add dynamodb handler to g8 (#9)

* add dynamodb handler to g8

* renamed new relic attribute to fit DynamoDB

dynamodb_handler.go

@@ -0,0 +1,67 @@
+package g8
+
+import (
+	"context"
+
+	"github.com/aws/aws-lambda-go/events"
+	"github.com/aws/aws-lambda-go/lambda"
+	"github.com/google/uuid"
+	newrelic "github.com/newrelic/go-agent"
+	"github.com/newrelic/go-agent/_integrations/nrlambda"
+	"github.com/rs/zerolog"
+)
+
+type DynamoDbContext struct {
+	Context       context.Context
+	EventRecord   events.DynamoDBEventRecord
+	Logger        zerolog.Logger
+	NewRelicTx    newrelic.Transaction
+	CorrelationID string
+}
+
+type DynamoHandlerFunc func(c *DynamoDbContext) error
+
+func DynamoDbHandler(h DynamoHandlerFunc, conf HandlerConfig) func(context.Context, events.DynamoDBEvent) error {
+	return func(ctx context.Context, e events.DynamoDBEvent) error {
+		for _, record := range e.Records {
+			correlationID := uuid.New().String()
+
+			logger := configureLogger(conf).
+				Str("dynamodb_event_source", record.EventSource).
+				Str("correlation_id", correlationID).
+				Logger()
+
+			c := &DynamoDbContext{
+				Context:       ctx,
+				EventRecord:   record,
+				Logger:        logger,
+				NewRelicTx:    newrelic.FromContext(ctx),
+				CorrelationID: correlationID,
+			}
+
+			c.AddNewRelicAttribute("functionName", conf.FunctionName)
+			c.AddNewRelicAttribute("buildVersion", conf.BuildVersion)
+			c.AddNewRelicAttribute("correlationID", correlationID)
+			c.AddNewRelicAttribute("dynamoDBEventSource", record.EventSource)
+
+			if err := h(c); err != nil {
+				logUnhandledError(c.Logger, err)
+				return err
+			}
+		}
+		return nil
+	}
+}
+
+func DynamoDbHandlerWithNewRelic(h DynamoHandlerFunc, conf HandlerConfig) lambda.Handler {
+	return nrlambda.Wrap(DynamoDbHandler(h, conf), conf.NewRelicApp)
+}
+
+func (c *DynamoDbContext) AddNewRelicAttribute(key string, val interface{}) {
+	if c.NewRelicTx == nil {
+		return
+	}
+	if err := c.NewRelicTx.AddAttribute(key, val); err != nil {
+		c.Logger.Error().Msgf("failed to add attr '%s' to new relic tx: %+v", key, err)
+	}
+}

dynamodb_handler_test.go

@@ -0,0 +1,91 @@
+package g8_test
+
+import (
+	"context"
+	"fmt"
+	"io/ioutil"
+	"testing"
+
+	"github.com/aws/aws-lambda-go/events"
+	"github.com/rs/zerolog"
+	"github.com/stretchr/testify/assert"
+
+	"github.com/JSainsburyPLC/g8"
+)
+
+func TestDynamoDbHandler_SingleMessage(t *testing.T) {
+	timesCalled := 0
+	h := g8.DynamoDbHandler(func(c *g8.DynamoDbContext) error {
+		timesCalled++
+
+		assert.Equal(t, "event1", c.EventRecord.EventName)
+		assert.IsType(t, events.DynamoDBStreamRecord{}, c.EventRecord.Change)
+		assert.NotEmpty(t, c.CorrelationID)
+
+		return nil
+	}, g8.HandlerConfig{Logger: zerolog.New(ioutil.Discard)})
+
+	err := h(context.Background(), events.DynamoDBEvent{
+		Records: []events.DynamoDBEventRecord{
+			{
+				EventName: "event1",
+				Change:    events.DynamoDBStreamRecord{},
+			},
+		},
+	})
+
+	assert.Nil(t, err)
+	assert.Equal(t, 1, timesCalled)
+}
+
+func TestDynamoDbHandler_MultipleMessages(t *testing.T) {
+	timesCalled := 0
+	h := g8.DynamoDbHandler(func(c *g8.DynamoDbContext) error {
+		timesCalled++
+
+		assert.Equal(t, fmt.Sprintf("event-%d", timesCalled), c.EventRecord.EventName)
+		assert.NotEmpty(t, c.CorrelationID)
+		assert.IsType(t, events.DynamoDBStreamRecord{}, c.EventRecord.Change)
+
+		return nil
+	}, g8.HandlerConfig{Logger: zerolog.New(ioutil.Discard)})
+
+	err := h(context.Background(), events.DynamoDBEvent{
+		Records: []events.DynamoDBEventRecord{
+			{
+				EventName: "event-1",
+				Change:    events.DynamoDBStreamRecord{},
+			},
+			{
+				EventName: "event-2",
+				Change:    events.DynamoDBStreamRecord{},
+			},
+		},
+	})
+
+	assert.Nil(t, err)
+	assert.Equal(t, 2, timesCalled)
+}
+
+func TestDynamoDbHandler_HandlerError(t *testing.T) {
+	timesCalled := 0
+	handlerFunc := func(c *g8.DynamoDbContext) error {
+		timesCalled++
+		return assert.AnError
+	}
+
+	h := g8.DynamoDbHandler(handlerFunc, g8.HandlerConfig{
+		Logger: zerolog.New(ioutil.Discard),
+	})
+	err := h(context.Background(), events.DynamoDBEvent{
+		Records: []events.DynamoDBEventRecord{
+			{
+				EventName: "event-1",
+				Change:    events.DynamoDBStreamRecord{},
+			},
+		},
+	})
+
+	assert.Equal(t, assert.AnError, err)
+	assert.Equal(t, 1, timesCalled)
+}