[WIP] Use asyncio protocol

[seandstewart]

This supersedes #1216 and is an attempt to address the latency issues in #1208 -

Mainly I've gone through and added a Python parser which matches the hiredis implementation as closely as possible. I've also made a few adjustments to the RedisProtocol as introduced by @m-novikov in #1216.

I spent all day yesterday trying to get perfomance for this port to match something close to what @artesby & @m-novikov reported in their benchmarks in #1208, but I have a suspicion it's not possible.

@m-novikov and @artesby I'd be much obliged if you could test this implementation to see if we're actually going the right direction with this change. It's not yet ready for the real world and there are a few failing tests, but I don't want to keep barking up this tree if it won't get us where we need to go.

[lgtm-com]

This pull request introduces 6 alerts and fixes 1 when merging fbedfbe into 659a14d - view on LGTM.com

new alerts:

• 4 for Unused import
• 1 for Suspicious unused loop iteration variable
• 1 for Wrong name for an argument in a class instantiation

fixed alerts:

• 1 for Missing call to `__init__` during object initialization

[codecov]

Codecov Report

Merging #1287 (659a14d) into master (659a14d) will not change coverage.
The diff coverage is n/a.

❗ Current head 659a14d differs from pull request most recent head 834d431. Consider uploading reports for the commit 834d431 to get more accurate results

@@           Coverage Diff           @@
##           master    #1287   +/-   ##
=======================================
  Coverage   90.75%   90.75%           
=======================================
  Files          21       21           
  Lines        6947     6947           
  Branches      889      889           
=======================================
  Hits         6305     6305           
  Misses        469      469           
  Partials      173      173           

Flag	Coverage Δ
unit	90.68% <0.00%> (ø)

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[bmerry]

Sorry, I'm now in a different team that's not working with aioredis, so I'm not available for reviewing.

[Andrew-Chen-Wang]

thanks for all the help along the way @bmerry !

[seandstewart]

General update here -

Anything involving a MONITOR or PubSub SUBSCRIBE is not currently compatible. This is because both of these commands create an open channel which streams data as it is received, but the current Protocol implementation attaches all received data into a single future which is associated to the original packed command. We'll need an alternative implementation which allows these commands to listen on the stream decoupled from the original sent command.

[lgtm-com]

This pull request introduces 2 alerts and fixes 1 when merging 834d431 into 659a14d - view on LGTM.com

new alerts:

• 1 for Redundant assignment
• 1 for Wrong name for an argument in a class instantiation

fixed alerts:

• 1 for Missing call to `__init__` during object initialization

[matemax]

Hi guys. Any update? Performance degradation is blocks an update to 2.* version in our projects =(

[Andrew-Chen-Wang]

@matemax all updates are going to redis/redis-py. This repo at some point will convert back to its 1.3.1 version