func (h Handler) Touch(cmd common.TouchRequest) error {
// read metadata
// for 0 to metadata.numChunks
// touch item
// touch metadata
// We get the metadata and not GAT it in case the key is *just* about to expire.
// In this case if a chunk expires during the operation, we fail the touch instead of
// leaving a key in an inconsistent state where the metadata lives on and the data is
// incomplete. The metadata is touched last to make sure the data exists first.
metaKey, metaData, err := getMetadata(h.rw, cmd.Key)
if err != nil {
if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdTouchMissesMeta)
}
return err
}
// First touch all the chunks as a batch
for i := 0; i < int(metaData.NumChunks); i++ {
chunkKey := chunkKey(cmd.Key, i)
if err := binprot.WriteTouchCmd(h.rw.Writer, chunkKey, cmd.Exptime); err != nil {
return err
}
}
if err := h.rw.Flush(); err != nil {
return err
}
miss := false
for i := 0; i < int(metaData.NumChunks); i++ {
if err := simpleCmdLocal(h.rw, false); err != nil {
if err == common.ErrKeyNotFound && !miss {
metrics.IncCounter(MetricCmdTouchMissesChunk)
miss = true
}
}
}
if miss {
return common.ErrKeyNotFound
}
// Then touch the metadata
if err := binprot.WriteTouchCmd(h.rw.Writer, metaKey, cmd.Exptime); err != nil {
return err
}
if err := simpleCmdLocal(h.rw, true); err != nil {
if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdTouchMissesMeta)
}
return err
}
return nil
}
func (h Handler) Delete(cmd common.DeleteRequest) error {
// read metadata
// delete metadata
// for 0 to metadata.numChunks
// delete item
metaKey, metaData, err := getMetadata(h.rw, cmd.Key)
if err != nil {
if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdDeleteMissesMeta)
}
return err
}
// Delete metadata first
if err := binprot.WriteDeleteCmd(h.rw.Writer, metaKey); err != nil {
return err
}
if err := simpleCmdLocal(h.rw, true); err != nil {
if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdDeleteMissesMeta)
}
return err
}
// Then delete data chunks
for i := 0; i < int(metaData.NumChunks); i++ {
chunkKey := chunkKey(cmd.Key, i)
if err := binprot.WriteDeleteCmd(h.rw.Writer, chunkKey); err != nil {
return err
}
}
if err := h.rw.Flush(); err != nil {
return err
}
miss := false
for i := 0; i < int(metaData.NumChunks); i++ {
if err := simpleCmdLocal(h.rw, false); err != nil {
if err == common.ErrKeyNotFound && !miss {
metrics.IncCounter(MetricCmdDeleteMissesChunk)
miss = true
}
}
}
if miss {
return common.ErrKeyNotFound
}
return nil
}
func (l *L1OnlyOrca) Gat(req common.GATRequest) error {
metrics.IncCounter(MetricCmdGat)
//log.Println("gat", string(req.Key))
metrics.IncCounter(MetricCmdGatL1)
res, err := l.l1.GAT(req)
if err == nil {
if res.Miss {
metrics.IncCounter(MetricCmdGatMissesL1)
// TODO: Account for L2
metrics.IncCounter(MetricCmdGatMisses)
} else {
metrics.IncCounter(MetricCmdGatHits)
metrics.IncCounter(MetricCmdGatHitsL1)
}
l.res.GAT(res)
// There is no GetEnd call required here since this is only ever
// done in the binary protocol, where there's no END marker.
// Calling l.res.GetEnd was a no-op here and is just useless.
//l.res.GetEnd(0, false)
} else {
metrics.IncCounter(MetricCmdGatErrors)
metrics.IncCounter(MetricCmdGatErrorsL1)
}
return err
}
func (l *L1OnlyOrca) Get(req common.GetRequest) error {
metrics.IncCounter(MetricCmdGet)
metrics.IncCounterBy(MetricCmdGetKeys, uint64(len(req.Keys)))
//debugString := "get"
//for _, k := range req.Keys {
// debugString += " "
// debugString += string(k)
//}
//println(debugString)
metrics.IncCounter(MetricCmdGetL1)
metrics.IncCounterBy(MetricCmdGetKeysL1, uint64(len(req.Keys)))
resChan, errChan := l.l1.Get(req)
var err error
// Read all the responses back from l.l1.
// The contract is that the resChan will have GetResponse's for get hits and misses,
// and the errChan will have any other errors, such as an out of memory error from
// memcached. If any receive happens from errChan, there will be no more responses
// from resChan.
for {
select {
case res, ok := <-resChan:
if !ok {
resChan = nil
} else {
if res.Miss {
metrics.IncCounter(MetricCmdGetMissesL1)
metrics.IncCounter(MetricCmdGetMisses)
} else {
metrics.IncCounter(MetricCmdGetHits)
metrics.IncCounter(MetricCmdGetHitsL1)
}
l.res.Get(res)
}
case getErr, ok := <-errChan:
if !ok {
errChan = nil
} else {
metrics.IncCounter(MetricCmdGetErrors)
metrics.IncCounter(MetricCmdGetErrorsL1)
err = getErr
}
}
if resChan == nil && errChan == nil {
break
}
}
if err == nil {
l.res.GetEnd(req.NoopOpaque, req.NoopEnd)
}
return err
}
func (l *L1L2Orca) Set(req common.SetRequest) error {
//log.Println("set", string(req.Key))
// Try L2 first
metrics.IncCounter(MetricCmdSetL2)
start := timer.Now()
err := l.l2.Set(req)
metrics.ObserveHist(HistSetL2, timer.Since(start))
// If we fail to set in L2, don't set in L1
if err != nil {
metrics.IncCounter(MetricCmdSetErrorsL2)
metrics.IncCounter(MetricCmdSetErrors)
return err
}
metrics.IncCounter(MetricCmdSetSuccessL2)
// Now set in L1. If L1 fails, we log the error and fail the request.
