Add -value-avro-schema-id feature

To look for the schema using the identifier directly (low level)

README.md

@@ -257,6 +257,15 @@ Not only `TopicNameStrategy` is supported but `TopicRecordNameStrategy` is suppo
 a schema using `-value-avro-record-name`. This can be used in conjunction with `-value-avro-schema` or get
 latest version of the schema from the Schema Registry without providing any parameter.
 
+If the globally unique schema identifier is already known, it can be used instead:
+
+```sh
+$ echo '{"value": {"FirstName": "Cristina"}, "key": "id-44"}' | hkt produce -topic actors -registry http://localhost:8081 -value-avro-schema-id 100
+```
+
+Produces the record using schema whose identifier is `100`.
+
+
 </details>
 
 

coder.go

@@ -31,6 +31,7 @@ func (c *coder) addFlags(flags *flag.FlagSet) {
 	flags.StringVar(&c.registryURL, "registry", "", "The Avro schema registry server URL.")
 	flags.StringVar(&c.avscFile, "value-avro-schema", "", `Path to AVSC file to format the file. If it is set, then -valuecodec is set to "avro"`)
 	flags.StringVar(&c.avroRecordName, "value-avro-record-name", "", "Record name to use when using TopicRecordNameStrategy to find the schema subject in Schema Registry")
+	flags.Int64Var(&c.avroSchemaID, "value-avro-schema-id", 0, "Use it to select schema to produce Avro formatted schemas.")
 }
 
 // decoderForType returns a function to decode key or value depending of the expected format defined in typ
@@ -75,9 +76,9 @@ func (c *coder) makeAvroDecoder(keyOrValue string) func(m json.RawMessage) ([]by
 		}
 
 		enc := c.avroRegistry.Encoder(subject)
+		ctx := context.Background()
 
 		if c.avroSchemaID == 0 {
-			ctx := context.Background()
 			if c.avroSchema == nil {
 				sch, err := c.avroRegistry.Schema(ctx, subject, "latest")
 				if err != nil {
@@ -100,6 +101,15 @@ func (c *coder) makeAvroDecoder(keyOrValue string) func(m json.RawMessage) ([]by
 				c.avroSchemaID = id
 			}
 		}
+		if c.avroSchema == nil {
+			// only got the schemaID, gather from the registry
+			dec := c.avroRegistry.Decoder()
+			sch, err := dec.SchemaForID(ctx, c.avroSchemaID)
+			if err != nil {
+				return nil, err
+			}
+			c.avroSchema = sch
+		}
 
 		// Canonicalize the schema to remove default values and logical types
 		// to work around https://github.com/linkedin/goavro/issues/198

produce.go

@@ -97,6 +97,17 @@ func (cmd *produceCmd) run(args []string) error {
 	cmd.partitioner = partitioner
 	var err error
 
+	if cmd.avroSchemaID != 0 {
+		// Override -valuecodec flag
+		cmd.valueCodecType = "avro"
+		if cmd.avscFile != "" {
+			return fmt.Errorf("cannot use -value-avro-schema with -value-avro-schema-id")
+		}
+		if cmd.avroRecordName != "" {
+			return fmt.Errorf("cannot use -value-avro-record-name with -value-avro-schema-id")
+		}
+	}
+
 	if cmd.avscFile != "" {
 		// Override -valuecodec flag
 		cmd.valueCodecType = "avro"
@@ -363,4 +374,10 @@ Running the following command:
    $ echo '{"key": "id-44", "value": {"Band": "cloud nothings"}}' | hkt produce -topic topic-3 -registry http://localhost:8081 -value-avro-schema band.avsc
 
 In order to know the subject, "-value-avro-record-name" can be also used.
+
+3. Use the globally unique schema identifier
+
+It uses the schema identifier defined in "-value-avro-schema-id". (Warning: It does not perform any check against the registry)
+
+   $ echo '{"key": "id-45", "value": {"Field": 2}}' | hkt produce -topic topic-1 -registry http://localhost:8081 -value-avro-schema-id 109
 `, ENV_BROKERS, ENV_REGISTRY)

system_test.go

@@ -54,10 +54,12 @@ func TestSystem(t *testing.T) {
 		Setup: func(e *testscript.Env) error {
 			topic := randomString(6)
 			recordName := "alt"
-			deregisterFn := registerSchemas(t, topic, recordName)
+			schemaIDs, deregisterFn := registerSchemas(t, topic, recordName)
 			e.Vars = append(e.Vars,
 				"topic="+topic,
 				"recordName="+recordName,
+				fmt.Sprintf("schemaID=%d", schemaIDs[0]),
+				fmt.Sprintf("recordSchemaID=%d", schemaIDs[1]),
 				ENV_BROKERS+"="+testBrokerAddr,
 				ENV_REGISTRY+"="+testRegistryAddr,
 				"now="+time.Now().UTC().Format(time.RFC3339),
@@ -85,8 +87,8 @@ func randomString(length int) string {
 // registerSchemas registers to testRegistry two schemas:
 // 1. using ${topic}-value as subject -> TopicNameStrategy
 // 2. using ${topic}-${recordName} as subject -> TopicRecordNameStrategy
-// returns the function to call when the test ends.
-func registerSchemas(t *testing.T, topic, recordName string) func() {
+// returns the schema identifiers and the function to call when the test ends.
+func registerSchemas(t *testing.T, topic, recordName string) ([]int64, func()) {
 	c := qt.New(t)
 	ctx := context.Background()
 
@@ -103,7 +105,7 @@ func registerSchemas(t *testing.T, topic, recordName string) func() {
 	c.Check(err, qt.IsNil)
 
 	subject := topic + "-value"
-	_, err = reg.Register(ctx, subject, typ)
+	id, err := reg.Register(ctx, subject, typ)
 	c.Check(err, qt.IsNil)
 
 	type AltR struct {
@@ -114,10 +116,10 @@ func registerSchemas(t *testing.T, topic, recordName string) func() {
 	c.Check(err, qt.IsNil)
 
 	altSubject := topic + "-" + recordName
-	_, err = reg.Register(ctx, altSubject, typ)
+	altID, err := reg.Register(ctx, altSubject, typ)
 	c.Check(err, qt.IsNil)
 
-	return func() {
+	return []int64{id, altID}, func() {
 		err := reg.DeleteSubject(ctx, subject)
 		c.Check(err, qt.IsNil)
 		err = reg.DeleteSubject(ctx, altSubject)

testdata/avromessages-with-id.txt

@@ -0,0 +1,21 @@
+# Schemas are registered in system_test.go
+kt admin -createtopic $topic -topicdetail topic-detail.json
+
+stdin produce-schema-1-stdin.json
+kt produce -topic $topic -value-avro-schema-id $schemaID
+
+stdin produce-schema-2-stdin.json
+kt produce -topic $topic -value-avro-schema-id $recordSchemaID
+
+kt consume -valuecodec avro $topic
+cmp stdout consume-stdout.json
+
+-- topic-detail.json --
+{"NumPartitions": 1, "ReplicationFactor": 1}
+-- produce-schema-1-stdin.json --
+{"key":"k1","value":{"Foo":1},"time":"2021-11-16T01:01:01Z"}
+-- produce-schema-2-stdin.json --
+{"key":"k2","value":{"Bar":2.122121},"time":"2021-11-17T01:01:02Z"}
+-- consume-stdout.json --
+{"partition":0,"offset":0,"key":"k1","value":{"Foo":1},"time":"2021-11-16T01:01:01Z"}
+{"partition":0,"offset":1,"key":"k2","value":{"Bar":2.122121},"time":"2021-11-17T01:01:02Z"}