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32 lines
1.4 KiB
Go
32 lines
1.4 KiB
Go
// Package state provides interfaces to work with swarm cluster state.
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//
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// The primary interface is Store, which abstracts storage of this cluster
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// state. Store exposes a transactional interface for both reads and writes.
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// To perform a read transaction, View accepts a callback function that it
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// will invoke with a ReadTx object that gives it a consistent view of the
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// state. Similarly, Update accepts a callback function that it will invoke with
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// a Tx object that allows reads and writes to happen without interference from
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// other transactions.
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//
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// This is an example of making an update to a Store:
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//
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// err := store.Update(func(tx state.Tx) {
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// if err := tx.Nodes().Update(newNode); err != nil {
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// reutrn err
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// }
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// return nil
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// })
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// if err != nil {
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// return fmt.Errorf("transaction failed: %v", err)
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// }
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//
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// WatchableStore is a version of Store that exposes watch functionality.
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// These expose a publish/subscribe queue where code can subscribe to
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// changes of interest. This can be combined with the ViewAndWatch function to
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// "fork" a store, by making a snapshot and then applying future changes
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// to keep the copy in sync. This approach lets consumers of the data
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// use their own data structures and implement their own concurrency
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// strategies. It can lead to more efficient code because data consumers
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// don't necessarily have to lock the main data store if they are
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// maintaining their own copies of the state.
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package state
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