store

The object store that holds everything the nodes of a cluster share.

Users, groups, installed apps, app stores, templates, and the cluster's own records (cluster/) are objects under fixed keys. Every node reads and writes them through one ObjectStore, so the store is the authority and no node is:

• FileStore keeps each object as the file SealSkin has always kept it in, so a single server stores what it stored before and an administrator can still edit it by hand.
• S3Store keeps them in a bucket of any S3-compatible service.
• PeerStore reads and writes the FileStore of another node, for a small cluster with no bucket.

A write may be conditional on the object's entity tag (if_match) or on its absence (if_absent), which is all the locking the administrative writes need. Calls block: reads are served from the caches the callers keep, and writes are administrative and rare. A service that takes the conditions and ignores them would leave the nodes overwriting each other unseen, so verify proves them with one throwaway object before the node serves anything.

A remote store is mirrored into the local files as it is read, and a node that cannot reach it serves that mirror until it can.