merge 4.0.0-RC

10 files changed, 638 insertions, 660 deletions

diff --git a/internal/server/continuous.go b/internal/server/continuous.go
index f75c732..ac5c686 100644
--- a/internal/server/continuous.go
+++ b/internal/server/continuous.go
@@ -8,33 +8,29 @@ import (
 
 	"github.com/mimecast/dtail/internal/clients"
 	"github.com/mimecast/dtail/internal/config"
-	"github.com/mimecast/dtail/internal/io/logger"
+	"github.com/mimecast/dtail/internal/io/dlog"
 	"github.com/mimecast/dtail/internal/omode"
-
 	gossh "golang.org/x/crypto/ssh"
 )
 
-type continuous struct {
-}
+type continuous struct{}
 
 func newContinuous() *continuous {
 	return &continuous{}
 }
 
 func (c *continuous) start(ctx context.Context) {
-	logger.Info("Starting continuous job runner after 10s")
-	time.Sleep(time.Second * 10)
-
+	dlog.Server.Info("Starting continuous job runner after 2s")
+	time.Sleep(time.Second * 2)
 	c.runJobs(ctx)
 }
 
 func (c *continuous) runJobs(ctx context.Context) {
 	for _, job := range config.Server.Continuous {
 		if !job.Enable {
-			logger.Debug(job.Name, "Not running job as not enabled")
+			dlog.Server.Debug(job.Name, "Not running job as not enabled")
 			continue
 		}
-
 		go func(job config.Continuous) {
 			c.runJob(ctx, job)
 			for {
@@ -51,18 +47,17 @@ func (c *continuous) runJobs(ctx context.Context) {
 }
 
 func (c *continuous) runJob(ctx context.Context, job config.Continuous) {
-	logger.Debug(job.Name, "Processing job")
+	dlog.Server.Debug(job.Name, "Processing job")
 
 	files := fillDates(job.Files)
 	outfile := fillDates(job.Outfile)
-
 	servers := strings.Join(job.Servers, ",")
 	if servers == "" {
 		servers = config.Server.SSHBindAddress
 	}
 
-	args := clients.Args{
-		ConnectionsPerCPU: 10,
+	args := config.Args{
+		ConnectionsPerCPU: config.DefaultConnectionsPerCPU,
 		Discovery:         job.Discovery,
 		ServersStr:        servers,
 		What:              files,
@@ -71,35 +66,32 @@ func (c *continuous) runJob(ctx context.Context, job config.Continuous) {
 	}
 
 	args.SSHAuthMethods = append(args.SSHAuthMethods, gossh.Password(job.Name))
-
-	query := fmt.Sprintf("%s outfile %s", job.Query, outfile)
-	client, err := clients.NewMaprClient(args, query, clients.NonCumulativeMode)
+	args.QueryStr = fmt.Sprintf("%s outfile %s", job.Query, outfile)
+	client, err := clients.NewMaprClient(args, clients.NonCumulativeMode)
 	if err != nil {
-		logger.Error(fmt.Sprintf("Unable to create job %s", job.Name), err)
+		dlog.Server.Error(fmt.Sprintf("Unable to create job %s", job.Name), err)
 		return
 	}
 
 	jobCtx, cancel := context.WithCancel(ctx)
 	defer cancel()
-
 	if job.RestartOnDayChange {
 		go func() {
 			if c.waitForDayChange(ctx) {
-				logger.Info(fmt.Sprintf("Canceling job %s due to day change", job.Name))
+				dlog.Server.Info(fmt.Sprintf("Canceling job %s due to day change", job.Name))
 				cancel()
 			}
 		}()
 	}
 
-	logger.Info(fmt.Sprintf("Starting job %s", job.Name))
+	dlog.Server.Info(fmt.Sprintf("Starting job %s", job.Name))
 	status := client.Start(jobCtx, make(chan string))
 	logMessage := fmt.Sprintf("Job exited with status %d", status)
-
 	if status != 0 {
-		logger.Warn(logMessage)
+		dlog.Server.Warn(logMessage)
 		return
 	}
-	logger.Info(logMessage)
+	dlog.Server.Info(logMessage)
 }
 
