_catchup.from_event_number == 1
async def test_unsubscription():
correlation_id = uuid.uuid4()
output = TeeQueue()
convo = CatchupSubscription("my-stream", conversation_id=correlation_id)
await convo.start(output)
await reply_to(convo, EMPTY_STREAM_PAGE, output)
await confirm_subscription(convo, output, event_number=10, commit_pos=10)
await reply_to(convo, EMPTY_STREAM_PAGE, output)
sub = convo.result.result()
await sub.unsubscribe()
[read_historical, subscribe, catch_up, unsubscribe] = output.items
assert unsubscribe.command == msg.TcpCommand.UnsubscribeFromStream
assert unsubscribe.conversation_id == correlation_id
async def test_paging():
"""
During the read phase, we expect to page through multiple batches of
events. In this scenario we have two batches, each of two events.
"""
convo = CatchupSubscription("my-stream")
output = TeeQueue()
await convo.start(output)
await output.get()
event_1_id = uuid.uuid4()
event_2_id = uuid.uuid4()
event_3_id = uuid.uuid4()
event_4_id = uuid.uuid4()
first_response = (ReadStreamEventsResponseBuilder().with_event(
event_id=event_1_id, event_number=32).with_event(
event_id=event_2_id,
event_number=33).with_next_event_number(34)).build()
second_response = (ReadStreamEventsResponseBuilder().with_event(
event_id=event_3_id,
event_number=34).with_event(event_id=event_4_id,
event_number=35)).build()
await reply_to(convo, first_response, output)
subscription = await convo.result
event_1 = await anext(subscription.events)
event_2 = await anext(subscription.events)
assert event_1.id == event_1_id
assert event_2.id == event_2_id
reply = await output.get()
body = proto.ReadStreamEvents()
body.ParseFromString(reply.payload)
assert body.from_event_number == 34
await reply_to(convo, second_response, output)
event_3 = await anext(subscription.events)
event_4 = await anext(subscription.events)
assert event_3.id == event_3_id
assert event_4.id == event_4_id
async def test_paging_projection():
"""
"""
convo = CatchupSubscription("my-stream")
output = TeeQueue()
await convo.start(output)
await output.get()
event_1_id = uuid.uuid4()
event_2_id = uuid.uuid4()
event_3_id = uuid.uuid4()
event_4_id = uuid.uuid4()
first_response = (ReadStreamEventsResponseBuilder().with_event(
event_id=event_1_id, event_number=0, link_event_number=32).with_event(
event_id=event_2_id, event_number=0,
link_event_number=33).with_next_event_number(34)).build()
second_response = (ReadStreamEventsResponseBuilder().with_event(
event_id=event_3_id, event_number=0,
link_event_number=34).with_event(event_id=event_4_id,
event_number=0,
link_event_number=35)).build()
await reply_to(convo, first_response, output)
subscription = await convo.result
event_1 = await anext(subscription.events)
event_2 = await anext(subscription.events)
assert event_1.id == event_1_id
assert event_2.id == event_2_id
reply = await output.get()
body = proto.ReadStreamEvents()
body.ParseFromString(reply.payload)
assert body.from_event_number == 34
await reply_to(convo, second_response, output)
event_3 = await anext(subscription.events)
event_4 = await anext(subscription.events)
assert event_3.id == event_3_id
assert event_4.id == event_4_id
async def test_subscription_failure_mid_stream():
output = TeeQueue()
convo = CatchupSubscription("my-stream")
event_id = uuid.uuid4()
await reply_to(convo, EMPTY_STREAM_PAGE, output)
await confirm_subscription(convo, output, event_number=10, commit_pos=10)
await reply_to(convo, EMPTY_STREAM_PAGE, output)
subscription = convo.result.result()
await reply_to(convo, event_appeared(event_id=event_id), output)
await drop_subscription(
convo, output, msg.SubscriptionDropReason.SubscriberMaxCountReached)
with pytest.raises(exn.SubscriptionFailed):
event = await anext(subscription.events)
assert event.id == event_id
await anext(subscription.events)
async def test_live_restart():
"""
If we reset the conversation while we are live, we should first unsubscribe
then start a historical read from the last read event.
