334 lines
8.2 KiB
Go
334 lines
8.2 KiB
Go
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package memcached
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import (
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"bytes"
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"encoding/binary"
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"fmt"
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"io"
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"math"
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"github.com/couchbase/gomemcached"
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"github.com/couchbase/goutils/logging"
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)
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// TAP protocol docs: <http://www.couchbase.com/wiki/display/couchbase/TAP+Protocol>
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// TapOpcode is the tap operation type (found in TapEvent)
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type TapOpcode uint8
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// Tap opcode values.
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const (
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TapBeginBackfill = TapOpcode(iota)
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TapEndBackfill
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TapMutation
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TapDeletion
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TapCheckpointStart
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TapCheckpointEnd
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tapEndStream
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)
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const tapMutationExtraLen = 16
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var tapOpcodeNames map[TapOpcode]string
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func init() {
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tapOpcodeNames = map[TapOpcode]string{
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TapBeginBackfill: "BeginBackfill",
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TapEndBackfill: "EndBackfill",
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TapMutation: "Mutation",
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TapDeletion: "Deletion",
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TapCheckpointStart: "TapCheckpointStart",
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TapCheckpointEnd: "TapCheckpointEnd",
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tapEndStream: "EndStream",
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}
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}
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func (opcode TapOpcode) String() string {
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name := tapOpcodeNames[opcode]
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if name == "" {
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name = fmt.Sprintf("#%d", opcode)
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}
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return name
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}
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// TapEvent is a TAP notification of an operation on the server.
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type TapEvent struct {
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Opcode TapOpcode // Type of event
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VBucket uint16 // VBucket this event applies to
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Flags uint32 // Item flags
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Expiry uint32 // Item expiration time
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Key, Value []byte // Item key/value
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Cas uint64
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}
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func makeTapEvent(req gomemcached.MCRequest) *TapEvent {
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event := TapEvent{
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VBucket: req.VBucket,
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}
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switch req.Opcode {
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case gomemcached.TAP_MUTATION:
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event.Opcode = TapMutation
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event.Key = req.Key
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event.Value = req.Body
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event.Cas = req.Cas
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case gomemcached.TAP_DELETE:
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event.Opcode = TapDeletion
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event.Key = req.Key
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event.Cas = req.Cas
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case gomemcached.TAP_CHECKPOINT_START:
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event.Opcode = TapCheckpointStart
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case gomemcached.TAP_CHECKPOINT_END:
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event.Opcode = TapCheckpointEnd
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case gomemcached.TAP_OPAQUE:
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if len(req.Extras) < 8+4 {
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return nil
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}
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switch op := int(binary.BigEndian.Uint32(req.Extras[8:])); op {
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case gomemcached.TAP_OPAQUE_INITIAL_VBUCKET_STREAM:
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event.Opcode = TapBeginBackfill
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case gomemcached.TAP_OPAQUE_CLOSE_BACKFILL:
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event.Opcode = TapEndBackfill
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case gomemcached.TAP_OPAQUE_CLOSE_TAP_STREAM:
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event.Opcode = tapEndStream
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case gomemcached.TAP_OPAQUE_ENABLE_AUTO_NACK:
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return nil
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case gomemcached.TAP_OPAQUE_ENABLE_CHECKPOINT_SYNC:
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return nil
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default:
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logging.Infof("TapFeed: Ignoring TAP_OPAQUE/%d", op)
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return nil // unknown opaque event
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}
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case gomemcached.NOOP:
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return nil // ignore
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default:
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logging.Infof("TapFeed: Ignoring %s", req.Opcode)
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return nil // unknown event
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}
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if len(req.Extras) >= tapMutationExtraLen &&
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(event.Opcode == TapMutation || event.Opcode == TapDeletion) {
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event.Flags = binary.BigEndian.Uint32(req.Extras[8:])
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event.Expiry = binary.BigEndian.Uint32(req.Extras[12:])
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}
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return &event
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}
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func (event TapEvent) String() string {
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switch event.Opcode {
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case TapBeginBackfill, TapEndBackfill, TapCheckpointStart, TapCheckpointEnd:
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return fmt.Sprintf("<TapEvent %s, vbucket=%d>",
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event.Opcode, event.VBucket)
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default:
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return fmt.Sprintf("<TapEvent %s, key=%q (%d bytes) flags=%x, exp=%d>",
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event.Opcode, event.Key, len(event.Value),
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event.Flags, event.Expiry)
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}
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}
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// TapArguments are parameters for requesting a TAP feed.
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//
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// Call DefaultTapArguments to get a default one.
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type TapArguments struct {
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// Timestamp of oldest item to send.
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//
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// Use TapNoBackfill to suppress all past items.
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Backfill uint64
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// If set, server will disconnect after sending existing items.
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Dump bool
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// The indices of the vbuckets to watch; empty/nil to watch all.
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VBuckets []uint16
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// Transfers ownership of vbuckets during cluster rebalance.
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Takeover bool
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// If true, server will wait for client ACK after every notification.
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SupportAck bool
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// If true, client doesn't want values so server shouldn't send them.
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KeysOnly bool
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// If true, client wants the server to send checkpoint events.
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Checkpoint bool
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// Optional identifier to use for this client, to allow reconnects
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ClientName string
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// Registers this client (by name) till explicitly deregistered.