 func (c *continuous) waitForDayChange(ctx context.Context) bool {
diff --git a/internal/server/handlers/basehandler.go b/internal/server/handlers/basehandler.go
new file mode 100644
index 0000000..4fd718e
--- /dev/null
+++ b/internal/server/handlers/basehandler.go
@@ -0,0 +1,320 @@
+package handlers
+
+import (
+	"bytes"
+	"context"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/mimecast/dtail/internal"
+	"github.com/mimecast/dtail/internal/config"
+	"github.com/mimecast/dtail/internal/io/dlog"
+	"github.com/mimecast/dtail/internal/io/line"
+	"github.com/mimecast/dtail/internal/io/pool"
+	"github.com/mimecast/dtail/internal/lcontext"
+	"github.com/mimecast/dtail/internal/mapr/server"
+	"github.com/mimecast/dtail/internal/protocol"
+	user "github.com/mimecast/dtail/internal/user/server"
+)
+
+type handleCommandCb func(context.Context, lcontext.LContext, int, []string, string)
+
+type baseHandler struct {
+	done             *internal.Done
+	handleCommandCb  handleCommandCb
+	lines            chan *line.Line
+	aggregate        *server.Aggregate
+	maprMessages     chan string
+	serverMessages   chan string
+	hostname         string
+	user             *user.User
+	ackCloseReceived chan struct{}
+	activeCommands   int32
+	readBuf          bytes.Buffer
+	writeBuf         bytes.Buffer
+
+	// Some global options + sync primitives required.
+	once       sync.Once
+	mutex      sync.Mutex
+	quiet      bool
+	plain      bool
+	serverless bool
+}
+
+// Shutdown the handler.
+func (h *baseHandler) Shutdown() {
+	h.done.Shutdown()
+}
+
+// Done channel of the handler.
+func (h *baseHandler) Done() <-chan struct{} {
+	return h.done.Done()
+}
+
+// Read is to send data to the dtail client via Reader interface.
+func (h *baseHandler) Read(p []byte) (n int, err error) {
+	defer h.readBuf.Reset()
+
+	select {
+	case message := <-h.serverMessages:
+		if len(message) > 0 && message[0] == '.' {
+			// Handle hidden message (don't display to the user)
+			h.readBuf.WriteString(message)
+			h.readBuf.WriteByte(protocol.MessageDelimiter)
+			n = copy(p, h.readBuf.Bytes())
+			return
+		}
+
+		if h.serverless {
+			return
+		}
+
+		// Handle normal server message (display to the user)
+		h.readBuf.WriteString("SERVER")
+		h.readBuf.WriteString(protocol.FieldDelimiter)
+		h.readBuf.WriteString(h.hostname)
+		h.readBuf.WriteString(protocol.FieldDelimiter)
+		h.readBuf.WriteString(message)
+		h.readBuf.WriteByte(protocol.MessageDelimiter)
+		n = copy(p, h.readBuf.Bytes())
+
+	case message := <-h.maprMessages:
+		// Send mapreduce-aggregated data as a message.
+		h.readBuf.WriteString("AGGREGATE")
+		h.readBuf.WriteString(protocol.FieldDelimiter)
+		h.readBuf.WriteString(h.hostname)
+		h.readBuf.WriteString(protocol.FieldDelimiter)
+		h.readBuf.WriteString(message)
+		h.readBuf.WriteByte(protocol.MessageDelimiter)
+		n = copy(p, h.readBuf.Bytes())
+
+	case line := <-h.lines:
+		if !h.plain {
+			h.readBuf.WriteString("REMOTE")
+			h.readBuf.WriteString(protocol.FieldDelimiter)
+			h.readBuf.WriteString(h.hostname)
+			h.readBuf.WriteString(protocol.FieldDelimiter)
+			h.readBuf.WriteString(fmt.Sprintf("%3d", line.TransmittedPerc))
+			h.readBuf.WriteString(protocol.FieldDelimiter)
+			h.readBuf.WriteString(fmt.Sprintf("%v", line.Count))
+			h.readBuf.WriteString(protocol.FieldDelimiter)
+			h.readBuf.WriteString(line.SourceID)
+			h.readBuf.WriteString(protocol.FieldDelimiter)
+		}
+		h.readBuf.WriteString(line.Content.String())
+		h.readBuf.WriteByte(protocol.MessageDelimiter)
+		n = copy(p, h.readBuf.Bytes())
+		pool.RecycleBytesBuffer(line.Content)
+		line.Recycle()
+
+	case <-time.After(time.Second):
+		select {
+		case <-h.done.Done():
+			err = io.EOF
+			return
+		default:
+		}
+	}
+	return
+}
+
+// Write is to receive data from the dtail client via Writer interface.
+func (h *baseHandler) Write(p []byte) (n int, err error) {
+	for _, b := range p {
+		switch b {
+		case ';':
+			h.handleCommand(string(h.writeBuf.Bytes()))
+			h.writeBuf.Reset()
+		default:
+			h.writeBuf.WriteByte(b)
+		}
+	}
+	n = len(p)
+	return
+}
+
+func (h *baseHandler) handleCommand(commandStr string) {
+	dlog.Server.Debug(h.user, commandStr)
+
+	args, argc, add, err := h.handleProtocolVersion(strings.Split(commandStr, " "))
+	if err != nil {
+		h.send(h.serverMessages, dlog.Server.Error(h.user, err)+add)
+		return
+	}
+	args, argc, err = h.handleBase64(args, argc)
+	if err != nil {
+		h.send(h.serverMessages, dlog.Server.Error(h.user, err))
+		return
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		<-h.done.Done()