=> Read historial
<= empty
=> subscribe
<= confirmed
=> catchup
<= empty
<= event 1 appeared
<= event 2 appeared
RESTART
=> unsubscribe
<= dropped
=> Read historical from 2
"""
output = TeeQueue()
convo = CatchupSubscription("my-stream")
await convo.start(output)
await reply_to(convo, EMPTY_STREAM_PAGE, output)
await confirm_subscription(convo, output, event_number=10, commit_pos=10)
await reply_to(convo, EMPTY_STREAM_PAGE, output)
await reply_to(convo, event_appeared(event_number=1), output)
await reply_to(convo, event_appeared(event_number=2), output)
output.items.clear()
await convo.start(output)
await drop_subscription(convo, output)
[unsubscribe, read_historical] = output.items
read_historical = read_as(proto.ReadStreamEvents, read_historical)
assert unsubscribe.command == msg.TcpCommand.UnsubscribeFromStream
assert read_historical.from_event_number == 2
async def test_subscribes_at_end_of_stream():
"""
When we have read all the events in the stream, we should send a
request to subscribe for new events.
"""
convo = CatchupSubscription("my-stream")
output = TeeQueue()
await convo.start(output)
await output.get()
await reply_to(
convo,
ReadStreamEventsResponseBuilder().at_end_of_stream().build(), output)
reply = await output.get()
payload = proto.SubscribeToStream()
payload.ParseFromString(reply.payload)
assert reply.command == msg.TcpCommand.SubscribeToStream
assert payload.event_stream_id == "my-stream"
assert payload.resolve_link_tos is True
async def test_historical_duplicates():
"""
It's possible that we receive the reply to a ReadStreamEvents request after we've
resent the request. This will result in our receiving a duplicate page.
In this instance, we should not raise duplicate events.
=> Request historical
RESTART
=> Request historical
<= 2 events
<= 3 events
Should only see the 3 unique events
"""
two_events = (ReadStreamEventsResponseBuilder().with_event(
event_number=1).with_event(event_number=2).with_next_event_number(
2).at_end_of_stream().build())
three_events = (ReadStreamEventsResponseBuilder().with_event(
event_number=1).with_event(event_number=2).with_event(event_number=3).
with_next_event_number(3).at_end_of_stream().build())
output = TeeQueue()
convo = CatchupSubscription("my-stream")
await convo.start(output)
await convo.start(output)
await reply_to(convo, two_events, output)
await reply_to(convo, three_events, output)
[event_1, event_2, event_3] = await anext(convo.subscription.events, 3)
assert event_1.event_number == 1
assert event_2.event_number == 2
assert event_3.event_number == 3
async def test_end_of_stream():
"""
During the Read phase, we yield the events to the subscription so that the
user is unaware of the chicanery in the background.
When we reach the end of the stream, we should send a subscribe message to
start the volatile subscription.
"""
convo = CatchupSubscription("my-stream")
output = TeeQueue()
await convo.start(output)
event_1_id = uuid.uuid4()
event_2_id = uuid.uuid4()
response = (ReadStreamEventsResponseBuilder(
stream="stream-123").at_end_of_stream().with_event(
event_id=event_1_id,
event_number=32).with_event(event_id=event_2_id,
event_number=33)).build()
await reply_to(convo, response, output)
subscription = await convo.result
event_1 = await anext(subscription.events)
event_2 = await anext(subscription.events)
assert event_1.stream == "stream-123"
assert event_1.id == event_1_id
assert event_1.event_number == 32
assert event_2.stream == "stream-123"
assert event_2.id == event_2_id
assert event_2.event_number == 33
async def test_subscription_duplicates():
"""
If we receive subscription events while catching up, we buffer them internally.
If we restart the conversation at that point we need to make sure we clear our buffer
and do not raise duplicate events.
