[FAB-6552] Block-to-live policy for pvtdata

This CR introduces a BTL policy based on
configuration in the core.yaml file

Change-Id: Icef38b180d8a1f1c3336a59cca2f63dfbdab3964
Signed-off-by: manish <manish.sethi@gmail.com>

core/ledger/pvtdatapolicy/btlpolicy.go

@@ -0,0 +1,94 @@
+/*
+Copyright IBM Corp. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package pvtdatapolicy
+
+import (
+	"math"
+	"sync"
+
+	"github.com/spf13/viper"
+)
+
+var defaultBLT uint64 = math.MaxUint64
+var btlPolicyMap map[string]BTLPolicy
+var lock = &sync.Mutex{}
+
+func init() {
+	btlPolicyMap = make(map[string]BTLPolicy)
+}
+
+// BTLPolicy BlockToLive policy for the pvt data
+type BTLPolicy interface {
+	// init initializes BTLPolicy for the given channelName
+	init(channelName string) error
+	// GetBTL returns BlockToLive for a given namespace and collection
+	GetBTL(ns string, coll string) uint64
+	// GetExpiringBlock returns the block number by which the pvtdata for given namespace,collection, and committingBlock should expire
+	GetExpiringBlock(namesapce string, collection string, committingBlock uint64) uint64
+}
+
+// GetBTLPolicy constructs (if not already done) and returns the BTLPolicy for the given channel
+func GetBTLPolicy(channelName string) (BTLPolicy, error) {
+	lock.Lock()
+	defer lock.Unlock()
+	m := btlPolicyMap[channelName]
+	if m == nil {
+		m = &configBasedBTLPolicy{}
+		m.init(channelName)
+		btlPolicyMap[channelName] = m
+	}
+	return m, nil
+}
+
+// configBasedBTLPolicy implements interface BTLPolicy.
+// This implementation loads the BTL policy from configuration. This implementation is meant as a stop gap arrangement
+// until the config transaction framework is in place. This is becasue, the BTL policy should be consistent across peer
+// and should not change across different replays of transactions in the chain and hence it should be set via a config
+// transaction only. Later, another implementation should be provided that loads the BTL policy from config transactions
+type configBasedBTLPolicy struct {
+	channelName string
+	cache       map[btlkey]uint64
+}
+
+type btlkey struct {
+	ns   string
+	coll string
+}
+
+// Init implements corresponding function in interface `BTLPolicyMgr`
+func (m *configBasedBTLPolicy) init(channelName string) error {
+	m.channelName = channelName
+	m.cache = make(map[btlkey]uint64)
+	return nil
+}
+
+// GetBTL implements corresponding function in interface `BTLPolicyMgr`
+func (m *configBasedBTLPolicy) GetBTL(namesapce string, collection string) uint64 {
+	var btl uint64
+	var ok bool
+	key := btlkey{namesapce, collection}
+	btl, ok = m.cache[key]
+	if !ok {
+		btlConfigured := viper.GetInt("ledger.pvtdata.btlpolicy." + m.channelName + "." + namesapce + "." + collection)
+		if btlConfigured > 0 {
+			btl = uint64(btlConfigured)
+		} else {
+			btl = defaultBLT
+		}
+		m.cache[key] = btl
+	}
+	return btl
+}
+
+func (m *configBasedBTLPolicy) GetExpiringBlock(namesapce string, collection string, committingBlock uint64) uint64 {
+	btl := m.GetBTL(namesapce, collection)
+	expiryBlk := committingBlock + btl + uint64(1)
+	if expiryBlk <= committingBlock { // committingBlk + btl overflows uint64-max
+		expiryBlk = math.MaxUint64
+	}
+	return expiryBlk
+}

core/ledger/pvtdatapolicy/btlpolicy_test.go

@@ -0,0 +1,34 @@
+/*
+Copyright IBM Corp. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package pvtdatapolicy
+
+import (
+	"math"
+	"testing"
+
+	"github.com/spf13/viper"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBTLPolicy(t *testing.T) {
+	viper.Set("ledger.pvtdata.btlpolicy.ch1.ns1.coll1", 1)
+	viper.Set("ledger.pvtdata.btlpolicy.ch1.ns2.coll2", 2)
+	viper.Set("ledger.pvtdata.btlpolicy.ch2.ns2.coll2", 3)
+	viper.Set("ledger.pvtdata.btlpolicy.ch2.ns3.coll4", 4)
+
+	btlCh1, _ := GetBTLPolicy("ch1")
+	btlCh2, _ := GetBTLPolicy("ch2")
+
+	assert.Equal(t, uint64(1), btlCh1.GetBTL("ns1", "coll1"))
+	assert.Equal(t, uint64(4), btlCh2.GetBTL("ns3", "coll4"))
+	assert.Equal(t, defaultBLT, btlCh2.GetBTL("ns1", "coll5"))
+
+	assert.Equal(t, uint64(5), btlCh1.GetExpiringBlock("ns1", "coll1", 3))
+	assert.Equal(t, uint64(8), btlCh2.GetExpiringBlock("ns3", "coll4", 3))
+	assert.Equal(t, uint64(math.MaxUint64), btlCh2.GetExpiringBlock("ns3", "coll4", math.MaxUint64-uint64(2)))
+	assert.Equal(t, uint64(math.MaxUint64), btlCh2.GetExpiringBlock("ns1", "coll5", math.MaxUint64-uint64(2)))
+}