+		cancel()
+	}()
+
+	parts := strings.Split(args[0], ":")
+	commandName := parts[0]
+
+	// Either no options or empty options provided.
+	if len(parts) == 1 || len(parts[1]) == 0 {
+		h.handleCommandCb(ctx, lcontext.LContext{}, argc, args, commandName)
+		return
+	}
+
+	options, ltx, err := config.DeserializeOptions(parts[1:])
+	if err != nil {
+		h.send(h.serverMessages, dlog.Server.Error(h.user, err))
+		return
+	}
+	h.handleOptions(options)
+	h.handleCommandCb(ctx, ltx, argc, args, commandName)
+}
+
+func (h *baseHandler) handleProtocolVersion(args []string) ([]string, int, string, error) {
+	argc := len(args)
+	var add string
+
+	if argc <= 2 || args[0] != "protocol" {
+		return args, argc, add, errors.New("unable to determine protocol version")
+	}
+
+	if args[1] != protocol.ProtocolCompat {
+		clientCompat, _ := strconv.Atoi(args[1])
+		serverCompat, _ := strconv.Atoi(protocol.ProtocolCompat)
+		if clientCompat <= 3 {
+			// Protocol version 3 or lower expect a newline as message separator
+			// One day (after 2 major versions) this exception may be removed!
+			add = "\n"
+		}
+
+		toUpdate := "client"
+		if clientCompat > serverCompat {
+			toUpdate = "server"
+		}
+		err := fmt.Errorf("the DTail server protocol version '%s' does not match "+
+			"client protocol version '%s', please update DTail %s",
+			protocol.ProtocolCompat, args[1], toUpdate)
+		return args, argc, add, err
+	}
+
+	return args[2:], argc - 2, add, nil
+}
+
+func (h *baseHandler) handleBase64(args []string, argc int) ([]string, int, error) {
+	err := errors.New("unable to decode client message, DTail server and client " +
+		"versions may not be compatible")
+	if argc != 2 || args[0] != "base64" {
+		return args, argc, err
+	}
+
+	decoded, err := base64.StdEncoding.DecodeString(args[1])
+	if err != nil {
+		return args, argc, err
+	}
+	decodedStr := string(decoded)
+
+	args = strings.Split(decodedStr, " ")
+	argc = len(decodedStr)
+	dlog.Server.Trace(h.user, "Base64 decoded received command",
+		decodedStr, argc, args)
+
+	return args, argc, nil
+}
+
+func (h *baseHandler) handleAckCommand(argc int, args []string) {
+	if argc < 3 {
+		if !h.quiet {
+			h.send(h.serverMessages, dlog.Server.Warn(h.user,
+				"Unable to parse command", args, argc))
+		}
+		return
+	}
+	if args[1] == "close" && args[2] == "connection" {
+		select {
+		case <-h.ackCloseReceived:
+		default:
+			close(h.ackCloseReceived)
+		}
+	}
+}
+
+func (h *baseHandler) handleOptions(options map[string]string) {
+	// We have to make sure that this block is executed only once.
+	h.mutex.Lock()
+	defer h.mutex.Unlock()
+	// We can read the options only once, will cause a data race otherwise if
+	// changed multiple times for multiple incoming commands.
+	h.once.Do(func() {
+		if quiet, _ := options["quiet"]; quiet == "true" {
+			dlog.Server.Debug(h.user, "Enabling quiet mode")
+			h.quiet = true
+		}
+		if plain, _ := options["plain"]; plain == "true" {
+			dlog.Server.Debug(h.user, "Enabling plain mode")
+			h.plain = true
+		}
+		if serverless, _ := options["serverless"]; serverless == "true" {
+			dlog.Server.Debug(h.user, "Enabling serverless mode")
+			h.serverless = true
+		}
+	})
+}
+
+func (h *baseHandler) send(ch chan<- string, message string) {
+	select {
+	case ch <- message:
+	case <-h.done.Done():
+	}
+}
+
+func (h *baseHandler) flush() {
+	dlog.Server.Trace(h.user, "flush()")
+	numUnsentMessages := func() int {
+		return len(h.lines) + len(h.serverMessages) + len(h.maprMessages)
+	}
+	for i := 0; i < 10; i++ {
+		if numUnsentMessages() == 0 {
+			dlog.Server.Debug(h.user, "ALL lines sent", fmt.Sprintf("%p", h))
+			return
+		}
+		dlog.Server.Debug(h.user, "Still lines to be sent")
+		time.Sleep(time.Millisecond * 10)
+	}
+	dlog.Server.Warn(h.user, "Some lines remain unsent", numUnsentMessages())
+}
+
+func (h *baseHandler) shutdown() {
+	dlog.Server.Debug(h.user, "shutdown()")
+	h.flush()
+
+	go func() {
+		select {
+		case h.serverMessages <- ".syn close connection":
+		case <-h.done.Done():
+		}
+	}()
+
+	select {
+	case <-h.ackCloseReceived:
+	case <-time.After(time.Second * 5):
+		dlog.Server.Debug(h.user, "Shutdown timeout reached, enforcing shutdown")
+	case <-h.done.Done():
+	}
+	h.done.Shutdown()
+}
+
+func (h *baseHandler) incrementActiveCommands() {
+	atomic.AddInt32(&h.activeCommands, 1)
+}
+
+func (h *baseHandler) decrementActiveCommands() int32 {
+	atomic.AddInt32(&h.activeCommands, -1)
+	return atomic.LoadInt32(&h.activeCommands)
+}
