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kubernetes.go
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kubernetes.go
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package swarm
import (
"crypto/tls"
"crypto/x509"
"errors"
"io"
"net"
"net/http"
"os"
"time"
"github.com/cenkalti/backoff"
log "github.com/sirupsen/logrus"
)
const (
// DefaultNamespace is the default namespace where swarm searches for peer information
DefaultNamespace = "kube-system"
// DefaultLabelSelectorKey is the default label key to select Pods for peer information
DefaultLabelSelectorKey = "application"
// DefaultLabelSelectorValue is the default label value to select Pods for peer information
DefaultLabelSelectorValue = "skipper-ingress"
defaultKubernetesURL = "http://localhost:8001"
serviceAccountDir = "/var/run/secrets/kubernetes.io/serviceaccount/"
serviceAccountTokenKey = "token"
serviceAccountRootCAKey = "ca.crt"
serviceHostEnvVar = "KUBERNETES_SERVICE_HOST"
servicePortEnvVar = "KUBERNETES_SERVICE_PORT"
maxRetries = 12
)
var (
errAPIServerURLNotFound = errors.New("kubernetes API server URL could not be constructed from env vars")
errInvalidCertificate = errors.New("invalid CA")
)
// KubernetesOptions are Kubernetes specific swarm options, that are
// needed to find peers.
type KubernetesOptions struct {
KubernetesInCluster bool
KubernetesAPIBaseURL string
Namespace string
LabelSelectorKey string
LabelSelectorValue string
}
// ClientKubernetes is the client to access kubernetes resources to find the
// peers to join a swarm.
type ClientKubernetes struct {
httpClient *http.Client
apiURL string
token string
retry backoff.BackOff
quit chan struct{}
}
// Get does the http GET call to kubernetes API to find the initial
// peers of a swarm.
func (c *ClientKubernetes) Get(s string) (*http.Response, error) {
var (
err error
rsp *http.Response
)
req, err := c.createRequest("GET", s, nil)
if err != nil {
return nil, err
}
err = backoff.Retry(func() error {
rsp, err = c.httpClient.Do(req)
if err != nil {
log.Infof("SWARM: request to %s failed: %v, retrying..", s, err)
}
return err
}, c.retry)
if err != nil {
log.Errorf("SWARM: Give up now, request to %s failed: %v", s, err)
return nil, err
}
return rsp, err
}
func (c *ClientKubernetes) Stop() {
if c != nil && c.quit != nil {
close(c.quit)
}
}
// NewClientKubernetes creates and initializes a Kubernetes client to
// find peers. A partial copy of the Kubernetes dataclient.
func NewClientKubernetes(kubernetesInCluster bool, kubernetesURL string) (*ClientKubernetes, error) {
quit := make(chan struct{})
httpClient, err := buildHTTPClient(serviceAccountDir+serviceAccountRootCAKey, kubernetesInCluster, quit)
if err != nil {
return nil, err
}
apiURL, err := buildAPIURL(kubernetesInCluster, kubernetesURL)
if err != nil {
return nil, err
}
token, err := readServiceAccountToken(serviceAccountDir+serviceAccountTokenKey, kubernetesInCluster)
if err != nil {
return nil, err
}
return &ClientKubernetes{
httpClient: httpClient,
apiURL: apiURL,
token: token,
retry: backoff.WithMaxRetries(backoff.NewConstantBackOff(5*time.Second), maxRetries),
quit: quit,
}, nil
}
func buildHTTPClient(certFilePath string, inCluster bool, quit chan struct{}) (*http.Client, error) {
if !inCluster {
return http.DefaultClient, nil
}
rootCA, err := os.ReadFile(certFilePath)
if err != nil {
return nil, err
}
certPool := x509.NewCertPool()
if !certPool.AppendCertsFromPEM(rootCA) {
return nil, errInvalidCertificate
}
tlsConfig := &tls.Config{
MinVersion: tls.VersionTLS12,
RootCAs: certPool,
}
transport := &http.Transport{
DialContext: (&net.Dialer{
Timeout: 10 * time.Second,
KeepAlive: 30 * time.Second,
DualStack: false,
}).DialContext,
TLSHandshakeTimeout: 10 * time.Second,
ResponseHeaderTimeout: 10 * time.Second,
ExpectContinueTimeout: 30 * time.Second,
MaxIdleConns: 5,
MaxIdleConnsPerHost: 5,
TLSClientConfig: tlsConfig,
}
// regularly force closing idle connections
go func() {
ticker := time.NewTicker(10 * time.Second)
defer ticker.Stop()
for {
select {
case <-ticker.C:
transport.CloseIdleConnections()
case <-quit:
return
}
}
}()
return &http.Client{
Transport: transport,
}, nil
}
func buildAPIURL(kubernetesInCluster bool, kubernetesURL string) (string, error) {
if !kubernetesInCluster {
if kubernetesURL == "" {
return defaultKubernetesURL, nil
}
return kubernetesURL, nil
}
host, port := os.Getenv(serviceHostEnvVar), os.Getenv(servicePortEnvVar)
if host == "" || port == "" {
return "", errAPIServerURLNotFound
}
return "https://" + net.JoinHostPort(host, port), nil
}
func readServiceAccountToken(tokenFilePath string, inCluster bool) (string, error) {
if !inCluster {
return "", nil
}
bToken, err := os.ReadFile(tokenFilePath)
if err != nil {
return "", err
}
return string(bToken), nil
}
func (c *ClientKubernetes) createRequest(method, url string, body io.Reader) (*http.Request, error) {
req, err := http.NewRequest(method, url, body)
if err != nil {
return nil, err
}
if c.token != "" {
req.Header.Set("Authorization", "Bearer "+c.token)
}
return req, nil
}