// If a user was writing a new piece of information, the error would be OK,
// since the next GET would be able to put the L2 information back into L1.
// In the case that the user was overwriting information, a failed set in L1
// and successful one in L2 would leave us inconsistent. If the response was
// positive in this situation, it would look like the server successfully
// processed the request but didn't store the information. Clients will
// retry failed writes. In this case L2 will get two writes for the same key
// but this is better because it is more correct overall, though less
// efficient. Note there are no retries at this level.
//
// It should be noted that errors on a straight set are nearly always fatal
// for the connection. It's likely that if this branch is taken that the
// connections to everyone will be severed (for this one client connection)
// and that the client will reconnect to try again.
metrics.IncCounter(MetricCmdSetL1)
start = timer.Now()
err = l.l1.Set(req)
metrics.ObserveHist(HistSetL1, timer.Since(start))
if err != nil {
metrics.IncCounter(MetricCmdSetErrorsL1)
metrics.IncCounter(MetricCmdSetErrors)
return err
}
metrics.IncCounter(MetricCmdSetSuccessL1)
metrics.IncCounter(MetricCmdSetSuccess)
return l.res.Set(req.Opaque, req.Quiet)
}
func (l *L1OnlyOrca) Replace(req common.SetRequest) error {
//log.Println("replace", string(req.Key))
metrics.IncCounter(MetricCmdReplaceL1)
start := timer.Now()
err := l.l1.Replace(req)
metrics.ObserveHist(HistReplaceL1, timer.Since(start))
if err == nil {
metrics.IncCounter(MetricCmdReplaceStoredL1)
metrics.IncCounter(MetricCmdReplaceStored)
err = l.res.Replace(req.Opaque, req.Quiet)
} else if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdReplaceNotStoredL1)
metrics.IncCounter(MetricCmdReplaceNotStored)
} else {
metrics.IncCounter(MetricCmdReplaceErrorsL1)
metrics.IncCounter(MetricCmdReplaceErrors)
}
return err
}
func (l *L1L2BatchOrca) Set(req common.SetRequest) error {
//log.Println("set", string(req.Key))
// Try L2 first
metrics.IncCounter(MetricCmdSetL2)
start := timer.Now()
err := l.l2.Set(req)
metrics.ObserveHist(HistSetL2, timer.Since(start))
// If we fail to set in L2, don't do anything in L1
if err != nil {
metrics.IncCounter(MetricCmdSetErrorsL2)
metrics.IncCounter(MetricCmdSetErrors)
return err
}
metrics.IncCounter(MetricCmdSetSuccessL2)
// Replace the entry in L1.
metrics.IncCounter(MetricCmdSetReplaceL1)
start = timer.Now()
err = l.l1.Replace(req)
metrics.ObserveHist(HistReplaceL1, timer.Since(start))
if err != nil {
if err == common.ErrKeyNotFound {
// For a replace not stored in L1, there's no problem.
// There is no hot data to replace
metrics.IncCounter(MetricCmdSetReplaceNotStoredL1)
} else {
metrics.IncCounter(MetricCmdSetReplaceErrorsL1)
metrics.IncCounter(MetricCmdSetErrors)
return err
}
} else {
metrics.IncCounter(MetricCmdSetReplaceStoredL1)
}
metrics.IncCounter(MetricCmdSetSuccess)
return l.res.Set(req.Opaque, req.Quiet)
}
func (l *L1OnlyOrca) Delete(req common.DeleteRequest) error {
//log.Println("delete", string(req.Key))
metrics.IncCounter(MetricCmdDeleteL1)
start := timer.Now()
err := l.l1.Delete(req)
metrics.ObserveHist(HistDeleteL1, timer.Since(start))
if err == nil {
metrics.IncCounter(MetricCmdDeleteHits)
metrics.IncCounter(MetricCmdDeleteHitsL1)
l.res.Delete(req.Opaque)
} else if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdDeleteMissesL1)
metrics.IncCounter(MetricCmdDeleteMisses)
} else {
metrics.IncCounter(MetricCmdDeleteErrorsL1)
metrics.IncCounter(MetricCmdDeleteErrors)
}
return err
}
func (l *L1OnlyOrca) Touch(req common.TouchRequest) error {
//log.Println("touch", string(req.Key))
metrics.IncCounter(MetricCmdTouchL1)
start := timer.Now()
err := l.l1.Touch(req)
metrics.ObserveHist(HistTouchL1, timer.Since(start))
if err == nil {
metrics.IncCounter(MetricCmdTouchHitsL1)
metrics.IncCounter(MetricCmdTouchHits)
l.res.Touch(req.Opaque)
} else if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdTouchMissesL1)
metrics.IncCounter(MetricCmdTouchMisses)
} else {
metrics.IncCounter(MetricCmdTouchMissesL1)
metrics.IncCounter(MetricCmdTouchMisses)
}
return err
}
func (l *L1OnlyOrca) Add(req common.SetRequest) error {
//log.Println("add", string(req.Key))
metrics.IncCounter(MetricCmdAddL1)
start := timer.Now()
err := l.l1.Add(req)
metrics.ObserveHist(HistAddL1, timer.Since(start))
if err == nil {
metrics.IncCounter(MetricCmdAddStoredL1)
metrics.IncCounter(MetricCmdAddStored)
err = l.res.Add(req.Opaque, req.Quiet)
} else if err == common.ErrKeyExists {
metrics.IncCounter(MetricCmdAddNotStoredL1)