diff --git a/internal/server/handlers/controlhandler.go b/internal/server/handlers/controlhandler.go
deleted file mode 100644
index 1e17c78..0000000
--- a/internal/server/handlers/controlhandler.go
+++ /dev/null
@@ -1,98 +0,0 @@
-package handlers
-
-import (
-	"fmt"
-	"io"
-	"os"
-	"strings"
-
-	"github.com/mimecast/dtail/internal"
-	"github.com/mimecast/dtail/internal/io/logger"
-	user "github.com/mimecast/dtail/internal/user/server"
-)
-
-// ControlHandler is used for control functions and health monitoring.
-type ControlHandler struct {
-	done           *internal.Done
-	hostname       string
-	payload        []byte
-	serverMessages chan string
-	user           *user.User
-}
-
-// NewControlHandler returns a new control handler.
-func NewControlHandler(user *user.User) *ControlHandler {
-	logger.Debug(user, "Creating control handler")
-
-	h := ControlHandler{
-		done:           internal.NewDone(),
-		serverMessages: make(chan string, 10),
-		user:           user,
-	}
-
-	fqdn, err := os.Hostname()
-	if err != nil {
-		logger.FatalExit(err)
-	}
-
-	s := strings.Split(fqdn, ".")
-	h.hostname = s[0]
-
-	return &h
-}
-
-// Shutdown the handler.
-func (h *ControlHandler) Shutdown() {
-	h.done.Shutdown()
-}
-
-// Done channel of the handler.
-func (h *ControlHandler) Done() <-chan struct{} {
-	return h.done.Done()
-}
-
-// Read is to send data to the client via the Reader interface.
-func (h *ControlHandler) Read(p []byte) (n int, err error) {
-	for {
-		select {
-		case message := <-h.serverMessages:
-			wholePayload := []byte(fmt.Sprintf("SERVER|%s|%s\n", h.hostname, message))
-			n = copy(p, wholePayload)
-			return
-		case <-h.done.Done():
-			return 0, io.EOF
-		}
-	}
-}
-
-// Write is to read data to the client via the Writer interface.
-func (h *ControlHandler) Write(p []byte) (n int, err error) {
-	for _, c := range p {
-		switch c {
-		case ';':
-			wholePayload := strings.TrimSpace(string(h.payload))
-			h.handleCommand(wholePayload)
-			h.payload = nil
-
-		default:
-			h.payload = append(h.payload, c)
-		}
-	}
-
-	n = len(p)
-	return
-}
-
-func (h *ControlHandler) handleCommand(command string) {
-	logger.Info(h.user, command)
-	s := strings.Split(command, " ")
-	logger.Debug(h.user, "Receiving command", command, s)
-
-	switch s[0] {
-	case "health":
-		h.serverMessages <- "OK: DTail SSH Server seems fine"
-		h.serverMessages <- "done;"
-	default:
-		h.serverMessages <- logger.Error(h.user, "Received unknown control command", command, s)
-	}
-}
diff --git a/internal/server/handlers/healthhandler.go b/internal/server/handlers/healthhandler.go
new file mode 100644
index 0000000..362fe24
--- /dev/null
+++ b/internal/server/handlers/healthhandler.go
@@ -0,0 +1,58 @@
+package handlers
+
+import (
+	"context"
+	"strings"
+
+	"github.com/mimecast/dtail/internal"
+	"github.com/mimecast/dtail/internal/config"
+	"github.com/mimecast/dtail/internal/io/dlog"
+	"github.com/mimecast/dtail/internal/io/line"
+	"github.com/mimecast/dtail/internal/lcontext"
+	user "github.com/mimecast/dtail/internal/user/server"
+)
+
+// HealthHandler is for the remote health check.
+type HealthHandler struct {
+	baseHandler
+}
+
+// NewHealthHandler returns the server handler.
+func NewHealthHandler(user *user.User) *HealthHandler {
+	dlog.Server.Debug(user, "Creating new server health handler")
+	h := HealthHandler{
+		baseHandler: baseHandler{
+			done:             internal.NewDone(),
+			lines:            make(chan *line.Line, 100),
+			serverMessages:   make(chan string, 10),
+			maprMessages:     make(chan string, 10),
+			ackCloseReceived: make(chan struct{}),
+			user:             user,
+		},
+	}
+	h.handleCommandCb = h.handleHealthCommand
+
+	fqdn, err := config.Hostname()
+	if err != nil {
+		dlog.Server.FatalPanic(err)
+	}
+	s := strings.Split(fqdn, ".")
+	h.hostname = s[0]
+	return &h
+}
+
+func (h *HealthHandler) handleHealthCommand(ctx context.Context,
+	ltx lcontext.LContext, argc int, args []string, commandName string) {
+
+	dlog.Server.Debug(h.user, "Handling health command", argc, args)
+	switch commandName {
+	case "health":
+		h.send(h.serverMessages, "OK")
+	case ".ack":
+		h.handleAckCommand(argc, args)
+	default:
+		h.send(h.serverMessages, dlog.Server.Error(h.user,
+			"Received unknown health command", commandName, argc, args))
+	}
+	h.shutdown()
+}
diff --git a/internal/server/handlers/mapcommand.go b/internal/server/handlers/mapcommand.go
index c3e600e..65e0ed8 100644
--- a/internal/server/handlers/mapcommand.go
+++ b/internal/server/handlers/mapcommand.go
@@ -14,18 +14,17 @@ type mapCommand struct {
 }
 
