与 AWS SDK StartLiveTail 配合使用

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以下代码示例演示如何使用 StartLiveTail。

.NET

AWS SDK for .NET

包含所需的文件。

using Amazon;
using Amazon.CloudWatchLogs;
using Amazon.CloudWatchLogs.Model;

启动 Live Tail 会话

            var client = new AmazonCloudWatchLogsClient();
            var request = new StartLiveTailRequest
            {
                LogGroupIdentifiers = logGroupIdentifiers,
                LogStreamNames = logStreamNames,
                LogEventFilterPattern = filterPattern,
            };

            var response = await client.StartLiveTailAsync(request);

            // Catch if request fails
            if (response.HttpStatusCode != System.Net.HttpStatusCode.OK)
            {
                Console.WriteLine("Failed to start live tail session");
                return;
            }

您可以通过两种方式处理 Live Tail 会话中的事件：

            /* Method 1
            * 1). Asynchronously loop through the event stream
            * 2). Set a timer to dispose the stream and stop the Live Tail session at the end.
            */
            var eventStream = response.ResponseStream;
            var task = Task.Run(() => 
            {
                foreach (var item in eventStream)
                {
                    if (item is LiveTailSessionUpdate liveTailSessionUpdate)
                    {
                        foreach (var sessionResult in liveTailSessionUpdate.SessionResults)
                        {
                            Console.WriteLine("Message : {0}", sessionResult.Message);
                        }
                    }
                    if (item is LiveTailSessionStart)
                    {
                        Console.WriteLine("Live Tail session started");
                    }
                    // On-stream exceptions are processed here
                    if (item is CloudWatchLogsEventStreamException)
                    {
                        Console.WriteLine($"ERROR: {item}");
                    }
                }
            });
            // Close the stream to stop the session after a timeout
            if (!task.Wait(TimeSpan.FromSeconds(10))){
                eventStream.Dispose();
                Console.WriteLine("End of line");
            }

            /* Method 2
            * 1). Add event handlers to each event variable
            * 2). Start processing the stream and wait for a timeout using AutoResetEvent
            */
            AutoResetEvent endEvent = new AutoResetEvent(false);
            var eventStream = response.ResponseStream;
            using (eventStream) // automatically disposes the stream to stop the session after execution finishes
            {
                eventStream.SessionStartReceived += (sender, e) =>
                {
                    Console.WriteLine("LiveTail session started");
                };
                eventStream.SessionUpdateReceived += (sender, e) =>
                {   
                    foreach (LiveTailSessionLogEvent logEvent in e.EventStreamEvent.SessionResults){
                        Console.WriteLine("Message: {0}", logEvent.Message);
                    }
                };
                // On-stream exceptions are captured here
                eventStream.ExceptionReceived += (sender, e) => 
                {
                    Console.WriteLine($"ERROR: {e.EventStreamException.Message}");
                };

                eventStream.StartProcessing();
                // Stream events for this amount of time.
                endEvent.WaitOne(TimeSpan.FromSeconds(10));
                Console.WriteLine("End of line");
            }

• 有关 API 的详细信息，请参阅 AWS SDK for .NET API 参考StartLiveTail中的。

Go

适用于 Go V2 的 SDK

包含所需的文件。

import (
	"context"
	"log"
	"time"

	"github.com/aws/aws-sdk-go-v2/config"
	"github.com/aws/aws-sdk-go-v2/service/cloudwatchlogs"
	"github.com/aws/aws-sdk-go-v2/service/cloudwatchlogs/types"
)

处理 Live Tail 会话中的事件。

func handleEventStreamAsync(stream *cloudwatchlogs.StartLiveTailEventStream) {
	eventsChan := stream.Events()
	for {
		event := <-eventsChan
		switch e := event.(type) {
		case *types.StartLiveTailResponseStreamMemberSessionStart:
			log.Println("Received SessionStart event")
		case *types.StartLiveTailResponseStreamMemberSessionUpdate:
			for _, logEvent := range e.Value.SessionResults {
				log.Println(*logEvent.Message)
			}
		default:
			// Handle on-stream exceptions
			if err := stream.Err(); err != nil {
				log.Fatalf("Error occured during streaming: %v", err)
			} else if event == nil {
				log.Println("Stream is Closed")
				return
			} else {
				log.Fatalf("Unknown event type: %T", e)
			}
		}
	}
}

启动 Live Tail 会话。

	cfg, err := config.LoadDefaultConfig(context.TODO())
	if err != nil {
		panic("configuration error, " + err.Error())
	}
	client := cloudwatchlogs.NewFromConfig(cfg)

	request := &cloudwatchlogs.StartLiveTailInput{
		LogGroupIdentifiers:   logGroupIdentifiers,
		LogStreamNames:        logStreamNames,
		LogEventFilterPattern: logEventFilterPattern,
	}

	response, err := client.StartLiveTail(context.TODO(), request)
	// Handle pre-stream Exceptions
	if err != nil {
		log.Fatalf("Failed to start streaming: %v", err)
	}

