client/fingerprint/consul: refactor the consul fingerprinter to test …

…individual attributes

This PR refactors the ConsulFingerprint implementation, breaking individual attributes
into individual functions to make testing them easier. This is in preparation for
additional extractors about to be added. Behavior should be otherwise unchanged.

It adds the attribute consul.sku, which can be used to differentiate between Consul
OSS vs Consul ENT.

client/fingerprint/consul.go

@@ -3,10 +3,12 @@ package fingerprint
 import (
 	"fmt"
 	"strconv"
+	"strings"
 	"time"
 
 	consul "github.com/hashicorp/consul/api"
 	log "github.com/hashicorp/go-hclog"
+	"github.com/hashicorp/go-version"
 )
 
 const (
@@ -16,108 +18,175 @@ const (
 
 // ConsulFingerprint is used to fingerprint for Consul
 type ConsulFingerprint struct {
-	logger    log.Logger
-	client    *consul.Client
-	lastState string
+	logger     log.Logger
+	client     *consul.Client
+	lastState  string
+	extractors map[string]consulExtractor
 }
 
+// consulInfo aliases the type returned from the Consul agent self endpoint.
+type consulInfo = map[string]map[string]interface{}
+
+// consulExtractor is used to parse out one attribute from consulInfo. Returns
+// the value of the attribute, and whether the attribute exists.
+type consulExtractor func(consulInfo) (string, bool)
+
 // NewConsulFingerprint is used to create a Consul fingerprint
 func NewConsulFingerprint(logger log.Logger) Fingerprint {
-	return &ConsulFingerprint{logger: logger.Named("consul"), lastState: consulUnavailable}
+	return &ConsulFingerprint{
+		logger:    logger.Named("consul"),
+		lastState: consulUnavailable,
+	}
 }
 
 func (f *ConsulFingerprint) Fingerprint(req *FingerprintRequest, resp *FingerprintResponse) error {
-	// Only create the client once to avoid creating too many connections to
-	// Consul.
+
+	// establish consul client if necessary
+	if err := f.initialize(req); err != nil {
+		return err
+	}
+
+	// query consul for agent self api
+	info := f.query(resp)
+	if len(info) == 0 {
+		// unable to reach consul, nothing to do this time
+		return nil
+	}
+
+	// apply the extractor for each attribute
+	for attr, extractor := range f.extractors {
+		if s, ok := extractor(info); !ok {
+			f.logger.Warn("unable to fingerprint consul", "attribute", attr)
+		} else {
+			resp.AddAttribute(attr, s)
+		}
+	}
+
+	// create link for consul
+	f.link(resp)
+
+	// indicate Consul is now available
+	if f.lastState == consulUnavailable {
+		f.logger.Info("consul agent is available")
+	}
+
+	f.lastState = consulAvailable
+	resp.Detected = true
+	return nil
+}
+
+func (f *ConsulFingerprint) Periodic() (bool, time.Duration) {
+	return true, 15 * time.Second
+}
+
+// clearConsulAttributes removes consul attributes and links from the passed Node.
+func (f *ConsulFingerprint) clearConsulAttributes(r *FingerprintResponse) {
+	for attr := range f.extractors {
+		r.RemoveAttribute(attr)
+	}
+	r.RemoveLink("consul")
+}
+
+func (f *ConsulFingerprint) initialize(req *FingerprintRequest) error {
+	// Only create the Consul client once to avoid creating many connections
 	if f.client == nil {
 		consulConfig, err := req.Config.ConsulConfig.ApiConfig()
 		if err != nil {
-			return fmt.Errorf("Failed to initialize the Consul client config: %v", err)
+			return fmt.Errorf("failed to initialize Consul client config: %v", err)
 		}
 
 		f.client, err = consul.NewClient(consulConfig)
 		if err != nil {
-			return fmt.Errorf("Failed to initialize consul client: %s", err)
+			return fmt.Errorf("failed to initialize Consul client: %s", err)
+		}
+
+		f.extractors = map[string]consulExtractor{
+			"consul.server":      f.server,
+			"consul.version":     f.version,
+			"consul.sku":         f.sku,
+			"consul.revision":    f.revision,
+			"unique.consul.name": f.name,
+			"consul.datacenter":  f.dc,
+			"consul.segment":     f.segment,
 		}
 	}
 
+	return nil
+}
+
+func (f *ConsulFingerprint) query(resp *FingerprintResponse) consulInfo {
 	// We'll try to detect consul by making a query to to the agent's self API.
 	// If we can't hit this URL consul is probably not running on this machine.
 	info, err := f.client.Agent().Self()
 	if err != nil {
 		f.clearConsulAttributes(resp)
 