metrics.IncCounter(MetricCmdAddNotStored)
} else {
metrics.IncCounter(MetricCmdAddErrorsL1)
metrics.IncCounter(MetricCmdAddErrors)
}
return err
}
func readRequestHeader(r io.Reader) (RequestHeader, error) {
buf := bufPool.Get().([]byte)
br, err := io.ReadAtLeast(r, buf, ReqHeaderLen)
metrics.IncCounterBy(common.MetricBytesReadRemote, uint64(br))
if err != nil {
bufPool.Put(buf)
return emptyReqHeader, err
}
if buf[0] != MagicRequest {
bufPool.Put(buf)
metrics.IncCounter(MetricBinaryRequestHeadersBadMagic)
return emptyReqHeader, ErrBadMagic
}
rh := reqHeadPool.Get().(RequestHeader)
rh.Magic = buf[0]
rh.Opcode = buf[1]
rh.KeyLength = binary.BigEndian.Uint16(buf[2:4])
rh.ExtraLength = buf[4]
// ignore DataType, unused
//rh.DataType = buf[5]
rh.DataType = 0
// ignore VBucket, unused
//rh.VBucket = binary.BigEndian.Uint16(buf[6:8])
rh.VBucket = 0
rh.TotalBodyLength = binary.BigEndian.Uint32(buf[8:12])
rh.OpaqueToken = binary.BigEndian.Uint32(buf[12:16])
// ignore CAS, unused in rend
//rh.CASToken = binary.BigEndian.Uint64(buf[16:24])
rh.CASToken = 0
bufPool.Put(buf)
metrics.IncCounter(MetricBinaryRequestHeadersParsed)
return rh, nil
}
func (l *L1OnlyOrca) Set(req common.SetRequest) error {
//log.Println("set", string(req.Key))
metrics.IncCounter(MetricCmdSetL1)
start := timer.Now()
err := l.l1.Set(req)
metrics.ObserveHist(HistSetL1, timer.Since(start))
if err == nil {
metrics.IncCounter(MetricCmdSetSuccessL1)
metrics.IncCounter(MetricCmdSetSuccess)
err = l.res.Set(req.Opaque, req.Quiet)
} else {
metrics.IncCounter(MetricCmdSetErrorsL1)
metrics.IncCounter(MetricCmdSetErrors)
}
return err
}
func (l *L1OnlyOrca) Touch(req common.TouchRequest) error {
metrics.IncCounter(MetricCmdTouch)
//log.Println("touch", string(req.Key))
metrics.IncCounter(MetricCmdTouchL1)
err := l.l1.Touch(req)
if err == nil {
metrics.IncCounter(MetricCmdTouchHitsL1)
metrics.IncCounter(MetricCmdTouchHits)
l.res.Touch(req.Opaque)
} else if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdTouchMissesL1)
metrics.IncCounter(MetricCmdTouchMisses)
} else {
metrics.IncCounter(MetricCmdTouchMissesL1)
metrics.IncCounter(MetricCmdTouchMisses)
}
return err
}
func (l *L1OnlyOrca) Add(req common.SetRequest) error {
metrics.IncCounter(MetricCmdAdd)
//log.Println("add", string(req.Key))
metrics.IncCounter(MetricCmdAddL1)
err := l.l1.Add(req)
if err == nil {
metrics.IncCounter(MetricCmdAddStoredL1)
metrics.IncCounter(MetricCmdAddStored)
err = l.res.Add(req.Opaque, req.Quiet)
} else if err == common.ErrKeyExists {
metrics.IncCounter(MetricCmdAddNotStoredL1)
metrics.IncCounter(MetricCmdAddNotStored)
} else {
metrics.IncCounter(MetricCmdAddErrorsL1)
metrics.IncCounter(MetricCmdAddErrors)
}
return err
}
func (l *L1OnlyOrca) Replace(req common.SetRequest) error {
metrics.IncCounter(MetricCmdReplace)
//log.Println("replace", string(req.Key))
metrics.IncCounter(MetricCmdReplaceL1)
err := l.l1.Replace(req)
if err == nil {
metrics.IncCounter(MetricCmdReplaceStoredL1)
metrics.IncCounter(MetricCmdReplaceStored)
err = l.res.Replace(req.Opaque, req.Quiet)
} else if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdReplaceNotStoredL1)
metrics.IncCounter(MetricCmdReplaceNotStored)
} else {
metrics.IncCounter(MetricCmdReplaceErrorsL1)
metrics.IncCounter(MetricCmdReplaceErrors)
}
return err
}
func (l *L1OnlyOrca) Delete(req common.DeleteRequest) error {
metrics.IncCounter(MetricCmdDelete)
//log.Println("delete", string(req.Key))
metrics.IncCounter(MetricCmdDeleteL1)
err := l.l1.Delete(req)
if err == nil {
metrics.IncCounter(MetricCmdDeleteHits)
metrics.IncCounter(MetricCmdDeleteHitsL1)
l.res.Delete(req.Opaque)
} else if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdDeleteMissesL1)
metrics.IncCounter(MetricCmdDeleteMisses)
} else {
metrics.IncCounter(MetricCmdDeleteErrorsL1)
metrics.IncCounter(MetricCmdDeleteErrors)
}
return err
}
func (l *L1OnlyOrca) Set(req common.SetRequest) error {
metrics.IncCounter(MetricCmdSet)
//log.Println("set", string(req.Key))
metrics.IncCounter(MetricCmdSetL1)
err := l.l1.Set(req)
if err == nil {
metrics.IncCounter(MetricCmdSetSuccessL1)
metrics.IncCounter(MetricCmdSetSuccess)
err = l.res.Set(req.Opaque, req.Quiet)
} else {
metrics.IncCounter(MetricCmdSetErrorsL1)
metrics.IncCounter(MetricCmdSetErrors)
}
return err
}
func (l *L1L2Orca) Gat(req common.GATRequest) error {
metrics.IncCounter(MetricCmdGat)
//log.Println("gat", string(req.Key))
// Try L1 first, since it'll be faster if it succeeds
metrics.IncCounter(MetricCmdGatL1)
res, err := l.l1.GAT(req)
// Errors here are genrally fatal to the connection, as something has gone
// seriously wrong. Bail out early.
