feat(parser) add flag to log diff on failure

Add a new --log-failed-config flag. When enabled, if the reconciliation
loop encounters an error, perform a diff against the last known good
configuration and write it to a temporary file.

cli/ingress-controller/flags.go

@@ -77,8 +77,9 @@ type cliConfig struct {
 	EnableReverseSync bool
 
 	// Logging
-	LogLevel  string
-	LogFormat string
+	LogLevel        string
+	LogFormat       string
+	LogFailedConfig bool
 
 	// k8s connection details
 	APIServerHost      string
@@ -310,6 +311,7 @@ func parseFlags() (cliConfig, error) {
 	// Logging
 	config.LogLevel = viper.GetString("log-level")
 	config.LogFormat = viper.GetString("log-format")
+	config.LogFailedConfig = viper.GetBool("log-failed-config")
 
 	// k8s connection details
 	config.APIServerHost = viper.GetString("apiserver-host")

cli/ingress-controller/main.go

@@ -102,6 +102,8 @@ func controllerConfigFromCLIConfig(cliConfig cliConfig) controller.Configuration
 		UpdateStatus:           cliConfig.UpdateStatus,
 		UpdateStatusOnShutdown: cliConfig.UpdateStatusOnShutdown,
 		ElectionID:             cliConfig.ElectionID,
+
+		LogFailedConfig: cliConfig.LogFailedConfig,
 	}
 }
 

go.mod

@@ -20,6 +20,7 @@ require (
 	github.com/stretchr/testify v1.5.1
 	github.com/tidwall/gjson v1.2.1
 	github.com/tidwall/match v1.0.1 // indirect
+	github.com/yudai/gojsondiff v1.0.0
 	golang.org/x/sync v0.0.0-20200625203802-6e8e738ad208
 	gopkg.in/go-playground/assert.v1 v1.2.1 // indirect
 	gopkg.in/go-playground/pool.v3 v3.1.1

internal/ingress/controller/controller.go

@@ -19,6 +19,7 @@ package controller
 import (
 	"context"
 	"fmt"
+	"io/ioutil"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -90,7 +91,8 @@ type Configuration struct {
 
 	EnableKnativeIngressSupport bool
 
-	Logger logrus.FieldLogger
+	Logger          logrus.FieldLogger
+	LogFailedConfig bool
 }
 
 // sync collects all the pieces required to assemble the configuration file and
@@ -223,6 +225,7 @@ type KongController struct {
 	backgroundGroup errgroup.Group
 
 	runningConfigHash []byte
+	lastConfig        []byte
 
 	isShuttingDown uint32
 
@@ -231,12 +234,19 @@ type KongController struct {
 	PluginSchemaStore PluginSchemaStore
 
 	Logger logrus.FieldLogger
+
+	tmpDir string
 }
 
 // Start starts a new master process running in foreground, blocking until the next call to
 // Stop.
 func (n *KongController) Start() {
 	n.Logger.Debugf("startin up controller")
+	var err error
+	n.tmpDir, err = ioutil.TempDir("", "controller")
+	if err != nil {
+		panic(fmt.Errorf("failed to create a temporary working directory: %v", err))
+	}
 
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()

internal/ingress/controller/kong.go

@@ -22,6 +22,7 @@ import (
 	"crypto/sha256"
 	"encoding/json"
 	"fmt"
+	"io/ioutil"
 	"net/http"
 	"reflect"
 	"sort"
@@ -36,8 +37,28 @@ import (
 	"github.com/kong/go-kong/kong"
 	"github.com/kong/kubernetes-ingress-controller/internal/ingress/controller/parser/kongstate"
 	"github.com/kong/kubernetes-ingress-controller/internal/ingress/utils"
+	"github.com/yudai/gojsondiff"
+	"github.com/yudai/gojsondiff/formatter"
 )
 
+func getDiff(a []byte, b []byte) (string, error) {
+	differ := gojsondiff.New()
+	d, err := differ.Compare(a, b)
+	if err != nil {
+		return "", err
+	}
+	var rightObject map[string]interface{}
+	err = json.Unmarshal(b, &rightObject)
+	if err != nil {
+		return "", err
+	}
+
+	formatter := formatter.NewAsciiFormatter(rightObject,
+		formatter.AsciiFormatterConfig{})
+	diffString, err := formatter.Format(d)
+	return diffString, err
+}
+
 // OnUpdate is called periodically by syncQueue to keep the configuration in sync.
 // returning nil implies the synchronization finished correctly.
 // Returning an error means requeue the update.
@@ -67,15 +88,22 @@ func (n *KongController) OnUpdate(ctx context.Context, state *kongstate.KongStat
 			return nil
 		}
 	}
+	target, _ := json.Marshal(targetContent)
 	if n.cfg.InMemory {
 		err = n.onUpdateInMemoryMode(ctx, targetContent, customEntities)
 	} else {
 		err = n.onUpdateDBMode(targetContent)
 	}
 	if err != nil {
+		if n.cfg.LogFailedConfig {
+			diff, _ := getDiff(target, n.lastConfig)
+			_ = ioutil.WriteFile(n.tmpDir+"/target.json", target, 0600)
+			_ = ioutil.WriteFile(n.tmpDir+"/diff.json", []byte(diff), 0600)
+		}
 		return err
 	}
 	n.runningConfigHash = shaSum
+	n.lastConfig = target
 	n.Logger.Info("successfully synced configuration to kong")
 	return nil
 }