[wip] Raw MySQL packets

go.mod

@@ -48,7 +48,7 @@ require (
 	github.com/pires/go-proxyproto v0.7.0
 	github.com/pkg/errors v0.9.1
 	github.com/planetscale/pargzip v0.0.0-20201116224723-90c7fc03ea8a
-	github.com/planetscale/vtprotobuf v0.5.0
+	github.com/planetscale/vtprotobuf v0.6.0
 	github.com/prometheus/client_golang v1.19.0
 	github.com/prometheus/common v0.49.0
 	github.com/rcrowley/go-metrics v0.0.0-20201227073835-cf1acfcdf475

go.sum

@@ -395,6 +395,8 @@ github.com/planetscale/pargzip v0.0.0-20201116224723-90c7fc03ea8a h1:y0OpQ4+5tKx
 github.com/planetscale/pargzip v0.0.0-20201116224723-90c7fc03ea8a/go.mod h1:GJFUzQuXIoB2Kjn1ZfDhJr/42D5nWOqRcIQVgCxTuIE=
 github.com/planetscale/vtprotobuf v0.5.0 h1:l8PXm6Colok5z6qQLNhAj2Jq5BfoMTIHxLER5a6nDqM=
 github.com/planetscale/vtprotobuf v0.5.0/go.mod h1:wm1N3qk9G/4+VM1WhpkLbvY/d8+0PbwYYpP5P5VhTks=
+github.com/planetscale/vtprotobuf v0.6.0 h1:nBeETjudeJ5ZgBHUz1fVHvbqUKnYOXNhsIEabROxmNA=
+github.com/planetscale/vtprotobuf v0.6.0/go.mod h1:t/avpk3KcrXxUnYOhZhMXJlSEyie6gQbtLq5NM3loB8=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 h1:Jamvg5psRIccs7FGNTlIRMkT8wgtp5eCXdBlqhYGL6U=
 github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=

go/mathstats/ewma.go

@@ -0,0 +1,42 @@
+package mathstats
+
+import (
+	"math"
+	"sync/atomic"
+)
+
+type SimpleEWMA struct {
+	// The current value of the average. After adding with Add(), this is
+	// updated to reflect the average of all values seen thus far.
+	value atomic.Uint64
+}
+
+// Add adds a value to the series and updates the moving average.
+func (e *SimpleEWMA) Add(value uint64) {
+	const (
+		AVG_METRIC_AGE float64 = 30.0
+		DECAY          float64 = 2 / (float64(AVG_METRIC_AGE) + 1)
+	)
+
+	fvalue := float64(value)
+
+	for {
+		v := e.value.Load()
+
+		var nv float64
+		if v == 0 {
+			nv = fvalue
+		} else {
+			nv = (fvalue * DECAY) + (math.Float64frombits(v) * (1 - DECAY))
+		}
+
+		if e.value.CompareAndSwap(v, math.Float64bits(nv)) {
+			return
+		}
+	}
+}
+
+// Value returns the current value of the moving average.
+func (e *SimpleEWMA) Value() uint64 {
+	return uint64(math.Float64frombits(e.value.Load()))
+}

go/mysql/conn.go

@@ -409,6 +409,35 @@ func (c *Conn) readHeaderFrom(r io.Reader) (int, error) {
 	return int(uint32(c.header[0]) | uint32(c.header[1])<<8 | uint32(c.header[2])<<16), nil
 }
 
+func (c *Conn) readPacketAsProto(b *queryResultBuilder) ([]byte, error) {
+	r := c.getReader()
+
+	length, err := c.readHeaderFrom(r)
+	if err != nil {
+		return nil, err
+	}
+
+	if length == 0 {
+		// This can be caused by the packet after a packet of
+		// exactly size MaxPacketSize.
+		return nil, nil
+	}
+
+	// Use the bufPool.
+	if length < MaxPacketSize {
+		buf := b.Packet(length)
+		if _, err := io.ReadFull(r, buf); err != nil {
+			return nil, vterrors.Wrapf(err, "io.ReadFull(packet body of length %v) failed", length)
+		}
+		return buf, nil
+	}
+
+	// Much slower path, revert to allocating everything from scratch.
+	// We're going to concatenate a lot of data anyway, can't really
+	// optimize this code path easily.
+	panic("TODO: large packets")
+}
+
 // readEphemeralPacket attempts to read a packet into buffer from sync.Pool.  Do
 // not use this method if the contents of the packet needs to be kept
 // after the next readEphemeralPacket.