From f7cce5cb39e239677675c199d15a167954b169cf Mon Sep 17 00:00:00 2001
From: Svarog <feanorr@gmail.com>
Date: Sun, 4 Jul 2021 11:47:43 +0300
Subject: [PATCH] Cache virtual past median time (#1775)

* Add cache for virtual pastMedianTime

* Implement InvalidateVirtualPastMedianTimeCache for mocPastMedianTimeManager
---
 ...terface_processes_pastmediantimemanager.go |  1 +
 .../blockprocessor/validateandinsertblock.go  |  2 ++
 .../pastmediantimemanager.go                  | 20 ++++++++++++++++++-
 .../transactionvalidator_test.go              |  4 ++++
 4 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/domain/consensus/model/interface_processes_pastmediantimemanager.go b/domain/consensus/model/interface_processes_pastmediantimemanager.go
index 096859215..35961fdcd 100644
--- a/domain/consensus/model/interface_processes_pastmediantimemanager.go
+++ b/domain/consensus/model/interface_processes_pastmediantimemanager.go
@@ -6,4 +6,5 @@ import "github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
 // past median time of a block
 type PastMedianTimeManager interface {
 	PastMedianTime(stagingArea *StagingArea, blockHash *externalapi.DomainHash) (int64, error)
+	InvalidateVirtualPastMedianTimeCache()
 }
diff --git a/domain/consensus/processes/blockprocessor/validateandinsertblock.go b/domain/consensus/processes/blockprocessor/validateandinsertblock.go
index fc207b9f0..45792d732 100644
--- a/domain/consensus/processes/blockprocessor/validateandinsertblock.go
+++ b/domain/consensus/processes/blockprocessor/validateandinsertblock.go
@@ -184,6 +184,8 @@ func (bp *blockProcessor) validateAndInsertBlock(stagingArea *model.StagingArea,
 		return nil, err
 	}
 
+	bp.pastMedianTimeManager.InvalidateVirtualPastMedianTimeCache()
+
 	bp.blockLogger.LogBlock(block)
 
 	return &externalapi.BlockInsertionResult{
diff --git a/domain/consensus/processes/pastmediantimemanager/pastmediantimemanager.go b/domain/consensus/processes/pastmediantimemanager/pastmediantimemanager.go
index d2d68a988..bfe65f1a3 100644
--- a/domain/consensus/processes/pastmediantimemanager/pastmediantimemanager.go
+++ b/domain/consensus/processes/pastmediantimemanager/pastmediantimemanager.go
@@ -23,6 +23,8 @@ type pastMedianTimeManager struct {
 	ghostdagDataStore model.GHOSTDAGDataStore
 
 	genesisHash *externalapi.DomainHash
+
+	virtualPastMedianTimeCache int64
 }
 
 // New instantiates a new PastMedianTimeManager
@@ -47,6 +49,9 @@ func New(timestampDeviationTolerance int,
 
 // PastMedianTime returns the past median time for some block
 func (pmtm *pastMedianTimeManager) PastMedianTime(stagingArea *model.StagingArea, blockHash *externalapi.DomainHash) (int64, error) {
+	if blockHash == model.VirtualBlockHash && pmtm.virtualPastMedianTimeCache != 0 {
+		return pmtm.virtualPastMedianTimeCache, nil
+	}
 	window, err := pmtm.dagTraversalManager.BlockWindow(stagingArea, blockHash, 2*pmtm.timestampDeviationTolerance-1)
 	if err != nil {
 		return 0, err
@@ -59,7 +64,16 @@ func (pmtm *pastMedianTimeManager) PastMedianTime(stagingArea *model.StagingArea
 		return header.TimeInMilliseconds(), nil
 	}
 
-	return pmtm.windowMedianTimestamp(stagingArea, window)
+	pastMedianTime, err := pmtm.windowMedianTimestamp(stagingArea, window)
+	if err != nil {
+		return 0, err
+	}
+
+	if blockHash == model.VirtualBlockHash {
+		pmtm.virtualPastMedianTimeCache = pastMedianTime
+	}
+
+	return pastMedianTime, nil
 }
 
 func (pmtm *pastMedianTimeManager) windowMedianTimestamp(
@@ -82,3 +96,7 @@ func (pmtm *pastMedianTimeManager) windowMedianTimestamp(
 
 	return timestamps[len(timestamps)/2], nil
 }
+
+func (pmtm *pastMedianTimeManager) InvalidateVirtualPastMedianTimeCache() {
+	pmtm.virtualPastMedianTimeCache = 0
+}
diff --git a/domain/consensus/processes/transactionvalidator/transactionvalidator_test.go b/domain/consensus/processes/transactionvalidator/transactionvalidator_test.go
index 81c95e49c..28bcf0669 100644
--- a/domain/consensus/processes/transactionvalidator/transactionvalidator_test.go
+++ b/domain/consensus/processes/transactionvalidator/transactionvalidator_test.go
@@ -23,6 +23,10 @@ type mocPastMedianTimeManager struct {
 	pastMedianTimeForTest int64
 }
 
+func (mdf *mocPastMedianTimeManager) InvalidateVirtualPastMedianTimeCache() {
+	// do nothing
+}
+
 // PastMedianTime returns the past median time for the test.
 func (mdf *mocPastMedianTimeManager) PastMedianTime(*model.StagingArea, *externalapi.DomainHash) (int64, error) {
 	return mdf.pastMedianTimeForTest, nil