diff options
Diffstat (limited to 'util')
| -rw-r--r-- | util/lamport/clock_testing.go | 4 | ||||
| -rw-r--r-- | util/lamport/mem_clock.go | 12 |
2 files changed, 12 insertions, 4 deletions
diff --git a/util/lamport/clock_testing.go b/util/lamport/clock_testing.go index 4bf6d2bf..de66c5c9 100644 --- a/util/lamport/clock_testing.go +++ b/util/lamport/clock_testing.go @@ -14,11 +14,11 @@ func testClock(t *testing.T, c Clock) { assert.Equal(t, Time(2), val) assert.Equal(t, Time(2), c.Time()) - err = c.Witness(41) + err = c.Witness(42) assert.NoError(t, err) assert.Equal(t, Time(42), c.Time()) - err = c.Witness(41) + err = c.Witness(42) assert.NoError(t, err) assert.Equal(t, Time(42), c.Time()) diff --git a/util/lamport/mem_clock.go b/util/lamport/mem_clock.go index f113b501..d824d834 100644 --- a/util/lamport/mem_clock.go +++ b/util/lamport/mem_clock.go @@ -25,6 +25,14 @@ */ +// Note: this code originally originate from Hashicorp's Serf but has been changed since to fit git-bug's need. + +// Note: this Lamport clock implementation is different than the algorithms you can find, notably Wikipedia or the +// original Serf implementation. The reason is lie to what constitute an event in this distributed system. +// Commonly, events happen when messages are sent or received, whereas in git-bug events happen when some data is +// written, but *not* when read. This is why Witness set the time to the max seen value instead of max seen value +1. +// See https://cs.stackexchange.com/a/133730/129795 + package lamport import ( @@ -72,12 +80,12 @@ WITNESS: // If the other value is old, we do not need to do anything cur := atomic.LoadUint64(&mc.counter) other := uint64(v) - if other < cur { + if other <= cur { return nil } // Ensure that our local clock is at least one ahead. - if !atomic.CompareAndSwapUint64(&mc.counter, cur, other+1) { + if !atomic.CompareAndSwapUint64(&mc.counter, cur, other) { // CAS: CompareAndSwap // The CAS failed, so we just retry. Eventually our CAS should // succeed or a future witness will pass us by and our witness |