walt-log-echo
logging tool¶
walt-log-echo
is a logging tool provided on all nodes. It allows to
emit loglines. For more info about WalT logging in general, see
walt help show logging.
Basic usage¶
You can run walt-log-echo
like this:
[node]$ walt-log-echo <stream-name> <log-line>
This will emit a new <log-line>
attached to logstream
<stream-name>
. You can obviously call this in the experiment scripts
you run on nodes.
Advanced usage and performance tips¶
If you want to emit many log lines, you should consider using
walt-log-cat
instead. (see
walt help show log-cat)
If you have means to record precise event timestamps (e.g. network
timestamps), you can specify them by using option --timestamp
:
[node]$ walt-log-echo --timestamp <ts> <stream-name> <log-line>
The <ts>
value must be a UNIX timestamp, i.e. a floating point
number of seconds since the ‘EPOCH’ (january 1, 1970). Without this
option, the timestamp recorded will be the current time when
walt-log-echo
is run.
Simple example¶
I first run this in a first terminal:
$ walt log show --realtime
This will catch all loglines emitted from my nodes. (see walt help show log-realtime for more info)
Then, on a second terminal:
$ walt node shell node1
Caution: changes outside /persist will be lost on next node reboot.
Run 'walt help show shells' for more info.
root@node1:~# walt-log-echo 'exp1' 'this is a logline of exp1'
root@node1:~#
And immediately the logline is catched on first terminal:
$ walt log show --realtime
17:35:53.147851 node1.exp1 -> this is a logline of exp1