Checking in vendor folder for ease of using go get.

vendor/github.com/paypal/gorealis/zk.go

@@ -0,0 +1,174 @@
+/**
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package realis
+
+import (
+	"encoding/json"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/pkg/errors"
+	"github.com/samuel/go-zookeeper/zk"
+)
+
+type Endpoint struct {
+	Host string `json:"host"`
+	Port int    `json:"port"`
+}
+
+type ServiceInstance struct {
+	Service             Endpoint            `json:"serviceEndpoint"`
+	AdditionalEndpoints map[string]Endpoint `json:"additionalEndpoints"`
+	Status              string              `json:"status"`
+}
+
+type zkConfig struct {
+	endpoints []string
+	path      string
+	backoff   Backoff
+	timeout   time.Duration
+	logger    Logger
+}
+
+type ZKOpt func(z *zkConfig)
+
+func ZKEndpoints(endpoints ...string) ZKOpt {
+	return func(z *zkConfig) {
+		z.endpoints = endpoints
+	}
+}
+
+func ZKPath(path string) ZKOpt {
+	return func(z *zkConfig) {
+		z.path = path
+	}
+}
+
+func ZKBackoff(b Backoff) ZKOpt {
+	return func(z *zkConfig) {
+		z.backoff = b
+	}
+}
+
+func ZKTimeout(d time.Duration) ZKOpt {
+	return func(z *zkConfig) {
+		z.timeout = d
+	}
+}
+
+func ZKLogger(l Logger) ZKOpt {
+	return func(z *zkConfig) {
+		z.logger = l
+	}
+}
+
+// Retrieves current Aurora leader from ZK.
+func LeaderFromZK(cluster Cluster) (string, error) {
+	return LeaderFromZKOpts(ZKEndpoints(strings.Split(cluster.ZK, ",")...), ZKPath(cluster.SchedZKPath))
+}
+
+// Retrieves current Aurora leader from ZK with a custom configuration.
+func LeaderFromZKOpts(options ...ZKOpt) (string, error) {
+	var leaderURL string
+
+	// Load the default configuration for Zookeeper followed by overriding values with those provided by the caller.
+	config := &zkConfig{backoff: defaultBackoff, timeout: time.Second * 10, logger: NoopLogger{}}
+	for _, opt := range options {
+		opt(config)
+	}
+
+	if len(config.endpoints) == 0 {
+		return "", errors.New("no Zookeeper endpoints supplied")
+	}
+
+	if config.path == "" {
+		return "", errors.New("no Zookeeper path supplied")
+	}
+
+	// Create a closure that allows us to use the ExponentialBackoff function.
+	retryErr := ExponentialBackoff(config.backoff, config.logger, func() (bool, error) {
+
+		c, _, err := zk.Connect(config.endpoints, config.timeout, func(c *zk.Conn) { c.SetLogger(config.logger) })
+		if err != nil {
+			return false, NewTemporaryError(errors.Wrap(err, "Failed to connect to Zookeeper"))
+		}
+
+		defer c.Close()
+
+		// Open up descriptor for the ZK path given
+		children, _, _, err := c.ChildrenW(config.path)
+		if err != nil {
+
+			// Sentinel error check as there is no other way to check.
+			if err == zk.ErrInvalidPath {
+				return false, errors.Wrapf(err, "path %s is an invalid Zookeeper path", config.path)
+			}
+
+			return false, NewTemporaryError(errors.Wrapf(err, "Path %s doesn't exist on Zookeeper ", config.path))
+		}
+
+		// Search for the leader through all the children in the given path
+		serviceInst := new(ServiceInstance)
+		for _, child := range children {
+
+			// Only the leader will start with member_
+			if strings.HasPrefix(child, "member_") {
+
+				childPath := config.path + "/" + child
+				data, _, err := c.Get(childPath)
+				if err != nil {
+					if err == zk.ErrInvalidPath {
+						return false, errors.Wrapf(err, "path %s is an invalid Zookeeper path", childPath)
+					}
+
+					return false, NewTemporaryError(errors.Wrap(err, "Error fetching contents of leader"))
+				}
+
+				err = json.Unmarshal([]byte(data), serviceInst)
+				if err != nil {
+					return false, NewTemporaryError(errors.Wrap(err, "Unable to unmarshall contents of leader"))
+				}
+
+				// Should only be one endpoint.
+				// This should never be encountered as it would indicate Aurora
+				// writing bad info into Zookeeper but is kept here as a safety net.
+				if len(serviceInst.AdditionalEndpoints) > 1 {
+					return false, NewTemporaryError(errors.New("ambiguous endpoints in json blob, Aurora wrote bad info to ZK"))
+				}
+
+				var scheme, host, port string
+				for k, v := range serviceInst.AdditionalEndpoints {
+					scheme = k
+					host = v.Host
+					port = strconv.Itoa(v.Port)
+				}
+
+				leaderURL = scheme + "://" + host + ":" + port
+				return true, nil
+			}
+		}
+
+		// Leader data might not be available yet, try to fetch again.
+		return false, NewTemporaryError(errors.New("No leader found"))
+	})
+
+	if retryErr != nil {
+		config.logger.Printf("Failed to determine leader after %v attempts", config.backoff.Steps)
+		return "", retryErr
+	}
+
+	return leaderURL, nil
+}