Add input plugin for DC/OS (#3519)

plugins/inputs/dcos/creds.go

@@ -0,0 +1,72 @@
+package dcos
+
+import (
+	"context"
+	"crypto/rsa"
+	"fmt"
+	"io/ioutil"
+	"strings"
+	"time"
+	"unicode/utf8"
+)
+
+const (
+	// How long before expiration to renew token
+	relogDuration = 5 * time.Minute
+)
+
+type Credentials interface {
+	Token(ctx context.Context, client Client) (string, error)
+	IsExpired() bool
+}
+
+type ServiceAccount struct {
+	AccountID  string
+	PrivateKey *rsa.PrivateKey
+
+	auth *AuthToken
+}
+
+type TokenCreds struct {
+	Path string
+}
+
+type NullCreds struct {
+}
+
+func (c *ServiceAccount) Token(ctx context.Context, client Client) (string, error) {
+	auth, err := client.Login(ctx, c)
+	if err != nil {
+		return "", err
+	}
+	c.auth = auth
+	return auth.Text, nil
+}
+
+func (c *ServiceAccount) IsExpired() bool {
+	return c.auth.Text != "" || c.auth.Expire.Add(relogDuration).After(time.Now())
+}
+
+func (c *TokenCreds) Token(ctx context.Context, client Client) (string, error) {
+	octets, err := ioutil.ReadFile(c.Path)
+	if err != nil {
+		return "", fmt.Errorf("Error reading token file %q: %s", c.Path, err)
+	}
+	if !utf8.Valid(octets) {
+		return "", fmt.Errorf("Token file does not contain utf-8 encoded text: %s", c.Path)
+	}
+	token := strings.TrimSpace(string(octets))
+	return token, nil
+}
+
+func (c *TokenCreds) IsExpired() bool {
+	return true
+}
+
+func (c *NullCreds) Token(ctx context.Context, client Client) (string, error) {
+	return "", nil
+}
+
+func (c *NullCreds) IsExpired() bool {
+	return true
+}