In general, CloudBees tries to maintain compatibility between older versions of eMake and newer versions of the Cluster Manager and the Electric Agent. However, cross-version compatibility between other components is not ensured. Newer eMake version compatibility with older clusters is not ensured. The following matrix illustrates CloudBees’ compatibility philosophy:
| Newer Electric Agent | Older Electric Agent | Newer Cluster Manager | Older Cluster Manager | Newer eMake | Older eMake | |
|---|---|---|---|---|---|---|
eMake |
Yes |
No |
Yes |
No |
No |
No |
Electric Agent |
N/A |
N/A |
No |
No |
No |
Yes |
Cluster Manager |
No |
No |
N/A |
N/A |
No |
Yes |
eMake and the Electric Agent use a custom protocol to communicate with each other. CloudBees evolves this protocol in a backwards compatible manner so older eMake versions are compatible with newer Electric Agent versions. This means you can upgrade the cluster anytime you want, then upgrade eMake installations later.
eMake also uses a custom protocol to communicate with remote instances of itself, for example, during remote parse jobs. This protocol is less tolerant than the eMake/Agent protocol. In general, it is best to have the same version of eMake on the cluster as you have on your build machine—CloudBees simplifies this because old versions of eMake are preserved on the cluster whenever the cluster is upgraded. For example, if your cluster originally had version 7.x installed and was upgraded to 8.x, the 7.x eMake version remains on the cluster—in a special directory in the install tree. You do not have to do anything to ensure this version is used when you run a build using a 7.x eMake version (the system handles that for you).
| Old versions are not installed! What is already there during upgrades is preserved. So, if you install 8.0 on a fresh agent machine, you will not be able to use a 7.2 eMake with that agent unless you obtain archives of that earlier eMake version from the CloudBees FTP site. See Installing the Backward-Compatible eMake Package on Agent Machines. |
eMake and the Cluster Manager use yet another protocol to communicate with each other. Again, CloudBees evolves this protocol so old eMake versions can work with newer Cluster Managers. For example, you should have no problem using a 7.x eMake version with an 8.x Cluster Manager.
Finally, the Electric Agent uses a custom protocol to communicate with the Cluster Manager. CloudBees does not try to maintain compatibility between these two components—generally, if the agent version is “close” to the Cluster Manager version, it is compatible. However, you cannot use 8.x agents with a 7.x Cluster Manager or vice-versa.