Gli argomenti possono utilizzare degli schemi per definire un formato che i loro messaggi devono seguire. Quando sottoscrivi un argomento con uno schema, i messaggi inviati al sottoscrittore sono garantiti come messaggi validi. Questi messaggi sono conformi al tipo e alla codifica specificati nelle impostazioni dello schema associate all'argomento.
Il sottoscrittore può determinare le impostazioni dello schema associate a un argomento osservando i seguenti attributi:
googclient_schemaname: il nome dello schema utilizzato per la convalida. Se lo schema viene eliminato, il nome è_deleted-schema_.googclient_schemaencoding: la codifica del messaggio, JSON su BINARY.googclient_schemarevisionid: l'ID revisione dello schema utilizzato per analizzare e convalidare il messaggio. A ogni revisione è associato un ID revisione univoco. L'ID revisione è un UUID di otto caratteri generato automaticamente.
Per saperne di più sugli schemi, consulta la Panoramica degli schemi.
Esempi di codice per l'iscrizione ad argomenti associati a uno schema
Questi esempi mostrano come elaborare i messaggi in fase di sottoscrizione ad argomenti configurati con lo schema.
C++
Prima di provare questo esempio, segui le istruzioni di configurazione di C++ riportate nella Guida rapida sull'utilizzo delle librerie client. Per ulteriori informazioni, consulta la documentazione di riferimento dell'API C++ Pub/Sub.
Avronamespace pubsub = ::google::cloud::pubsub;
using ::google::cloud::future;
using ::google::cloud::StatusOr;
return [](pubsub::Subscriber subscriber) {
auto session = subscriber.Subscribe(
[](pubsub::Message const& m, pubsub::AckHandler h) {
std::cout << "Message contents: " << m.data() << "\n";
std::move(h).ack();
});
return session;
}namespace pubsub = ::google::cloud::pubsub;
using ::google::cloud::future;
using ::google::cloud::StatusOr;
return [](pubsub::Subscriber subscriber) {
auto session = subscriber.Subscribe(
[](pubsub::Message const& m, pubsub::AckHandler h) {
google::cloud::pubsub::samples::State state;
state.ParseFromString(std::string{m.data()});
std::cout << "Message contents: " << state.DebugString() << "\n";
std::move(h).ack();
});
return session;
}C#
Prima di provare questo esempio, segui le istruzioni di configurazione di C# nella Guida rapida sull'utilizzo delle librerie client. Per ulteriori informazioni, consulta la documentazione di riferimento dell'API C# di Pub/Sub.
Avro
using Avro.IO;
using Avro.Specific;
using Google.Api.Gax;
using Google.Cloud.PubSub.V1;
using Newtonsoft.Json;
using System;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
public class PullAvroMessagesAsyncSample
{
public async Task<int> PullAvroMessagesAsync(string projectId, string subscriptionId, bool acknowledge)
{
SubscriptionName subscriptionName = SubscriptionName.FromProjectSubscription(projectId, subscriptionId);
int messageCount = 0;
SubscriberClient subscriber = await new SubscriberClientBuilder
{
SubscriptionName = subscriptionName,
Settings = new SubscriberClient.Settings
{
AckExtensionWindow = TimeSpan.FromSeconds(4),
AckDeadline = TimeSpan.FromSeconds(10),
FlowControlSettings = new FlowControlSettings(maxOutstandingElementCount: 100, maxOutstandingByteCount: 10240)
}
}.BuildAsync();
// SubscriberClient runs your message handle function on multiple
// threads to maximize throughput.
Task startTask = subscriber.StartAsync((PubsubMessage message, CancellationToken cancel) =>
{
string encoding = message.Attributes["googclient_schemaencoding"];
AvroUtilities.State state = new AvroUtilities.State();
switch (encoding)
{
case "BINARY":
using (var ms = new MemoryStream(message.Data.ToByteArray()))
{
var decoder = new BinaryDecoder(ms);
var reader = new SpecificDefaultReader(state.Schema, state.Schema);
reader.Read<AvroUtilities.State>(state, decoder);
}
break;
case "JSON":
state = JsonConvert.DeserializeObject<AvroUtilities.State>(message.Data.ToStringUtf8());
break;
default:
Console.WriteLine($"Encoding not provided in message.");
break;
}
Console.WriteLine($"Message {message.MessageId}: {state}");
Interlocked.Increment(ref messageCount);
return Task.FromResult(acknowledge ? SubscriberClient.Reply.Ack : SubscriberClient.Reply.Nack);
});
// Run for 5 seconds.
await Task.Delay(5000);
await subscriber.StopAsync(CancellationToken.None);
// Lets make sure that the start task finished successfully after the call to stop.
await startTask;
return messageCount;
}
}
using Google.Api.Gax;
using Google.Cloud.PubSub.V1;
using System;
using System.Threading;
using System.Threading.Tasks;
public class PullProtoMessagesAsyncSample
{
public async Task<int> PullProtoMessagesAsync(string projectId, string subscriptionId, bool acknowledge)
{
SubscriptionName subscriptionName = SubscriptionName.FromProjectSubscription(projectId, subscriptionId);
int messageCount = 0;
SubscriberClient subscriber = await new SubscriberClientBuilder
{
SubscriptionName = subscriptionName,
Settings = new SubscriberClient.Settings
{
AckExtensionWindow = TimeSpan.FromSeconds(4),
AckDeadline = TimeSpan.FromSeconds(10),
FlowControlSettings = new FlowControlSettings(maxOutstandingElementCount: 100, maxOutstandingByteCount: 10240)
}
}.BuildAsync();
// SubscriberClient runs your message handle function on multiple
// threads to maximize throughput.
