I have some groovy code that, under certain conditions, changes the
labels on nodes, and I've been having a hard time figuring out exactly
how to do it in a way that takes effect right away.
I can do something like
def slave = Hudson.instance.getSlave("slave-name")
slave.labelString = "new labels here"
This works "eventually". The slave shows the new labels immediately, but
for some period of time, Jenkins will continue to assign jobs based on
the old labels.
Something more like this
def h = Hudson.instance
def slave = h.getSlave("slave-name")
h.removeNode(slave)
h.labelString = "new labels here"
h.addNode(slave)
works immediately but has the disadvantage of temporarily removing the
slave, which causes various race conditions including possibly aborting
a job that jumped onto the slave right as we were about to change the
label. Reading the source code, I can see that stuff has to be updated
in Jenkins' internal idea of which slaves have which labels, that this
happens periodically for various reasons, and that adding and removing
the node triggers it at least for the affected node, but I can't find an
API to force it to happen for all nodes or for a specific node when I
want it to happen. Calling slave.save() doesn't seem to affect this. I
am trying to dig through the code path that is traversed when a slave is
reconfigured, but I'm hoping to find some simpler way.
For what it's worth, my use case is that we have dynamic slaves, and we
remove slaves that have been idle for a certain amount of time. The
problem is that sometimes a job may jump onto the slave as it's being
removed. This actually happens regularly. I want to work around the race
condition by first removing the labels that allow jobs to go there and
then rechecking whether it's idle, but I can't find a way to do that
that doesn't have an equally bad race condition.
--Jay
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