Re: [libvirt] [PATCH v2 1/1] tools: do not loop in libvirt-guests test_connect

[Daniel P . Berrangé]

On Mon, Dec 16, 2019 at 08:20:59AM +0100, Christian Ehrhardt wrote:
> These days libvirt is pretty reliable and even remote connections
> (not the default for libvirt-guests anyway) either work or fail but are
> uncommon to be flaky.
> 
> On the other hand users might have disabled the service and while we are
> After=libvirtd for ordering we are not Requiring it. Adding that or any
> harder dependency might break our ordering. But if people have disabled
> libvirt they will do a full retry loop until timeout.
> 
> Lets drop the loop to be much faster if a remote is not reachable.
> 
> Fixes: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1854653

I extended this to add:

This reverts

  commit 4e7fc8305a53676ba2362bfaa8ca05c4851b7e12
  Author: Michal Prívozník 
  Date:   Fri Feb 21 12:46:08 2014 +0100

libvirt-guests: Wait for libvirtd to initialize

The race described in that commit no longer exists using systemd as
we now have socket activation. If not using systemd, then it is also
safe if using the libvirtd --daemon flag, since the parent process
won't return to the caller until the child is accepting connections.

and have now pushed this fix.

> 
> Reported-by: Doug Smythies 
> Signed-off-by: Christian Ehrhardt 
> ---
>  tools/libvirt-guests.sh.in | 21 ++---
>  1 file changed, 6 insertions(+), 15 deletions(-)



Regards,
Daniel
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[libvirt] [PATCH v2 1/1] tools: do not loop in libvirt-guests test_connect

[Christian Ehrhardt]

These days libvirt is pretty reliable and even remote connections
(not the default for libvirt-guests anyway) either work or fail but are
uncommon to be flaky.

On the other hand users might have disabled the service and while we are
After=libvirtd for ordering we are not Requiring it. Adding that or any
harder dependency might break our ordering. But if people have disabled
libvirt they will do a full retry loop until timeout.

Lets drop the loop to be much faster if a remote is not reachable.

Fixes: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1854653

Reported-by: Doug Smythies 
Signed-off-by: Christian Ehrhardt 
---
 tools/libvirt-guests.sh.in | 21 ++---
 1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/tools/libvirt-guests.sh.in b/tools/libvirt-guests.sh.in
index 4bc6e866f0..a881f6266e 100644
--- a/tools/libvirt-guests.sh.in
+++ b/tools/libvirt-guests.sh.in
@@ -37,8 +37,6 @@ SHUTDOWN_TIMEOUT=300
 PARALLEL_SHUTDOWN=0
 START_DELAY=0
 BYPASS_CACHE=0
-CONNECT_RETRIES=10
-RETRIES_SLEEP=1
 SYNC_TIME=0
 
 test -f "$sysconfdir"/sysconfig/libvirt-guests &&
@@ -90,19 +88,12 @@ test_connect()
 {
 uri=$1
 
-i=${CONNECT_RETRIES}
-while [ $i -gt 0 ]; do
-run_virsh "$uri" connect 2>/dev/null
-if [ $? -eq 0 ]; then
-return 0;
-fi
-sleep ${RETRIES_SLEEP}
-eval_gettext "Unable to connect to libvirt currently. Retrying .. \$i"
-i=$(($i-1))
-done
-eval_gettext "Can't connect to \$uri. Skipping."
-echo
-return 1
+if run_virsh "$uri" connect 2>/dev/null; then
+return 0;
+else
+eval_gettext "Can't connect to \$uri. Skipping."
+return 1
+fi
 }
 
 # list_guests URI PERSISTENT
-- 
2.24.1


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