1 概述
1.0 关键依赖包
spring-boot-autoconfigure: 2.3.12.RELEASEspring-boot: 2.3.12.RELEASEspring-context: 5.2.15.RELEASEspring-webmvc: 5.2.15.RELEASEtomcat-embed-core:9.0.46tomcat-embed-jasper:9.0.46
1.1 内嵌 Web Server 的优势
我们在使用 springboot 开发 web 项目时，大多数时候采用的是内置的 Tomcat （当然也可配置支持内置的 jett y），内置 Tomcat 有什么好处呢？
- 方便微服务部署，减少繁杂的配置
- 方便项目启动，不需要单独下载web容器，如Tomcat，jetty等。
1.2 Web Server 的优化思路
针对目前的容器优化，可以从以下几点考虑：
- 1、线程数
- 2、超时时间
- 3、JVM优化
1.3 Tomcat Web Server的核心配置参数
min-spare-threads
max-threads
accept-count
max-connections
connection-timeout
keepAliveTimeout
http keep-alive与tcp keep-alive，不是同一回事，意图不一样。
http keep-alive是为了让tcp活得更久一点，以便在同一个连接上传送多个http，提高socket的效率。
而tcp keep-alive是TCP的一种检测TCP连接状况的保鲜机制。
tcp keep-alive保鲜定时器，支持三个系统内核配置参数：
echo 1800 > /proc/sys/net/ipv4/tcp_keepalive_time
echo 15 > /proc/sys/net/ipv4/tcp_keepalive_intvl
echo 5 > /proc/sys/net/ipv4/tcp_keepalive_probes
keepalive是TCP保鲜定时器，当网络两端建立了TCP连接之后，闲置idle（双方没有任何数据流发送往来）了tcp_keepalive_time后，服务器内核就会尝试向客户端发送侦测包，来判断TCP连接状况(有可能客户端崩溃、强制关闭了应用、主机不可达等等)。如果没有收到对方的回答(ack包)，则会在 tcp_keepalive_intvl后再次尝试发送侦测包，直到收到对对方的ack,如果一直没有收到对方的ack,一共会尝试 tcp_keepalive_probes次，每次的间隔时间在这里分别是15s, 30s, 45s, 60s, 75s。如果尝试tcp_keepalive_probes,依然没有收到对方的ack包，则会丢弃该TCP连接。TCP连接默认闲置时间是2小时，一般设置为30分钟足够了。
总结一下，实际上tcp keep-alive是一个协议级别的心跳检测实现，当超过规定的时间，tcp就断开，而这边是讨论的http的keepalive，描述的http高层多次tcp链接共享，根本不是一个网络层级的东西，一定注意不要混淆。
1.4 springboot --> tomcat 源码分析
spring-boot-autoconfigure : 2.3.12.RELEASE
-> org.springframework.boot.autoconfigure.web.embedded.EmbeddedWebServerFactoryCustomizerAutoConfiguration
@ConditionalOnClass({Tomcat.class, UpgradeProtocol.class})
public static class TomcatWebServerFactoryCustomizerConfiguration { [*]
@Bean
public TomcatWebServerFactoryCustomizer tomcatWebServerFactoryCustomizer(Environment environment, ServerProperties serverProperties){
return new TomcatWebServerFactoryCustomizer(environment, serverProperties);
}
}
-> org.springframework.boot.autoconfigure.web.embedded.TomcatWebServerFactoryCustomizer
+ 关系: public class TomcatWebServerFactoryCustomizer implements WebServerFactoryCustomizer<ConfigurableTomcatWebServerFactory>, Ordered { /** ... **/ }
+ 属性:
private final Environment environment;
private final org.springframework.boot.autoconfigure.web.ServerProperties serverProperties; [*]
+ 方法:
public void customize(ConfigurableTomcatWebServerFactory factory) {
ServerProperties properties = this.serverProperties;
ServerProperties.Tomcat tomcatProperties = properties.getTomcat();
--> Tomcat { // 内部类
private final Threads threads = new Threads();
...
private int maxConnections;
private int acceptCount;
...
private Duration connectionTimeout;
...
private Charset uriEncoding;
--> Threads { // 内部类
private int max = 200;
private int minSpare = 10;
}
}
PropertyMapper propertyMapper = PropertyMapper.get();
ServerProperties.Tomcat.Threads threadProperties = tomcatProperties.getThreads();
...
propertyMapper.from(threadProperties::getMax).when(this::isPositive).to((maxThreads) -> {
this.customizeMaxThreads(factory, threadProperties.getMax());
});
...
propertyMapper.from(threadProperties::getMinSpare).when(this::isPositive).to((minSpareThreads) -> {
this.customizeMinThreads(factory, minSpareThreads);
});
...
propertyMapper.from(tomcatProperties::getMaxHttpFormPostSize).asInt(DataSize::toBytes).when((maxHttpFormPostSize) -> {
return maxHttpFormPostSize != 0;
}).to((maxHttpFormPostSize) -> {
this.customizeMaxHttpFormPostSize(factory, maxHttpFormPostSize);
});
...
propertyMapper.from(tomcatProperties::getAccesslog).when(ServerProperties.Tomcat.Accesslog::isEnabled).to((enabled) -> {
this.customizeAccessLog(factory);
});
...
propertyMapper.from(tomcatProperties::getUriEncoding).whenNonNull().to(factory::setUriEncoding);
...
propertyMapper.from(tomcatProperties::getConnectionTimeout).whenNonNull().to((connectionTimeout) -> {
this.customizeConnectionTimeout(factory, connectionTimeout);
});
...
propertyMapper.from(tomcatProperties::getMaxConnections).when(this::isPositive).to((maxConnections) -> {
this.customizeMaxConnections(factory, maxConnections);
});
...
propertyMapper.from(tomcatProperties::getAcceptCount).when(this::isPositive).to((acceptCount) -> {
this.customizeAcceptCount(factory, acceptCount);
});
}
private void customizeAcceptCount(ConfigurableTomcatWebServerFactory factory, int acceptCount) {
factory.addConnectorCustomizers(new TomcatConnectorCustomizer[]{(connector) -> {
ProtocolHandler handler = connector.getProtocolHandler();
if (handler instanceof AbstractProtocol) {
AbstractProtocol<?> protocol = (AbstractProtocol)handler;
protocol.setAcceptCount(acceptCount);
}
}});
}
...
private void customizeMaxConnections(ConfigurableTomcatWebServerFactory factory, int maxConnections) {
factory.addConnectorCustomizers(new TomcatConnectorCustomizer[]{(connector) -> {
ProtocolHandler handler = connector.getProtocolHandler();
if (handler instanceof AbstractProtocol) {
AbstractProtocol<?> protocol = (AbstractProtocol)handler;
protocol.setMaxConnections(maxConnections);
}
}});
}
...