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perform_handler_with_json.go
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perform_handler_with_json.go
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package handler
import (
"encoding/json"
bosherr "github.com/cloudfoundry/bosh-utils/errors"
boshlog "github.com/cloudfoundry/bosh-utils/logger"
)
const (
mbusHandlerLogTag = "MBus Handler"
responseMaxLengthErrMsg = "Response exceeded maximum allowed length"
UnlimitedResponseLength = -1
)
func PerformHandlerWithJSON(rawJSON []byte, handler Func, maxResponseLength int, logger boshlog.Logger) ([]byte, Request, error) {
var request Request
err := json.Unmarshal(rawJSON, &request)
if err != nil {
return []byte{}, request, bosherr.WrapError(err, "Unmarshalling JSON payload")
}
request.Payload = rawJSON
response := handler(request)
if response == nil {
logger.Info(mbusHandlerLogTag, "Nil response returned from handler")
return []byte{}, request, nil
}
respJSON, err := marshalResponse(response, maxResponseLength, logger)
if err != nil {
return respJSON, request, err
}
logger.Info(mbusHandlerLogTag, "Responding")
logger.DebugWithDetails(mbusHandlerLogTag, "Payload", respJSON)
return respJSON, request, nil
}
func BuildErrorWithJSON(msg string, logger boshlog.Logger) ([]byte, error) {
response := NewExceptionResponse(bosherr.Error(msg))
respJSON, err := json.Marshal(response)
if err != nil {
return respJSON, bosherr.WrapError(err, "Marshalling JSON")
}
logger.Info(mbusHandlerLogTag, "Building error", msg)
return respJSON, nil
}
func marshalResponse(response Response, maxResponseLength int, logger boshlog.Logger) ([]byte, error) {
respJSON, err := json.Marshal(response)
if err != nil {
logger.Error(mbusHandlerLogTag, "Failed to marshal response: %s", err.Error())
return respJSON, bosherr.WrapError(err, "Marshalling JSON response")
}
if maxResponseLength == UnlimitedResponseLength {
return respJSON, nil
}
if len(respJSON) > maxResponseLength {
respJSON, err = json.Marshal(response.Shorten())
if err != nil {
logger.Error(mbusHandlerLogTag, "Failed to marshal response: %s", err.Error())
return respJSON, bosherr.WrapError(err, "Marshalling JSON response")
}
}
if len(respJSON) > maxResponseLength {
respJSON, err = BuildErrorWithJSON(responseMaxLengthErrMsg, logger)
if err != nil {
logger.Error(mbusHandlerLogTag, "Failed to build 'max length exceeded' response: %s", err.Error())
return respJSON, bosherr.WrapError(err, "Building error")
}
}
return respJSON, nil
}