 // NewMapCommand returns a new server side mapreduce command.
-func newMapCommand(serverHandler *ServerHandler, argc int, args []string) (mapCommand, *server.Aggregate, error) {
-	m := mapCommand{server: serverHandler}
+func newMapCommand(serverHandler *ServerHandler, argc int,
+	args []string) (mapCommand, *server.Aggregate, error) {
 
+	m := mapCommand{server: serverHandler}
 	queryStr := strings.Join(args[1:], " ")
 	aggregate, err := server.NewAggregate(queryStr)
 	if err != nil {
 		return m, nil, err
 	}
-
 	m.aggregate = aggregate
 	return m, aggregate, nil
-
 }
 
 func (m mapCommand) Start(ctx context.Context, aggregatedMessages chan<- string) {
diff --git a/internal/server/handlers/readcommand.go b/internal/server/handlers/readcommand.go
index b659c06..85f5b2d 100644
--- a/internal/server/handlers/readcommand.go
+++ b/internal/server/handlers/readcommand.go
@@ -2,13 +2,15 @@ package handlers
 
 import (
 	"context"
+	"os"
 	"path/filepath"
 	"strings"
 	"sync"
 	"time"
 
+	"github.com/mimecast/dtail/internal/io/dlog"
 	"github.com/mimecast/dtail/internal/io/fs"
-	"github.com/mimecast/dtail/internal/io/logger"
+	"github.com/mimecast/dtail/internal/io/line"
 	"github.com/mimecast/dtail/internal/lcontext"
 	"github.com/mimecast/dtail/internal/omode"
 	"github.com/mimecast/dtail/internal/regex"
@@ -26,39 +28,56 @@ func newReadCommand(server *ServerHandler, mode omode.Mode) *readCommand {
 	}
 }
 
-func (r *readCommand) Start(ctx context.Context, lContext lcontext.LContext, argc int, args []string, retries int) {
-	re := regex.NewNoop()
+func (r *readCommand) Start(ctx context.Context, ltx lcontext.LContext,
+	argc int, args []string, retries int) {
 
