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Bug
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Resolution: Fixed
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Minor
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Jenkins 2.7.2
When "# of executors" is set to 0 for a node, not only does the node disappear from the listing (as abayer pointed out to me), but the node will 404 on it's /computer/$node page.
The work around is either to edit the config.xml and restart jenkins or use the script feature. The linked gist contains a script to set the number of executors to 2 which was used a temporary fix in our case.
[0] - https://gist.github.com/pono/8ab92fddb9461cd62e45923b910ce81f
- is duplicated by
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- Resolved
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- Resolved
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- links to
[JENKINS-41182] Nodes disappear if "# of executors" is set to 0
I see this issue too.
I set the executors to 0 by going to the node's config page, changing the executor number, and saving.
Then the node disappears.
The way I got the node back was to edit the node's config in JENKINS_HOME/nodes/NODE_NAME/config.xml, changing the executors count, and restarting my Jenkins instance. Then the node reappeared.
noob alot
added a comment - - edited I see this issue too.
I set the executors to 0 by going to the node's config page, changing the executor number, and saving.
Then the node disappears.
The way I got the node back was to edit the node's config in JENKINS_HOME/nodes/NODE_NAME/config.xml, changing the executors count, and restarting my Jenkins instance. Then the node reappeared. 
Alec Matschiner
added a comment - When I had set the node executor to 0 I observed all of the same issues described in the description here. I then tried to just create a new node with the same name, that didn't work since its still in the file system. As noob alot (nice name) mentioned you can edit the config and change the # of executors. I also noticed deleting that node's directory, restarting Jenkins, and then I'm able to create a new node with that name but then you'll have to reconfigure it.
I'd like to suggest maybe adding more of a warning when when someone is trying to change the executors to 0 in the node config page.
Alec Matschiner
added a comment - When I had set the node executor to 0 I observed all of the same issues described in the description here. I then tried to just create a new node with the same name, that didn't work since its still in the file system. As noob alot (nice name) mentioned you can edit the config and change the # of executors. I also noticed deleting that node's directory, restarting Jenkins, and then I'm able to create a new node with that name but then you'll have to reconfigure it.
I'd like to suggest maybe adding more of a warning when when someone is trying to change the executors to 0 in the node config page. This used to be a valid means of taking a node out of service, such that existing jobs would complete without new jobs being assigned. Is this functionality available some other way? If not, it would be a shame for the fix to be just preventing zero (though that's far better than the current behavior).
some other way?
Mark this node as temporarily offline.
IIRC there's going to be a message in the build log indicating the node went offline during the build (i.e. disconnected), but it's a bug.
After JENKINS-47793 (PR 3141), and the followup fix in PR 3292, nodes are no longer able to be configured to have 0 executors, so I think this can be closed as resolved.
The second PR was merged into 2.108 as 5c8cc45.
Here is a screenshot of the error I get when attempting to configure a node with 0 executors:
How are you setting nodes count to 0?