fix missing import in socketrpc.py (branch 0.8)

[Shuliyey]

Issue

This pull-request is to branch 0.8.
Locust pure python RPC not working in distributed mode (this makes, message seem confusing) - (#680)

Currrent/Expected Behaviour

pure Python socket RPC implementation works (when pyzmq is not installed/detected)

~ # locust --host=http://qq.com --master
/usr/local/lib/python3.6/site-packages/locust/rpc/__init__.py:6: UserWarning: WARNING: Using pure Python socket RPC implementation instead of zmq. If running in distributed mode, this could cause a performance decrease. We recommend you to install the pyzmq python package when running in distributed mode.
  warnings.warn("WARNING: Using pure Python socket RPC implementation instead of zmq. If running in distributed mode, this could cause a performance decrease. We recommend you to install the pyzmq python package when running in distributed mode.")
[2017-11-12 21:37:49,379] 1e2974af6aec/INFO/locust.main: Starting web monitor at *:8089
[2017-11-12 21:37:49,380] 1e2974af6aec/INFO/locust.main: Starting Locust 0.8.1

Previous Behavour

pure Python socket RPC implementation doesn't work (when pyzmq is not installed/detected)

~ # locust --host=http://qq.com --master
/usr/local/lib/python3.6/site-packages/locust/rpc/__init__.py:6: UserWarning: WARNING: Using pure Python socket RPC implementation instead of zmq. If running in distributed mode, this could cause a performance decrease. We recommend you to install the pyzmq python package when running in distributed mode.
  warnings.warn("WARNING: Using pure Python socket RPC implementation instead of zmq. If running in distributed mode, this could cause a performance decrease. We recommend you to install the pyzmq python package when running in distributed mode.")
[2017-11-12 21:35:24,985] 1e2974af6aec/INFO/locust.main: Starting web monitor at *:8089
[2017-11-12 21:35:24,986] 1e2974af6aec/ERROR/stderr: Traceback (most recent call last):
[2017-11-12 21:35:24,986] 1e2974af6aec/ERROR/stderr: File "/usr/local/bin/locust", line 11, in <module>
[2017-11-12 21:35:24,987] 1e2974af6aec/ERROR/stderr: 
[2017-11-12 21:35:24,987] 1e2974af6aec/ERROR/stderr: sys.exit(main())
[2017-11-12 21:35:24,988] 1e2974af6aec/ERROR/stderr: 
[2017-11-12 21:35:24,988] 1e2974af6aec/ERROR/stderr: File "/usr/local/lib/python3.6/site-packages/locust/main.py", line 439, in main
[2017-11-12 21:35:24,989] 1e2974af6aec/ERROR/stderr: 
[2017-11-12 21:35:24,989] 1e2974af6aec/ERROR/stderr: runners.locust_runner = MasterLocustRunner(locust_classes, options)
[2017-11-12 21:35:24,990] 1e2974af6aec/ERROR/stderr: 
[2017-11-12 21:35:24,990] 1e2974af6aec/ERROR/stderr: File "/usr/local/lib/python3.6/site-packages/locust/runners.py", line 247, in __init__
[2017-11-12 21:35:24,991] 1e2974af6aec/ERROR/stderr: 
[2017-11-12 21:35:24,992] 1e2974af6aec/ERROR/stderr: self.server = rpc.Server(self.master_bind_host, self.master_bind_port)
[2017-11-12 21:35:24,992] 1e2974af6aec/ERROR/stderr: 
[2017-11-12 21:35:24,993] 1e2974af6aec/ERROR/stderr: File "/usr/local/lib/python3.6/site-packages/locust/rpc/socketrpc.py", line 74, in __init__
[2017-11-12 21:35:24,993] 1e2974af6aec/ERROR/stderr: 
[2017-11-12 21:35:24,994] 1e2974af6aec/ERROR/stderr: self.event_queue = gevent.queue.Queue()
[2017-11-12 21:35:24,994] 1e2974af6aec/ERROR/stderr: 
[2017-11-12 21:35:24,994] 1e2974af6aec/ERROR/stderr: AttributeError
[2017-11-12 21:35:24,995] 1e2974af6aec/ERROR/stderr: :
[2017-11-12 21:35:24,995] 1e2974af6aec/ERROR/stderr: module 'gevent' has no attribute 'queue'
[2017-11-12 21:35:24,996] 1e2974af6aec/ERROR/stderr: 

[cgoldberg]

0.8 is a release branch... this has already been taken care of in master (the rpc code was removed)

[Shuliyey]

if 0.8 is a release branch, we need to release hot fix, if there're bugs in it right. e.g. increase maintenance version 0.8.2 (users could install this specific version)

the pip install locustio also installs the 0.8 branch by default

[cgoldberg]

the rpc code has already been removed in master and this change will go out in the next release.

[Shuliyey]

so this next release, is it a new major version from the master branch? e.g. 1.0 .1
or is it a new maintenance version from the master branch? e.g. 0.8.2

i can see the 0.8.1 version installed by pip install locustio is the code from the 0.8 branch

[cgoldberg]

Locust doesn't really have a release cadence or an established release plan. The last few were cut from release candidate branches tagged from master. Once tagged and designated a release, a tarball is uploaded to PyPI (which is the official release channel).

…

On Sun, Nov 12, 2017 at 6:48 PM, 叶泽宇 ***@***.***> wrote: so do you release a new major version from the master branch? e.g. 0.9 .1 or do you release a new minor version from the master branch? e.g. 0.8.2 i can see the 0.8.1 version installed by pip install locustio has the same code as the 0.8 branch — You are receiving this because you modified the open/close state. Reply to this email directly, view it on GitHub <#681 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABD7-cLnZeoHoSFzDxRP68tXvUh-siYUks5s14O-gaJpZM4QbDeD> .

[Shuliyey]

so are we gonna leave branch 0.8 code as it is now, or we're merging master branch code into branch 0.8 (to abandon/remove the socketrpc.py file)? (because the current 0.8 branch has broken code in socketrpc.py)

[heyman]

The 0.8 version has a dependency on pyzmq (https://github.com/locustio/locust/blob/0.8/setup.py#L44) which means that if it's trying to import the pure socket implementation, something has already gone wrong since it failed to import zmq (see https://github.com/locustio/locust/blob/0.8/locust/rpc/__init__.py#L3-L7 and https://github.com/locustio/locust/blob/0.8/locust/rpc/zmqrpc.py#L1).

Therefore the real issue is how that can happen in the first place.

[Shuliyey]

@heyman, if you want to know how this can happen in the first place, you can check this thread #302, there's an edge case for alpine (when g++ is uninstalled).

here's also an example https://github.com/Shuliyey/locust-docker (that demonstrates pyzmq installed but not detected by locust, after g++ is uninstalled on alpine)

The purpose of this pull request is to raise the fact that in 0.8 branch code, it tries to switch to the socketrpc.py implementation under the cases when pyzmq is not installed/detected. When this happens it outputs the message it will use pure python rpc implementation to run locust in distributed mode. However this socketrpc.py implementation is not working, hence we should either remove the socketrpc.py implementation from branch 0.8 (this way we throw an error instead of warning on pyzmq not installed/detected) or we could implement socketrpc.py correctly in branch 0.8