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patch.go
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patch.go
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package main
import (
"path/filepath"
"strconv"
"strings"
corev1 "k8s.io/api/core/v1"
)
// patchOperation is an operation of a JSON patch, see
// https://tools.ietf.org/html/rfc6902.
type patchOperation struct {
Op string `json:"op"`
Path string `json:"path"`
Value interface{} `json:"value,omitempty"`
}
const (
volumeName = "elastic-apm-agent"
mountPath = "/elastic/apm/agent"
)
var (
volumeMounts = corev1.VolumeMount{
Name: volumeName,
MountPath: mountPath,
}
agentVolume = corev1.Volume{
Name: volumeName,
VolumeSource: corev1.VolumeSource{EmptyDir: &corev1.EmptyDirVolumeSource{}},
}
kubernetesEnvironmentVariables = map[string]string{
"KUBERNETES_NODE_NAME": "spec.nodeName",
"KUBERNETES_POD_NAME": "metadata.name",
"KUBERNETES_NAMESPACE": "metadata.namespace",
"KUBERNETES_POD_UID": "metadata.uid",
}
)
func createPatch(config agentConfig, spec corev1.PodSpec) []patchOperation {
// Create patch operations
var patches []patchOperation
envVariables := generateEnvironmentVariables(config)
// Add a volume mount to the pod
patches = append(patches, createVolumePatch(spec.Volumes == nil))
// Add an init container, that will fetch the agent Docker image and
// extract the agent jar to the agent volume
patches = append(patches, createInitContainerPatch(config, spec.InitContainers == nil))
// Add agent env variables for each container at the pod, as well as
// the volume mount
containers := spec.Containers
for index, container := range containers {
// Filter out environment variables from the agent config to
// not overwrite environment variables set directly on the
// container.
envVars := uniqueEnvironmentVariables(envVariables, container.Env)
patches = append(patches, createVolumeMountsPatch(container.VolumeMounts == nil, index))
patches = append(patches, createEnvVariablesPatches(envVars, container.Env == nil, index)...)
}
return patches
}
func uniqueEnvironmentVariables(configEnvironmentVariables, containerEnvironmentVariables []corev1.EnvVar) []corev1.EnvVar {
if len(containerEnvironmentVariables) == 0 {
return configEnvironmentVariables
}
unique := make([]corev1.EnvVar, 0, len(configEnvironmentVariables))
containerKeys := make(map[string]struct{}, len(containerEnvironmentVariables))
for _, v := range containerEnvironmentVariables {
containerKeys[v.Name] = struct{}{}
}
for _, v := range configEnvironmentVariables {
if _, ok := containerKeys[v.Name]; ok {
continue
}
unique = append(unique, v)
}
return unique
}
func generateEnvironmentVariables(config agentConfig) []corev1.EnvVar {
vars := make([]corev1.EnvVar, 1, len(config.Environment)+5)
vars[0] = corev1.EnvVar{
Name: "ELASTIC_APM_SECRET_TOKEN",
ValueFrom: &corev1.EnvVarSource{
SecretKeyRef: &corev1.SecretKeySelector{
LocalObjectReference: corev1.LocalObjectReference{Name: "apm-server-apm-token"},
Key: "secret-token",
},
},
}
if _, ok := config.Environment["ELASTIC_APM_SERVER_URL"]; !ok {
// No apm-server url present, inject the local node address.
vars = append(vars,
corev1.EnvVar{
Name: "HOST_IP",
ValueFrom: &corev1.EnvVarSource{
FieldRef: &corev1.ObjectFieldSelector{
FieldPath: "status.hostIP",
},
},
},
corev1.EnvVar{Name: "ELASTIC_APM_SERVER_URL", Value: "http://$(HOST_IP):8200"})
}
for k, v := range kubernetesEnvironmentVariables {
vars = append(vars, corev1.EnvVar{
Name: k,
ValueFrom: &corev1.EnvVarSource{
FieldRef: &corev1.ObjectFieldSelector{
FieldPath: v,
},
},
})
}
for name, value := range config.Environment {
vars = append(vars, corev1.EnvVar{Name: name, Value: value})
}
return vars
}
func createVolumePatch(createArray bool) patchOperation {
if createArray {
return patchOperation{
Op: "add",
Path: "/spec/volumes",
Value: []corev1.Volume{agentVolume},
}
}
return patchOperation{
Op: "add",
Path: "/spec/volumes/-",
Value: agentVolume,
}
}
func createInitContainerPatch(config agentConfig, createArray bool) patchOperation {
bp := filepath.Base(config.Image)
name := strings.Split(bp, ":")
agentInitContainer := corev1.Container{
Name: name[0],
Image: config.Image,
VolumeMounts: []corev1.VolumeMount{volumeMounts},
// TODO: should this be a default, and then users can modify it
// *if needed*?
Command: []string{"cp", "-v", config.ArtifactPath, mountPath},
}
if createArray {
return patchOperation{
Op: "add",
Path: "/spec/initContainers",
Value: []corev1.Container{agentInitContainer},
}
}
return patchOperation{
Op: "add",
Path: "/spec/initContainers/-",
Value: agentInitContainer,
}
}
// If the env variable array does not already exist, this method will return a
// single patch operation for the addition of the entire list, otherwise it
// would return a list of patches for each env variable
func createEnvVariablesPatches(envVariables []corev1.EnvVar, createArray bool, index int) []patchOperation {
containerIndex := strconv.Itoa(index)
envVariablesPath := "/spec/containers/" + containerIndex + "/env"
if createArray {
return []patchOperation{{
Op: "add",
Path: envVariablesPath,
Value: envVariables,
}}
}
patches := make([]patchOperation, len(envVariables))
envVariablesPath += "/-"
for i, variable := range envVariables {
patches[i] = patchOperation{
Op: "add",
Path: envVariablesPath,
Value: variable,
}
}
return patches
}
func createVolumeMountsPatch(createArray bool, index int) patchOperation {
containerIndex := strconv.Itoa(index)
volumeMountsPath := "/spec/containers/" + containerIndex + "/volumeMounts"
if createArray {
return patchOperation{
Op: "add",
Path: volumeMountsPath,
Value: []corev1.VolumeMount{volumeMounts},
}
}
return patchOperation{
Op: "add",
Path: volumeMountsPath + "/-",
Value: volumeMounts,
}
}