// I should note that this is different than the other commands, where there
// are some benevolent "errors" that include KeyNotFound or KeyExists. In
// both Get and GAT the mini-internal-protocol is different because the Get
// command uses a channel to send results back and an error channel to signal
// some kind of fatal problem. The result signals non-fatal "errors"; in this
// case it's ErrKeyNotFound --> res.Miss is true.
if err != nil {
metrics.IncCounter(MetricCmdGatErrorsL1)
metrics.IncCounter(MetricCmdGatErrors)
return err
}
if res.Miss {
// If we miss here, we have to GAT L2 to get the data, then put it back
// into L1 with the new TTL.
metrics.IncCounter(MetricCmdGatMissesL1)
metrics.IncCounter(MetricCmdGatL2)
res, err = l.l2.GAT(req)
// fatal error
if err != nil {
metrics.IncCounter(MetricCmdGatErrorsL2)
metrics.IncCounter(MetricCmdGatErrors)
return err
}
// A miss on L2 after L1 is a true miss
if res.Miss {
metrics.IncCounter(MetricCmdGatMissesL2)
metrics.IncCounter(MetricCmdGatMisses)
return l.res.GAT(res)
}
// Take the data from the L2 GAT and set into L1 with the new TTL.
// There's several problems that could arise from interleaving of other
// operations. Another GAT isn't a problem.
//
// Intermediate sets might get clobbered in L1 but remain in L2 if we
// used Set, but since we use Add we should not overwrite a Set that
// happens between the L2 GAT hit and subsequent L1 reconciliation.
//
// Deletes would be a possible problem since a delete hit in L2 and miss
// in L1 would interleave to have data in L1 not in L2. This is a risk
// that is understood and accepted. The typical use cases at Netflix
// will not use deletes concurrently with GATs.
setreq := common.SetRequest{
Key: req.Key,
Exptime: req.Exptime,
Flags: res.Flags,
Data: res.Data,
}
metrics.IncCounter(MetricCmdGatAddL1)
if err := l.l1.Add(setreq); err != nil {
// we were trampled in the middle of performing the GAT operation
// In this case, it's fine; no error for the overall op. We still
// want to track this with a metric, though, and return success.
if err == common.ErrKeyExists {
metrics.IncCounter(MetricCmdGatAddNotStoredL1)
} else {
metrics.IncCounter(MetricCmdGatAddErrorsL1)
// Gat errors here and not Add. The metrics for L1/L2 correspond to
// direct interaction with the two. THe overall metrics correspond
// to the more abstract orchestrator operation.
metrics.IncCounter(MetricCmdGatErrors)
return err
}
} else {
metrics.IncCounter(MetricCmdGatAddStoredL1)
}
// the overall operation succeeded
metrics.IncCounter(MetricCmdGatHits)
} else {
metrics.IncCounter(MetricCmdGatHitsL1)
// Set in L2 to play to the L2's strengths (fast writes) and avoid some
// pitfalls (slow touches and replaces, which require reads)
//
// The first possibility is a Set. A set into L2 would possibly cause a
// concurrent delete to not take, meaning the delete could say it was
// successful and then a subsequent get call would show the old data
// that was just deleted.
//
// Another option is to just send a touch, which allows us to send less
// data but gives the possibility of a touch miss on L2, which will be a
// problematic situation. If we get a touch miss, then we know we are
// inconsistent but we don't affect concurrent deletes.
//
// A third option is to use Replace, which could be helpful to avoid
// overriding concurrent deletes. This also might cause problems with
// othr sets at the same time, as it might overwrite a set that just
// finished.
//
// Many heavy users of EVCache at Netflix use GAT commands to lengthen
// TTLs of their data in use and to shorten the TTL of data they will
// not be using which is then async TTL'd out. I am explicitly
// discounting the concurrent delete situation here and accepting that
// they might not be exactly correct.
setreq := common.SetRequest{
Key: req.Key,
Exptime: req.Exptime,
Flags: res.Flags,
Data: res.Data,
}
metrics.IncCounter(MetricCmdGatSetL2)
err := l.l2.Set(setreq)
if err != nil {
// set error? Return it as our error. Yes, the GAT succeeded in L1
// but if L2 didn't get the set, then likely something is seriously
// wrong.
metrics.IncCounter(MetricCmdGatSetErrorsL2)
metrics.IncCounter(MetricCmdGatErrors)
return err
}
metrics.IncCounter(MetricCmdGatSetSuccessL2)
// overall operation succeeded
metrics.IncCounter(MetricCmdGatHits)
}
return l.res.GAT(res)
}
func (l *L1OnlyOrca) GetE(req common.GetRequest) error {
// For an L1 only orchestrator, this will fail if the backend is memcached.
