启动时阻止应用程序仅意味着阻止应用程序？

编程问答 2022-08-14

问题描述

众所周知，Spring Webflux应用程序不应阻止应用程序。

我只是想知道，如果启动时有阻塞调用，但业务逻辑上没有阻塞调用，那么该应用程序是否被视为阻塞应用程序？只是一个普遍的问题。

我有一个示例（超级容易重现），其中我正在使用Blockhound来测试应用程序是否被阻止。 在我的单元测试和集成测试中实例化Bloudhound时，已证明该流程无阻塞（非常高兴）。

但是，在启动时实例化Blockhound时，Spring Webflux + 反应性 Cassandra像这样：

package com.webflux.question.blockingg;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import reactor.blockhound.BlockHound;

@SpringBootApplication
public class Application {

    static {
        BlockHound.install();
    }

    public static void main(String[] args) {
        SpringApplication.run(Application.class);
    }

}


(the Cassandra parts)
package com.webflux.question.blockingg.configuration;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.cassandra.config.AbstractReactiveCassandraConfiguration;
import org.springframework.data.cassandra.config.CqlSessionFactoryBean;
import org.springframework.data.cassandra.repository.config.EnableReactiveCassandraRepositories;
import org.springframework.lang.NonNull;

@Configuration
@EnableReactiveCassandraRepositories
public class CassandraConfiguration extends AbstractReactiveCassandraConfiguration {

    @Value("${spring.data.cassandra.username}")
    private String username;
    @Value("${spring.data.cassandra.password}")
    private String passPhrase;
    @Value("${spring.data.cassandra.keyspace-name}")
    private String keyspace;
    @Value("${spring.data.cassandra.datacenter}")
    private String datacenter;
    @Value("${spring.data.cassandra.contact-points}")
    private String contactPoints;
    @Value("${spring.data.cassandra.port}")
    private int    port;

    @Bean
    @NonNull
    @Override
    public CqlSessionFactoryBean cassandraSession() {
        final CqlSessionFactoryBean cqlSessionFactoryBean = new CqlSessionFactoryBean();
        cqlSessionFactoryBean.setContactPoints(contactPoints);
        cqlSessionFactoryBean.setKeyspaceName(keyspace);
        cqlSessionFactoryBean.setLocalDatacenter(datacenter);
        cqlSessionFactoryBean.setPort(port);
        cqlSessionFactoryBean.setUsername(username);
        cqlSessionFactoryBean.setPassword(passPhrase);
        return cqlSessionFactoryBean;
    }

    @NonNull
    @Override
    protected String getKeyspaceName() {
        return keyspace;
    }

    @Override
    protected String getLocalDataCenter() {
        return datacenter;
    }

    @NonNull
    @Override
    protected String getContactPoints() {
        return contactPoints;
    }

    @Override
    protected int getPort() {
        return port;
    }

}

pom：

   <?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://maven.apache.org/POM/4.0.0"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.3.RELEASE</version>
        <relativePath/>
    </parent>

    <groupId>com.webflux.question</groupId>
    <artifactId>blocking</artifactId>
    <version>0.2</version>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>11</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-webflux</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-cassandra-reactive</artifactId>
        </dependency>
        <dependency>
            <groupId>io.projectreactor.tools</groupId>
            <artifactId>blockhound</artifactId>
            <version>1.0.4.RELEASE</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>11</source>
                    <target>11</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

