segment: Compare 'identify' using a fnv hash

This adds a layer of indirection compared to direct use of
reflect.DeepEqual, but has the benefit that this hash value can be
written to disk if we want to persist it over crc runs.
The fnv hash is used as it does not need any initial seed (as opposed to
maphash, crc32, crc64), and it's likely faster than md5/sha*

pkg/crc/segment/segment.go

@@ -4,12 +4,14 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"hash/fnv"
+	"io"
 	"io/ioutil"
 	"net"
 	"net/http"
 	"os"
 	"path/filepath"
-	"reflect"
+	"sort"
 	"strings"
 	"time"
 
@@ -22,15 +24,16 @@ import (
 	crcos "github.com/code-ready/crc/pkg/os"
 	"github.com/pborman/uuid"
 	"github.com/segmentio/analytics-go"
+	"github.com/spf13/cast"
 )
 
 var WriteKey = "R7jGNYYO5gH0Nl5gDlMEuZ3gPlDJKQak" // test
 
 type Client struct {
-	segmentClient  analytics.Client
-	config         *crcConfig.Config
-	userID         string
-	cachedIdentify *analytics.Identify
+	segmentClient analytics.Client
+	config        *crcConfig.Config
+	userID        string
+	identifyHash  uint64
 }
 
 func NewClient(config *crcConfig.Config, transport http.RoundTripper) (*Client, error) {
@@ -76,11 +79,39 @@ func (c *Client) UploadCmd(ctx context.Context, action string, duration time.Dur
 	return c.upload(action, properties(ctx, err, duration))
 }
 
-func (c *Client) identifyNeeded(identify *analytics.Identify) bool {
-	if c.cachedIdentify == nil {
-		return true
+func identifyHash(identify *analytics.Identify) (uint64, error) {
+	h := fnv.New64a()
+	_, err := io.WriteString(h, identify.UserId)
+	if err != nil {
+		logging.Warnf("Failed to calculate checksum for userID '%s'", identify.UserId)
+		return 0, err
+	}
+
+	// Make sure we hash the map fields always in the same order
+	traits := []string{}
+	for trait := range identify.Traits {
+		traits = append(traits, trait)
 	}
-	return (identify.UserId != c.cachedIdentify.UserId) || !reflect.DeepEqual(identify, c.cachedIdentify)
+	sort.Strings(traits)
+	for _, trait := range traits {
+		_, err := io.WriteString(h, trait)
+		if err != nil {
+			logging.Warnf("Failed to calculate checksum for '%s'", trait)
+			return 0, err
+		}
+		str, err := cast.ToStringE(identify.Traits[trait])
+		if err != nil {
+			logging.Warnf("Could not convert 'Traits[%s]' to string, extraneous 'identify' may be sent to segment", trait)
+			return 0, err
+		}
+		_, err = io.WriteString(h, str)
+		if err != nil {
+			logging.Warnf("Failed to calculate checksum for '%s'", str)
+			return 0, err
+		}
+	}
+
+	return h.Sum64(), nil
 }
 
 func (c *Client) identify() *analytics.Identify {
@@ -96,12 +127,13 @@ func (c *Client) upload(action string, a analytics.Properties) error {
 	}
 
 	identify := c.identify()
-	if c.identifyNeeded(identify) {
+	hash, err := identifyHash(identify)
+	if err != nil || hash != c.identifyHash {
 		logging.Debug("Sending 'identify' to segment")
 		if err := c.segmentClient.Enqueue(identify); err != nil {
 			return err
 		}
-		c.cachedIdentify = identify
+		c.identifyHash = hash
 	}
 
 	return c.segmentClient.Enqueue(analytics.Track{