// It should be talking to another rend-based server, such as the L2 for the
// EVCache server project.
metrics.IncCounterBy(MetricCmdGetEKeys, uint64(len(req.Keys)))
//debugString := "gete"
//for _, k := range req.Keys {
// debugString += " "
// debugString += string(k)
//}
//println(debugString)
metrics.IncCounter(MetricCmdGetEL1)
metrics.IncCounterBy(MetricCmdGetEKeysL1, uint64(len(req.Keys)))
start := timer.Now()
resChan, errChan := l.l1.GetE(req)
var err error
// Read all the responses back from l.l1.
// The contract is that the resChan will have GetEResponse's for get hits and misses,
// and the errChan will have any other errors, such as an out of memory error from
// memcached. If any receive happens from errChan, there will be no more responses
// from resChan.
for {
select {
case res, ok := <-resChan:
if !ok {
resChan = nil
} else {
if res.Miss {
metrics.IncCounter(MetricCmdGetEMissesL1)
metrics.IncCounter(MetricCmdGetEMisses)
} else {
metrics.IncCounter(MetricCmdGetEHits)
metrics.IncCounter(MetricCmdGetEHitsL1)
}
l.res.GetE(res)
}
case getErr, ok := <-errChan:
if !ok {
errChan = nil
} else {
metrics.IncCounter(MetricCmdGetEErrors)
metrics.IncCounter(MetricCmdGetEErrorsL1)
err = getErr
}
}
if resChan == nil && errChan == nil {
break
}
}
metrics.ObserveHist(HistGetEL1, timer.Since(start))
if err == nil {
l.res.GetEnd(req.NoopOpaque, req.NoopEnd)
}
return err
}
func (l *L1L2Orca) Replace(req common.SetRequest) error {
metrics.IncCounter(MetricCmdReplace)
//log.Println("replace", string(req.Key))
// Add in L2 first, since it has the larger state
metrics.IncCounter(MetricCmdReplaceL2)
err := l.l2.Replace(req)
if err != nil {
// A key already existing is not an error per se, it's a part of the
// functionality of the replace command to respond with a "not stored"
// in the form of an ErrKeyNotFound. Hence no error metrics.
if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdReplaceNotStoredL2)
metrics.IncCounter(MetricCmdReplaceNotStored)
return err
}
// otherwise we have a real error on our hands
metrics.IncCounter(MetricCmdReplaceErrorsL2)
metrics.IncCounter(MetricCmdReplaceErrors)
return err
}
metrics.IncCounter(MetricCmdReplaceStoredL2)
// Now on to L1. For a replace, the L2 succeeding means that the key is
// successfully replaced in L2, but in the middle here "anything can happen"
// so we have to think about concurrent operations. In a concurrent set
// situation, both L2 and L1 might have the same value from the set. In this
// case an add will fail and cause correct behavior. In a concurrent delete
// that hits in L2 (for the newly replaced data) and hits in L1 (for the
// data that was about to be replaced) then an add will cause a consistency
// problem by setting a key that shouldn't exist in L1 because it's not in
// L2. set and replace have the opposite problem, since they might overwrite
// a legitimate set that happened concurrently in the middle of the two
// operations. There is no one operation that solves these, so:
//
// The use of replace here explicitly assumes there is no concurrent set for
// the same key.
//
// The other risk here is a concurrent replace for the same key, which will
// possibly interleave to produce inconsistency in L2 and L1.
metrics.IncCounter(MetricCmdReplaceL1)
err = l.l1.Replace(req)
if err != nil {
// In this case, the replace worked fine, and we don't worry about it not
// being replaced in L1 because it did not exist. In this case, L2 has
// the data and L1 is empty. This is still correct, and the next get
// would place the data back into L1. Hence, we do not return the error.
if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdReplaceNotStoredL1)
metrics.IncCounter(MetricCmdReplaceNotStored)
return l.res.Replace(req.Opaque, req.Quiet)
}
// otherwise we have a real error on our hands
metrics.IncCounter(MetricCmdReplaceErrorsL1)
metrics.IncCounter(MetricCmdReplaceErrors)
return err
}
metrics.IncCounter(MetricCmdReplaceStoredL1)
metrics.IncCounter(MetricCmdReplaceStored)
return l.res.Replace(req.Opaque, req.Quiet)
}
func (l *L1L2Orca) Add(req common.SetRequest) error {
metrics.IncCounter(MetricCmdAdd)
//log.Println("add", string(req.Key))
// Add in L2 first, since it has the larger state
metrics.IncCounter(MetricCmdAddL2)
err := l.l2.Add(req)
if err != nil {
// A key already existing is not an error per se, it's a part of the
// functionality of the add command to respond with a "not stored" in
// the form of a ErrKeyExists. Hence no error metrics.
if err == common.ErrKeyExists {
metrics.IncCounter(MetricCmdAddNotStoredL2)
metrics.IncCounter(MetricCmdAddNotStored)
return err
}
// otherwise we have a real error on our hands
metrics.IncCounter(MetricCmdAddErrorsL2)
metrics.IncCounter(MetricCmdAddErrors)
return err
}
metrics.IncCounter(MetricCmdAddStoredL2)
// Now on to L1. For L1 we also do an add operation to protect (partially)
// against concurrent operations modifying the same key. For concurrent sets
// that complete between the two stages, this will fail, leaving the cache
// consistent.
