[Go Functions] Add newOuputMessage interface for Go Function (apache#8327)

Signed-off-by: xiaolong.ran <[email protected]>

Fixes apache#8266 


### Motivation

Implement the context object to be able to send to different topics. Like with the java SDK that allows you to return a future, which makes sending to arbitrary topics easy and fast, we may want to think of an analogous approach

### Modifications

- Add `NewOuputMessage()` interface for Go Function
- Add examples for `NewOuputMessage()`
- Add docs for `NewOuputMessage()`

### Verifying this change

- [x] Make sure that the change passes the CI checks.

This change added tests and can be verified as follows:

- Added unit tests for `FunctionContext#NewOutputMessage`

### Does this pull request potentially affect one of the following parts:

  - The public API: (yes)
  - The default values of configurations: (yes)

### Documentation

  - Does this pull request introduce a new feature? (yes )
  - If yes, how is the feature documented? (docs)

Author: wolfstudy

pulsar-function-go/examples/go.sum

@@ -1,7 +1,9 @@
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 golang.org/x/crypto v0.0.0-20190701094942-4def268fd1a4/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/lint v0.0.0-20181026193005-c67002cb31c3/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
@@ -154,8 +178,10 @@ golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn
 golang.org/x/net v0.0.0-20190613194153-d28f0bde5980/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20190724013045-ca1201d0de80/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20200520004742-59133d7f0dd7 h1:AeiKBIuRw3UomYXSbLy0Mc2dDLfdtbT/IVn4keq83P0=
 golang.org/x/net v0.0.0-20200520004742-59133d7f0dd7/go.mod h1:qpuaurCH72eLCgpAm/N6yyVIVM9cpaDIP3A8BGJEC5A=
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
+golang.org/x/oauth2 v0.0.0-20200107190931-bf48bf16ab8d h1:TzXSXBo42m9gQenoE3b9BGiEpg5IG2JkU5FkPIawgtw=
 golang.org/x/oauth2 v0.0.0-20200107190931-bf48bf16ab8d/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
@@ -179,9 +205,11 @@ golang.org/x/sys v0.0.0-20191220142924-d4481acd189f/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20200106162015-b016eb3dc98e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200519105757-fe76b779f299/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200615200032-f1bc736245b1 h1:ogLJMz+qpzav7lGMh10LMvAkM/fAoGlaiiHYiFYdm80=
 golang.org/x/sys v0.0.0-20200615200032-f1bc736245b1/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/text v0.3.2 h1:tW2bmiBqwgJj/UpqtC8EpXEZVYOwU0yG4iWbprSVAcs=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20181030221726-6c7e314b6563/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
@@ -206,6 +234,7 @@ google.golang.org/protobuf v0.0.0-20200221191635-4d8936d0db64/go.mod h1:kwYJMbMJ
 google.golang.org/protobuf v0.0.0-20200228230310-ab0ca4ff8a60/go.mod h1:cfTl7dwQJ+fmap5saPgwCLgHXTUD7jkjRqWcaiX5VyM=
 google.golang.org/protobuf v1.20.1-0.20200309200217-e05f789c0967/go.mod h1:A+miEFZTKqfCUM6K7xSMQL9OKL/b6hQv+e19PK+JZNE=
 google.golang.org/protobuf v1.21.0/go.mod h1:47Nbq4nVaFHyn7ilMalzfO3qCViNmqZ2kzikPIcrTAo=
+google.golang.org/protobuf v1.23.0 h1:4MY060fB1DLGMB/7MBTLnwQUY6+F09GEiz6SsrNqyzM=
 google.golang.org/protobuf v1.23.0/go.mod h1:EGpADcykh3NcUnDUJcl1+ZksZNG86OlYog2l/sGQquU=
 gopkg.in/alecthomas/kingpin.v2 v2.2.6/go.mod h1:FMv+mEhP44yOT+4EoQTLFTRgOQ1FBLkstjWtayDeSgw=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
@@ -222,6 +251,7 @@ gopkg.in/yaml.v2 v2.2.5/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.7/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.8 h1:obN1ZagJSUGI0Ek/LBmuj4SNLPfIny3KsKFopxRdj10=
 gopkg.in/yaml.v2 v2.2.8/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.3.0 h1:clyUAQHOM3G0M3f5vQj7LuJrETvjVot3Z5el9nffUtU=
 gopkg.in/yaml.v2 v2.3.0/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 honnef.co/go/tools v0.0.0-20190523083050-ea95bdfd59fc/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=

pulsar-function-go/examples/publishFunc/publishFunc.go

@@ -0,0 +1,54 @@
+//
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+//
+
+package main
+
+import (
+	"context"
+	"errors"
+	"log"
+
+	"github.com/apache/pulsar-client-go/pulsar"
+	"github.com/apache/pulsar/pulsar-function-go/pf"
+)
+
+func PublishFunc(ctx context.Context, in []byte) error {
+	fctx, ok := pf.FromContext(ctx)
+	if !ok {
+		return errors.New("get Go Functions Context error")
+	}
+
+	publishTopic := "publish-topic"
+	output := append(in, 110)
+
+	producer := fctx.NewOutputMessage(publishTopic)
+	msgID, err := producer.Send(ctx, &pulsar.ProducerMessage{
+		Payload: output,
+	})
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	log.Printf("The output message ID is: %+v", msgID)
+	return nil
+}
+
+func main() {
+	pf.Start(PublishFunc)
+}

pulsar-function-go/pf/context.go

@@ -28,10 +28,11 @@ import (
 )
 
 type FunctionContext struct {
-	instanceConf *instanceConf
-	userConfigs  map[string]interface{}
-	logAppender  *LogAppender
-	record       pulsar.Message
+	instanceConf  *instanceConf
+	userConfigs   map[string]interface{}
+	logAppender   *LogAppender
+	outputMessage func(topic string) pulsar.Producer
+	record        pulsar.Message
 }
 
 func NewFuncContext() *FunctionContext {
@@ -119,6 +120,12 @@ func (c *FunctionContext) GetUserConfMap() map[string]interface{} {
 	return c.userConfigs
 }
 
+// NewOutputMessage send message to the topic
+// @param topicName: The name of the topic for output message
+func (c *FunctionContext) NewOutputMessage(topicName string) pulsar.Producer {
+	return c.outputMessage(topicName)
+}
+
 // SetCurrentRecord sets the current message into the function context
 // called for each message before executing a handler function
 func (c *FunctionContext) SetCurrentRecord(record pulsar.Message) {
@@ -128,6 +135,7 @@ func (c *FunctionContext) SetCurrentRecord(record pulsar.Message) {
 // GetCurrentRecord gets the current message from the function context
 func (c *FunctionContext) GetCurrentRecord() pulsar.Message {
 	return c.record
+
 }
 
 // An unexported type to be used as the key for types in this package.

pulsar-function-go/pf/context_test.go

@@ -24,6 +24,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/apache/pulsar-client-go/pulsar"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -69,3 +70,15 @@ func TestFunctionContext_setCurrentRecord(t *testing.T) {
 
 	assert.IsType(t, &MockMessage{}, fc.record)
 }
+
+func TestFunctionContext_NewOutputMessage(t *testing.T) {
+	fc := NewFuncContext()
+	publishTopic := "publish-topic"
+
+	fc.outputMessage = func(topic string) pulsar.Producer {
+		return &MockPulsarProducer{}
+	}
+
+	actualProducer := fc.NewOutputMessage(publishTopic)
+	assert.IsType(t, &MockPulsarProducer{}, actualProducer)
+}