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RegisteredClient bool
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}
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// Value for TapArguments.Backfill denoting that no past events at all
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// should be sent.
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const TapNoBackfill = math.MaxUint64
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// DefaultTapArguments returns a default set of parameter values to
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// pass to StartTapFeed.
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func DefaultTapArguments() TapArguments {
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return TapArguments{
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Backfill: TapNoBackfill,
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}
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}
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func (args *TapArguments) flags() []byte {
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var flags gomemcached.TapConnectFlag
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if args.Backfill != 0 {
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flags |= gomemcached.BACKFILL
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}
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if args.Dump {
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flags |= gomemcached.DUMP
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}
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if len(args.VBuckets) > 0 {
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flags |= gomemcached.LIST_VBUCKETS
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}
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if args.Takeover {
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flags |= gomemcached.TAKEOVER_VBUCKETS
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}
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if args.SupportAck {
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flags |= gomemcached.SUPPORT_ACK
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}
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if args.KeysOnly {
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flags |= gomemcached.REQUEST_KEYS_ONLY
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}
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if args.Checkpoint {
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flags |= gomemcached.CHECKPOINT
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}
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if args.RegisteredClient {
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flags |= gomemcached.REGISTERED_CLIENT
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}
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encoded := make([]byte, 4)
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binary.BigEndian.PutUint32(encoded, uint32(flags))
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return encoded
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}
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func must(err error) {
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if err != nil {
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panic(err)
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}
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}
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func (args *TapArguments) bytes() (rv []byte) {
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buf := bytes.NewBuffer([]byte{})
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if args.Backfill > 0 {
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must(binary.Write(buf, binary.BigEndian, uint64(args.Backfill)))
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}
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if len(args.VBuckets) > 0 {
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must(binary.Write(buf, binary.BigEndian, uint16(len(args.VBuckets))))
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for i := 0; i < len(args.VBuckets); i++ {
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must(binary.Write(buf, binary.BigEndian, uint16(args.VBuckets[i])))
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}
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}
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return buf.Bytes()
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}
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// TapFeed represents a stream of events from a server.
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type TapFeed struct {
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C <-chan TapEvent
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Error error
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closer chan bool
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}
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// StartTapFeed starts a TAP feed on a client connection.
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//
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// The events can be read from the returned channel. The connection
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// can no longer be used for other purposes; it's now reserved for
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// receiving the TAP messages. To stop receiving events, close the
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// client connection.
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func (mc *Client) StartTapFeed(args TapArguments) (*TapFeed, error) {
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rq := &gomemcached.MCRequest{
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Opcode: gomemcached.TAP_CONNECT,
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Key: []byte(args.ClientName),
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Extras: args.flags(),
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Body: args.bytes()}
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err := mc.Transmit(rq)
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if err != nil {
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return nil, err
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}
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ch := make(chan TapEvent)
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feed := &TapFeed{
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C: ch,
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closer: make(chan bool),
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}
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go mc.runFeed(ch, feed)
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return feed, nil
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}
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// TapRecvHook is called after every incoming tap packet is received.
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var TapRecvHook func(*gomemcached.MCRequest, int, error)
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// Internal goroutine that reads from the socket and writes events to
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// the channel
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func (mc *Client) runFeed(ch chan TapEvent, feed *TapFeed) {
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defer close(ch)
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var headerBuf [gomemcached.HDR_LEN]byte
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loop:
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for {
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// Read the next request from the server.
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//
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// (Can't call mc.Receive() because it reads a
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// _response_ not a request.)
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var pkt gomemcached.MCRequest
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n, err := pkt.Receive(mc.conn, headerBuf[:])
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if TapRecvHook != nil {
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TapRecvHook(&pkt, n, err)
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}
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if err != nil {
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if err != io.EOF {
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feed.Error = err
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}
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break loop
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}
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//logging.Infof("** TapFeed received %#v : %q", pkt, pkt.Body)
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if pkt.Opcode == gomemcached.TAP_CONNECT {
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// This is not an event from the server; it's
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// an error response to my connect request.
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feed.Error = fmt.Errorf("tap connection failed: %s", pkt.Body)
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break loop
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}
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event := makeTapEvent(pkt)
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if event != nil {
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if event.Opcode == tapEndStream {
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break loop
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}
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select {
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case ch <- *event:
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case <-feed.closer:
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break loop
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}
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}
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if len(pkt.Extras) >= 4 {
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reqFlags := binary.BigEndian.Uint16(pkt.Extras[2:])
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if reqFlags&gomemcached.TAP_ACK != 0 {
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if _, err := mc.sendAck(&pkt); err != nil {
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feed.Error = err
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break loop
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}
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}
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}
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}
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if err := mc.Close(); err != nil {
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logging.Errorf("Error closing memcached client: %v", err)
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}
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}
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func (mc *Client) sendAck(pkt *gomemcached.MCRequest) (int, error) {
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res := gomemcached.MCResponse{
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Opcode: pkt.Opcode,
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Opaque: pkt.Opaque,
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Status: gomemcached.SUCCESS,
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}
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return res.Transmit(mc.conn)
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}
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// Close terminates a TapFeed.
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//
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// Call this if you stop using a TapFeed before its channel ends.
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func (feed *TapFeed) Close() {
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close(feed.closer)
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}
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