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[dhcp_relay] Only attempt to start 'isc-dhcp-relay' group if it is not empty #1713

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May 16, 2018
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[dhcp_relay] Only attempt to start 'isc-dhcp-relay' group if it is not empty #1713

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21 changes: 12 additions & 9 deletions dockers/docker-dhcp-relay/start.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -6,13 +6,16 @@ rm -f /var/run/rsyslogd.pid
# Start rsyslog
supervisorctl start rsyslogd

# Wait for all interfaces to come up and be assigned IPv4 addresses before
# starting the DHCP relay agent(s). If an interface the relay should listen
# on is down, the relay agent will not start. If an interface the relay should
# listen on is up but does not have an IP address assigned when the relay
# agent starts, it will not listen or send on that interface for the lifetime
# of the process.
/usr/bin/wait_for_intf.sh
# If our supervisor config has entries in the "isc-dhcp-relay" group...
if [ $(supervisorctl status | grep -c "^isc-dhcp-relay:") -gt 0 ]; then
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if supervisorctl status | grep -q "^isc-dhcp-relay:"; then do the same, but faster

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Hmm... "grep -q" actually seems slower for me...

root@sonic:/# time supervisorctl status | grep -c "^isc-dhcp-relay:"
1

real    0m0.443s
user    0m0.348s
sys     0m0.088s
root@sonic:/# time supervisorctl status | grep -q "^isc-dhcp-relay:"

real    0m0.470s
user    0m0.384s
sys     0m0.068s

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:) when you write [ you run an external command in the bash script

$ which [
/usr/bin/[

So bash must to run subprocess to calculate the boolean for your if
Executing the subprocess is not so fast.
Faster would be use [[ which is internal bash instruction.
Or just use error code from grep directly as I wrote in the first comment.

# Wait for all interfaces to come up and be assigned IPv4 addresses before
# starting the DHCP relay agent(s). If an interface the relay should listen
# on is down, the relay agent will not start. If an interface the relay
# should listen on is up but does not have an IP address assigned when the
# relay agent starts, it will not listen or send on that interface for the
# lifetime of the process.
/usr/bin/wait_for_intf.sh

# Start the DHCP relay agent(s)
supervisorctl start isc-dhcp-relay:*
# Start all DHCP relay agent(s)
supervisorctl start isc-dhcp-relay:*
fi