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eventhandler.go
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eventhandler.go
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package buildserver
import (
"compress/gzip"
"encoding/json"
"fmt"
"io"
"net/http"
"strings"
"code.cloudfoundry.org/lager"
"github.com/concourse/atc/dbng"
"github.com/vito/go-sse/sse"
)
const ProtocolVersionHeader = "X-ATC-Stream-Version"
const CurrentProtocolVersion = "2.0"
func NewEventHandler(logger lager.Logger, build dbng.Build) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
clientNotifier := w.(http.CloseNotifier)
var eventID uint = 0
if r.Header.Get("Last-Event-ID") != "" {
startString := r.Header.Get("Last-Event-ID")
_, err := fmt.Sscanf(startString, "%d", &eventID)
if err != nil {
logger.Info("failed-to-parse-last-event-id", lager.Data{"last-event-id": startString})
w.WriteHeader(http.StatusBadRequest)
return
}
eventID++
}
w.Header().Add("Content-Type", "text/event-stream; charset=utf-8")
w.Header().Add("Cache-Control", "no-cache, no-store, must-revalidate")
w.Header().Add("X-Accel-Buffering", "no")
w.Header().Add(ProtocolVersionHeader, CurrentProtocolVersion)
writer := eventWriter{
responseWriter: w,
writeFlusher: nil,
responseFlusher: w.(http.Flusher),
}
w.Header().Add("Vary", "Accept-Encoding")
if strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
w.Header().Set("Content-Encoding", "gzip")
gz := gzip.NewWriter(w)
defer gz.Close()
writer.responseWriter = gz
writer.writeFlusher = gz
}
events, err := build.Events(eventID)
if err != nil {
logger.Error("failed-to-get-build-events", err, lager.Data{"build-id": build.ID(), "start": eventID})
w.WriteHeader(http.StatusInternalServerError)
return
}
defer events.Close()
for {
logger = logger.WithData(lager.Data{"id": eventID})
ev, err := events.Next()
if err != nil {
if err == dbng.ErrEndOfBuildEventStream {
err := writer.WriteEnd(eventID)
if err != nil {
logger.Info("failed-to-write-end", lager.Data{"error": err.Error()})
return
}
<-clientNotifier.CloseNotify()
} else {
logger.Error("failed-to-get-next-build-event", err)
return
}
return
}
err = writer.WriteEvent(eventID, ev)
if err != nil {
logger.Info("failed-to-write-event", lager.Data{"error": err.Error()})
return
}
eventID++
}
})
}
type flusher interface {
Flush() error
}
type eventWriter struct {
responseWriter io.Writer
writeFlusher flusher
responseFlusher http.Flusher
}
func (writer eventWriter) WriteEvent(id uint, envelope interface{}) error {
payload, err := json.Marshal(envelope)
if err != nil {
return err
}
err = sse.Event{
ID: fmt.Sprintf("%d", id),
Name: "event",
Data: payload,
}.Write(writer.responseWriter)
if err != nil {
return err
}
return writer.flush()
}
func (writer eventWriter) WriteEnd(id uint) error {
err := sse.Event{ID: fmt.Sprintf("%d", id), Name: "end"}.Write(writer.responseWriter)
if err != nil {
return err
}
return writer.flush()
}
func (writer eventWriter) flush() error {
if writer.writeFlusher != nil {
err := writer.writeFlusher.Flush()
if err != nil {
return err
}
}
writer.responseFlusher.Flush()
return nil
}