Add pkg/loadbalancing/dnslb.Block() function.

pkg/loadbalancing/dnslb/api.go

@@ -85,6 +85,14 @@ func New(config Config, params Params) (*LoadBalancer, error) {
 	return newLoadBalancer(config, params)
 }
 
+// Block will block a server instance with the specified IP address from
+// adding itself to DNS for the specified time or until a message is received on
+// cancelChannel.
+func Block(config Config, params Params, ip string, duration time.Duration,
+	cancelChannel <-chan struct{}, logger log.DebugLogger) error {
+	return block(config, params, ip, duration, cancelChannel, logger)
+}
+
 // RollingReplace will use the provided configuration and will roll through all
 // server instances in the specified region triggering replacements by removing
 // each server from DNS, destroying it and waiting for (some other mechanism) to

pkg/loadbalancing/dnslb/block.go

@@ -0,0 +1,45 @@
+package dnslb
+
+import (
+	crand "crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"time"
+
+	"github.com/Cloud-Foundations/golib/pkg/log"
+)
+
+func block(config Config, params Params, ip string, duration time.Duration,
+	cancelChannel <-chan struct{}, logger log.DebugLogger) error {
+	if duration < time.Minute {
+		return fmt.Errorf("duration: %s is under a minute", duration)
+	} else if duration > time.Hour {
+		return fmt.Errorf("duration: %s is over an hour", duration)
+	}
+	lb := &LoadBalancer{
+		config: config,
+		p:      params,
+	}
+	crandData := make([]byte, 4)
+	if _, err := crand.Read(crandData); err != nil {
+		return err
+	}
+	myId := hex.EncodeToString(crandData)
+	stopTime := time.Now().Add(duration)
+	for keepGoing := true; keepGoing; {
+		if time.Until(stopTime) <= 0 {
+			break
+		}
+		if err := lb.block(myId, ip, time.Minute); err != nil {
+			return err
+		}
+		timer := time.NewTimer(time.Minute)
+		select {
+		case <-cancelChannel:
+			keepGoing = false
+			timer.Stop()
+		case <-timer.C:
+		}
+	}
+	return lb.cleanupBlock()
+}