Task startTask = subscriber.StartAsync((PubsubMessage message, CancellationToken cancel) =>
{
string encoding = message.Attributes["googclient_schemaencoding"];
Utilities.State state = null;
switch (encoding)
{
case "BINARY":
state = Utilities.State.Parser.ParseFrom(message.Data.ToByteArray());
break;
case "JSON":
state = Utilities.State.Parser.ParseJson(message.Data.ToStringUtf8());
break;
default:
Console.WriteLine($"Encoding not provided in message.");
break;
}
Console.WriteLine($"Message {message.MessageId}: {state}");
Interlocked.Increment(ref messageCount);
return Task.FromResult(acknowledge ? SubscriberClient.Reply.Ack : SubscriberClient.Reply.Nack);
});
// Run for 5 seconds.
await Task.Delay(5000);
await subscriber.StopAsync(CancellationToken.None);
// Lets make sure that the start task finished successfully after the call to stop.
await startTask;
return messageCount;
}
}Go
Prima di provare questo esempio, segui le istruzioni di configurazione di Go nella Guida rapida sull'utilizzo delle librerie client. Per ulteriori informazioni, consulta la documentazione di riferimento dell'API Go Pub/Sub.
Avroimport (
"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
}
import (
"context"
"fmt"
"io"
"sync"
"time"
"cloud.google.com/go/pubsub"
statepb "github.com/GoogleCloudPlatform/golang-samples/internal/pubsub/schemas"
"google.golang.org/protobuf/encoding/protojson"
"google.golang.org/protobuf/proto"
)
func subscribeWithProtoSchema(w io.Writer, projectID, subID, protoFile string) error {
// projectID := "my-project-id"
// subID := "my-sub"
// protoFile = "path/to/a/proto/schema/file(.proto)/formatted/in/protocol/buffers"
ctx := context.Background()
client, err := pubsub.NewClient(ctx, projectID)
if err != nil {
return fmt.Errorf("pubsub.NewClient: %w", err)
}
// Create an instance of the message to be decoded (a single U.S. state).
state := &statepb.State{}
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"]
if encoding == "BINARY" {
if err := proto.Unmarshal(msg.Data, state); err != nil {
fmt.Fprintf(w, "proto.Unmarshal err: %v\n", err)
msg.Nack()
return
}
fmt.Printf("Received a binary-encoded message:\n%#v\n", state)
} else if encoding == "JSON" {
if err := protojson.Unmarshal(msg.Data, state); err != nil {
fmt.Fprintf(w, "proto.Unmarshal err: %v\n", err)
msg.Nack()
return
}
fmt.Fprintf(w, "Received a JSON-encoded message:\n%#v\n", state)
} 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.PostAbbr)
msg.Ack()
})
return nil
}
Java
Prima di provare questo esempio, segui le istruzioni di configurazione di Go nella Guida rapida sull'utilizzo delle librerie client. Per ulteriori informazioni, consulta la documentazione di riferimento dell'API Go Pub/Sub.
Avro
import com.google.cloud.pubsub.v1.AckReplyConsumer;
import com.google.cloud.pubsub.v1.MessageReceiver;
import com.google.cloud.pubsub.v1.Subscriber;
import com.google.protobuf.ByteString;
import com.google.pubsub.v1.ProjectSubscriptionName;
import com.google.pubsub.v1.PubsubMessage;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import org.apache.avro.io.Decoder;
import org.apache.avro.io.DecoderFactory;
import org.apache.avro.specific.SpecificDatumReader;
import utilities.State;
public class SubscribeWithAvroSchemaExample {
public static void main(String... args) throws Exception {
// TODO(developer): Replace these variables before running the sample.
String projectId = "your-project-id";
// Use an existing subscription.
String subscriptionId = "your-subscription-id";
subscribeWithAvroSchemaExample(projectId, subscriptionId);
}
public static void subscribeWithAvroSchemaExample(String projectId, String subscriptionId) {
ProjectSubscriptionName subscriptionName =
ProjectSubscriptionName.of(projectId, subscriptionId);
// Prepare a reader for the encoded Avro records.
SpecificDatumReader<State> reader = new SpecificDatumReader<>(State.getClassSchema());
// Instantiate an asynchronous message receiver.
MessageReceiver receiver =
(PubsubMessage message, AckReplyConsumer consumer) -> {
ByteString data = message.getData();
// Get the schema encoding type.
String encoding = message.getAttributesMap().get("googclient_schemaencoding");
// Send the message data to a byte[] input stream.
