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package handlers
import (
"strings"
"github.com/mimecast/dtail/internal"
"github.com/mimecast/dtail/internal/io/dlog"
"github.com/mimecast/dtail/internal/mapr/client"
"github.com/mimecast/dtail/internal/protocol"
)
// aggregateMessagePrefix is the leading part of a mapreduce aggregate-data
// wire message (AGGREGATE|host|data). Classifying incoming messages against
// this full prefix, rather than just their first byte, prevents plain-mode
// protocol acks (e.g. "AUTHKEY OK") from being fed to the aggregate parser.
const aggregateMessagePrefix = protocol.AggregateMessageID + protocol.FieldDelimiter
// MaprHandler is the handler used on the client side for running mapreduce
// aggregations.
type MaprHandler struct {
baseHandler
aggregate *client.Aggregate
removedNl bool
}
// NewMaprHandler returns a new mapreduce client handler.
func NewMaprHandler(server string, session *client.SessionState) *MaprHandler {
return &MaprHandler{
baseHandler: baseHandler{
server: server,
shellStarted: false,
commands: make(chan string),
status: -1,
done: internal.NewDone(),
capabilities: make(map[string]struct{}),
capabilitiesCh: make(chan struct{}),
sessionAcks: make(chan SessionAck, 4),
},
aggregate: client.NewAggregate(server, session),
}
}
// Read data from the dtail server via Writer interface.
func (h *MaprHandler) Write(p []byte) (n int, err error) {
for _, b := range p {
switch b {
case '\n':
h.removedNl = true
case protocol.MessageDelimiter:
message := h.baseHandler.receiveBuf.String()
if len(message) == 0 {
h.baseHandler.receiveBuf.Reset()
h.removedNl = false
continue
}
dlog.Client.Debug(message)
if isAggregateMessage(message) {
h.handleAggregateMessage(message)
} else {
if h.removedNl {
h.baseHandler.handleMessage(message + "\n")
} else {
h.baseHandler.handleMessage(message)
}
}
h.baseHandler.receiveBuf.Reset()
h.removedNl = false
default:
h.baseHandler.receiveBuf.WriteByte(b)
}
}
return len(p), nil
}
// isAggregateMessage reports whether a wire message carries mapreduce
// aggregate data (AGGREGATE|host|data). Only such messages may be handed to
// the aggregate parser. Matching the full AggregateMessageID field prefix,
// rather than just the first byte 'A', keeps plain-mode protocol acks such as
// "AUTHKEY OK" out of the parser; those would otherwise trigger a spurious
// "Unable to aggregate data ... expected 3 parts" error. Non-aggregate
// messages are routed to the base handler, which recognises acks as control.
func isAggregateMessage(message string) bool {
return strings.HasPrefix(message, aggregateMessagePrefix)
}
// Handle a message received from server including mapr aggregation related data.
func (h *MaprHandler) handleAggregateMessage(message string) {
parts := strings.SplitN(message, protocol.FieldDelimiter, 3)
if len(parts) != 3 {
dlog.Client.Error("Unable to aggregate data", h.server, message, parts,
len(parts), "expected 3 parts")
return
}
if err := h.aggregate.Aggregate(parts[2]); err != nil {
dlog.Client.Error("Unable to aggregate data", h.server, message, err)
}
}
// Shutdown flushes any pending aggregate state before marking the handler done.
func (h *MaprHandler) Shutdown() {
if h.aggregate != nil {
if err := h.aggregate.Flush(); err != nil {
dlog.Client.Error("Unable to flush aggregate data on shutdown", h.server, err)
}
}
h.baseHandler.Shutdown()
}
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