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status.go
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status.go
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// Copyright (c) 2018 Palantir Technologies. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package status
import (
"net/http"
"sync/atomic"
"github.com/palantir/conjure-go-runtime/v2/conjure-go-contract/errors"
"github.com/palantir/conjure-go-runtime/v2/conjure-go-server/httpserver"
"github.com/palantir/pkg/refreshable"
"github.com/palantir/witchcraft-go-health/conjure/witchcraft/api/health"
"github.com/palantir/witchcraft-go-health/status"
)
// HealthHandler is responsible for checking the health-check-shared-secret if it is provided and
// invoking a HealthCheckSource if the secret is correct or unset.
type healthHandlerImpl struct {
healthCheckSharedSecret refreshable.String
check status.HealthCheckSource
previousHealth *atomic.Value
changeHandler HealthStatusChangeHandler
}
func NewHealthCheckHandler(checkSource status.HealthCheckSource, sharedSecret refreshable.String, healthStatusChangeHandlers []HealthStatusChangeHandler) http.Handler {
previousHealth := &atomic.Value{}
previousHealth.Store(health.HealthStatus{})
allHandlers := []HealthStatusChangeHandler{loggingHealthStatusChangeHandler()}
if len(healthStatusChangeHandlers) > 0 {
allHandlers = append(allHandlers, healthStatusChangeHandlers...)
}
return &healthHandlerImpl{
healthCheckSharedSecret: sharedSecret,
check: checkSource,
previousHealth: previousHealth,
changeHandler: multiHealthStatusChangeHandler(allHandlers),
}
}
func (h *healthHandlerImpl) ServeHTTP(w http.ResponseWriter, req *http.Request) {
if sharedSecret := h.healthCheckSharedSecret.CurrentString(); sharedSecret != "" {
token, err := httpserver.ParseBearerTokenHeader(req)
if err != nil {
errors.WriteErrorResponse(w, errors.NewUnauthorized())
return
}
if !httpserver.SecretStringEqual(sharedSecret, token) {
errors.WriteErrorResponse(w, errors.NewPermissionDenied())
return
}
}
metadata := h.check.HealthStatus(req.Context())
newHealthStatusCode := status.HealthStatusCode(metadata)
previousHealth := h.previousHealth.Load()
if previousHealth != nil {
if previousHealthTyped, ok := previousHealth.(health.HealthStatus); ok && checksDiffer(previousHealthTyped.Checks, metadata.Checks) {
h.changeHandler.HandleHealthStatusChange(req.Context(), previousHealthTyped, metadata)
}
}
h.previousHealth.Store(metadata)
httpserver.WriteJSONResponse(w, metadata, newHealthStatusCode)
}
func checksDiffer(previousChecks, newChecks map[health.CheckType]health.HealthCheckResult) bool {
if len(previousChecks) != len(newChecks) {
return true
}
for previousCheckType, previouscheckResult := range previousChecks {
newCheckResult, checkTypePresent := newChecks[previousCheckType]
if !checkTypePresent {
return true
}
if previouscheckResult.State != newCheckResult.State {
return true
}
}
return false
}