This is related to my previous question, but a different one.
I have the following fabfile:
from fabric.api import *
host1 = '192.168.200.181'
offline_host2 = '192.168.200.199'
host3 = '192.168.200.183'
env.hosts = [host1, offline_host2, host3]
env.warn_only = True
def df_h():
with settings(warn_only=True):
run("df -h | grep sda3")
And the output is:
[192.168.200.199] run: df -h | grep sda3
Fatal error: Low level socket error connecting to host 192.168.200.199: No route to host
Aborting.
After the execution hits the offline server, it aborts immediately, regardless of the other servers in the env.hosts list.
I have used the env setting "warn_only=True", but maybe I'm using it improperly.
How can I modify this behavior so that it will only prints the error and continue executing?
As of version 1.4 Fabric has a --skip-bad-hosts
option that can be set from the command line, or by setting the variable in your fab file.
env.skip_bad_hosts = True
Documentation for the option is here: http://docs.fabfile.org/en/latest/usage/fab.html#cmdoption--skip-bad-hosts
Don't forget to explicitly set the timeout value also.
According to the Fabric documentation on warn_only,
env.warn_only
"specifies whether or not to warn, instead of abort, whenrun
/sudo
/local
encounter error conditions.
This will not help in the case of a server being down, since the failure occurs during the SSH attempt before executing run
/sudo
/local
.
One solution would be to create a function to check if each server is up prior to executing your tasks. Below is the code that I used.
from __future__ import print_function
from fabric.api import run, sudo, local, env
import paramiko
import socket
host1 = '192.168.200.181'
offline_host2 = '192.168.200.199'
host3 = '192.168.200.183'
env.hosts = [host1, offline_host2, host3]
def df_h():
if _is_host_up(env.host, int(env.port)) is True:
run("df -h | grep sda1")
def _is_host_up(host, port):
# Set the timeout
original_timeout = socket.getdefaulttimeout()
new_timeout = 3
socket.setdefaulttimeout(new_timeout)
host_status = False
try:
transport = paramiko.Transport((host, port))
host_status = True
except:
print('***Warning*** Host {host} on port {port} is down.'.format(
host=host, port=port)
)
socket.setdefaulttimeout(original_timeout)
return host_status
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