Please assume there's an app/script which prints a great deal of logging data to stdout
. When something bad but expected happens within the script (exception handling), scripts reports an error to stderr
and then continues doing what it was doing.
systemd
for sure is capable to collect this data and put it into the journal
:
# systemctl show sd_test.service | grep 'Standard[OE]'
StandardOutput=journal
StandardError=inherit
My sd_test.service
:
[Unit]
Description=A Test Service simply printing to stdout and stderr
[Service]
Type=simple
ExecStart=/home/narunas/sd_test.py
[Install]
WantedBy=multi-user.target
journalctl
now has required data:
# systemctl reenable sd_test.service
# systemctl restart sd_test.service
# journalctl -n -u sd_test
-- Logs begin at Fri 2016-11-11 15:49:33 GMT, end at Tue 2017-01-03 19:23:18 GMT. --
Jan 03 19:23:01 dev-box sd_test.py[13183]: This is "stderr": 2
Jan 03 19:23:02 dev-box sd_test.py[13183]: This is "stdout": 2
Jan 03 19:23:03 dev-box sd_test.py[13183]: This is "stderr": 3
Jan 03 19:23:07 dev-box sd_test.py[13183]: This is "stdout": 3
Jan 03 19:23:07 dev-box sd_test.py[13183]: This is "stderr": 4
Jan 03 19:23:11 dev-box sd_test.py[13183]: This is "stdout": 4
Jan 03 19:23:12 dev-box sd_test.py[13183]: This is "stderr": 5
Jan 03 19:23:15 dev-box sd_test.py[13183]: This is "stdout": 5
Jan 03 19:23:17 dev-box sd_test.py[13183]: This is "stdout": 6
Jan 03 19:23:18 dev-box sd_test.py[13183]: This is "stderr": 6
I know there's _TRANSPORT
journal field, sadly stderr
is tagged with the same tag:
stdout
for those read from a service's standard output or error output
I can of course change my ExecStart
like so:
ExecStart=/bin/bash -c '/home/narunas/sd_test.py 2> /some/file/path'
But that is not ideal as I'm mixing up journal
with files...
Could you recommend a better way to view stderr
log only?
EDIT_1
As suggested in the comments I just tried -o verbose
option:
Tue 2017-01-03 20:23:49.994171 GMT [s=0b15e5c69e2f476eb200d2bdda769465;i=12e28;b=db55b41f61144ae69cc86acfb75209fb;m=42e034d52dc;t=5453672322abb;x=8b696c5447bc2bce]
PRIORITY=6
_UID=0
_GID=0
_CAP_EFFECTIVE=3fffffffff
_SYSTEMD_SLICE=system.slice
_BOOT_ID=db55b41f61144ae69cc86acfb75209fb
_MACHINE_ID=c5a9e78e2c854065a9b041c58f07c2b2
_HOSTNAME=dev-box
SYSLOG_FACILITY=3
_TRANSPORT=stdout
SYSLOG_IDENTIFIER=sd_test.py
_COMM=python3
_EXE=/usr/bin/python3.5
_CMDLINE=python3 /home/narunas/sd_test.py
_SYSTEMD_CGROUP=/system.slice/sd_test.service
_SYSTEMD_UNIT=sd_test.service
MESSAGE=This is "stdout": 729
_PID=13183
Tue 2017-01-03 20:23:52.979981 GMT [s=0b15e5c69e2f476eb200d2bdda769465;i=12e29;b=db55b41f61144ae69cc86acfb75209fb;m=42e037ae22e;t=54536725fba0d;x=8802c0df56848907]
PRIORITY=6
_UID=0
_GID=0
_CAP_EFFECTIVE=3fffffffff
_SYSTEMD_SLICE=system.slice
_BOOT_ID=db55b41f61144ae69cc86acfb75209fb
_MACHINE_ID=c5a9e78e2c854065a9b041c58f07c2b2
_HOSTNAME=dev-box
SYSLOG_FACILITY=3
_TRANSPORT=stdout
SYSLOG_IDENTIFIER=sd_test.py
_COMM=python3
_EXE=/usr/bin/python3.5
_CMDLINE=python3 /home/narunas/sd_test.py
_SYSTEMD_CGROUP=/system.slice/sd_test.service
_SYSTEMD_UNIT=sd_test.service
MESSAGE=This is "stderr": 745
_PID=13183
-o json-pretty
produce same results as -o verbose
, but in a different format.