+	re := regex.NewNoop()
 	if argc >= 4 {
 		deserializedRegex, err := regex.Deserialize(strings.Join(args[2:], " "))
 		if err != nil {
-			r.server.sendServerMessage(logger.Error(r.server.user, commandParseWarning, err))
+			r.server.send(r.server.serverMessages, dlog.Server.Error(r.server.user,
+				"Unable to parse command", err))
 			return
 		}
 		re = deserializedRegex
 	}
 	if argc < 3 {
-		r.server.sendServerWarnMessage(logger.Warn(r.server.user, commandParseWarning, args, argc))
+		r.server.send(r.server.serverMessages, dlog.Server.Warn(r.server.user,
+			"Unable to parse command", args, argc))
+		return
+	}
+
+	// In serverless mode, can also read data from pipe
+	// e.g.: grep foo bar.log | dmap 'from STATS select ...'
+	if r.isInputFromPipe() {
+		dlog.Server.Debug("Reading data from stdin pipe")
+		// Empty file path and globID "-" represents reading from the stdin pipe.
+		r.read(ctx, ltx, "", "-", re)
 		return
 	}
-	r.readGlob(ctx, lContext, args[1], re, retries)
+
+	dlog.Server.Debug("Reading data from file(s)")
+	r.readGlob(ctx, ltx, args[1], re, retries)
 }
 
-func (r *readCommand) readGlob(ctx context.Context, lContext lcontext.LContext, glob string, re regex.Regex, retries int) {
+func (r *readCommand) readGlob(ctx context.Context, ltx lcontext.LContext,
+	glob string, re regex.Regex, retries int) {
+
 	retryInterval := time.Second * 5
 	glob = filepath.Clean(glob)
 
 	for retryCount := 0; retryCount < retries; retryCount++ {
 		paths, err := filepath.Glob(glob)
 		if err != nil {
-			logger.Warn(r.server.user, glob, err)
+			dlog.Server.Warn(r.server.user, glob, err)
 			time.Sleep(retryInterval)
 			continue
 		}
 
 		if numPaths := len(paths); numPaths == 0 {
-			logger.Error(r.server.user, "No such file(s) to read", glob)
-			r.server.sendServerWarnMessage(logger.Warn(r.server.user, "Unable to read file(s), check server logs"))
+			dlog.Server.Error(r.server.user, "No such file(s) to read", glob)
+			r.server.send(r.server.serverMessages, dlog.Server.Warn(r.server.user,
+				"Unable to read file(s), check server logs"))
 			select {
 			case <-ctx.Done():
 				return
@@ -68,61 +87,93 @@ func (r *readCommand) readGlob(ctx context.Context, lContext lcontext.LContext,
 			continue
 		}
 
-		r.readFiles(ctx, lContext, paths, glob, re, retryInterval)
+		r.readFiles(ctx, ltx, paths, glob, re, retryInterval)
 		return
 	}
 
-	r.server.sendServerWarnMessage(logger.Warn(r.server.user, "Giving up to read file(s)"))
+	r.server.send(r.server.serverMessages, dlog.Server.Warn(r.server.user,
+		"Giving up to read file(s)"))
 	return
 }
 
-func (r *readCommand) readFiles(ctx context.Context, lContext lcontext.LContext, paths []string, glob string, re regex.Regex, retryInterval time.Duration) {
+func (r *readCommand) readFiles(ctx context.Context, ltx lcontext.LContext,
+	paths []string, glob string, re regex.Regex, retryInterval time.Duration) {
+
 	var wg sync.WaitGroup
 	wg.Add(len(paths))
-
 	for _, path := range paths {
-		go r.readFileIfPermissions(ctx, lContext, &wg, path, glob, re)
+		go r.readFileIfPermissions(ctx, ltx, &wg, path, glob, re)
 	}
-
 	wg.Wait()
 }
 
-func (r *readCommand) readFileIfPermissions(ctx context.Context, lContext lcontext.LContext, wg *sync.WaitGroup, path, glob string, re regex.Regex) {
+func (r *readCommand) readFileIfPermissions(ctx context.Context, ltx lcontext.LContext,
+	wg *sync.WaitGroup, path, glob string, re regex.Regex) {
+
 	defer wg.Done()
 	globID := r.makeGlobID(path, glob)
-
 	if !r.server.user.HasFilePermission(path, "readfiles") {
-		logger.Error(r.server.user, "No permission to read file", path, globID)
-		r.server.sendServerWarnMessage(logger.Warn(r.server.user, "Unable to read file(s), check server logs"))
+		dlog.Server.Error(r.server.user, "No permission to read file", path, globID)
+		r.server.send(r.server.serverMessages, dlog.Server.Warn(r.server.user,
+			"Unable to read file(s), check server logs"))
 		return
 	}
-
-	r.readFile(ctx, lContext, path, globID, re)
+	r.read(ctx, ltx, path, globID, re)
 }
 