	// Start a Goroutine to handle events over stream
	stream := response.GetStream()
	go handleEventStreamAsync(stream)

经过一段时间后停止 Live Tail 会话。

	// Close the stream (which ends the session) after a timeout
	time.Sleep(10 * time.Second)
	stream.Close()
	log.Println("Event stream closed")

• 有关 API 的详细信息，请参阅 适用于 Go 的 AWS SDK API 参考StartLiveTail中的。

Java

适用于 Java 的 SDK 2.x

包含所需的文件。

import io.reactivex.FlowableSubscriber;
import io.reactivex.annotations.NonNull;
import org.reactivestreams.Subscription;
import software.amazon.awssdk.auth.credentials.ProfileCredentialsProvider;
import software.amazon.awssdk.services.cloudwatchlogs.CloudWatchLogsAsyncClient;
import software.amazon.awssdk.services.cloudwatchlogs.model.LiveTailSessionLogEvent;
import software.amazon.awssdk.services.cloudwatchlogs.model.LiveTailSessionStart;
import software.amazon.awssdk.services.cloudwatchlogs.model.LiveTailSessionUpdate;
import software.amazon.awssdk.services.cloudwatchlogs.model.StartLiveTailRequest;
import software.amazon.awssdk.services.cloudwatchlogs.model.StartLiveTailResponseHandler;
import software.amazon.awssdk.services.cloudwatchlogs.model.CloudWatchLogsException;
import software.amazon.awssdk.services.cloudwatchlogs.model.StartLiveTailResponseStream;

import java.util.Date;
import java.util.List;
import java.util.concurrent.atomic.AtomicReference;

处理 Live Tail 会话中的事件。

    private static StartLiveTailResponseHandler getStartLiveTailResponseStreamHandler(
            AtomicReference<Subscription> subscriptionAtomicReference) {
        return StartLiveTailResponseHandler.builder()
            .onResponse(r -> System.out.println("Received initial response"))
            .onError(throwable -> {
                CloudWatchLogsException e = (CloudWatchLogsException) throwable.getCause();
                System.err.println(e.awsErrorDetails().errorMessage());
                System.exit(1);
            })
            .subscriber(() -> new FlowableSubscriber<>() {
                @Override
                public void onSubscribe(@NonNull Subscription s) {
                    subscriptionAtomicReference.set(s);
                    s.request(Long.MAX_VALUE);
                }

                @Override
                public void onNext(StartLiveTailResponseStream event) {
                    if (event instanceof LiveTailSessionStart) {
                        LiveTailSessionStart sessionStart = (LiveTailSessionStart) event;
                        System.out.println(sessionStart);
                    } else if (event instanceof LiveTailSessionUpdate) {
                        LiveTailSessionUpdate sessionUpdate = (LiveTailSessionUpdate) event;
                        List<LiveTailSessionLogEvent> logEvents = sessionUpdate.sessionResults();
                        logEvents.forEach(e -> {
                            long timestamp = e.timestamp();
                            Date date = new Date(timestamp);
                            System.out.println("[" + date + "] " + e.message());
                        });
                    } else {
                        throw CloudWatchLogsException.builder().message("Unknown event type").build();
                    }
                }

                @Override
                public void onError(Throwable throwable) {
                    System.out.println(throwable.getMessage());
                    System.exit(1);
                }

                @Override
                public void onComplete() {
                    System.out.println("Completed Streaming Session");
                }
            })
            .build();
    }

启动 Live Tail 会话。

        CloudWatchLogsAsyncClient cloudWatchLogsAsyncClient =
                CloudWatchLogsAsyncClient.builder()
                    .credentialsProvider(ProfileCredentialsProvider.create())
                    .build();

        StartLiveTailRequest request =
                StartLiveTailRequest.builder()
                    .logGroupIdentifiers(logGroupIdentifiers)
                    .logStreamNames(logStreamNames)
                    .logEventFilterPattern(logEventFilterPattern)
                    .build();

        /* Create a reference to store the subscription */ 
        final AtomicReference<Subscription> subscriptionAtomicReference = new AtomicReference<>(null);

        cloudWatchLogsAsyncClient.startLiveTail(request, getStartLiveTailResponseStreamHandler(subscriptionAtomicReference));

经过一段时间后停止 Live Tail 会话。

        /* Set a timeout for the session and cancel the subscription. This will:
         * 1). Close the stream
         * 2). Stop the Live Tail session
         */
        try {
            Thread.sleep(10000);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
        if (subscriptionAtomicReference.get() != null) {
            subscriptionAtomicReference.get().cancel();
            System.out.println("Subscription to stream closed");
        }