InputStream inputStream = new ByteArrayInputStream(data.toByteArray());
Decoder decoder = null;
// Prepare an appropriate decoder for the message data in the input stream
// based on the schema encoding type.
block:
try {
switch (encoding) {
case "BINARY":
decoder = DecoderFactory.get().directBinaryDecoder(inputStream, /*reuse=*/ null);
System.out.println("Receiving a binary-encoded message:");
break;
case "JSON":
decoder = DecoderFactory.get().jsonDecoder(State.getClassSchema(), inputStream);
System.out.println("Receiving a JSON-encoded message:");
break;
default:
break block;
}
// Obtain an object of the generated Avro class using the decoder.
State state = reader.read(null, decoder);
System.out.println(state.getName() + " is abbreviated as " + state.getPostAbbr());
} catch (IOException e) {
System.err.println(e);
}
// Ack the message.
consumer.ack();
};
Subscriber subscriber = null;
try {
subscriber = Subscriber.newBuilder(subscriptionName, receiver).build();
subscriber.startAsync().awaitRunning();
System.out.printf("Listening for messages on %s:\n", subscriptionName.toString());
subscriber.awaitTerminated(30, TimeUnit.SECONDS);
} catch (TimeoutException timeoutException) {
subscriber.stopAsync();
}
}
}
import com.google.cloud.pubsub.v1.AckReplyConsumer;
import com.google.cloud.pubsub.v1.MessageReceiver;
import com.google.cloud.pubsub.v1.Subscriber;
import com.google.protobuf.ByteString;
import com.google.protobuf.InvalidProtocolBufferException;
import com.google.protobuf.util.JsonFormat;
import com.google.pubsub.v1.ProjectSubscriptionName;
import com.google.pubsub.v1.PubsubMessage;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import utilities.StateProto.State;
public class SubscribeWithProtoSchemaExample {
public static void main(String... args) throws Exception {
// TODO(developer): Replace these variables before running the sample.
String projectId = "your-project-id";
// Use an existing subscription.
String subscriptionId = "your-subscription-id";
subscribeWithProtoSchemaExample(projectId, subscriptionId);
}
public static void subscribeWithProtoSchemaExample(String projectId, String subscriptionId) {
ProjectSubscriptionName subscriptionName =
ProjectSubscriptionName.of(projectId, subscriptionId);
MessageReceiver receiver =
(PubsubMessage message, AckReplyConsumer consumer) -> {
ByteString data = message.getData();
// Get the schema encoding type.
String encoding = message.getAttributesMap().get("googclient_schemaencoding");
block:
try {
switch (encoding) {
case "BINARY":
// Obtain an object of the generated proto class.
State state = State.parseFrom(data);
System.out.println("Received a BINARY-formatted message: " + state);
break;
case "JSON":
State.Builder stateBuilder = State.newBuilder();
JsonFormat.parser().merge(data.toStringUtf8(), stateBuilder);
System.out.println("Received a JSON-formatted message:" + stateBuilder.build());
break;
default:
break block;
}
} catch (InvalidProtocolBufferException e) {
e.printStackTrace();
}
consumer.ack();
System.out.println("Ack'ed the message");
};
// Create subscriber client.
Subscriber subscriber = Subscriber.newBuilder(subscriptionName, receiver).build();
try {
subscriber.startAsync().awaitRunning();
System.out.printf("Listening for messages on %s:\n", subscriptionName);
subscriber.awaitTerminated(30, TimeUnit.SECONDS);
} catch (TimeoutException timeoutException) {
subscriber.stopAsync();
}
}
}Node.js
Prima di provare questo esempio, segui le istruzioni di configurazione di Node.js in Guida rapida sull'utilizzo delle librerie client. Per ulteriori informazioni, consulta la documentazione di riferimento dell'API Node.js Pub/Sub.
Avro/**
* TODO(developer): Uncomment these variables before running the sample.
*/
// const subscriptionNameOrId = 'YOUR_SUBSCRIPTION_NAME_OR_ID';
// const timeout = 60;
// Imports the Google Cloud client library
const {PubSub, Schema, Encodings} = require('@google-cloud/pubsub');
// Node FS library, to load definitions
const fs = require('fs');
// And the Apache Avro library
const avro = require('avro-js');
// Creates a client; cache this for further use
const pubSubClient = new PubSub();
function listenForAvroRecords(subscriptionNameOrId, timeout) {
// References an existing subscription
const subscription = pubSubClient.subscription(subscriptionNameOrId);
// Make an encoder using the official avro-js library.
const definition = fs
.readFileSync('system-test/fixtures/provinces.avsc')
.toString();
const type = avro.parse(definition);
// Create an event handler to handle messages
let messageCount = 0;
const messageHandler = async message => {
// "Ack" (acknowledge receipt of) the message
message.ack();
// Get the schema metadata from the message.
const schemaMetadata = Schema.metadataFromMessage(message.attributes);
let result;
switch (schemaMetadata.encoding) {
case Encodings.Binary:
result = type.fromBuffer(message.data);
break;
case Encodings.Json:
result = type.fromString(message.data.toString());
break;
default:
console.log(`Unknown schema encoding: ${schemaMetadata.encoding}`);
break;
}
console.log(`Received message ${message.id}:`);
console.log(`\tData: ${JSON.stringify(result, null, 4)}`);
console.log(`\tAttributes: ${message.attributes}`);
messageCount += 1;
};
// Listen for new messages until timeout is hit
subscription.on('message', messageHandler);
setTimeout(() => {
subscription.removeListener('message', messageHandler);
console.log(`${messageCount} message(s) received.`);
}, timeout * 1000);
}/**
* TODO(developer): Uncomment these variables before running the sample.
