batch: add external batching engine for bbolt operations

batch/interface.go

@@ -0,0 +1,38 @@
+package batch
+
+import "github.com/lightningnetwork/lnd/channeldb/kvdb"
+
+// Request defines an operation that can be batched into a single bbolt
+// transaction.
+type Request struct {
+	// Reset is called before each invocation of Update and is used to clear
+	// any possible modifications to local state as a result of previous
+	// calls to Update that were not committed due to a concurrent batch
+	// failure.
+	//
+	// NOTE: This field is optional.
+	Reset func()
+
+	// Update is applied alongside other operations in the batch.
+	//
+	// NOTE: This method MUST NOT acquire any mutexes.
+	Update func(tx kvdb.RwTx) error
+
+	// OnCommit is called if the batch or a subset of the batch including
+	// this request all succeeded without failure. The passed error should
+	// contain the result of the transaction commit, as that can still fail
+	// even if none of the closures returned an error.
+	//
+	// NOTE: This field is optional.
+	OnCommit func(commitErr error) error
+}
+
+// Scheduler abstracts a generic batching engine that accumulates an incoming
+// set of Requests, executes them, and returns the error from the operation.
+type Scheduler interface {
+	// Execute schedules a Request for execution with the next available
+	// batch. This method blocks until the the underlying closure has been
+	// run against the databse. The resulting error is returned to the
+	// caller.
+	Execute(req *Request) error
+}