The totalSpace and usableSpace reported by Metrics API are still based on coreRootDirectory (which is used as the instance dir for individual cores).
SOLR-6671 introduced a new solr.data.home configuration for the root directory of all data dirs. So we should expose data home's disk metrics as well.
Since the current metric names are just totalSpace and usableSpace under the Container group, we need to figure out how to differentiate between them and the data home's metrics. A few options:
- We can introduce new metrics such as dataHomeTotalSpace and dataHomeUsableSpace.
- We use the current names for the data home's metrics and introduce new ones for coreRootDirectory
I lean towards #2 because of backcompat reasons. Existing users (and monitoring vendors/products) would be using the existing metric names to track disk stats for their solr installations. If a user configures a solr.data.home then they shouldn't get a surprise one day if the data home directory runs out of space when they have monitoring already in place which used to work for earlier versions of Solr. The probability of surprise still exists because one fine day you can run out of space for the coreRootDirectory and solr will refuse to create any cores but that is a less likely scenario than running out of disk space because of increasing size of data directories.