//
// There is a possibility in add that concurrent deletes will cause an
// inconsistent state. A concurrent delete could hit in L2 and miss in
// L1 between the two add operations, causing the L2 to be deleted and
// the L1 to have the data.
metrics.IncCounter(MetricCmdAddL1)
err = l.l1.Add(req)
if err != nil {
// This is kind of a problem. What has happened here is that the L2
// cache has successfully added the key but L1 did not. In this case
// we have to fail with a ErrKeyExists/Not Stored because the overall
// operation failed. If we assume a retry on the client, then it will
// likely fail again at the L2 step.
//
// One possible scenario here is that an add started and completed L2,
// then a set ran to full completion, overwriting the data in L2 then
// writing into L1, then the second step here ran and got an error.
if err == common.ErrKeyExists {
metrics.IncCounter(MetricCmdAddNotStoredL1)
metrics.IncCounter(MetricCmdAddNotStored)
return err
}
// otherwise we have a real error on our hands
metrics.IncCounter(MetricCmdAddErrorsL1)
metrics.IncCounter(MetricCmdAddErrors)
return err
}
metrics.IncCounter(MetricCmdAddStoredL1)
metrics.IncCounter(MetricCmdAddStored)
return l.res.Add(req.Opaque, req.Quiet)
}
func (l *L1L2Orca) Unknown(req common.Request) error {
metrics.IncCounter(MetricCmdUnknown)
return common.ErrUnknownCmd
}
func (l *L1L2Orca) Version(req common.VersionRequest) error {
metrics.IncCounter(MetricCmdVersion)
return l.res.Version(req.Opaque)
}
func (l *L1L2Orca) Quit(req common.QuitRequest) error {
metrics.IncCounter(MetricCmdQuit)
return l.res.Quit(req.Opaque, req.Quiet)
}
func (l *L1L2Orca) Delete(req common.DeleteRequest) error {
metrics.IncCounter(MetricCmdDelete)
//log.Println("delete", string(req.Key))
// Try L2 first
metrics.IncCounter(MetricCmdDeleteL2)
err := l.l2.Delete(req)
if err != nil {
// On a delete miss in L2 don't bother deleting in L1. There might be no
// key at all, or another request may be deleting the same key. In that
// case the other will finish up. Returning a key not found will trigger
// error handling to send back an error response.
if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdDeleteMissesL2)
metrics.IncCounter(MetricCmdDeleteMisses)
return err
}
// If we fail to delete in L2, don't delete in L1. This can leave us in
// an inconsistent state if the request succeeded in L2 but some
// communication error caused the problem. In the typical deployment of
// rend, the L1 and L2 caches are both on the same box with
// communication happening over a unix domain socket. In this case, the
// likelihood of this error path happening is very small.
metrics.IncCounter(MetricCmdDeleteErrorsL2)
metrics.IncCounter(MetricCmdDeleteErrors)
return err
}
metrics.IncCounter(MetricCmdDeleteHitsL2)
// Now delete in L1. This means we're temporarily inconsistent, but also
// eliminated the interleaving where the data is deleted from L1, read from
// L2, set in L1, then deleted in L2. By deleting from L2 first, if L1 goes
// missing then no other request can undo part of this request.
metrics.IncCounter(MetricCmdDeleteL1)
if err := l.l1.Delete(req); err != nil {
// Delete misses in L1 are fine. If we get here, that means the delete
// in L2 hit. This isn't a miss per se since the overall effect is a
// delete. Concurrent deletes might interleave to produce this, or the
// data might have TTL'd out. Both cases are still fine.
if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdDeleteMissesL1)
metrics.IncCounter(MetricCmdDeleteHits)
// disregard the miss, don't return the error
return l.res.Delete(req.Opaque)
}
metrics.IncCounter(MetricCmdDeleteErrorsL1)
metrics.IncCounter(MetricCmdDeleteErrors)
return err
}
metrics.IncCounter(MetricCmdDeleteHitsL1)
metrics.IncCounter(MetricCmdDeleteHits)
return l.res.Delete(req.Opaque)
}
func (s *DefaultServer) Loop() {
defer func() {
if r := recover(); r != nil {
if r != io.EOF {
log.Println("Recovered from runtime panic:", r)
log.Println("Panic location: ", identifyPanic())
}
}
}()
for {
start := time.Now()
request, reqType, err := s.rp.Parse()
if err != nil {
if err == common.ErrBadRequest ||
err == common.ErrBadLength ||
err == common.ErrBadFlags ||
err == common.ErrBadExptime {
s.orca.Error(nil, common.RequestUnknown, err)
continue
} else {
// Otherwise IO error. Abort!