-func (r *readCommand) readFile(ctx context.Context, lContext lcontext.LContext, path, globID string, re regex.Regex) {
-	logger.Info(r.server.user, "Start reading file", path, globID)
+func (r *readCommand) read(ctx context.Context, ltx lcontext.LContext,
+	path, globID string, re regex.Regex) {
 
+	dlog.Server.Info(r.server.user, "Start reading", path, globID)
 	var reader fs.FileReader
+	var limiter chan struct{}
+
 	switch r.mode {
-	case omode.TailClient:
-		reader = fs.NewTailFile(path, globID, r.server.serverMessages, r.server.tailLimiter)
 	case omode.GrepClient, omode.CatClient:
-		reader = fs.NewCatFile(path, globID, r.server.serverMessages, r.server.catLimiter)
+		reader = fs.NewCatFile(path, globID, r.server.serverMessages)
+		limiter = r.server.catLimiter
+	case omode.TailClient:
+		fallthrough
 	default:
-		reader = fs.NewTailFile(path, globID, r.server.serverMessages, r.server.tailLimiter)
+		reader = fs.NewTailFile(path, globID, r.server.serverMessages)
+		limiter = r.server.tailLimiter
 	}
 
-	lines := r.server.lines
+	defer func() {
+		select {
+		case <-limiter:
+		default:
+		}
+	}()
 
-	// Plug in mappreduce engine
-	if r.server.aggregate != nil {
-		lines = r.server.aggregate.Lines
+	select {
+	case limiter <- struct{}{}:
+	case <-ctx.Done():
+		return
+	default:
+		dlog.Server.Info("Server limit hit, queueing file", len(limiter), path)
+		select {
+		case limiter <- struct{}{}:
+			dlog.Server.Info("Server limit OK now, processing file", len(limiter), path)
+		case <-ctx.Done():
+			return
+		}
 	}
 
+	lines := r.server.lines
+	aggregate := r.server.aggregate
+
 	for {
-		if err := reader.Start(ctx, lContext, lines, re); err != nil {
-			logger.Error(r.server.user, path, globID, err)
+		if aggregate != nil {
+			lines = make(chan *line.Line, 100)
+			aggregate.NextLinesCh <- lines
+		}
+		if err := reader.Start(ctx, ltx, lines, re); err != nil {
+			dlog.Server.Error(r.server.user, path, globID, err)
+		}
+		if aggregate != nil {
+			// Also makes aggregate to Flush
+			close(lines)
 		}
 
 		select {
@@ -133,9 +184,8 @@ func (r *readCommand) readFile(ctx context.Context, lContext lcontext.LContext,
 				return
 			}
 		}
-
 		time.Sleep(time.Second * 2)
-		logger.Info(path, globID, "Reading file again")
+		dlog.Server.Info(path, globID, "Reading file again")
 	}
 }
 
@@ -152,11 +202,20 @@ func (r *readCommand) makeGlobID(path, glob string) string {
 	if len(idParts) > 0 {
 		return strings.Join(idParts, "/")
 	}
-
 	if len(pathParts) > 0 {
 		return pathParts[len(pathParts)-1]
 	}
 
-	r.server.sendServerWarnMessage(logger.Warn("Empty file path given?", path, glob))
+	r.server.send(r.server.serverMessages,
+		dlog.Server.Warn("Empty file path given?", path, glob))
 	return ""
 }
+
+func (r *readCommand) isInputFromPipe() bool {
+	if !r.server.serverless {
+		// Can read from pipe only in serverless mode.
+		return false
+	}
+	fileInfo, _ := os.Stdin.Stat()
+	return fileInfo.Mode()&os.ModeCharDevice == 0
+}
diff --git a/internal/server/handlers/serverhandler.go b/internal/server/handlers/serverhandler.go
index 39d5d5f..bc22c88 100644
--- a/internal/server/handlers/serverhandler.go
+++ b/internal/server/handlers/serverhandler.go
@@ -2,69 +2,50 @@ package handlers
 
 import (
 	"context"
-	"encoding/base64"
-	"errors"
-	"fmt"
-	"io"
-	"os"
-	"strconv"
 	"strings"
-	"sync/atomic"
-	"time"
 
 	"github.com/mimecast/dtail/internal"
 	"github.com/mimecast/dtail/internal/config"
+	"github.com/mimecast/dtail/internal/io/dlog"
 	"github.com/mimecast/dtail/internal/io/line"
-	"github.com/mimecast/dtail/internal/io/logger"
 	"github.com/mimecast/dtail/internal/lcontext"
-	"github.com/mimecast/dtail/internal/mapr/server"
 	"github.com/mimecast/dtail/internal/omode"
 	user "github.com/mimecast/dtail/internal/user/server"
-	"github.com/mimecast/dtail/internal/version"
-)
-
-const (
-	commandParseWarning string = "Unable to parse command"
 )
 
