I am using CentOS 7 with uwsgi(2.0.17.1), uwsgi-plugin-python2 (2.0.17)
and Flask (1.0.2).
I have a flask application that runs many shell commands. Some of them
hangs indefinitely. I am sharing one of them as an example below, it is
easy to reproduce.
I am using uwsgi in threaded mode.
* #!/usr/bin/python**
** from flask import Flask**
** import subprocess**
****
** app = Flask(__name__)**
****
** @app.route("/test/")**
** def test():**
** print 'state 1'**
** p = subprocess.Popen(['ntpdate', '-u',
'0.pool.ntp.org'],close_fds=True)**
** print 'state 2'**
** out, err = p.communicate()**
** print 'state 3'**
****
** print 'output: {}'.format(out)**
** print 'error: {}'.format(err)**
** return 'finish'*
uwsgi command:
*> \# uwsgi --ini uwsgi.conf --http-socket :8001*
uwsgi conf file:
* [uwsgi]**
** #virtual env's base folder**
** base = /root/plaground**
** home = /usr/**
****
** #cmd options**
** bin = /usr/sbin/uwsgi**
****
** #python module to import**
** module = app:app**
****
** pythonpath = /root/playground**
****
** catch-exceptions = true**
****
** plugins-dir = /usr/lib64/uwsgi/**
** plugins = python**
****
** need-app = true**
****
** master = true**
** threads = 10*
After starting uwsgi, first request to /test route completes
succesfully, Second one stucking on command line execution and holds
response forever.
The first call output:
*state 1**
** state 2**
** 21 Sep 16:02:48 ntpdate[19943]: adjust time server 78.46.53.11
offset -0.000224 sec**
** state 3**
** output: None**
** error: None*
The second call output:
*state 1**
** state 2*
ps aux output after second call:
*# ps aux | grep ntpdate**
** root 20820 0.0 0.0 23632 1516 pts/3 S<+ 16:03 0:00
ntpdate -u 0.pool.ntp.org*
strace -p 20820 output:
* # strace -p 20820**
** strace: Process 20820 attached**
** restart_syscall(<... resuming interrupted call ...>) = 0 **
** poll([{fd=3, events=POLLIN}, {fd=4, events=POLLIN}], 2, 60000) = 0
(Timeout)**
** poll([{fd=3, events=POLLIN}, {fd=4, events=POLLIN}], 2, 60000) = 0
(Timeout*)
process fd list:
* # ls -l /proc/20820/fd**
** total 0**
** lr-x------ 1 root root 64 Eyl 21 16:05 0 -> /dev/null**
** lrwx------ 1 root root 64 Eyl 21 16:05 1 -> /dev/pts/3**
** lrwx------ 1 root root 64 Eyl 21 16:03 2 -> /dev/pts/3**
** lrwx------ 1 root root 64 Eyl 21 16:05 3 -> socket:[463358]**
** lrwx------ 1 root root 64 Eyl 21 16:05 4 -> socket:[463359]*
lsof output:
*# lsof -p 20820**
** COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME**
** ntpdate 20820 root cwd DIR 253,0 53 17726086
/root/playground**
** ntpdate 20820 root rtd DIR 253,0 244 64 / **
** ntpdate 20820 root txt REG 253,0 110240 224413
/usr/sbin/ntpdate **
** ntpdate 20820 root mem REG 253,0 106848 361769
/usr/lib64/libresolv-2.17.so **
** ntpdate 20820 root mem REG 253,0 31824 31549
/usr/lib64/libnss_dns-2.17.so **
** ntpdate 20820 root mem REG 253,0 62184 31551
/usr/lib64/libnss_files-2.17.so **
** ntpdate 20820 root mem REG 253,0 19896 142588
/usr/lib64/libattr.so.1.1.0 **
** ntpdate 20820 root mem REG 253,0 90664 142317
/usr/lib64/libz.so.1.2.7 **
** ntpdate 20820 root mem REG 253,0 19776 95386
/usr/lib64/libdl-2.17.so **
** ntpdate 20820 root mem REG 253,0 2173512 95380
/usr/lib64/libc-2.17.so **
** ntpdate 20820 root mem REG 253,0 20032 142590
/usr/lib64/libcap.so.2.22 **
** ntpdate 20820 root mem REG 253,0 2512832 190324
/usr/lib64/libcrypto.so.1.0.2k **
** ntpdate 20820 root mem REG 253,0 164240 95374
/usr/lib64/ld-2.17.so **
** ntpdate 20820 root 0r CHR 1,3 0t0 5078 /dev/null **
** ntpdate 20820 root 1u CHR 136,3 0t0 6 /dev/pts/3 **
** ntpdate 20820 root 2u CHR 136,3 0t0 6 /dev/pts/3 **
** ntpdate 20820 root 3u sock 0,7 0t0 463358 protocol:
UDP **
** ntpdate 20820 root 4u sock 0,7 0t0 463359 protocol:
UDPv6 *
If I try ntpdate command with shell or flask builtin web server, this
problem is not occuring.
I found similar problem on uwsgi github
(https://github.com/unbit/uwsgi/issues/1034) page but this fix does not
solve my problem.
I also tried it with uwsgi parameters close-on-exec and close-on-exec2.
No luck with these also.
Thanks for helping.
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