这篇文章主要讲解了“spring cloud consul中TtlScheduler的原理和作用是什么”，文中的讲解内容简单清晰，易于学习与理解，下面请大家跟着小编的思路慢慢深入，一起来研究和学习“spring cloud consul中TtlScheduler的原理和作用是什么”吧！

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序

本文主要研究一下spring cloud consul的TtlScheduler

TtlScheduler

spring-cloud-consul-discovery-2.1.2.RELEASE-sources.jar!/org/springframework/cloud/consul/discovery/TtlScheduler.java

public class TtlScheduler {

	private static final Log log = LogFactory.getLog(ConsulDiscoveryClient.class);

	private final Map serviceHeartbeats = new ConcurrentHashMap<>();

	private final TaskScheduler scheduler = new ConcurrentTaskScheduler(
			Executors.newSingleThreadScheduledExecutor());

	private HeartbeatProperties configuration;

	private ConsulClient client;

	public TtlScheduler(HeartbeatProperties configuration, ConsulClient client) {
		this.configuration = configuration;
		this.client = client;
	}

	@Deprecated
	public void add(final NewService service) {
		add(service.getId());
	}

	/**
	 * Add a service to the checks loop.
	 * @param instanceId instance id
	 */
	public void add(String instanceId) {
		ScheduledFuture task = this.scheduler.scheduleAtFixedRate(
				new ConsulHeartbeatTask(instanceId), this.configuration
						.computeHearbeatInterval().toStandardDuration().getMillis());
		ScheduledFuture previousTask = this.serviceHeartbeats.put(instanceId, task);
		if (previousTask != null) {
			previousTask.cancel(true);
		}
	}

	public void remove(String instanceId) {
		ScheduledFuture task = this.serviceHeartbeats.get(instanceId);
		if (task != null) {
			task.cancel(true);
		}
		this.serviceHeartbeats.remove(instanceId);
	}

	private class ConsulHeartbeatTask implements Runnable {

		private String checkId;

		ConsulHeartbeatTask(String serviceId) {
			this.checkId = serviceId;
			if (!this.checkId.startsWith("service:")) {
				this.checkId = "service:" + this.checkId;
			}
		}

		@Override
		public void run() {
			TtlScheduler.this.client.agentCheckPass(this.checkId);
			if (log.isDebugEnabled()) {
				log.debug("Sending consul heartbeat for: " + this.checkId);
			}
		}

	}

}

• TtlScheduler的构造器接收HeartbeatProperties、ConsulClient；add方法会往scheduler注册一个定时执行的ConsulHeartbeatTask，执行间隔由HeartbeatProperties的ttlValue及intervalRatio计算而来，同时如果previousTask不为null则对其进行cancel；remove方法则cancel调用ScheduledFuture，然后将其从serviceHeartbeats中移除；ConsulHeartbeatTask的run方法则是执行client.agentCheckPass

HeartbeatProperties

spring-cloud-consul-discovery-2.1.2.RELEASE-sources.jar!/org/springframework/cloud/consul/discovery/HeartbeatProperties.java

@ConfigurationProperties(prefix = "spring.cloud.consul.discovery.heartbeat")
@Validated
public class HeartbeatProperties {

	private static final Log log = org.apache.commons.logging.LogFactory
			.getLog(HeartbeatProperties.class);

	// TODO: change enabled to default to true when I stop seeing messages like
	// [WARN] agent: Check 'service:testConsulApp:xtest:8080' missed TTL, is now critical
	boolean enabled = false;

	@Min(1)
	private int ttlValue = 30;

	@NotNull
	private String ttlUnit = "s";

	@DecimalMin("0.1")
	@DecimalMax("0.9")
	private double intervalRatio = 2.0 / 3.0;

	// TODO: did heartbeatInterval need to be a field?

	protected Period computeHearbeatInterval() {
		// heartbeat rate at ratio * ttl, but no later than ttl -1s and, (under lesser
		// priority), no sooner than 1s from now
		double interval = this.ttlValue * this.intervalRatio;
		double max = Math.max(interval, 1);
		int ttlMinus1 = this.ttlValue - 1;
		double min = Math.min(ttlMinus1, max);
		Period heartbeatInterval = new Period(Math.round(1000 * min));
		log.debug("Computed heartbeatInterval: " + heartbeatInterval);
		return heartbeatInterval;
	}

	public String getTtl() {
		return this.ttlValue + this.ttlUnit;
	}

	public boolean isEnabled() {
		return this.enabled;
	}

	public void setEnabled(boolean enabled) {
		this.enabled = enabled;
	}

	public @Min(1) int getTtlValue() {
		return this.ttlValue;
	}

	public void setTtlValue(@Min(1) int ttlValue) {
		this.ttlValue = ttlValue;
	}

	public @NotNull String getTtlUnit() {
		return this.ttlUnit;
	}

	public void setTtlUnit(@NotNull String ttlUnit) {
		this.ttlUnit = ttlUnit;
	}

	public @DecimalMin("0.1") @DecimalMax("0.9") double getIntervalRatio() {
		return this.intervalRatio;
	}

	public void setIntervalRatio(
			@DecimalMin("0.1") @DecimalMax("0.9") double intervalRatio) {
		this.intervalRatio = intervalRatio;
	}

