consensus: add calculation for proposal step waits from pbts (#7290)

* initial proposerWaitsUntil implementation

* switch to duration for easier use with timeout scheduling

* add proposal step waiting time with tests

* minor aesthetic change to IsTimely

* minor language fix

* Update internal/consensus/state.go

Co-authored-by: M. J. Fromberger <fromberger@interchain.io>

* reword comment

* change accuracy to precision

* move tests to separate pbts test file

Co-authored-by: M. J. Fromberger <fromberger@interchain.io>

internal/consensus/pbts_test.go

@@ -0,0 +1,115 @@
+package consensus
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	tmtimemocks "github.com/tendermint/tendermint/libs/time/mocks"
+	"github.com/tendermint/tendermint/types"
+)
+
+func TestProposerWaitTime(t *testing.T) {
+	genesisTime, err := time.Parse(time.RFC3339, "2019-03-13T23:00:00Z")
+	require.NoError(t, err)
+	testCases := []struct {
+		name         string
+		blockTime    time.Time
+		localTime    time.Time
+		expectedWait time.Duration
+	}{
+		{
+			name:         "block time greater than local time",
+			blockTime:    genesisTime.Add(5 * time.Nanosecond),
+			localTime:    genesisTime.Add(1 * time.Nanosecond),
+			expectedWait: 4 * time.Nanosecond,
+		},
+		{
+			name:         "local time greater than block time",
+			blockTime:    genesisTime.Add(1 * time.Nanosecond),
+			localTime:    genesisTime.Add(5 * time.Nanosecond),
+			expectedWait: 0,
+		},
+		{
+			name:         "both times equal",
+			blockTime:    genesisTime.Add(5 * time.Nanosecond),
+			localTime:    genesisTime.Add(5 * time.Nanosecond),
+			expectedWait: 0,
+		},
+	}
+	for _, testCase := range testCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			b := types.Block{
+				Header: types.Header{
+					Time: testCase.blockTime,
+				},
+			}
+
+			mockSource := new(tmtimemocks.Source)
+			mockSource.On("Now").Return(testCase.localTime)
+
+			ti := proposerWaitTime(mockSource, b.Header)
+			assert.Equal(t, testCase.expectedWait, ti)
+		})
+	}
+}
+
+func TestProposalTimeout(t *testing.T) {
+	genesisTime, err := time.Parse(time.RFC3339, "2019-03-13T23:00:00Z")
+	require.NoError(t, err)
+	testCases := []struct {
+		name              string
+		localTime         time.Time
+		previousBlockTime time.Time
+		precision         time.Duration
+		msgDelay          time.Duration
+		expectedDuration  time.Duration
+	}{
+		{
+			name:              "MsgDelay + Precision has not quite elapsed",
+			localTime:         genesisTime.Add(525 * time.Millisecond),
+			previousBlockTime: genesisTime.Add(6 * time.Millisecond),
+			precision:         time.Millisecond * 20,
+			msgDelay:          time.Millisecond * 500,
+			expectedDuration:  1 * time.Millisecond,
+		},
+		{
+			name:              "MsgDelay + Precision equals current time",
+			localTime:         genesisTime.Add(525 * time.Millisecond),
+			previousBlockTime: genesisTime.Add(5 * time.Millisecond),
+			precision:         time.Millisecond * 20,
+			msgDelay:          time.Millisecond * 500,
+			expectedDuration:  0,
+		},
+		{
+			name:              "MsgDelay + Precision has elapsed",
+			localTime:         genesisTime.Add(725 * time.Millisecond),
+			previousBlockTime: genesisTime.Add(5 * time.Millisecond),
+			precision:         time.Millisecond * 20,
+			msgDelay:          time.Millisecond * 500,
+			expectedDuration:  0,
+		},
+	}
+	for _, testCase := range testCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			b := types.Block{
+				Header: types.Header{
+					Time: testCase.previousBlockTime,
+				},
+			}
+
+			mockSource := new(tmtimemocks.Source)
+			mockSource.On("Now").Return(testCase.localTime)
+
+			tp := types.TimestampParams{
+				Precision: testCase.precision,
+				MsgDelay:  testCase.msgDelay,
+			}
+
+			ti := proposalStepWaitingTime(mockSource, b.Header, tp)
+			assert.Equal(t, testCase.expectedDuration, ti)
+		})
+	}
+}

internal/consensus/state.go

@@ -2416,3 +2416,39 @@ func repairWalFile(src, dst string) error {
 
 	return nil
 }
+
+// proposerWaitTime determines how long the proposer should wait to propose its next block.
+// If the result is zero, a block can be proposed immediately.
+//
+// Block times must be monotonically increasing, so if the block time of the previous
+// block is larger than the proposer's current time, then the proposer will sleep
+// until its local clock exceeds the previous block time.
+func proposerWaitTime(lt tmtime.Source, h types.Header) time.Duration {
+	t := lt.Now()
+	if h.Time.After(t) {
+		return h.Time.Sub(t)
+	}
+	return 0
+}
+
+// proposalStepWaitingTime is used along with the `timeout-propose` configuration
+// parameter to determines how long a validator will wait for a block to be sent from a proposer.
+// proposalStepWaitingTime ensures that the validator waits long enough for the proposer to
+// deliver a block with a monotically increasing timestamp.
+//
+// To ensure that the validator waits long enough, it must wait until the previous
+// block's timestamp. It also must account for the difference between its own clock and
+// the proposer's clock, i.e. the 'Precision', and the amount of time for the message to be transmitted,
+// i.e. the MsgDelay.
+//
+// The result of proposalStepWaitingTime is compared with the configured `timeout-propose` duration,
+// and the validator waits for whichever duration is larger before advancing to the next step
+// and prevoting nil.
+func proposalStepWaitingTime(lt tmtime.Source, h types.Header, tp types.TimestampParams) time.Duration {
+	t := lt.Now()
+	wt := h.Time.Add(tp.Precision).Add(tp.MsgDelay)
+	if t.After(wt) {
+		return 0
+	}
+	return wt.Sub(t)
+}

types/proposal.go

@@ -92,7 +92,7 @@ func (p *Proposal) IsTimely(clock tmtime.Source, tp TimestampParams) bool {
 	lt := clock.Now()
 	lhs := lt.Add(-tp.Precision)
 	rhs := lt.Add(tp.Precision).Add(tp.MsgDelay)
-	if lhs.Before(p.Timestamp) && p.Timestamp.Before(rhs) {
+	if lhs.Before(p.Timestamp) && rhs.After(p.Timestamp) {
 		return true
 	}
 	return false