• 有关 API 的详细信息，请参阅 AWS SDK for Java 2.x API 参考StartLiveTail中的。

JavaScript

适用于 JavaScript (v3) 的软件开发工具包

包含所需的文件。

import { CloudWatchLogsClient, StartLiveTailCommand } from "@aws-sdk/client-cloudwatch-logs";

处理 Live Tail 会话中的事件。

async function handleResponseAsync(response) {
    try {
      for await (const event of response.responseStream) {
        if (event.sessionStart !== undefined) {
          console.log(event.sessionStart);
        } else if (event.sessionUpdate !== undefined) {
          for (const logEvent of event.sessionUpdate.sessionResults) {
            const timestamp = logEvent.timestamp;
            const date = new Date(timestamp);
            console.log("[" + date + "] " + logEvent.message);
          } 
        } else {
            console.error("Unknown event type");
        }
      }
    } catch (err) {  
        // On-stream exceptions are captured here
        console.error(err)
    }
}

启动 Live Tail 会话。

    const client = new CloudWatchLogsClient();

    const command = new StartLiveTailCommand({
        logGroupIdentifiers: logGroupIdentifiers,
        logStreamNames: logStreamNames,
        logEventFilterPattern: filterPattern
    });
    try{
        const response = await client.send(command);
        handleResponseAsync(response);
    } catch (err){
        // Pre-stream exceptions are captured here
        console.log(err);
    }

经过一段时间后停止 Live Tail 会话。

    /* Set a timeout to close the client. This will stop the Live Tail session. */
    setTimeout(function() {
        console.log("Client timeout");
        client.destroy();
      }, 10000);

• 有关 API 的详细信息，请参阅 AWS SDK for JavaScript API 参考StartLiveTail中的。

Kotlin

适用于 Kotlin 的 SDK

包含所需的文件。

import aws.sdk.kotlin.services.cloudwatchlogs.CloudWatchLogsClient
import aws.sdk.kotlin.services.cloudwatchlogs.model.StartLiveTailRequest
import aws.sdk.kotlin.services.cloudwatchlogs.model.StartLiveTailResponseStream
import kotlinx.coroutines.flow.takeWhile

启动 Live Tail 会话

    val client = CloudWatchLogsClient.fromEnvironment()

    val request = StartLiveTailRequest {
        logGroupIdentifiers = logGroupIdentifiersVal
        logStreamNames = logStreamNamesVal
        logEventFilterPattern = logEventFilterPatternVal
    }

    val startTime = System.currentTimeMillis()

    try {
        client.startLiveTail(request) { response ->
            val stream = response.responseStream
            if (stream != null) {
                /* Set a timeout to unsubcribe from the flow. This will:
                * 1). Close the stream
                * 2). Stop the Live Tail session
                */
                stream.takeWhile { System.currentTimeMillis() - startTime < 10000 }.collect { value ->
                    if (value is StartLiveTailResponseStream.SessionStart) {
                        println(value.asSessionStart())
                    } else if (value is StartLiveTailResponseStream.SessionUpdate) {
                        for (e in value.asSessionUpdate().sessionResults!!) {
                            println(e)
                        }
                    } else {
                        throw IllegalArgumentException("Unknown event type")
                    }
                }
            } else {
                throw IllegalArgumentException("No response stream")
            }
        }
    } catch (e: Exception) {
        println("Exception occurred during StartLiveTail: $e")
        System.exit(1)
    }

• 有关 API 的详细信息，请参阅适用StartLiveTail于 K otlin 的AWS SDK API 参考。

Python

适用于 Python 的 SDK（Boto3）

包含所需的文件。

import boto3 
import time
from datetime import datetime

启动 Live Tail 会话

    # Initialize the client
    client = boto3.client('logs')

    start_time = time.time()

    try:
        response = client.start_live_tail(
            logGroupIdentifiers=log_group_identifiers,
            logStreamNames=log_streams,
            logEventFilterPattern=filter_pattern
        )
        event_stream = response['responseStream']
        # Handle the events streamed back in the response
        for event in event_stream:
            # Set a timeout to close the stream.
            # This will end the Live Tail session.
            if (time.time() - start_time >= 10):
                event_stream.close()
                break
            # Handle when session is started
            if 'sessionStart' in event:
                session_start_event = event['sessionStart']
                print(session_start_event)
            # Handle when log event is given in a session update
            elif 'sessionUpdate' in event:
                log_events = event['sessionUpdate']['sessionResults']
                for log_event in log_events:
                    print('[{date}] {log}'.format(date=datetime.fromtimestamp(log_event['timestamp']/1000),log=log_event['message']))
            else:
                # On-stream exceptions are captured here
                raise RuntimeError(str(event))
    except Exception as e:
        print(e)

• 有关 API 的详细信息，请参阅适用StartLiveTail于 Python 的AWS SDK (Boto3) API 参考。