*/
// const subscriptionNameOrId = 'YOUR_SUBSCRIPTION_NAME_OR_ID';
// const timeout = 60;
// Imports the Google Cloud client library
const {PubSub, Schema, Encodings} = require('@google-cloud/pubsub');
// And the protobufjs library
const protobuf = require('protobufjs');
// Creates a client; cache this for further use
const pubSubClient = new PubSub();
async function listenForProtobufMessages(subscriptionNameOrId, timeout) {
// References an existing subscription
const subscription = pubSubClient.subscription(subscriptionNameOrId);
// Make an decoder using the protobufjs library.
//
// Since we're providing the test message for a specific schema here, we'll
// also code in the path to a sample proto definition.
const root = protobuf.loadSync('system-test/fixtures/provinces.proto');
const Province = root.lookupType('utilities.Province');
// Create an event handler to handle messages
let messageCount = 0;
const messageHandler = async message => {
// "Ack" (acknowledge receipt of) the message
message.ack();
// Get the schema metadata from the message.
const schemaMetadata = Schema.metadataFromMessage(message.attributes);
let result;
switch (schemaMetadata.encoding) {
case Encodings.Binary:
result = Province.decode(message.data);
break;
case Encodings.Json:
// This doesn't require decoding with the protobuf library,
// since it's plain JSON. But you can still validate it against
// your schema.
result = JSON.parse(message.data.toString());
console.log(`Validation of JSON: ${Province.verify(result)}`);
break;
default:
console.log(`Unknown schema encoding: ${schemaMetadata.encoding}`);
break;
}
console.log(`Received message ${message.id}:`);
console.log(`\tData: ${JSON.stringify(result, null, 4)}`);
console.log(`\tAttributes: ${JSON.stringify(message.attributes, null, 4)}`);
messageCount += 1;
};
// Listen for new messages until timeout is hit
subscription.on('message', messageHandler);
setTimeout(() => {
subscription.removeListener('message', messageHandler);
console.log(`${messageCount} message(s) received.`);
}, timeout * 1000);
}Node.js
Prima di provare questo esempio, segui le istruzioni di configurazione di Node.js in Guida rapida sull'utilizzo delle librerie client. Per ulteriori informazioni, consulta la documentazione di riferimento dell'API Node.js Pub/Sub.
Avro/**
* TODO(developer): Uncomment these variables before running the sample.
*/
// const subscriptionNameOrId = 'YOUR_SUBSCRIPTION_NAME_OR_ID';
// const timeout = 60;
// Imports the Google Cloud client library
import {PubSub, Schema, Encodings, Message} from '@google-cloud/pubsub';
// Node FS library, to load definitions
import * as fs from 'fs';
// And the Apache Avro library
import * as avro from 'avro-js';
// Creates a client; cache this for further use
const pubSubClient = new PubSub();
function listenForAvroRecords(subscriptionNameOrId: string, timeout: number) {
// References an existing subscription
const subscription = pubSubClient.subscription(subscriptionNameOrId);
// Make an encoder using the official avro-js library.
const definition = fs
.readFileSync('system-test/fixtures/provinces.avsc')
.toString();
const type = avro.parse(definition);
// Create an event handler to handle messages
let messageCount = 0;
const messageHandler = async (message: Message) => {
// "Ack" (acknowledge receipt of) the message
message.ack();
// Get the schema metadata from the message.
const schemaMetadata = Schema.metadataFromMessage(message.attributes);
let result: object | undefined;
switch (schemaMetadata.encoding) {
case Encodings.Binary:
result = type.fromBuffer(message.data);
break;
case Encodings.Json:
result = type.fromString(message.data.toString());
break;
default:
console.log(`Unknown schema encoding: ${schemaMetadata.encoding}`);
break;
}
console.log(`Received message ${message.id}:`);
console.log(`\tData: ${JSON.stringify(result, null, 4)}`);
console.log(`\tAttributes: ${message.attributes}`);
messageCount += 1;
};
// Listen for new messages until timeout is hit
subscription.on('message', messageHandler);
setTimeout(() => {
subscription.removeListener('message', messageHandler);
console.log(`${messageCount} message(s) received.`);
}, timeout * 1000);
}/**
* TODO(developer): Uncomment these variables before running the sample.
*/
// const subscriptionNameOrId = 'YOUR_SUBSCRIPTION_NAME_OR_ID';
// const timeout = 60;
// Imports the Google Cloud client library
import {PubSub, Schema, Encodings, Message} from '@google-cloud/pubsub';
// And the protobufjs library
import * as protobuf from 'protobufjs';
// Creates a client; cache this for further use
const pubSubClient = new PubSub();
async function listenForProtobufMessages(
subscriptionNameOrId: string,
timeout: number
) {
// References an existing subscription
const subscription = pubSubClient.subscription(subscriptionNameOrId);
// Make an decoder using the protobufjs library.
