[FAB-5863] Collection-related APIs

This commit defines 2 APIs:

- An API that declares the needed methods that the coordinator
  would invoke on gossip, in gossip/api/subchannel.go

- An API that the coordinator would use to fetch policies for sub-channels,
  in core/common/privdata/policies.go

Change-Id: I6e7b7176e2c3b29e069b998214c6aaddd0a37008
Signed-off-by: yacovm <yacovm@il.ibm.com>

Author: yacovm

core/common/privdata/policies.go

@@ -0,0 +1,43 @@
+/*
+Copyright IBM Corp. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package privdata
+
+import "github.com/hyperledger/fabric/protos/ledger/rwset"
+
+// SerializedPolicy defines a persisted policy
+type SerializedPolicy interface {
+	// Channel returns the channel this SerializedPolicy corresponds to
+	Channel() string
+	// Raw returns the policy in its raw form
+	Raw() []byte
+}
+
+// SerializedIdentity defines an identity of a network participant
+type SerializedIdentity []byte
+
+// PolicyStore defines an object that retrieves stored SerializedPolicies
+// based on the collection's properties
+type PolicyStore interface {
+	// GetPolicy retrieves the collection policy from in the following way:
+	// If the TxID exists in the ledger, the policy that is returned is the latest policy
+	// which was committed into the ledger before this txID was committed.
+	// Else - it's the latest policy for the collection.
+	CollectionPolicy(rwset.CollectionCriteria) SerializedPolicy
+}
+
+// Filter defines a rule that filters out SerializedIdentities
+// that the policy doesn't hold for them.
+// Returns: True, if the policy holds for the given SerializedIdentity,
+//          False otherwise
+type Filter func(SerializedIdentity) bool
+
+// PolicyParser parses SerializedPolicies and returns a Filter
+type PolicyParser interface {
+	// Parse parses a given SerializedPolicy and returns a Filter
+	// that is derived from it
+	Parse(SerializedPolicy) Filter
+}

gossip/api/subchannel.go

@@ -0,0 +1,24 @@
+/*
+Copyright IBM Corp. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package api
+
+import "github.com/hyperledger/fabric/gossip/common"
+
+// RoutingFilter defines which peers should receive a certain message,
+// or which peers are eligible of receiving a certain message
+type RoutingFilter func(peerIdentity PeerIdentityType) bool
+
+// CollectionCriteria describes a certain sub-channel, or a part of it
+type CollectionCriteria []byte
+
+// RoutingFilterFactory defines an object that given a CollectionCriteria and a channel,
+// it can ascertain which peers should be aware of the data related to the
+// CollectionCriteria.
+type RoutingFilterFactory interface {
+	// Peers returns a RoutingFilter for given chainID and CollectionCriteria
+	Peers(common.ChainID, CollectionCriteria) RoutingFilter
+}

protos/gossip/message.pb.go

@@ -62,4 +62,12 @@ message NsPvtReadWriteSet {
 message CollectionPvtReadWriteSet {
     string collection_name = 1;
     bytes rwset = 2; // Data model specific serialized proto message (e.g., kvrwset.KVRWSet for KV and Document data models)
+}
+
+// CollectionProperty defines an element of a private data that corresponds
+// to a certain transaction and collection
+message CollectionCriteria {
+    string channel = 1;
+    string tx_id = 2;
+    string collection = 3;
 }