下面主要分為Client端和Server端兩大類進行簡述，Eureka的幾個核心參數

客戶端參數

Client端的核心參數

定時任務參數

http參數

Eureka Client底層httpClient與Eureka Server通訊，提供的相關參數

服務端端參數

主要包含這幾類：基本參數、response cache參數、peer相參數、http參數

基本參數

response cache參數

Eureka Server為了提升自身REST API介面的效能，提供了兩個快取：一個是基於ConcurrentMap的readOnlyCacheMap，一個是基於Guava Cache的readWriteCacheMap。其相關參數如下：

peer相關參數

http參數

Eureka Server需要與其他peer節點進行通訊，複製例項資訊，其底層使用httpClient，提供相關的參數

參數調優

常見問題

1.為什麼服務下線了，Eureka Server介面返回的資訊還會存在？

2.為什麼服務上線了，Eureka Client不能及時獲取到？

3.為什麼會有以下提示：

EMERGENCY!EUREKA MAY BE INCORRECTLY CLAIMING INSTANCES ARE UP WHEN THEY’RE NOT. RENEWALS ARE LESSER THAN THRESHOLD AND HENCE THE INSTANCES ARE NOT BEING EXPIRED JUST TO BE SAFE

解決方法：

1.Eureka Server並不是強一致的，因此registry中會議保留過期的例項資訊。原因如下：

• 應用例項異常掛掉，沒能在掛掉之前告知Eureka Server要下線掉該服務例項資訊。這個就需要依賴Eureka Server的EvictionTask去剔除。
• 應用例項下線是有告知Eureka Server下線，但是由於Eureka Server的REST API有response cache，因此需要等待快取過期才能更新。
• 由於Eureka Server開啟並以入了SELF PRESERVATION(自我保護)模式，導致registry的資訊不會因為過期而被剔除掉，直到退出SELF PRESERVATION(自我保護)模式。

針對Client下線而沒有通知Eureka Server的問題，可以調整EvictionTask的排程頻率，比如把預設的時間間隔60s，調整為5s：

eureka:  server:    eviction-interval-timer-in-ms: 5000

針對response cache的問題，可以根據情況考慮關閉readOnlyCacheMap：

eureka:  server:    use-read-only-response-cache: false

或者調整readWriteCacheMap的過期時間：

eureka:  server:    response-cache-auto-expiration-in-seconds: 60

針對SELF PRESERVATION(自我保護)的問題，在測試環境可以將enable-self-preservation設定為false：

eureka:  server:    enable-self-preservation: false

關閉之後會提示：

THE SELF PRESER VAT ION MODE IS TURNED OFF.  THIS MAY NOT PRO TECT INSTANCE EXPIRY IN CASE OF NETWORK/OTHER PROBLEMS.

或者：

RENEWALS ARE LESSER THAN THE THRESHOLD.THE SELF PRESERVATION MODE IS TURNED OFF.THIS MAY  NOT PROTECT INSTANCE EXPIRY IN CASE OF NETWORK/OTHER PROBLEMS.

2.針對新服務上線，Eureka Client獲取不及時的問題，在測試環境，可以適當提高client端拉取Server註冊資訊的頻率，例如下面將預設的30s改為5s：

eureka:  client:    registry-fetch-interval-seconds: 5

3.在實際生產過程中，經常會有網路抖動等問題造成服務例項與Eureka Server的心跳未能如期保持，但是服務例項本身是健康的，這個時候如果按照租約剔除機制剔除的話，會造成誤判無果大範圍誤判的話，可能導致整個服務註冊列表的大部分註冊資訊被刪除，從而沒有可用服務。Eureka為了解決這個問題引入了SELF PRESERVATION機制，當最近一分鐘接收到的租約次數小於等於指定閾值的話，則關閉租約失效剔除，禁止定時任務失效的例項，從而保護註冊資訊。

在生產環境下，可以吧renewwalPercentThreshold及leaseRenewalIntervalInSeconds參數調小一點，從而提高觸發SELF PRESERVATION機制的閾值。

eureka:  instance:    lease-renewal-interval-in-seconds: 10 #預設是30    renewal-percent-threshold: 0.49       #預設是0.85

監控指標

Eureka內建了基於servo的指標統計，具體在com.netflix.eureka.util.EurekaMonitors。Spring Boot 2.x版本改為使用Micrometer，不再支援Neflix Servo，轉而支援Neflix Servo的替代品Neflix Spectator。不過對於Servo，可以通過DefaultMonitorRegistry.getInstance().getRegisteredMonitors來獲取所有註冊了的Monitor，進而獲取其指標值。