//
// Since we're providing the test message for a specific schema here, we'll
// also code in the path to a sample proto definition.
const root = protobuf.loadSync('system-test/fixtures/provinces.proto');
const Province = root.lookupType('utilities.Province');
// Create an event handler to handle messages
let messageCount = 0;
const messageHandler = async (message: Message) => {
// "Ack" (acknowledge receipt of) the message
message.ack();
// Get the schema metadata from the message.
const schemaMetadata = Schema.metadataFromMessage(message.attributes);
let result;
switch (schemaMetadata.encoding) {
case Encodings.Binary:
result = Province.decode(message.data);
break;
case Encodings.Json:
// This doesn't require decoding with the protobuf library,
// since it's plain JSON. But you can still validate it against
// your schema.
result = JSON.parse(message.data.toString());
console.log(`Validation of JSON: ${Province.verify(result)}`);
break;
default:
console.log(`Unknown schema encoding: ${schemaMetadata.encoding}`);
break;
}
console.log(`Received message ${message.id}:`);
console.log(`\tData: ${JSON.stringify(result, null, 4)}`);
console.log(`\tAttributes: ${JSON.stringify(message.attributes, null, 4)}`);
messageCount += 1;
};
// Listen for new messages until timeout is hit
subscription.on('message', messageHandler);
setTimeout(() => {
subscription.removeListener('message', messageHandler);
console.log(`${messageCount} message(s) received.`);
}, timeout * 1000);
}PHP
Prima di provare questo esempio, segui le istruzioni di configurazione PHP nella Guida rapida sull'utilizzo delle librerie client. Per ulteriori informazioni, consulta la documentazione di riferimento dell'API PHP Pub/Sub.
Avrouse Google\Cloud\PubSub\PubSubClient;
/**
* Subscribe and pull messages using an AVRO schema.
*
* @param string $projectId
* @param string $subscriptionId
*/
function subscribe_avro_records($projectId, $subscriptionId, $definitionFile)
{
$pubsub = new PubSubClient([
'projectId' => $projectId,
]);
$subscription = $pubsub->subscription($subscriptionId);
$definition = file_get_contents($definitionFile);
$messages = $subscription->pull();
foreach ($messages as $message) {
$decodedMessageData = '';
$encoding = $message->attribute('googclient_schemaencoding');
switch ($encoding) {
case 'BINARY':
$io = new \AvroStringIO($message->data());
$schema = \AvroSchema::parse($definition);
$reader = new \AvroIODatumReader($schema);
$decoder = new \AvroIOBinaryDecoder($io);
$decodedMessageData = json_encode($reader->read($decoder));
break;
case 'JSON':
$decodedMessageData = $message->data();
break;
}
printf('Received a %d-encoded message %s', $encoding, $decodedMessageData);
}
}use Google\Cloud\PubSub\PubSubClient;
/**
* Subscribe and pull messages using a protocol buffer schema.
*
* Relies on a proto message of the following form:
* ```
* syntax = "proto3";
*
* package utilities;
*
* message StateProto {
* string name = 1;
* string post_abbr = 2;
* }
* ```
*
* @param string $projectId
* @param string $subscriptionId
*/
function subscribe_proto_messages($projectId, $subscriptionId)
{
$pubsub = new PubSubClient([
'projectId' => $projectId,
]);
$subscription = $pubsub->subscription($subscriptionId);
$messages = $subscription->pull();
foreach ($messages as $message) {
$decodedMessageData = '';
$encoding = $message->attribute('googclient_schemaencoding');
switch ($encoding) {
case 'BINARY':
$protobufMessage = new \Utilities\StateProto();
$protobufMessage->mergeFromString($message->data());
$decodedMessageData = $protobufMessage->serializeToJsonString();
break;
case 'JSON':
$decodedMessageData = $message->data();
break;
}
printf('Received a %d-encoded message %s', $encoding, $decodedMessageData);
}
}Python
Prima di provare questo esempio, segui le istruzioni di configurazione di Python in Guida rapida sull'utilizzo delle librerie client. Per ulteriori informazioni, consulta la documentazione di riferimento dell'API Python Pub/Sub.
Avroimport avro.schema as schema
from avro.io import BinaryDecoder, DatumReader
from concurrent.futures import TimeoutError
import io
import json
from google.cloud.pubsub import SubscriberClient
# TODO(developer)
# project_id = "your-project-id"
# subscription_id = "your-subscription-id"
# avsc_file = "path/to/an/avro/schema/file/(.avsc)/formatted/in/json"
# Number of seconds the subscriber listens for messages
# timeout = 5.0
subscriber = SubscriberClient()
subscription_path = subscriber.subscription_path(project_id, subscription_id)
with open(avsc_file, "rb") as file:
avro_schema = schema.parse(file.read())
def callback(message: pubsub_v1.subscriber.message.Message) -> None:
# Get the message serialization type.
encoding = message.attributes.get("googclient_schemaencoding")
# Deserialize the message data accordingly.
if encoding == "BINARY":
bout = io.BytesIO(message.data)
decoder = BinaryDecoder(bout)
reader = DatumReader(avro_schema)
message_data = reader.read(decoder)
print(f"Received a binary-encoded message:\n{message_data}")
elif encoding == "JSON":
message_data = json.loads(message.data)
print(f"Received a JSON-encoded message:\n{message_data}")
else:
print(f"Received a message with no encoding:\n{message}")
message.ack()
streaming_pull_future = subscriber.subscribe(subscription_path, callback=callback)
print(f"Listening for messages on {subscription_path}..\n")
# Wrap subscriber in a 'with' block to automatically call close() when done.
with subscriber:
try:
# When `timeout` is not set, result() will block indefinitely,
# unless an exception occurs first.
streaming_pull_future.result(timeout=timeout)
except TimeoutError:
streaming_pull_future.cancel() # Trigger the shutdown.
