[FAB-9833] iface to retrieve key-level validation parm

This change set introduces the interface that validation plugins will use to
retrieve key-level validation parametres.

Change-Id: I01d68f6ce9cbb3c8dab2100a21e06996e35ea458
Signed-off-by: Alessandro Sorniotti <ale.linux@sopit.net>
Signed-off-by: Matthias Neugschwandtner <eug@zurich.ibm.com>

core/common/validation/statebased/vpmanager.go

@@ -0,0 +1,64 @@
+/*
+Copyright IBM Corp. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package statebased
+
+import (
+	"fmt"
+
+	"github.com/hyperledger/fabric/protos/peer"
+)
+
+// ValidationParameterUpdatedErr is returned whenever
+// Validation Parameters for a key could not be
+// supplied because they are being updated
+type ValidationParameterUpdatedErr struct {
+	Key    string
+	Height uint64
+}
+
+func (f ValidationParameterUpdatedErr) Error() string {
+	return fmt.Sprintf("validation parameters for key %s have been changed in a transaction in block %d", f.Key, f.Height)
+}
+
+// KeyLevelValidationParameterManager is used by validation plugins in order
+// to retrieve validation parameters for individual KVS keys.
+// The functions are supposed to be called in the following order:
+// 1) the validation plugin called to validate a certain tx calls ExtractValidationParameterDependency
+//    in order for the manager to be able to determine whether validation parameters from the ledger
+//    can be used or whether they are being updated by a transaction in this block.
+// 2) the validation plugin issues 0 or more calls to GetValidationParameterForKey.
+// 3) the validation plugin determines the validation code for the tx and calls SetTxValidationCode.
+type KeyLevelValidationParameterManager interface {
+	// GetValidationParameterForKey returns the validation parameter for the
+	// supplied KVS key identified by (ch, cc, coll, key) at the specified block
+	// TODO: remove ch from the comment on the previous line as part of FAB-9908
+	// height h. The function returns the validation parameter and no error in case of
+	// success, or nil and an error otherwise. One particular error that may be
+	// returned is ValidationParameterUpdatedErr, which is returned in case the
+	// validation parmeters for the given KVS key have been changed by a transaction
+	// with txNum smaller than the one supplied by the caller. This protects from a
+	// scenario where a transaction changing validation parameters is marked as valid
+	// by VSCC and is later invalidated by the committer for other reasons (e.g. MVCC
+	// conflicts).  This function may be blocking until sufficient information has
+	// been passed (by calling ApplyRWSetUpdates and ApplyValidatedRWSetUpdates) for
+	// all txes with txNum smaller than the one supplied by the caller.
+	GetValidationParameterForKey(ch, cc, coll, key string, blockNum, txNum uint64) ([]byte, error)
+	// TODO: remove the channel argument as part of FAB-9908
+
+	// ExtractValidationParameterDependency is used to determine which validation parameters are
+	// updated by transaction at height `h` on channel `ch`. This is needed to determine which txes
+	// have dependencies for specific validation parameters and will determine whether
+	// GetValidationParameterForKey may block.
+	ExtractValidationParameterDependency(ch, cc string, blockNum, txNum uint64, rwset []byte)
+	// TODO: remove the channel argument as part of FAB-9908
+
+	// SetTxValidationCode sets the validation code transaction at height `h` on channel `ch`.
+	// This is used to determine whether the dependencies set by
+	// ExtractValidationParameterDependency matter or not.
+	SetTxValidationCode(ch, cc string, blockNum, txNum uint64, vc peer.TxValidationCode)
+	// TODO: remove the channel argument as part of FAB-9908
+}