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Add routing via X-CF-PROCESS-INSTANCE #467

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geofffranks merged 5 commits into from
Mar 18, 2025
Merged

Add routing via X-CF-PROCESS-INSTANCE #467

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611bfca
add X-CF-PROCESS-INSTANCE header that accepts guid:index
ameowlia Mar 17, 2025
6696339
allow X-CF-PROCESS-INSTANCE routing without index
ameowlia Mar 17, 2025
7511e50
only compile regex matchers once
ameowlia Mar 18, 2025
2183ada
add different error message when index is not provided for process in…
ameowlia Mar 18, 2025
66256bf
refactor: combine parse and vallidate header functions
ameowlia Mar 18, 2025
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1 change: 1 addition & 0 deletions common/http/headers.go
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ const (
VcapTraceHeader = "X-Vcap-Trace"
CfInstanceIdHeader = "X-CF-InstanceID"
CfAppInstance = "X-CF-APP-INSTANCE"
CfProcessInstance = "X-CF-PROCESS-INSTANCE"
CfRouterError = "X-Cf-RouterError"
)

Expand Down
96 changes: 76 additions & 20 deletions handlers/lookup.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,6 @@ import (
"log/slog"
"net/http"
"regexp"
"strings"

"github.com/urfave/negroni/v3"

Expand All @@ -19,14 +18,22 @@ import (

const CfAppInstance = "X-CF-APP-INSTANCE"

type InvalidInstanceHeaderError struct {
type InvalidAppInstanceHeaderError struct {
headerValue string
}

func (err InvalidInstanceHeaderError) Error() string {
func (err InvalidAppInstanceHeaderError) Error() string {
return fmt.Sprintf("invalid-app-instance-header: %s", err.headerValue)
}

type InvalidProcessInstanceHeaderError struct {
headerValue string
}

func (err InvalidProcessInstanceHeaderError) Error() string {
return fmt.Sprintf("invalid-process-instance-header: %s", err.headerValue)
}

type lookupHandler struct {
registry registry.Registry
reporter metrics.ProxyReporter
Expand Down Expand Up @@ -75,8 +82,13 @@ func (l *lookupHandler) ServeHTTP(rw http.ResponseWriter, r *http.Request, next
}

pool, err := l.lookup(r, logger)
if _, ok := err.(InvalidInstanceHeaderError); ok {
l.handleInvalidInstanceHeader(rw, r, logger)
if _, ok := err.(InvalidAppInstanceHeaderError); ok {
l.handleInvalidAppInstanceHeader(rw, r, logger)
return
}

if _, ok := err.(InvalidProcessInstanceHeaderError); ok {
l.handleInvalidProcessInstanceHeader(rw, r, logger)
return
}

Expand Down Expand Up @@ -109,7 +121,7 @@ func (l *lookupHandler) ServeHTTP(rw http.ResponseWriter, r *http.Request, next
next(rw, r)
}

func (l *lookupHandler) handleInvalidInstanceHeader(rw http.ResponseWriter, r *http.Request, logger *slog.Logger) {
func (l *lookupHandler) handleInvalidAppInstanceHeader(rw http.ResponseWriter, r *http.Request, logger *slog.Logger) {
l.reporter.CaptureBadRequest()

AddRouterErrorHeader(rw, "invalid_cf_app_instance_header")
Expand All @@ -123,6 +135,20 @@ func (l *lookupHandler) handleInvalidInstanceHeader(rw http.ResponseWriter, r *h
)
}

func (l *lookupHandler) handleInvalidProcessInstanceHeader(rw http.ResponseWriter, r *http.Request, logger *slog.Logger) {
l.reporter.CaptureBadRequest()

AddRouterErrorHeader(rw, "invalid_cf_process_instance_header")
addNoCacheControlHeader(rw)

l.errorWriter.WriteError(
rw,
http.StatusBadRequest,
"Invalid X-CF-Process-Instance Header",
logger,
)
}

func (l *lookupHandler) handleMissingHost(rw http.ResponseWriter, r *http.Request, logger *slog.Logger) {
l.reporter.CaptureBadRequest()

