[!] add Patroni REST API support (#263)

* [!] add Patroni REST API support
* [-] fix nil pointer dereference

Author: pashagolub

README.md

@@ -6,7 +6,7 @@
 
 # vip-manager
 
-Manages a virtual IP based on state kept in `etcd` or `Consul`
+Manages a virtual IP based on state kept in `etcd`, `Consul` or using `Patroni` REST API
 
 ## Table of Contents
 - [Prerequisites](#prerequisites)
@@ -159,4 +159,4 @@ Either:
 
 ## Author
 
-Cybertec Schönig & Schönig GmbH, https://www.cybertec-postgresql.com
+CYBERTEC PostgreSQL International GmbH, https://www.cybertec-postgresql.com

checker/leader_checker.go

@@ -25,6 +25,8 @@ func NewLeaderChecker(con *vipconfig.Config) (LeaderChecker, error) {
 		lc, err = NewConsulLeaderChecker(con)
 	case "etcd", "etcd3":
 		lc, err = NewEtcdLeaderChecker(con)
+	case "patroni":
+		lc, err = NewPatroniLeaderChecker(con)
 	default:
 		err = ErrUnsupportedEndpointType
 	}

checker/patroni_leader_checker.go

@@ -0,0 +1,41 @@
+package checker
+
+import (
+	"context"
+	"log"
+	"strconv"
+	"time"
+
+	"net/http"
+
+	"github.com/cybertec-postgresql/vip-manager/vipconfig"
+)
+
+// PatroniLeaderChecker will use Patroni REST API to check the leader.
+// --trigger-key is used to specify the endpoint to check, e.g. /leader.
+// --trigger-value is used to specify the HTTP code to expect, e.g. 200.
+type PatroniLeaderChecker struct {
+	*vipconfig.Config
+}
+
+// NewPatroniLeaderChecker returns a new instance
+func NewPatroniLeaderChecker(conf *vipconfig.Config) (*PatroniLeaderChecker, error) {
+	return &PatroniLeaderChecker{conf}, nil
+}
+
+// GetChangeNotificationStream checks the status in the loop
+func (c *PatroniLeaderChecker) GetChangeNotificationStream(ctx context.Context, out chan<- bool) error {
+	for {
+		select {
+		case <-ctx.Done():
+			return nil
+		case <-time.After(time.Duration(c.Interval) * time.Millisecond):
+			r, err := http.Get(c.Endpoints[0] + c.Key)
+			if err != nil {
+				log.Printf("patroni REST API error: %s", err)
+				continue
+			}
+			out <- strconv.Itoa(r.StatusCode) == c.Nodename
+		}
+	}
+}

vipconfig/config.go

@@ -55,9 +55,9 @@ func defineFlags() {
 	pflag.String("trigger-key", "", "Key in the DCS to monitor, e.g. \"/service/batman/leader\".")
 	pflag.String("trigger-value", "", "Value to monitor for.")
 
-	pflag.String("dcs-type", "etcd", "Type of endpoint used for key storage. Supported values: etcd, consul.")
+	pflag.String("dcs-type", "etcd", "Type of endpoint used for key storage. Supported values: etcd, consul, patroni.")
 	// note: can't put a default value into dcs-endpoints as that would mess with applying default localhost when using consul
-	pflag.String("dcs-endpoints", "", "DCS endpoint(s), separate multiple endpoints using commas. (default \"http://127.0.0.1:2379\" or \"http://127.0.0.1:8500\" depending on dcs-type.)")
+	pflag.String("dcs-endpoints", "", "DCS endpoint(s), separate multiple endpoints using commas. (default \"http://127.0.0.1:2379\", \"http://127.0.0.1:8500\" or \"http://127.0.0.1:8008/\" depending on dcs-type.)")
 	pflag.String("etcd-user", "", "Username for etcd DCS endpoints.")
 	pflag.String("etcd-password", "", "Password for etcd DCS endpoints.")
 	pflag.String("etcd-ca-file", "", "Trusted CA certificate for the etcd server.")
@@ -302,12 +302,18 @@ func NewConfig() (*Config, error) {
 			viper.Set("dcs-endpoints", []string{"http://127.0.0.1:8500"})
 		case "etcd", "etcd3":
 			viper.Set("dcs-endpoints", []string{"http://127.0.0.1:2379"})
+		case "patroni":
+			viper.Set("dcs-endpoints", []string{"http://127.0.0.1:8008/"})
 		}
 	}
 
-	// set trigger-value to hostname if nothing is specified
-	if len(viper.GetString("trigger-value")) == 0 {
-		triggerValue, err := os.Hostname()
+	// set trigger-value to default value if nothing is specified
+	if triggerValue := viper.GetString("trigger-value"); len(triggerValue) == 0 {
+		if viper.GetString("dcs-type") == "patroni" {
+			triggerValue = "200"
+		} else {
+			triggerValue, err = os.Hostname()
+		}
 		if err != nil {
 			log.Printf("No trigger-value specified, hostname could not be retrieved: %s", err)
 		} else {

vipconfig/vip-manager.yml

@@ -15,13 +15,13 @@ interface: enp0s3 #interface to which the virtual ip will be added
 # how the virtual ip should be managed. we currently support "ip addr add/remove" through shell commands or the Hetzner api
 hosting-type: basic # possible values: basic, or hetzner.
 
-dcs-type: etcd # etcd or consul
+dcs-type: etcd # etcd, consul or patroni
 # a list that contains all DCS endpoints to which vip-manager could talk.
 dcs-endpoints:
   - http://127.0.0.1:2379
   - https://192.168.0.42:2379
   # A single list-item is also fine.
-  # consul will always only use the first entry from this list.
+  # consul and patroni will always only use the first entry from this list.
   # For consul, you'll obviously need to change the port to 8500. Unless you're using a different one. Maybe you're a rebel and are running consul on port 2379? Just to confuse people? Why would you do that? Oh, I get it.
 
 etcd-user: "patroni"