SSH Slaves vs JNLP Slaves
What are the advantages / disadvantages of each? Which is preferred?
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Hi Owen,
Firstly let's talk about agents (and not slaves which are sooo Jenkins 1.x) :-)
Technically speaking the major part of existing agents are nowadays using JNLP protocol. What could be different is how you will start your agent:
- You may ask to Jenkins master to connect on a remote host (using SSH for exemple) and it will start the agent automatically (it may install a JVM if required too). This is what we are calling SSH agents.
- But in some cases you might no be able to allow Jenkins master to connect on the remote host by itself. In that case you can manually start from the remote host the agent and this is what we often call JNLP agents.
HTH
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Upgrade of slave.jar
SSH Agents are upgraded automatically after a Jenkins upgrade. Jenkins master copy the slave.jar on SSH Agent's machines. The slave.jar on JNLP Agents need to be copied manually.
Memory Consumption
If I remember correctly, JNLP Nodes use less memory (~200 kB) than SSH Nodes (~1.1 MB) due to a flight recording stream. This seems negligible but need to be considered in order to scale. (see Jenkins World 2016 - So, You Want to Build the World's Biggest Jenkins Cluster? for reference)
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> The slave.jar on JNLP Agents need to be copied manually.
FYI the Windows service should manage the upgrade automatically 'soon'.
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> FYI the Windows service should manage the upgrade automatically 'soon'.
Well, that's my favourite news of the day :)1 -
> FYI the Windows service should manage the upgrade automatically 'soon'.
It's going to land in 2.50 along with other Windows service improvements: https://github.com/jenkinsci/windows-slave-installer-module/blob/master/CHANGELOG.md#17. Automatic upgrade will be enabled only for new agents on instances behind HTTPS.
Regarding automatic upgrades of JNLP agents, there are middle-term plans to have this feature (no ETA)
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It is now possible to enable the automatic download since the 2.60.1 LTS: https://jenkins.io/doc/upgrade-guide/2.60/windows/.
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