The issue appears on my custom build of the Jenkins core, but seems it could be reproduced on newest versions as well.
We've experienced a network overloading, which has let to the exception in the PingThread on Jenkins master, which has closed the communication channel. However, the slave stills online and takes jobs, but any remote action fails (see logs above) => All scheduled builds fail with an error
The issue affects ssh-slaves only:
- Linux SSH slaves are "online", but all jobs on the fail with the error above
- Windows services have reconnected automatically...
- Windows JNLP slaves have reconnected as well