Wait for connection_lost in StreamWriter.drain

[asvetlov]

BPO	36801
Nosy	@vstinner, @asvetlov, @1st1, @miss-islington
PRs	bpo-36801: Fix waiting in StreamWriter.drain for closing SSL transport #13098 [3.7] bpo-36801: Fix waiting in StreamWriter.drain for closing SSL transport (GH-13098) #13176 [3.7] Revert "bpo-36801: Fix waiting in StreamWriter.drain for closing SSL transport (GH-13098)" #13328 Revert "bpo-36801: Fix waiting in StreamWriter.drain for closing SSL transport (GH-13098)" #13329 bpo-36801: Temporarily fix regression in writer.drain() #13330

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-05-05.13:44:32.210>
labels = ['3.8', 'type-bug', '3.7', 'expert-asyncio']
title = 'Wait for connection_lost in StreamWriter.drain'
updated_at = <Date 2019-05-14.21:39:18.302>
user = 'https://github.com/asvetlov'

bugs.python.org fields:

activity = <Date 2019-05-14.21:39:18.302>
actor = 'asvetlov'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['asyncio']
creation = <Date 2019-05-05.13:44:32.210>
creator = 'asvetlov'
dependencies = []
files = []
hgrepos = []
issue_num = 36801
keywords = ['patch']
message_count = 6.0
messages = ['341445', '341820', '341834', '342513', '342516', '342521']
nosy_count = 4.0
nosy_names = ['vstinner', 'asvetlov', 'yselivanov', 'miss-islington']
pr_nums = ['13098', '13176', '13328', '13329', '13330']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue36801'
versions = ['Python 3.7', 'Python 3.8']

[asvetlov]

Now await writer.drain() performs await sleep(0) if underlying transport is closing.

It works well only for plain sockets. SSL transport needs more context switches to shut down the SSL connection.
Drain wakes up too early to check if the transport is actually closed.

[miss-islington]

New changeset 1cc0ee7 by Miss Islington (bot) (Andrew Svetlov) in branch 'master':
bpo-36801: Fix waiting in StreamWriter.drain for closing SSL transport (GH-13098)
1cc0ee7

[miss-islington]

New changeset 93aa57a by Miss Islington (bot) in branch '3.7':
bpo-36801: Fix waiting in StreamWriter.drain for closing SSL transport (GH-13098)
93aa57a

[asvetlov]

Looks like the change introduced by the PR is not stable at least on Windows boxes

[vstinner]

New changeset c647ad9 by Victor Stinner in branch '3.7':
Revert "bpo-36801: Fix waiting in StreamWriter.drain for closing SSL transport (GH-13098)" (GH-13328)
c647ad9

[asvetlov]

New changeset 54b74fe by Andrew Svetlov in branch 'master':
bpo-36801: Temporarily fix regression in writer.drain() (bpo-13330)
54b74fe