have a function to report disk usage and %age free as a message in a build log

[jstrachan]

right now its easy to run out of PV space for your /root/.mvnrepository/ directory.

So it'd be nice if we had a little function in the pipeline library that would find out the disk space and %age free and log it to the build log (maybe with a nice big WARNING if its, say, less than 20% free).

We could then include this function call into the standard pipellines / functions. e.g. for all java projects we should check the disk before we start and after a release? Maybe at the end of the pipeline too (in case integration tests clog things up too much).

So maybe the function looks like...

// in the pipeline library...
def checkDiskUsage(operation, folderName, folderPath) { ... }

// in the jenkinsfile or pipeline library functions....
checkDiskUsage("Starting release", "maven repo", "/root/.mvnrepository")
....
checkDiskUsage("Completed release", "maven repo", "/root/.mvnrepository")
...
checkDiskUsage("Finished pipeline", "maven repo", "/root/.mvnrepository")

We may want to output this data into Elasticsearch / Prometheus too; including more metadata like the namespace / job name / build number too etc?

Then we can start doing tools to visualise the users disk over time and so forth