Expand All @@ -147,11 +173,23 @@ func (l *lookupHandler) handleMissingRoute(rw http.ResponseWriter, r *http.Reque
returnStatus := http.StatusNotFound

if appInstanceHeader := r.Header.Get(router_http.CfAppInstance); appInstanceHeader != "" {
guid, idx := splitInstanceHeader(appInstanceHeader)
// parseAppInstanceHeader had already been called. So the error has already been checked.
guid, idx, _ := parseAppInstanceHeader(appInstanceHeader)
errorMsg = fmt.Sprintf("Requested instance ('%s') with guid ('%s') does not exist for route ('%s')", idx, guid, r.Host)
returnStatus = http.StatusBadRequest
}

if processInstanceHeader := r.Header.Get(router_http.CfProcessInstance); processInstanceHeader != "" {
// parseProcessInstanceHeader had already been called. So the error has already been checked.
guid, idx, _ := parseProcessInstanceHeader(processInstanceHeader)
if idx == "" {
errorMsg = fmt.Sprintf("Requested instance with process guid ('%s') does not exist for route ('%s')", guid, r.Host)
} else {
errorMsg = fmt.Sprintf("Requested instance ('%s') with process guid ('%s') does not exist for route ('%s')", idx, guid, r.Host)
}
returnStatus = http.StatusBadRequest
}

l.errorWriter.WriteError(
rw,
returnStatus,
Expand Down Expand Up @@ -193,29 +231,47 @@ func (l *lookupHandler) lookup(r *http.Request, logger *slog.Logger) (*route.End
appInstanceHeader := r.Header.Get(router_http.CfAppInstance)

if appInstanceHeader != "" {
err := validateInstanceHeader(appInstanceHeader)
appID, appIndex, err := parseAppInstanceHeader(appInstanceHeader)
if err != nil {
logger.Error("invalid-app-instance-header", log.ErrAttr(err))
return nil, InvalidInstanceHeaderError{headerValue: appInstanceHeader}
return nil, InvalidAppInstanceHeaderError{headerValue: appInstanceHeader}
}

appID, appIndex := splitInstanceHeader(appInstanceHeader)
return l.registry.LookupWithInstance(uri, appID, appIndex), nil
return l.registry.LookupWithAppInstance(uri, appID, appIndex), nil
}

processInstanceHeader := r.Header.Get(router_http.CfProcessInstance)
if processInstanceHeader != "" {
processID, processIndex, err := parseProcessInstanceHeader(processInstanceHeader)
if err != nil {
logger.Error("invalid-process-instance-header", log.ErrAttr(err))
return nil, InvalidProcessInstanceHeaderError{headerValue: processInstanceHeader}
}

return l.registry.LookupWithProcessInstance(uri, processID, processIndex), nil
}

return l.registry.Lookup(uri), nil
}

func validateInstanceHeader(appInstanceHeader string) error {
// Regex to match format of `APP_GUID:INSTANCE_ID`
r := regexp.MustCompile(`^[\da-f]{8}-([\da-f]{4}-){3}[\da-f]{12}:\d+$`)
if !r.MatchString(appInstanceHeader) {
return fmt.Errorf("Incorrect %s header : %s", CfAppInstance, appInstanceHeader)
// Regex to match format of `APP_GUID:INSTANCE_ID`
var aReg = regexp.MustCompile(`^(?P<id>[\da-f]{8}-([\da-f]{4}-){3}[\da-f]{12}):(?P<idx>\d+)$`)

func parseAppInstanceHeader(appInstanceHeader string) (string, string, error) {
matches := aReg.FindStringSubmatch(appInstanceHeader)
if len(matches) == 0 {
return "", "", fmt.Errorf("Incorrect %s header : %s", router_http.CfAppInstance, appInstanceHeader)
}
return nil
return matches[aReg.SubexpIndex("id")], matches[aReg.SubexpIndex("idx")], nil
}

func splitInstanceHeader(appInstanceHeader string) (string, string) {
appDetails := strings.Split(appInstanceHeader, ":")
return appDetails[0], appDetails[1]
// Regex to match format of `PROCESS_GUID:INSTANCE_ID` and `PROCESS_GUID`
var pReg = regexp.MustCompile(`^(?P<id>[\da-f]{8}-([\da-f]{4}-){3}[\da-f]{12})(:(?P<idx>\d+))?$`)

func parseProcessInstanceHeader(processInstanceHeader string) (string, string, error) {
matches := pReg.FindStringSubmatch(processInstanceHeader)
if len(matches) == 0 {
return "", "", fmt.Errorf("Incorrect %s header : %s", router_http.CfProcessInstance, processInstanceHeader)
}
return matches[pReg.SubexpIndex("id")], matches[pReg.SubexpIndex("idx")], nil
}
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