Prometheus监控springboot应用Tomcat等待处理的请求数（accept队列长度）

Tomcat请求线程池默认线程数量为10，最大为200
min-spare-threads: 10
max-threads: 200

当超过最大值时，对进入到等待对列，队列长度默认为100
accept-count: 100

springboot1.×

@Autowired
ServletWebServerApplicationContext applicationContext;		
TomcatServletWebServerFactory tomcatServletWebServerFactory=applicationContext.getBean(TomcatServletWebServerFactory.class);
String tomcatLog = (((TomcatWebServer)(tomcatServletWebServerFactory.getWebServer())).getTomcat().getConnector()).getProtocolHandler().getExecutor().toString();

springboot2.×

@Autowired
ServletWebServerApplicationContext applicationContext;		
String tomcatLog = ((TomcatWebServer) applicationContext.getWebServer()).getTomcat().getConnector().getProtocolHandler().getExecutor().toString();

接下来如何融入到springboot项目中呢？

第一反应是写个定时任务，结果失败，因为要拿到Tomcat的连接。如果只是项目里的cron，并没涉及到Tomcat层面的连接，也就拿不到相关信息

第二反应是写个拦截器吧，拦截actuator/prometheus，并注入自定义的Prometheus参数。结果失败，拦截器默认是拦截不到这个接口，只能拦截到我们的业务接口。具体原理需回头探究。

第三反应是写个过滤器吧，过滤器是可以拿到接口的。但新的问题又来了。过滤器由于生命周期的原因，一些注入的bean是拿不到的。只得在配置类上加上component注解，不过付出的代价是，需要在内部处理url过滤的问题

最终代码如下

拦截器：

@Slf4j
@Component
public class PrometheusFilter implements Filter {

    @Autowired
    ServletWebServerApplicationContext applicationContext;

    @Autowired
    private PrometheusApacheThreadMonitor monitor;

    private static final String URL = "/actuator/prometheus";

    @Override
    public void init(FilterConfig filterConfig) {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        String path = ((HttpServletRequest) servletRequest).getServletPath();
        if(URL.equals(path)) {
            log.info("进入统计");
            Executor executor = ((TomcatWebServer) applicationContext.getWebServer()).getTomcat().getConnector().getProtocolHandler().getExecutor();
            String tomcatLog = executor.toString();
            String regex = "queued tasks = (\d+)";
            Pattern pattern = Pattern.compile(regex);
            Matcher matcher = pattern.matcher(tomcatLog);
            matcher.find();
            Integer size = Integer.valueOf(matcher.group(1));
            monitor.getQueuedTasks().set(size);
        }

        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void destroy() {

    }
}

@Component
@Slf4j
public class PrometheusApacheThreadMonitor {

    private final CollectorRegistry registry;

    private Gauge register;

    @Autowired
    public PrometheusApacheThreadMonitor(CollectorRegistry registry) {
        this.registry = registry;
    }

    @PostConstruct
    private void init() {
        register = Gauge.build("queued_tasks", "help").register(registry);
    }

    public Gauge getQueuedTasks() {
        return register;
    }
}