abort(s.conns, err)
return
}
}
metrics.IncCounter(MetricCmdTotal)
// TODO: handle nil
switch reqType {
case common.RequestSet:
err = s.orca.Set(request.(common.SetRequest))
case common.RequestAdd:
err = s.orca.Add(request.(common.SetRequest))
case common.RequestReplace:
err = s.orca.Replace(request.(common.SetRequest))
case common.RequestDelete:
err = s.orca.Delete(request.(common.DeleteRequest))
case common.RequestTouch:
err = s.orca.Touch(request.(common.TouchRequest))
case common.RequestGet:
err = s.orca.Get(request.(common.GetRequest))
case common.RequestGetE:
err = s.orca.GetE(request.(common.GetRequest))
case common.RequestGat:
err = s.orca.Gat(request.(common.GATRequest))
case common.RequestNoop:
err = s.orca.Noop(request.(common.NoopRequest))
case common.RequestQuit:
s.orca.Quit(request.(common.QuitRequest))
abort(s.conns, err)
return
case common.RequestVersion:
err = s.orca.Version(request.(common.VersionRequest))
case common.RequestUnknown:
err = s.orca.Unknown(request)
}
if err != nil {
if common.IsAppError(err) {
if err != common.ErrKeyNotFound {
metrics.IncCounter(MetricErrAppError)
}
s.orca.Error(request, reqType, err)
} else {
metrics.IncCounter(MetricErrUnrecoverable)
abort(s.conns, err)
return
}
}
dur := uint64(time.Since(start))
switch reqType {
case common.RequestSet:
metrics.ObserveHist(HistSet, dur)
case common.RequestAdd:
metrics.ObserveHist(HistAdd, dur)
case common.RequestReplace:
metrics.ObserveHist(HistReplace, dur)
case common.RequestDelete:
metrics.ObserveHist(HistDelete, dur)
case common.RequestTouch:
metrics.ObserveHist(HistTouch, dur)
case common.RequestGet:
metrics.ObserveHist(HistGet, dur)
case common.RequestGetE:
metrics.ObserveHist(HistGetE, dur)
case common.RequestGat:
metrics.ObserveHist(HistGat, dur)
}
}
}
func (l *L1L2Orca) Touch(req common.TouchRequest) error {
metrics.IncCounter(MetricCmdTouch)
//log.Println("touch", string(req.Key))
// Try L2 first
metrics.IncCounter(MetricCmdTouchL2)
err := l.l2.Touch(req)
if err != nil {
// On a touch miss in L2 don't bother touch in L1. The data should be
// TTL'd out within a second. This is yet another place where it's
// possible to be inconsistent, but only for a short time. Any
// concurrent requests will see the same behavior as this one. If the
// touch misses here, any other request will see the same view.
if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdTouchMissesL2)
metrics.IncCounter(MetricCmdTouchMisses)
return err
}
// If we fail to touch in L2, don't touch in L1. If the touch succeeded
// but for some reason the communication failed, then this is still OK
// since L1 can TTL out while L2 still has the data. On the next get
// request the data would still be retrievable, albeit more slowly.
metrics.IncCounter(MetricCmdTouchErrorsL2)
metrics.IncCounter(MetricCmdTouchErrors)
return err
}
metrics.IncCounter(MetricCmdTouchHitsL2)
// In the case of concurrent touches with different values, it's possible
// that the touches for L1 and L2 interleave and produce an inconsistent
// state. The L2 could be touched long, then L2 and L1 touched short on
// another request, then L1 touched long. In this case the data in L1 would
// outlive L2. This situation is uncommon and is therefore discounted.
metrics.IncCounter(MetricCmdTouchL1)
if err := l.l1.Touch(req); err != nil {
// Touch misses in L1 after a hit in L2 are nto a big deal. The
// touch operation here explicitly does *not* act as a pre-warm putting
// data into L1. A miss here after a hit is the same as a hit.
if err == common.ErrKeyNotFound {
metrics.IncCounter(MetricCmdTouchMissesL1)
// Note that we increment the overall hits here (not misses) on
// purpose because L2 hit.
metrics.IncCounter(MetricCmdTouchHits)
return l.res.Touch(req.Opaque)
}
metrics.IncCounter(MetricCmdTouchErrorsL1)
metrics.IncCounter(MetricCmdTouchErrors)
return err
}
metrics.IncCounter(MetricCmdTouchHitsL1)
metrics.IncCounter(MetricCmdTouchHits)
return l.res.Touch(req.Opaque)
}
func (l *L1L2Orca) Noop(req common.NoopRequest) error {
metrics.IncCounter(MetricCmdNoop)
return l.res.Noop(req.Opaque)
}
func ListenAndServe(l ListenArgs, s ServerConst, o orcas.OrcaConst, h1, h2 handlers.HandlerConst) {
var listener net.Listener
var err error
switch l.Type {
case ListenTCP:
listener, err = net.Listen("tcp", fmt.Sprintf(":%d", l.Port))
if err != nil {
log.Panicf("Error binding to port %d: %v\n", l.Port, err.Error())
}
case ListenUnix:
err = os.Remove(l.Path)
if err != nil && !os.IsNotExist(err) {
log.Panicf("Error removing previous unix socket file at %s\n", l.Path)
}
listener, err = net.Listen("unix", l.Path)
if err != nil {
log.Panicf("Error binding to unix socket at %s: %v\n", l.Path, err.Error())
}
default:
log.Panicf("Unsupported server listen type: %v", l.Type)
}
for {
remote, err := listener.Accept()
if err != nil {
log.Println("Error accepting connection from remote:", err.Error())
remote.Close()
continue
}
metrics.IncCounter(MetricConnectionsEstablishedExt)
if l.Type == ListenTCP {
tcpRemote := remote.(*net.TCPConn)
tcpRemote.SetKeepAlive(true)
tcpRemote.SetKeepAlivePeriod(30 * time.Second)
}
// construct L1 handler using given constructor
l1, err := h1()
if err != nil {
log.Println("Error opening connection to L1:", err.Error())
remote.Close()
continue
}
metrics.IncCounter(MetricConnectionsEstablishedL1)
// construct l2
l2, err := h2()
if err != nil {
log.Println("Error opening connection to L2:", err.Error())
l1.Close()
remote.Close()
continue
}
metrics.IncCounter(MetricConnectionsEstablishedL2)
// spin off a goroutine here to handle determining the protocol used for the connection.