	@Override
	public String toString() {
		return new ToStringCreator(this).append("enabled", this.enabled)
				.append("ttlValue", this.ttlValue).append("ttlUnit", this.ttlUnit)
				.append("intervalRatio", this.intervalRatio).toString();
	}

}

• HeartbeatProperties有ttlValue、intervalRatio等属性，其computeHearbeatInterval方法会取ttlMinus1及Math.max(interval, 1)的最小值作为heartbeatInterval

ConsulDiscoveryClientConfiguration

spring-cloud-consul-discovery-2.1.2.RELEASE-sources.jar!/org/springframework/cloud/consul/discovery/ConsulDiscoveryClientConfiguration.java

@Configuration
@ConditionalOnConsulEnabled
@ConditionalOnProperty(value = "spring.cloud.consul.discovery.enabled", matchIfMissing = true)
@ConditionalOnDiscoveryEnabled
@EnableConfigurationProperties
@AutoConfigureBefore({ SimpleDiscoveryClientAutoConfiguration.class,
		CommonsClientAutoConfiguration.class })
public class ConsulDiscoveryClientConfiguration {

	/**
	 * Name of the catalog watch task scheduler bean.
	 */
	public static final String CATALOG_WATCH_TASK_SCHEDULER_NAME = "catalogWatchTaskScheduler";

	@Autowired
	private ConsulClient consulClient;

	@Bean
	@ConditionalOnMissingBean
	@ConditionalOnProperty("spring.cloud.consul.discovery.heartbeat.enabled")
	// TODO: move to service-registry for Edgware
	public TtlScheduler ttlScheduler(HeartbeatProperties heartbeatProperties) {
		return new TtlScheduler(heartbeatProperties, this.consulClient);
	}

	@Bean
	@ConditionalOnMissingBean
	// TODO: move to service-registry for Edgware
	public HeartbeatProperties heartbeatProperties() {
		return new HeartbeatProperties();
	}

	@Bean
	@ConditionalOnMissingBean
	// TODO: Split appropriate values to service-registry for Edgware
	public ConsulDiscoveryProperties consulDiscoveryProperties(InetUtils inetUtils) {
		return new ConsulDiscoveryProperties(inetUtils);
	}

	@Bean
	@ConditionalOnMissingBean
	public ConsulDiscoveryClient consulDiscoveryClient(
			ConsulDiscoveryProperties discoveryProperties) {
		return new ConsulDiscoveryClient(this.consulClient, discoveryProperties);
	}

	@Bean
	@ConditionalOnMissingBean
	@ConditionalOnProperty(name = "spring.cloud.consul.discovery.catalog-services-watch.enabled", matchIfMissing = true)
	public ConsulCatalogWatch consulCatalogWatch(
			ConsulDiscoveryProperties discoveryProperties,
			@Qualifier(CATALOG_WATCH_TASK_SCHEDULER_NAME) TaskScheduler taskScheduler) {
		return new ConsulCatalogWatch(discoveryProperties, this.consulClient,
				taskScheduler);
	}

	@Bean(name = CATALOG_WATCH_TASK_SCHEDULER_NAME)
	@ConditionalOnProperty(name = "spring.cloud.consul.discovery.catalog-services-watch.enabled", matchIfMissing = true)
	public TaskScheduler catalogWatchTaskScheduler() {
		return new ThreadPoolTaskScheduler();
	}
}

• ConsulDiscoveryClientConfiguration在@ConditionalOnMissingBean以及@ConditionalOnProperty("spring.cloud.consul.discovery.heartbeat.enabled")的条件下会自动注册ttlScheduler

小结

TtlScheduler的构造器接收HeartbeatProperties、ConsulClient；add方法会往scheduler注册一个定时执行的ConsulHeartbeatTask，执行间隔由HeartbeatProperties的ttlValue及intervalRatio计算而来，同时如果previousTask不为null则对其进行cancel；remove方法则cancel调用ScheduledFuture，然后将其从serviceHeartbeats中移除；ConsulHeartbeatTask的run方法则是执行client.agentCheckPass

感谢各位的阅读，以上就是“spring cloud consul中TtlScheduler的原理和作用是什么”的内容了，经过本文的学习后，相信大家对spring cloud consul中TtlScheduler的原理和作用是什么这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是创新互联，小编将为大家推送更多相关知识点的文章，欢迎关注！

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