//// Source code recreated from a .class file by IntelliJ IDEA// (powered by Fernflower decompiler)//package com.netflix.eureka.util;import com.netflix.appinfo.AmazonInfo;import com.netflix.appinfo.ApplicationInfoManager;import com.netflix.appinfo.DataCenterInfo;import com.netflix.appinfo.AmazonInfo.MetaDataKey;import com.netflix.appinfo.DataCenterInfo.Name;import com.netflix.servo.DefaultMonitorRegistry;import com.netflix.servo.annotations.DataSourceType;import com.netflix.servo.annotations.Monitor;import com.netflix.servo.monitor.Monitors;import java.util.concurrent.atomic.AtomicLong;public enum EurekaMonitors {    // 自啟動以來收到的總續約次數    RENEW("renewCounter", "Number of total renews seen since startup"),    // 自啟動以來收到的總取消租約次數    CANCEL("cancelCounter", "Number of total cancels seen since startup"),    // 自啟動以來查詢registry的總次數    GET_ALL_CACHE_MISS("getAllCacheMissCounter", "Number of total registery queries seen since startup"),    // 自啟動以來delta查詢registry的總次數    GET_ALL_CACHE_MISS_DELTA("getAllCacheMissDeltaCounter", "Number of total registery queries for delta seen since startup"),    // 自啟動以來使用remote region查詢registry的總次數    GET_ALL_WITH_REMOTE_REGIONS_CACHE_MISS("getAllWithRemoteRegionCacheMissCounter", "Number of total registry with remote region queries seen since startup"),  // 自啟動以來使用remote region及delta方式查詢registry的總次數  GET_ALL_WITH_REMOTE_REGIONS_CACHE_MISS_DELTA("getAllWithRemoteRegionCacheMissDeltaCounter", "Number of total registry queries for delta with remote region seen since startup"),    // 自啟動以來查詢delta的總次數    GET_ALL_DELTA("getAllDeltaCounter", "Number of total deltas since startup"),    // 自啟動以來傳遞regions查詢delta的總次數    GET_ALL_DELTA_WITH_REMOTE_REGIONS("getAllDeltaWithRemoteRegionCounter", "Number of total deltas with remote regions since startup"),    // 自啟動以來查詢'/{version}/apps'的次數    GET_ALL("getAllCounter", "Number of total registry queries seen since startup"),    // 自啟動以來傳遞regions參數查詢'/{version}/apps'的次數    GET_ALL_WITH_REMOTE_REGIONS("getAllWithRemoteRegionCounter", "Number of total registry queries with remote regions, seen since startup"),    // 自啟動以來請求/{version}/apps/{appId}的總次數    GET_APPLICATION("getApplicationCounter", "Number of total application queries seen since startup"),    // 自啟動以來register的總次數    REGISTER("registerCounter", "Number of total registers seen since startup"),    // 自啟動以來剔除過期例項的總次數    EXPIRED("expiredCounter", "Number of total expired leases since startup"),    // 自啟動以來statusUpdate的總次數    STATUS_UPDATE("statusUpdateCounter", "Number of total admin status updates since startup"),    // 自啟動以來deleteStatusOverride的總次數    STATUS_OVERRIDE_DELETE("statusOverrideDeleteCounter", "Number of status override removals"),    // 自啟動以來收到cancel請求時對應例項找不到的次數    CANCEL_NOT_FOUND("cancelNotFoundCounter", "Number of total cancel requests on non-existing instance since startup"),    // 自啟動以來收到renew請求時對應例項找不到的次數    RENEW_NOT_FOUND("renewNotFoundexpiredCounter", "Number of total renew on non-existing instance since startup"),    REJECTED_REPLICATIONS("numOfRejectedReplications", "Number of replications rejected because of full queue"),    FAILED_REPLICATIONS("numOfFailedReplications", "Number of failed replications - likely from timeouts"),    // 由於開啟rate limiter被丟棄的請求數量    RATE_LIMITED("numOfRateLimitedRequests", "Number of requests discarded by the rate limiter"),    // 如果開啟rate limiter的話，將被丟棄的請求數    RATE_LIMITED_CANDIDATES("numOfRateLimitedRequestCandidates", "Number of requests that would be discarded if the rate limiter's throttling is activated"),    // 開啟rate limiter時請求全量registry被丟棄的請求數    RATE_LIMITED_FULL_FETCH("numOfRateLimitedFullFetchRequests", "Number of full registry fetch requests discarded by the rate limiter"),    // 如果開啟rate limiter時請求全量registry將被丟棄的請求數    RATE_LIMITED_FULL_FETCH_CANDIDATES("numOfRateLimitedFullFetchRequestCandidates", "Number of full registry fetch requests that would be discarded if the rate limiter's throttling is activated");    private final String name;    private final String myZoneCounterName;    private final String description;    @Monitor(        name = "count",        type = DataSourceType.COUNTER    )    private final AtomicLong counter = new AtomicLong();    @Monitor(        name = "count-minus-replication",        type = DataSourceType.COUNTER    )    private final AtomicLong myZoneCounter = new AtomicLong();    private EurekaMonitors(String name, String description) {        this.name = name;        this.description = description;        DataCenterInfo dcInfo = ApplicationInfoManager.getInstance().getInfo().getDataCenterInfo();        if (dcInfo.getName() == Name.Amazon) {            this.myZoneCounterName = ((AmazonInfo)dcInfo).get(MetaDataKey.availabilityZone) + "." + name;        } else {            this.myZoneCounterName = "dcmaster." + name;        }    }    public void increment() {        this.increment(false);    }    public void increment(boolean isReplication) {        this.counter.incrementAndGet();        if (!isReplication) {            this.myZoneCounter.incrementAndGet();        }    }    public String getName() {        return this.name;    }    public String getZoneSpecificName() {        return this.myZoneCounterName;    }    public String getDescription() {        return this.description;    }    public long getCount() {        return this.counter.get();    }    public long getZoneSpecificCount() {        return this.myZoneCounter.get();    }    public static void registerAllStats() {        EurekaMonitors[] var0 = values();        int var1 = var0.length;        for(int var2 = 0; var2 < var1; ++var2) {            EurekaMonitors c = var0[var2];            Monitors.registerObject(c.getName(), c);        }    }    public static void shutdown() {        EurekaMonitors[] var0 = values();        int var1 = var0.length;        for(int var2 = 0; var2 < var1; ++var2) {            EurekaMonitors c = var0[var2];            DefaultMonitorRegistry.getInstance().unregister(Monitors.newObjectMonitor(c.getName(), c));        }    }}

作者：8aceSuper
連結：https://juejin.cn/post/6972785798298992648
來源：掘金