=> Request historical
<= Empty
=> Subscribe to stream
<= Confirmed
=> Request catchup
<= Subscribed event 2 appeared
<= Event 1, not end of stream
RESTART
=> Drop subscription
<= Dropped
=> Request historical from_event = 1
<= Receive event 2 at end of stream
=> Subscribe
<= Confirmed
=> Catchup
<= Subscribed event 3 appeared
<= Empty
Should yield [event 1, event 2, event 3]
"""
event_1_not_end_of_stream = (ReadStreamEventsResponseBuilder().with_event(
event_number=1).with_next_event_number(2).build())
event_2_at_end_of_stream = (ReadStreamEventsResponseBuilder().with_event(
event_number=2).with_next_event_number(2).at_end_of_stream().build())
output = TeeQueue()
convo = CatchupSubscription("my-stream")
await convo.start(output)
await reply_to(convo, EMPTY_STREAM_PAGE, output)
await confirm_subscription(convo, output, event_number=10, commit_pos=10)
await reply_to(convo, event_appeared(event_number=2), output)
await reply_to(convo, event_1_not_end_of_stream, output)
# RESTART
await convo.start(output)
output.items.clear()
await drop_subscription(convo, output)
second_read_historical = read_as(proto.ReadStreamEvents, output.items[0])
await reply_to(convo, event_2_at_end_of_stream, output)
await confirm_subscription(convo, output, event_number=10, commit_pos=10)
await reply_to(convo, event_appeared(event_number=3), output)
await reply_to(convo, EMPTY_STREAM_PAGE, output)
[event_1, event_2, event_3] = await anext(convo.subscription.events, 3)
assert event_1.event_number == 1
assert event_2.event_number == 2
assert event_3.event_number == 3
assert second_read_historical.from_event_number == 2
async def test_should_return_catchup_events_before_subscribed_events():
"""
It's possible that the following sequence of events occurs:
* The client reads the last batch of events from a stream containing
50 events.
* The client sends SubscribeToStream
* Event 51 is written to the stream
* The server creates a subscription starting at event 51 and
responds with SubscriptionConfirmed
* Event 52 is written to the stream
* The client receives event 52.
To solve this problem, the client needs to perform an additional read
to fetch any missing events created between the last batch and the
subscription confirmation.
--------------
In this scenario, we read a single event (1) from the end of the stream
and expect to create a subscription.
We receive event 4 immediately on the subscription. We expect that the
client requests missing events.
We receive two pages, of one event each: 3, and 4, and then drop the subscription.
Lastly, we expect that the events are yielded in the correct order
despite being received out of order and that we have no duplicates.
"""
convo = CatchupSubscription("my-stream")
output = TeeQueue()
await convo.start(output)
await output.get()
last_page = (
ReadStreamEventsResponseBuilder().at_end_of_stream().with_event(
event_number=1, type="a").build())
subscribed_event = event_appeared(event_number=4, type="d")
first_catchup = (ReadStreamEventsResponseBuilder().with_event(
event_number=2, type="b").build())
second_catchup = (ReadStreamEventsResponseBuilder().with_event(
event_number=3, type="c").with_event(event_number=4,
type="d")).build()
await reply_to(convo, last_page, output)
assert (await output.get()).command == msg.TcpCommand.SubscribeToStream
await confirm_subscription(convo, output, event_number=3)
await reply_to(convo, subscribed_event, output)
assert (await
output.get()).command == msg.TcpCommand.ReadStreamEventsForward
await reply_to(convo, first_catchup, output)
assert (await
output.get()).command == msg.TcpCommand.ReadStreamEventsForward
await reply_to(convo, second_catchup, output)
await drop_subscription(convo, output)
events = []
subscription = await convo.result
async for e in subscription.events:
events.append(e)
assert len(events) == 4
[a, b, c, d] = events
assert a.event_number == 1
assert b.event_number == 2
assert c.event_number == 3
assert d.event_number == 4
