Pruning is the mechanism for deleting old application heights from the disk. Depending on the use case, nodes may require different pruning strategies. For example, archive nodes must keep all the states and prune nothing. On the other hand, a regular validator node may want to only keep 100 latest heights for performance reasons.
The strategies are configured in app.toml, with the format pruning = "<strategy>" where the options are:
default: only the last 362,880 states(approximately 3.5 weeks worth of state) are kept; pruning at 10 block intervalsnothing: all historic states will be saved, nothing will be deleted (i.e. archiving node)everything: 2 latest states will be kept; pruning at 10 block intervals.custom: allow pruning options to be manually specified through 'pruning-keep-recent', and 'pruning-interval'
If no strategy is given to the BaseApp, nothing is selected. However, we perform validation on the CLI layer to require these to be always set in the config file.
These are applied if and only if the pruning strategy is custom:
pruning-keep-recent: N means to keep all of the last N statespruning-interval: N means to delete old states from disk every Nth block.
Snapshot settings are optional. However, if set, they have an effect on how pruning is done by
persisting the heights that are multiples of state-sync.snapshot-interval until after the snapshot is complete. See the "Relationship to Pruning" section in snapshots/README.md for more details.