-		// Print a message indicating that the Consul Agent is not available
-		// anymore
+		// indicate consul no longer available
 		if f.lastState == consulAvailable {
 			f.logger.Info("consul agent is unavailable")
 		}
 		f.lastState = consulUnavailable
 		return nil
 	}
+	return info
+}
 
-	if s, ok := info["Config"]["Server"].(bool); ok {
-		resp.AddAttribute("consul.server", strconv.FormatBool(s))
-	} else {
-		f.logger.Warn("unable to fingerprint consul.server")
-	}
-	if v, ok := info["Config"]["Version"].(string); ok {
-		resp.AddAttribute("consul.version", v)
-	} else {
-		f.logger.Warn("unable to fingerprint consul.version")
-	}
-	if r, ok := info["Config"]["Revision"].(string); ok {
-		resp.AddAttribute("consul.revision", r)
-	} else {
-		f.logger.Warn("unable to fingerprint consul.revision")
-	}
-	if n, ok := info["Config"]["NodeName"].(string); ok {
-		resp.AddAttribute("unique.consul.name", n)
-	} else {
-		f.logger.Warn("unable to fingerprint unique.consul.name")
-	}
-	if d, ok := info["Config"]["Datacenter"].(string); ok {
-		resp.AddAttribute("consul.datacenter", d)
-	} else {
-		f.logger.Warn("unable to fingerprint consul.datacenter")
-	}
-	if g, ok := info["Member"]["Tags"].(map[string]interface{}); ok {
-		if s, ok := g["segment"].(string); ok {
-			resp.AddAttribute("consul.segment", s)
-		}
-	} else {
-		f.logger.Warn("unable to fingerprint consul.segment")
-	}
+func (f *ConsulFingerprint) link(resp *FingerprintResponse) {
 	if dc, ok := resp.Attributes["consul.datacenter"]; ok {
 		if name, ok2 := resp.Attributes["unique.consul.name"]; ok2 {
 			resp.AddLink("consul", fmt.Sprintf("%s.%s", dc, name))
 		}
 	} else {
 		f.logger.Warn("malformed Consul response prevented linking")
 	}
+}
 
-	// If the Consul Agent was previously unavailable print a message to
-	// indicate the Agent is available now
-	if f.lastState == consulUnavailable {
-		f.logger.Info("consul agent is available")
+func (f *ConsulFingerprint) server(info consulInfo) (string, bool) {
+	s, ok := info["Config"]["Server"].(bool)
+	return strconv.FormatBool(s), ok
+}
+
+func (f *ConsulFingerprint) version(info consulInfo) (string, bool) {
+	v, ok := info["Config"]["Version"].(string)
+	return v, ok
+}
+
+func (f *ConsulFingerprint) sku(info consulInfo) (string, bool) {
+	v, ok := info["Config"]["Version"].(string)
+	if !ok {
+		return "", ok
 	}
-	f.lastState = consulAvailable
-	resp.Detected = true
-	return nil
+
+	ver, vErr := version.NewVersion(v)
+	if vErr != nil {
+		return "", false
+	}
+	if strings.Contains(ver.Metadata(), "ent") {
+		return "ent", true
+	}
+	return "oss", true
 }
 
-// clearConsulAttributes removes consul attributes and links from the passed
-// Node.
-func (f *ConsulFingerprint) clearConsulAttributes(r *FingerprintResponse) {
-	r.RemoveAttribute("consul.server")
-	r.RemoveAttribute("consul.version")
-	r.RemoveAttribute("consul.revision")
-	r.RemoveAttribute("unique.consul.name")
-	r.RemoveAttribute("consul.datacenter")
-	r.RemoveAttribute("consul.segment")
-	r.RemoveLink("consul")
+func (f *ConsulFingerprint) revision(info consulInfo) (string, bool) {
+	r, ok := info["Config"]["Revision"].(string)
+	return r, ok
 }
 
-func (f *ConsulFingerprint) Periodic() (bool, time.Duration) {
-	return true, 15 * time.Second
+func (f *ConsulFingerprint) name(info consulInfo) (string, bool) {
+	n, ok := info["Config"]["NodeName"].(string)
+	return n, ok
+}
+
+func (f *ConsulFingerprint) dc(info consulInfo) (string, bool) {
+	d, ok := info["Config"]["Datacenter"].(string)
+	return d, ok
+}
+
+func (f *ConsulFingerprint) segment(info consulInfo) (string, bool) {
+	tags, tagsOK := info["Member"]["Tags"].(map[string]interface{})
+	if !tagsOK {
+		return "", false
+	}
+	s, ok := tags["segment"].(string)
+	return s, ok
 }