spring cloud consul中TtlScheduler的原理和作用是什么

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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")@Validatedpublic 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

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