// The server loop can't be started until the protocol is known. Another goroutine is
// necessary here because we don't want to block accepting new connections if the current
// new connection doesn't send data immediately.
go func(remoteConn net.Conn) {
remoteReader := bufio.NewReader(remoteConn)
remoteWriter := bufio.NewWriter(remoteConn)
var reqParser common.RequestParser
var responder common.Responder
// A connection is either binary protocol or text. It cannot switch between the two.
// This is the way memcached handles protocols, so it can be as strict here.
binary, err := isBinaryRequest(remoteReader)
if err != nil {
// must be an IO error. Abort!
abort([]io.Closer{remoteConn, l1, l2}, err)
return
}
if binary {
reqParser = binprot.NewBinaryParser(remoteReader)
responder = binprot.NewBinaryResponder(remoteWriter)
} else {
reqParser = textprot.NewTextParser(remoteReader)
responder = textprot.NewTextResponder(remoteWriter)
}
server := s([]io.Closer{remoteConn, l1, l2}, reqParser, o(l1, l2, responder))
go server.Loop()
}(remote)
}
}
func (l *L1L2Orca) Get(req common.GetRequest) error {
metrics.IncCounter(MetricCmdGet)
metrics.IncCounterBy(MetricCmdGetKeys, uint64(len(req.Keys)))
//debugString := "get"
//for _, k := range req.Keys {
// debugString += " "
// debugString += string(k)
//}
//println(debugString)
metrics.IncCounter(MetricCmdGetL1)
metrics.IncCounterBy(MetricCmdGetKeysL1, uint64(len(req.Keys)))
resChan, errChan := l.l1.Get(req)
var err error
//var lastres common.GetResponse
var l2keys [][]byte
var l2opaques []uint32
var l2quiets []bool
// Read all the responses back from L1.
// The contract is that the resChan will have GetResponse's for get hits and misses,
// and the errChan will have any other errors, such as an out of memory error from
// memcached. If any receive happens from errChan, there will be no more responses
// from resChan.
for {
select {
case res, ok := <-resChan:
if !ok {
resChan = nil
} else {
if res.Miss {
metrics.IncCounter(MetricCmdGetMissesL1)
l2keys = append(l2keys, res.Key)
l2opaques = append(l2opaques, res.Opaque)
l2quiets = append(l2quiets, res.Quiet)
} else {
metrics.IncCounter(MetricCmdGetHits)
metrics.IncCounter(MetricCmdGetHitsL1)
l.res.Get(res)
}
}
case getErr, ok := <-errChan:
if !ok {
errChan = nil
} else {
metrics.IncCounter(MetricCmdGetErrors)
metrics.IncCounter(MetricCmdGetErrorsL1)
err = getErr
}
}
if resChan == nil && errChan == nil {
break
}
}
// leave early on all hits
if len(l2keys) == 0 {
if err != nil {
return err
}
return l.res.GetEnd(req.NoopOpaque, req.NoopEnd)
}
// Time for the same dance with L2
req = common.GetRequest{
Keys: l2keys,
NoopEnd: req.NoopEnd,
NoopOpaque: req.NoopOpaque,
Opaques: l2opaques,
Quiet: l2quiets,
}
metrics.IncCounter(MetricCmdGetEL2)
metrics.IncCounterBy(MetricCmdGetEKeysL2, uint64(len(l2keys)))
resChanE, errChan := l.l2.GetE(req)
for {
select {
case res, ok := <-resChanE:
if !ok {
resChanE = nil
} else {
if res.Miss {
metrics.IncCounter(MetricCmdGetEMissesL2)
// Missing L2 means a true miss
metrics.IncCounter(MetricCmdGetMisses)
} else {
metrics.IncCounter(MetricCmdGetEHitsL2)
//set in l1
metrics.IncCounter(MetricCmdGetSetL1)
setreq := common.SetRequest{
Key: res.Key,
Flags: res.Flags,
Exptime: res.Exptime,
Data: res.Data,
}
if err := l.l1.Set(setreq); err != nil {
metrics.IncCounter(MetricCmdGetSetErrorsL1)
return err
}
metrics.IncCounter(MetricCmdGetSetSucessL1)
// overall operation is considered a hit
metrics.IncCounter(MetricCmdGetHits)
}
getres := common.GetResponse{
Key: res.Key,
Flags: res.Flags,
Data: res.Data,
Miss: res.Miss,
Opaque: res.Opaque,
Quiet: res.Quiet,
}
l.res.Get(getres)
}
case getErr, ok := <-errChan:
if !ok {
errChan = nil
} else {
metrics.IncCounter(MetricCmdGetErrors)
metrics.IncCounter(MetricCmdGetEErrorsL2)
err = getErr
}
}
if resChanE == nil && errChan == nil {
break
}
}
if err == nil {
return l.res.GetEnd(req.NoopOpaque, req.NoopEnd)
}
return err
}