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|
package connectors
import (
"context"
"io"
"github.com/mimecast/dtail/internal/clients/handlers"
"github.com/mimecast/dtail/internal/io/dlog"
serverHandlers "github.com/mimecast/dtail/internal/server/handlers"
)
// ServerlessHandlerFactory creates the in-process server-side handler used by serverless mode.
type ServerlessHandlerFactory interface {
NewServerlessHandler(userName string) (serverHandlers.Handler, error)
}
// Serverless creates a server object directly without TCP.
type Serverless struct {
handler handlers.Handler
commands []string
userName string
handlerFactory ServerlessHandlerFactory
}
var _ Connector = (*Serverless)(nil)
// NewServerless starts a new serverless session.
func NewServerless(userName string, handler handlers.Handler,
commands []string, handlerFactory ServerlessHandlerFactory) *Serverless {
dlog.Client.Debug("Creating new serverless connector", handler, commands)
return &Serverless{
userName: userName,
handler: handler,
commands: commands,
handlerFactory: handlerFactory,
}
}
// Server returns serverless server indicator.
func (s *Serverless) Server() string {
return "local(serverless)"
}
// Handler returns the handler used for the serverless connection.
func (s *Serverless) Handler() handlers.Handler {
return s.handler
}
// Start the serverless connection.
func (s *Serverless) Start(ctx context.Context, cancel context.CancelFunc,
throttleCh, statsCh chan struct{}) {
dlog.Client.Debug("Starting serverless connector")
go func() {
defer cancel()
if err := s.handle(ctx, cancel); err != nil {
dlog.Client.Warn(err)
}
}()
<-ctx.Done()
}
func (s *Serverless) handle(ctx context.Context, cancel context.CancelFunc) error {
dlog.Client.Debug("Creating server handler for a serverless session")
if s.handlerFactory == nil {
return io.ErrClosedPipe
}
serverHandler, err := s.handlerFactory.NewServerlessHandler(s.userName)
if err != nil {
return err
}
terminate := func() {
dlog.Client.Debug("Terminating serverless connection")
serverHandler.Shutdown()
cancel()
}
// Use buffered channels to prevent deadlock
// This approach avoids the circular dependency of direct io.Copy
// Channels for data flow
toServer := make(chan []byte, 100)
fromServer := make(chan []byte, 100)
// Error tracking
errChan := make(chan error, 4)
// Read from client handler
go func() {
defer close(toServer)
buf := make([]byte, 32*1024)
for {
n, err := s.handler.Read(buf)
if n > 0 {
data := make([]byte, n)
copy(data, buf[:n])
select {
case toServer <- data:
case <-ctx.Done():
return
}
}
if err != nil {
if err != io.EOF {
errChan <- err
}
return
}
}
}()
// Write to server handler
go func() {
for data := range toServer {
if _, err := serverHandler.Write(data); err != nil {
errChan <- err
return
}
}
}()
// Read from server handler
go func() {
defer close(fromServer)
buf := make([]byte, 64*1024) // Larger buffer for server responses
for {
n, err := serverHandler.Read(buf)
if n > 0 {
data := make([]byte, n)
copy(data, buf[:n])
select {
case fromServer <- data:
case <-ctx.Done():
return
}
}
if err != nil {
if err != io.EOF {
errChan <- err
}
return
}
}
}()
// Write to client handler
serverDone := make(chan struct{})
go func() {
defer close(serverDone)
for data := range fromServer {
if _, err := s.handler.Write(data); err != nil {
errChan <- err
return
}
}
}()
// Send commands after setting up the data flow
for _, command := range s.commands {
dlog.Client.Debug("Sending command to serverless server", command)
if err := s.handler.SendMessage(command); err != nil {
dlog.Client.Debug(err)
}
}
// Monitor for completion
go func() {
defer terminate()
select {
case <-s.handler.Done():
dlog.Client.Trace("<-s.handler.Done()")
case <-serverDone:
dlog.Client.Trace("Server transfer done")
case <-ctx.Done():
dlog.Client.Trace("<-ctx.Done()")
}
}()
// Wait for completion
<-ctx.Done()
// Check for errors
select {
case err := <-errChan:
return err
default:
}
s.handler.Shutdown()
return nil
}
|