我在启动时看到以下内容。

这是否意味着我的应用正在阻止？

事件循环会因此而受到伤害吗？

有没有解决方法？

谢谢您的时间。

Caused by: java.lang.IllegalArgumentException: Error instantiating class AtomicTimestampGenerator (specified by advanced.timestamp-generator.class): Blocking call! java.io.FileOutputStream#writeBytes
    at com.datastax.oss.driver.internal.core.util.Reflection.buildFromConfig(Reflection.java:239)
    at com.datastax.oss.driver.internal.core.util.Reflection.buildFromConfig(Reflection.java:94)
    at com.datastax.oss.driver.internal.core.context.DefaultDriverContext.buildTimestampGenerator(DefaultDriverContext.java:368)
    at com.datastax.oss.driver.internal.core.util.concurrent.LazyReference.get(LazyReference.java:55)
    at com.datastax.oss.driver.internal.core.context.DefaultDriverContext.getTimestampGenerator(DefaultDriverContext.java:743)
    at com.datastax.oss.driver.internal.core.session.DefaultSession$SingleThreaded.init(DefaultSession.java:349)
    at com.datastax.oss.driver.internal.core.session.DefaultSession$SingleThreaded.access$1100(DefaultSession.java:300)
    at com.datastax.oss.driver.internal.core.session.DefaultSession.lambda$init$0(DefaultSession.java:146)
    at io.netty.util.concurrent.PromiseTask.runTask(PromiseTask.java:98)
    at io.netty.util.concurrent.PromiseTask.run(PromiseTask.java:106)
    at io.netty.channel.DefaultEventLoop.run(DefaultEventLoop.java:54)
    at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
    at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: reactor.blockhound.BlockingOperationError: Blocking call! java.io.FileOutputStream#writeBytes
    at java.base/java.io.FileOutputStream.writeBytes(FileOutputStream.java)
    at java.base/java.io.FileOutputStream.write(FileOutputStream.java:354)
    at org.apache.logging.log4j.core.appender.OutputStreamManager.writeToDestination(OutputStreamManager.java:250)
    at org.apache.logging.log4j.core.appender.FileManager.writeToDestination(FileManager.java:273)
    at org.apache.logging.log4j.core.appender.rolling.RollingFileManager.writeToDestination(RollingFileManager.java:240)
    at org.apache.logging.log4j.core.appender.OutputStreamManager.flushBuffer(OutputStreamManager.java:282)
    at org.apache.logging.log4j.core.appender.OutputStreamManager.flush(OutputStreamManager.java:291)
    at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.directEncodeEvent(AbstractOutputStreamAppender.java:199)
    at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.tryAppend(AbstractOutputStreamAppender.java:190)
    at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.append(AbstractOutputStreamAppender.java:181)
    at org.apache.logging.log4j.core.appender.RollingFileAppender.append(RollingFileAppender.java:312)
    at org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderControl.java:156)
    at org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderControl.java:129)
    at org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursion(AppenderControl.java:120)
    at org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:84)
    at org.apache.logging.log4j.core.config.LoggerConfig.callAppenders(LoggerConfig.java:543)
    at org.apache.logging.log4j.core.config.LoggerConfig.processLogEvent(LoggerConfig.java:502)
    at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:485)
    at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:460)
    at org.apache.logging.log4j.core.config.AwaitCompletionReliabilityStrategy.log(AwaitCompletionReliabilityStrategy.java:82)
    at org.apache.logging.log4j.core.Logger.log(Logger.java:161)
    at org.apache.logging.log4j.spi.AbstractLogger.tryLogMessage(AbstractLogger.java:2198)
    at org.apache.logging.log4j.spi.AbstractLogger.logMessageTrackRecursion(AbstractLogger.java:2152)
    at org.apache.logging.log4j.spi.AbstractLogger.logMessageSafely(AbstractLogger.java:2135)
    at org.apache.logging.log4j.spi.AbstractLogger.logMessage(AbstractLogger.java:2016)
    at org.apache.logging.log4j.spi.AbstractLogger.logIfEnabled(AbstractLogger.java:1875)
    at org.apache.logging.slf4j.Log4jLogger.info(Log4jLogger.java:179)
    at com.datastax.oss.driver.internal.core.time.Clock.getInstance(Clock.java:35)
    at com.datastax.oss.driver.internal.core.time.MonotonicTimestampGenerator.buildClock(MonotonicTimestampGenerator.java:109)
    at com.datastax.oss.driver.internal.core.time.MonotonicTimestampGenerator.<init>(MonotonicTimestampGenerator.java:43)
    at com.datastax.oss.driver.internal.core.time.AtomicTimestampGenerator.<init>(AtomicTimestampGenerator.java:52)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:490)
    at com.datastax.oss.driver.internal.core.util.Reflection.buildFromConfig(Reflection.java:232)
    ... 14 more

解决方法

Datastax团队的官方回应：

Spring在构建应用程序上下文时发生错误，该错误在应用程序启动时发生。在此阶段，即使对于反应性/非阻塞应用程序，通常也可以允许阻塞调用–否则，例如，由于这是阻塞调用，您的应用程序将完全无法读取配置文件。

现在正在积极研究JAVA-2449。我将更改Uuids.random（）以使用非阻塞性内容。

,

我遇到了同样的问题，并添加了线程谓词使其无法检测到阻塞调用。至少下面不会出错阻塞调用，但会记录跟踪并详细说明实际阻塞的内容。

希望能帮到别人。

static {
    BlockHound
        .install(builder -> { 
          builder.blockingMethodCallback(it -> {
            new Exception(it.toString()).printStackTrace();
          });
        });
}
blockingcassandradatastaxspring-bootspring-webflux

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