Apart my script's silly MESSAGE there's nothing useful that would let to distinguish what is stderr
or stdout
.
EDIT_2
With StandardError=journal
.
Unit:
[Unit]
Description=A Test Service simply printing to stdout and stderr
[Service]
Type=simple
ExecStart=/home/narunas/sd_test.py
StandardError=journal
[Install]
WantedBy=multi-user.target
journalctl:
# systemctl reenable sd_test.service
# systemctl restart sd_test.service
# journalctl -n -u sd_test -o verbose
Tue 2017-01-03 22:34:55.381341 GMT [s=0b15e5c69e2f476eb200d2bdda769465;i=13ab7;b=db55b41f61144ae69cc86acfb75209fb;m=42fd81d9b7e;t=545384702735d;x=e65570c85dfec1dc]
_TRANSPORT=stdout
PRIORITY=6
SYSLOG_FACILITY=3
SYSLOG_IDENTIFIER=sd_test.py
_UID=0
_GID=0
_COMM=python3
_EXE=/usr/bin/python3.5
_CMDLINE=python3 /home/narunas/sd_test.py
_CAP_EFFECTIVE=3fffffffff
_SYSTEMD_CGROUP=/system.slice/sd_test.service
_SYSTEMD_UNIT=sd_test.service
_SYSTEMD_SLICE=system.slice
_BOOT_ID=db55b41f61144ae69cc86acfb75209fb
_MACHINE_ID=c5a9e78e2c854065a9b041c58f07c2b2
_HOSTNAME=dev-box
MESSAGE=This is "stdout": 10
_PID=21280
Tue 2017-01-03 22:34:57.397880 GMT [s=0b15e5c69e2f476eb200d2bdda769465;i=13ab8;b=db55b41f61144ae69cc86acfb75209fb;m=42fd83c6099;t=5453847213878;x=610237e701d596d4]
_TRANSPORT=stdout
PRIORITY=6
SYSLOG_FACILITY=3
SYSLOG_IDENTIFIER=sd_test.py
_UID=0
_GID=0
_COMM=python3
_EXE=/usr/bin/python3.5
_CMDLINE=python3 /home/narunas/sd_test.py
_CAP_EFFECTIVE=3fffffffff
_SYSTEMD_CGROUP=/system.slice/sd_test.service
_SYSTEMD_UNIT=sd_test.service
_SYSTEMD_SLICE=system.slice
_BOOT_ID=db55b41f61144ae69cc86acfb75209fb
_MACHINE_ID=c5a9e78e2c854065a9b041c58f07c2b2
_HOSTNAME=dev-box
MESSAGE=This is "stderr": 11
_PID=21280
Tue 2017-01-03 22:35:02.403014 GMT [s=0b15e5c69e2f476eb200d2bdda769465;i=13abc;b=db55b41f61144ae69cc86acfb75209fb;m=42fd888bfe7;t=54538476d97c6;x=a6362820cb52ce9]
_TRANSPORT=stdout
PRIORITY=6
SYSLOG_FACILITY=3
SYSLOG_IDENTIFIER=sd_test.py
_UID=0
_GID=0
_COMM=python3
_EXE=/usr/bin/python3.5
_CMDLINE=python3 /home/narunas/sd_test.py
_CAP_EFFECTIVE=3fffffffff
_SYSTEMD_CGROUP=/system.slice/sd_test.service
_SYSTEMD_UNIT=sd_test.service
_SYSTEMD_SLICE=system.slice
_BOOT_ID=db55b41f61144ae69cc86acfb75209fb
_MACHINE_ID=c5a9e78e2c854065a9b041c58f07c2b2
_HOSTNAME=dev-box
MESSAGE=This is "stderr": 12
_PID=21280
journalctl … -o verbose
or-o json-pretty
to see if there is anything...StandardError=journal
get the _TRANSPORT set to stderr?