 // ServerHandler implements the Reader and Writer interfaces to handle
 // the Bi-directional communication between SSH client and server.
 // This handler implements the handler of the SSH server.
 type ServerHandler struct {
-	done               *internal.Done
-	lines              chan line.Line
-	regex              string
-	aggregate          *server.Aggregate
-	aggregatedMessages chan string
-	serverMessages     chan string
-	payload            []byte
-	hostname           string
-	user               *user.User
-	catLimiter         chan struct{}
-	tailLimiter        chan struct{}
-	ackCloseReceived   chan struct{}
-	activeCommands     int32
-	activeReaders      int32
-	quiet              bool
+	baseHandler
+	catLimiter  chan struct{}
+	tailLimiter chan struct{}
+	regex       string
 }
 
 // NewServerHandler returns the server handler.
-func NewServerHandler(user *user.User, catLimiter, tailLimiter chan struct{}) *ServerHandler {
-	h := ServerHandler{
-		done:               internal.NewDone(),
-		lines:              make(chan line.Line, 100),
-		serverMessages:     make(chan string, 10),
-		aggregatedMessages: make(chan string, 10),
-		ackCloseReceived:   make(chan struct{}),
-		catLimiter:         catLimiter,
-		tailLimiter:        tailLimiter,
-		regex:              ".",
-		user:               user,
-	}
+func NewServerHandler(user *user.User, catLimiter,
+	tailLimiter chan struct{}) *ServerHandler {
 
-	fqdn, err := os.Hostname()
+	dlog.Server.Debug(user, "Creating new server handler")
+	h := ServerHandler{
+		baseHandler: baseHandler{
+			done:             internal.NewDone(),
+			lines:            make(chan *line.Line, 100),
+			serverMessages:   make(chan string, 10),
+			maprMessages:     make(chan string, 10),
+			ackCloseReceived: make(chan struct{}),
+			user:             user,
+		},
+		catLimiter:  catLimiter,
+		tailLimiter: tailLimiter,
+		regex:       ".",
+	}
+	h.handleCommandCb = h.handleUserCommand
+
+	fqdn, err := config.Hostname()
 	if err != nil {
-		logger.FatalExit(err)
+		dlog.Server.FatalPanic(err)
 	}
 
 	s := strings.Split(fqdn, ".")
@@ -73,374 +54,49 @@ func NewServerHandler(user *user.User, catLimiter, tailLimiter chan struct{}) *S
 	return &h
 }
 
-// Shutdown the handler.
-func (h *ServerHandler) Shutdown() {
-	h.done.Shutdown()
-}
-
-// Done channel of the handler.
-func (h *ServerHandler) Done() <-chan struct{} {
-	return h.done.Done()
-}
-
-// Read is to send data to the dtail client via Reader interface.
-func (h *ServerHandler) Read(p []byte) (n int, err error) {
-	for {
-		select {
-		case message := <-h.serverMessages:
-			if len(message) == 0 {
-				logger.Warn(h.user, "Empty message received")
-				return
-			}
-			if message[0] == '.' {
-				// Handle hidden message (don't display to the user, interpreted by dtail client)
-				wholePayload := []byte(fmt.Sprintf("%s\n", message))
-				n = copy(p, wholePayload)
-				return
-			}
-
-			// Handle normal server message (display to the user)
-			wholePayload := []byte(fmt.Sprintf("SERVER|%s|%s\n", h.hostname, message))
-			n = copy(p, wholePayload)
-			return
-
-		case message := <-h.aggregatedMessages:
-			// Send mapreduce-aggregated data as a message.
-			data := fmt.Sprintf("AGGREGATE➔%s➔%s\n", h.hostname, message)
-			wholePayload := []byte(data)
-			n = copy(p, wholePayload)
-			return
-
-		case line := <-h.lines:
-			// Send normal file content data as a message.
-			serverInfo := []byte(fmt.Sprintf("REMOTE|%s|%3d|%v|%s|",
-				h.hostname, line.TransmittedPerc, line.Count, line.SourceID))
-			wholePayload := append(serverInfo, line.Content[:]...)
-			n = copy(p, wholePayload)
-			return
-
-		case <-time.After(time.Second):
-			// Once in a while check whether we are done.
-			select {
-			case <-h.done.Done():
-				return 0, io.EOF
-			default:
-			}
-		}
-	}
-}
-
-// Write is to receive data from the dtail client via Writer interface.
-func (h *ServerHandler) Write(p []byte) (n int, err error) {
-	for _, c := range