Reloading vs. restarting uWSGI to activate code changes

Question

After reading the uWSGI's documentation on reloading, my understanding was that, for an app that uses lazy-apps, writing w to uWSGI's master FIFO should trigger a restart of all workers (and hence activate changes in the Python code).

However, that doesn't seem to work for me. I need to restart the systemd service (systemctl restart myservice) for code changes to take effect. Am I misunderstanding the documentation, or is there an issue with my setup?

My myservice.service file looks like this:

...
ExecStart=/usr/lib/myservice/virtualenv/bin/uwsgi --ini /etc/myservice/uwsgi.ini
ExecReload=/bin/echo 'w' > /run/myservice/masterfifo
ExecStop=/bin/kill -INT $MAINPID
...

In particular, systemctl reload myservice should write w to the master FIFO. I can see from the logs in systemctl status myservice that the reload was executed, but the responses to HTTP requests tell me that the old code is still active.

My /etc/myservice/uwsgi.ini like this:

[uwsgi]
processes = 16
procname-master = myservice
master-fifo = /run/myservice/masterfifo
touch-chain-reload
listen = 128

thunder-lock
reload-on-as = 4096
limit-as = 8192
max-requests = 2000

; termination options
vacuum
die-on-term

; application
chdir = /usr/lib/myservice
virtualenv = /usr/lib/myservice/virtualenv
module = myservice.uwsgi
callable = app  
master
need-app
enable-threads
lazy = True
lazy-apps = True

; logging
logto = /var/log/myservice/uwsgi.log
log-maxsize = 5242880
logdate = [%%Y/%%m/%%d %%H:%%M:%%S]
disable-logging

; stats server
stats-server = :8201
memory-report

; unix socket config (nginx->uwsgi)
socket = /run/myservice/myservice.sock
chown-socket = api
chmod-socket = 660

I'm running version 2.0.19.1 of uWSGI.

Answer 1

All I know about uWSGI is that it exists, but I noticed a mistake here:

ExecReload=/bin/echo 'w' > /run/myservice/masterfifo

The man page explains the problem:

This syntax is inspired by shell syntax, but only the meta-characters and expansions described in the following paragraphs are understood, and the expansion of variables is different. Specifically, redirection using "<", "<<", ">", and ">>", pipes using "|", running programs in the background using "&", and other elements of shell syntax are not supported.

In other words, no redirection is taking place and echo will simply receive 3 arguments to print: char w, char > and the string /run/myservice/masterfifo.

Try this instead:

ExecReload=/bin/sh -c '/bin/echo w > /run/myservice/masterfifo'