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subscribe_avro_records.go
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/
subscribe_avro_records.go
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// Copyright 2021 Google LLC
//
// Licensed 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
//
// https://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 schema
// [START pubsub_subscribe_avro_records]
import (
"context"
"fmt"
"io"
"os"
"sync"
"time"
"cloud.google.com/go/pubsub"
"github.com/linkedin/goavro/v2"
)
func subscribeWithAvroSchema(w io.Writer, projectID, subID, avscFile string) error {
// projectID := "my-project-id"
// topicID := "my-topic"
// avscFile = "path/to/an/avro/schema/file(.avsc)/formatted/in/json"
ctx := context.Background()
client, err := pubsub.NewClient(ctx, projectID)
if err != nil {
return fmt.Errorf("pubsub.NewClient: %w", err)
}
avroSchema, err := os.ReadFile(avscFile)
if err != nil {
return fmt.Errorf("ioutil.ReadFile err: %w", err)
}
codec, err := goavro.NewCodec(string(avroSchema))
if err != nil {
return fmt.Errorf("goavro.NewCodec err: %w", err)
}
sub := client.Subscription(subID)
ctx2, cancel := context.WithTimeout(ctx, 10*time.Second)
defer cancel()
var mu sync.Mutex
sub.Receive(ctx2, func(ctx context.Context, msg *pubsub.Message) {
mu.Lock()
defer mu.Unlock()
encoding := msg.Attributes["googclient_schemaencoding"]
var state map[string]interface{}
if encoding == "BINARY" {
data, _, err := codec.NativeFromBinary(msg.Data)
if err != nil {
fmt.Fprintf(w, "codec.NativeFromBinary err: %v\n", err)
msg.Nack()
return
}
fmt.Fprintf(w, "Received a binary-encoded message:\n%#v\n", data)
state = data.(map[string]interface{})
} else if encoding == "JSON" {
data, _, err := codec.NativeFromTextual(msg.Data)
if err != nil {
fmt.Fprintf(w, "codec.NativeFromTextual err: %v\n", err)
msg.Nack()
return
}
fmt.Fprintf(w, "Received a JSON-encoded message:\n%#v\n", data)
state = data.(map[string]interface{})
} else {
fmt.Fprintf(w, "Unknown message type(%s), nacking\n", encoding)
msg.Nack()
return
}
fmt.Fprintf(w, "%s is abbreviated as %s\n", state["name"], state["post_abbr"])
msg.Ack()
})
return nil
}
// [END pubsub_subscribe_avro_records]