locust master crashes on Python 3.7: AttributeError: 'bytes' object has no attribute 'encode'

[sjagoe]

When running distributed, locust master crashes on Python 3.7.

Description of issue

In a master/slave (no-web) locust scenario, the master crashes immediately upon the slave connecting.

Expected behavior

The test starts and runs to completion.

Actual behavior

Sending hatch jobs to 1 ready clients
Traceback (most recent call last):
  File "/Users/sjagoe/.local/share/virtualenvs/locust/bin/locust", line 10, in <module>
    sys.exit(main())
  File "/Users/sjagoe/.local/share/virtualenvs/locust/lib/python3.7/site-packages/locust/main.py", line 505, in main
    runners.locust_runner.start_hatching(options.num_clients, options.hatch_rate)
  File "/Users/sjagoe/.local/share/virtualenvs/locust/lib/python3.7/site-packages/locust/runners.py", line 310, in start_hatching
    self.server.send_to_client(Message("hatch", data, client.id))
  File "/Users/sjagoe/.local/share/virtualenvs/locust/lib/python3.7/site-packages/locust/rpc/zmqrpc.py", line 15, in send_to_client
    self.socket.send_multipart([msg.node_id.encode(), msg.serialize()])
AttributeError: 'bytes' object has no attribute 'encode'

Environment settings

• OS: Mac OS 10.14.3 Mojave
• Python version: 3.7.1
• Locust version: 0.10.0

Steps to reproduce (for bug reports)

Code provided below.

1. Start a master locust

$ locust  -t 1m -c 10 -r 10 --no-web -H http://localhost:8000 --expect-slaves 1 --master

2. Start slave locust

$ locust --slave --master-host localhost

3. Check the master status; it crashes with the above error

locustfile

from locust import HttpLocust, TaskSet, task


class MyTasks(TaskSet):
    @task
    def task(self):
        self.client.get('/health')


class MyLocust(HttpLocust):
    min_wait = 1000
    max_wait = 1000
    task_set = MyTasks

A basic app to test

This is not really necessary; the test doesn't get far enough to make requests.

from flask import Flask
app = Flask('app')
@app.route('/health')
def health():
    return 'OK', 200

[sjagoe]

It seems this is fixed by 0.11.0 (#972), which I hadn't noticed released.

FYI 0.11.0 doesn't appear on github releases or in the changelog, nor is it tagged.