SpringCloud 再一个坑
12 Jul 2017决定要把微服务的架构搞明白，同时用一个项目来验证这套架构是否符合构建一个完整的微服务体系。
这段时间很受伤，经常熬到半夜穿着衣服就睡着了，严重拖延了我的金融学习…
不过既然要搞明白，就必须一个一个坑的过。
纪录一下今天的坑：
异常，永远都从Exception开始，不过有异常是好的，最怕是狗屁不出来…
废话不说，描述异常。
feign.RetryableException: connect timed out executing GET http://sc/users/] with root cause
因为用了feign进行业务与前台的脱离，晚上回家稍事休息后打开久久未开的电脑，从消费者调用service居然异常了。在网上查到的解释是：
feign client的retry及超时设置
默认值
默认maxAttempts值
/Users/xixicat/.m2/repository/io/github/openfeign/feign-core/9.3.1/feign-core-9.3.1-sources.jar!/feign/Retryer.java
public Default() {
this(100, SECONDS.toMillis(1), 5);
}
public Default(long period, long maxPeriod, int maxAttempts) {
this.period = period;
this.maxPeriod = maxPeriod;
this.maxAttempts = maxAttempts;
this.attempt = 1;
}
retry逻辑
/Users/xixicat/.m2/repository/io/github/openfeign/feign-core/9.3.1/feign-core-9.3.1-sources.jar!/feign/Retryer.java
public void continueOrPropagate(RetryableException e) {
if (attempt++ >= maxAttempts) {
throw e;
}
long interval;
if (e.retryAfter() != null) {
interval = e.retryAfter().getTime() - currentTimeMillis();
if (interval > maxPeriod) {
interval = maxPeriod;
}
if (interval < 0) {
return;
}
} else {
interval = nextMaxInterval();
}
try {
Thread.sleep(interval);
} catch (InterruptedException ignored) {
Thread.currentThread().interrupt();
}
sleptForMillis += interval;
}
这里attempt初始值为1，即把第一次的请求也算上去了，先执行attempt >= maxAttempts判断，再执行attempt++。因此maxAttempts设置为2表示重试1次。/Users/xixicat/.m2/repository/io/github/openfeign/feign-core/9.3.1/feign-core-9.3.1-sources.jar!/feign/SynchronousMethodHandler.java
@Override
public Object invoke(Object[] argv) throws Throwable {
RequestTemplate template = buildTemplateFromArgs.create(argv);
Retryer retryer = this.retryer.clone();
while (true) {
try {
return executeAndDecode(template);
} catch (RetryableException e) {
retryer.continueOrPropagate(e);
if (logLevel != Logger.Level.NONE) {
logger.logRetry(metadata.configKey(), logLevel);
}
continue;
}
}
}
关于++
@Test
public void testPlus(){
int attempt = 1;
int maxAttempts = 1;
try{
if(attempt++ == maxAttempts){
throw new RuntimeException("EXCEED");
}
}finally {
System.out.println(attempt);
}
}
输出
2
java.lang.RuntimeException: EXCEED
at XXXTest.testPlus(XXXTest.java:50)
默认超时时间
/Users/xixicat/.m2/repository/io/github/openfeign/feign-core/9.3.1/feign-core-9.3.1-sources.jar!/feign/Request.java
public Options(int connectTimeoutMillis, int readTimeoutMillis) {
this.connectTimeoutMillis = connectTimeoutMillis;
this.readTimeoutMillis = readTimeoutMillis;
}
public Options() {
this(10 * 1000, 60 * 1000);
}
参数设置
timeout设置
@Bean
Request.Options feignOptions() {
return new Request.Options(/**connectTimeoutMillis**/1 * 1000, /** readTimeoutMillis **/1 * 1000);
}
retry配置
@Bean
Retryer feignRetryer() {
return Retryer.NEVER_RETRY;
}
响应时间
默认retry响应时间(1s connectTimeout,1s readTimeout)
Percentage of the requests served within a certain time (ms)
50% 6718
66% 7020
75% 7371
80% 8237
90% 8404
95% 8404
98% 8404
99% 8404
100% 8404 (longest request)
不retry(1s connectTimeout,1s readTimeout)
Percentage of the requests served within a certain time (ms)
50% 1219
66% 1230
75% 1307
80% 1485
90% 1674
95% 1674
98% 1674
99% 1674
100% 1674 (longest request)
不retry(5s connectTimeout,5s readTimeout)
Percentage of the requests served within a certain time (ms)
50% 5561
66% 5592
75% 5653
80% 5677
90% 5778
95% 5778
98% 5778
99% 5778
100% 5778 (longest request)
小结
feign client默认的connectTimeout为10s，readTimeout为60.单纯设置timeout，可能没法立马见效，因为默认的retry为5次.因此，如果期望fail fast的话，需要同时自定义timeout以及retry的参数，而且要确保反向代理，比如nginx的proxy_connect_timeout以及proxy_read_timeout要大于feign的配置才能见效，不然对外部用户感知到的还是nginx的504 Gateway Time-out，起不到fallback的效果。
当前在开发模式，没有按照这个进行修改，重启好了。不过先收藏了，等了生产库的时候在进行调试。
当前最重要完成项目！
再来一个解释：
import feign.Request;
@Configuration @EnableDiscoveryClient @EnableFeignClients(basePackageClasses = { ServiceFeignClient.class }) @ComponentScan(basePackageClasses = { ServiceFeignClient.class }) public class FeignConfig {
/**
* Method to create a bean to increase the timeout value,
* It is used to overcome the Retryable exception while invoking the feign client.
* @param env,
* An {@link ConfigurableEnvironment}
* @return A {@link Request}
*/
@Bean
public static Request.Options requestOptions(ConfigurableEnvironment env) {
int ribbonReadTimeout = env.getProperty("ribbon.ReadTimeout", int.class, 70000);
int ribbonConnectionTimeout = env.getProperty("ribbon.ConnectTimeout", int.class, 60000);
return new Request.Options(ribbonConnectionTimeout, ribbonReadTimeout);
} }