streaming_pull_future.result() # Block until the shutdown is complete.from concurrent.futures import TimeoutError
from google.cloud.pubsub import SubscriberClient
from google.protobuf.json_format import Parse
from utilities import us_states_pb2
# TODO(developer)
# project_id = "your-project-id"
# subscription_id = "your-subscription-id"
# Number of seconds the subscriber listens for messages
# timeout = 5.0
subscriber = SubscriberClient()
subscription_path = subscriber.subscription_path(project_id, subscription_id)
# Instantiate a protoc-generated class defined in `us-states.proto`.
state = us_states_pb2.StateProto()
def callback(message: pubsub_v1.subscriber.message.Message) -> None:
# Get the message serialization type.
encoding = message.attributes.get("googclient_schemaencoding")
# Deserialize the message data accordingly.
if encoding == "BINARY":
state.ParseFromString(message.data)
print(f"Received a binary-encoded message:\n{state}")
elif encoding == "JSON":
Parse(message.data, state)
print(f"Received a JSON-encoded message:\n{state}")
else:
print(f"Received a message with no encoding:\n{message}")
message.ack()
streaming_pull_future = subscriber.subscribe(subscription_path, callback=callback)
print(f"Listening for messages on {subscription_path}..\n")
# Wrap subscriber in a 'with' block to automatically call close() when done.
with subscriber:
try:
# When `timeout` is not set, result() will block indefinitely,
# unless an exception occurs first.
streaming_pull_future.result(timeout=timeout)
except TimeoutError:
streaming_pull_future.cancel() # Trigger the shutdown.
streaming_pull_future.result() # Block until the shutdown is complete.Ruby
Prima di provare questo esempio, segui le istruzioni di configurazione di Ruby riportate in Guida rapida sull'utilizzo delle librerie client. Per ulteriori informazioni, consulta la documentazione di riferimento dell'API Ruby Pub/Sub.
Avro# subscription_id = "your-subscription-id"
# avsc_file = "path/to/an/avro/schema/file/(.avsc)/formatted/in/json"
pubsub = Google::Cloud::Pubsub.new
subscription = pubsub.subscription subscription_id
subscriber = subscription.listen do |received_message|
encoding = received_message.attributes["googclient_schemaencoding"]
case encoding
when "BINARY"
require "avro"
avro_schema = Avro::Schema.parse File.read(avsc_file)
buffer = StringIO.new received_message.data
decoder = Avro::IO::BinaryDecoder.new buffer
reader = Avro::IO::DatumReader.new avro_schema
message_data = reader.read decoder
puts "Received a binary-encoded message:\n#{message_data}"
when "JSON"
require "json"
message_data = JSON.parse received_message.data
puts "Received a JSON-encoded message:\n#{message_data}"
else
"Received a message with no encoding:\n#{received_message.message_id}"
end
received_message.acknowledge!
end
subscriber.start
# Let the main thread sleep for 60 seconds so the thread for listening
# messages does not quit
sleep 60
subscriber.stop.wait!# subscription_id = "your-subscription-id"
pubsub = Google::Cloud::Pubsub.new
subscription = pubsub.subscription subscription_id
subscriber = subscription.listen do |received_message|
encoding = received_message.attributes["googclient_schemaencoding"]
case encoding
when "BINARY"
state = Utilities::StateProto.decode received_message.data
puts "Received a binary-encoded message:\n#{state}"
when "JSON"
require "json"
state = Utilities::StateProto.decode_json received_message.data
puts "Received a JSON-encoded message:\n#{state}"
else
"Received a message with no encoding:\n#{received_message.message_id}"
end
received_message.acknowledge!
end
subscriber.start
# Let the main thread sleep for 60 seconds so the thread for listening
# messages does not quit
sleep 60
subscriber.stop.wait!Iscriviti a un argomento associato a uno schema Avro con revisioni
Avro richiede l'analisi dei messaggi utilizzando lo schema con cui sono codificati. Puoi anche tradurre i messaggi in uno schema diverso utilizzando la risoluzione dello schema Avro.
Pub/Sub garantisce che tutte le revisioni dello schema siano compatibili con le versioni precedenti e precedenti. Questa compatibilità consente a qualsiasi revisione di essere utilizzata come schema di lettore o autore.
Durante l'analisi di un messaggio codificato con una revisione dello schema diversa da quella utilizzata dal tuo sottoscrittore, potrebbe essere necessario recuperare lo schema originale e passarlo come schema del writer.
È preferibile memorizzare nella cache l'oggetto del lettore Avro in grado di analizzare i messaggi per
ogni revisione dello schema rilevata al fine di ridurre al minimo la latenza
e ridurre al minimo il numero di chiamate all'API GetSchema.
Il seguente codice mostra queste funzioni:
Leggi gli attributi descritti nella sezione precedente per determinare quale revisione dello schema viene utilizzata per codificare il messaggio.
Recupera la revisione dello schema e memorizza nella cache un lettore generato con questo metodo.
Analizza il messaggio nello schema utilizzato dal tuo sottoscrittore.
Go
Prima di provare questo esempio, segui le istruzioni di configurazione di Go nella Guida rapida sull'utilizzo delle librerie client. Per ulteriori informazioni, consulta la documentazione di riferimento dell'API Go Pub/Sub.
import (
"context"
"fmt"
"io"
"strings"
"sync"
"time"
"cloud.google.com/go/pubsub"
"github.com/linkedin/goavro/v2"
)
func subscribeWithAvroSchemaRevisions(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)
}
schemaClient, err := pubsub.NewSchemaClient(ctx, projectID)
if err != nil {
return fmt.Errorf("pubsub.NewSchemaClient: %w", err)
}
// Create the cache for the codecs for different revision IDs.
revisionCodecs := make(map[string]*goavro.Codec)
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()
name := msg.Attributes["googclient_schemaname"]
revision := msg.Attributes["googclient_schemarevisionid"]
codec, ok := revisionCodecs[revision]
// If the codec doesn't exist in the map, this is the first time we
// are seeing this revision. We need to fetch the schema and cache the
// codec. It would be more typical to do this asynchronously, but is
// shown here in a synchronous way to ease readability.
if !ok {
// Extract just the schema resource name
path := strings.Split(name, "/")
name = path[len(path)-1]
schema, err := schemaClient.Schema(ctx, fmt.Sprintf("%s@%s", name, revision), pubsub.SchemaViewFull)
if err != nil {
fmt.Fprintf(w, "Nacking, cannot read message without schema: %v\n", err)
msg.Nack()
return
}
codec, err = goavro.NewCodec(schema.Definition)
if err != nil {
msg.Nack()
fmt.Fprintf(w, "goavro.NewCodec err: %v\n", err)
}
revisionCodecs[revision] = codec
}
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
}
Java
Prima di provare questo esempio, segui le istruzioni di configurazione Java in Guida rapida sull'utilizzo delle librerie client. Per ulteriori informazioni, consulta la documentazione di riferimento dell'API Java Pub/Sub.
import com.google.cloud.pubsub.v1.AckReplyConsumer;
import com.google.cloud.pubsub.v1.MessageReceiver;
import com.google.cloud.pubsub.v1.SchemaServiceClient;
import com.google.cloud.pubsub.v1.Subscriber;
import com.google.protobuf.ByteString;
import com.google.pubsub.v1.ProjectSubscriptionName;
import com.google.pubsub.v1.PubsubMessage;
import com.google.pubsub.v1.Schema;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import org.apache.avro.io.Decoder;
import org.apache.avro.io.DecoderFactory;
import org.apache.avro.specific.SpecificDatumReader;
import utilities.State;
public class SubscribeWithAvroSchemaRevisionsExample {
public static void main(String... args) throws Exception {
// TODO(developer): Replace these variables before running the sample.
String projectId = "your-project-id";
// Use an existing subscription.
String subscriptionId = "your-subscription-id";
subscribeWithAvroSchemaRevisionsExample(projectId, subscriptionId);
}
static SchemaServiceClient getSchemaServiceClient() {
try {
return SchemaServiceClient.create();
} catch (IOException e) {
System.out.println("Could not get schema client: " + e);
return null;
}
}
public static void subscribeWithAvroSchemaRevisionsExample(
String projectId, String subscriptionId) {
// Used to get the schemas for revsions.
final SchemaServiceClient schemaServiceClient = getSchemaServiceClient();
if (schemaServiceClient == null) {
return;
}
// Cache for the readers for different revision IDs.
Map<String, SpecificDatumReader<State>> revisionReaders =
new HashMap<String, SpecificDatumReader<State>>();
ProjectSubscriptionName subscriptionName =
ProjectSubscriptionName.of(projectId, subscriptionId);
// Instantiate an asynchronous message receiver.
MessageReceiver receiver =
(PubsubMessage message, AckReplyConsumer consumer) -> {
// Get the schema encoding type.
String name = message.getAttributesMap().get("googclient_schemaname");
String revision = message.getAttributesMap().get("googclient_schemarevisionid");
SpecificDatumReader<State> reader = null;
synchronized (revisionReaders) {
reader = revisionReaders.get(revision);
}
if (reader == null) {
// This is the first time we are seeing this revision. We need to
// fetch the schema and cache its decoder. It would be more typical
// to do this asynchronously, but is shown here in a synchronous
// way to ease readability.
try {
Schema schema = schemaServiceClient.getSchema(name + "@" + revision);
org.apache.avro.Schema avroSchema =
new org.apache.avro.Schema.Parser().parse(schema.getDefinition());
reader = new SpecificDatumReader<State>(avroSchema, State.getClassSchema());
synchronized (revisionReaders) {
revisionReaders.put(revision, reader);
}
} catch (Exception e) {
System.out.println("Could not get schema: " + e);
// Without the schema, we cannot read the message, so nack it.
consumer.nack();
return;
}
}
ByteString data = message.getData();
// Send the message data to a byte[] input stream.
InputStream inputStream = new ByteArrayInputStream(data.toByteArray());
String encoding = message.getAttributesMap().get("googclient_schemaencoding");
Decoder decoder = null;
// Prepare an appropriate decoder for the message data in the input stream
// based on the schema encoding type.
try {
switch (encoding) {
case "BINARY":
decoder = DecoderFactory.get().directBinaryDecoder(inputStream, /*reuse=*/ null);
System.out.println("Receiving a binary-encoded message:");
break;
case "JSON":
decoder = DecoderFactory.get().jsonDecoder(State.getClassSchema(), inputStream);
System.out.println("Receiving a JSON-encoded message:");
break;
default:
System.out.println("Unknown message type; nacking.");
consumer.nack();
break;
}
// Obtain an object of the generated Avro class using the decoder.
State state = reader.read(null, decoder);
System.out.println(state.getName() + " is abbreviated as " + state.getPostAbbr());
// Ack the message.
consumer.ack();
} catch (IOException e) {
System.err.println(e);
// If we failed to process the message, nack it.
consumer.nack();
}
};
Subscriber subscriber = null;
try {
subscriber = Subscriber.newBuilder(subscriptionName, receiver).build();
subscriber.startAsync().awaitRunning();
System.out.printf("Listening for messages on %s:\n", subscriptionName.toString());
subscriber.awaitTerminated(30, TimeUnit.SECONDS);
} catch (TimeoutException timeoutException) {
subscriber.stopAsync();
}
}
}Python
Prima di provare questo esempio, segui le istruzioni di configurazione di Python in Guida rapida sull'utilizzo delle librerie client. Per ulteriori informazioni, consulta la documentazione di riferimento dell'API Python Pub/Sub.
import avro.schema as schema
from avro.io import BinaryDecoder, DatumReader
from concurrent.futures import TimeoutError
import io
import json
from google.api_core.exceptions import NotFound
from google.cloud.pubsub import SchemaServiceClient, SubscriberClient
schema_client = SchemaServiceClient()
# TODO(developer)
# project_id = "your-project-id"
# subscription_id = "your-subscription-id"
# avsc_file = "path/to/an/avro/schema/file/(.avsc)/formatted/in/json"
# Number of seconds the subscriber listens for messages
# timeout = 5.0
subscriber = SubscriberClient()
subscription_path = subscriber.subscription_path(project_id, subscription_id)
with open(avsc_file, "rb") as file:
reader_avro_schema = schema.parse(file.read())
# Dict to keep readers for different schema revisions.
revisions_to_readers = {}
def callback(message: pubsub_v1.subscriber.message.Message) -> None:
# Get the message serialization type.
schema_name = message.attributes.get("googclient_schemaname")
schema_revision_id = message.attributes.get("googclient_schemarevisionid")
encoding = message.attributes.get("googclient_schemaencoding")
if schema_revision_id not in revisions_to_readers:
schema_path = schema_name + "@" + schema_revision_id
try:
received_avro_schema = schema_client.get_schema(
request={"name": schema_path}
)
except NotFound:
print(f"{schema_path} not found.")
message.nack()
return
writer_avro_schema = schema.parse(received_avro_schema.definition)
revisions_to_readers[schema_revision_id] = DatumReader(
writer_avro_schema, reader_avro_schema
)
reader = revisions_to_readers[schema_revision_id]
# Deserialize the message data accordingly.
if encoding == "BINARY":
bout = io.BytesIO(message.data)
decoder = BinaryDecoder(bout)
message_data = reader.read(decoder)
print(f"Received a binary-encoded message:\n{message_data}")
elif encoding == "JSON":
message_data = json.loads(message.data)
print(f"Received a JSON-encoded message:\n{message_data}")
else:
print(f"Received a message with no encoding:\n{message}")
message.nack()
message.ack()
streaming_pull_future = subscriber.subscribe(subscription_path, callback=callback)
print(f"Listening for messages on {subscription_path}..\n")
# Wrap subscriber in a 'with' block to automatically call close() when done.
with subscriber:
try:
# When `timeout` is not set, result() will block indefinitely,
# unless an exception occurs first.
streaming_pull_future.result(timeout=timeout)
except TimeoutError:
streaming_pull_future.cancel() # Trigger the shutdown.
streaming_pull_future.result() # Block until the shutdown is complete.Ruoli obbligatori
Per ottenere le autorizzazioni necessarie per convalidare un messaggio in base a uno schema, completa uno dei seguenti passaggi:
- Concedi uno dei seguenti ruoli predefiniti a un account di servizio:
roles/pubsub.admin,roles/pubsub.editororoles/pubsub.viewer. Crea un ruolo personalizzato per un account di servizio e aggiungi le seguenti autorizzazioni
pubsub.schemas.validateepubsub.schemas.get.Per saperne di più sui ruoli personalizzati, consulta Creare e gestire i ruoli IAM personalizzati.