使用Kubernetes Java客户端的Config.fromConfig读取YAML配置失败

问题情况 #

在Java应用中使用Kubernetes API客户端读取k8s.config.yaml文件时出现异常，已通过调试确认YAML内容已正确加载为字符串，但Config.fromConfig方法仍抛出异常。

代码片段 #

private ApiClient readConfigFromFile(String filePath) throws IOException {
    String yamlContent = new String(Files.readAllBytes(Paths.get(filePath)));
    return Config.fromConfig(yamlContent);
}

k8s.config.yaml配置内容 #

apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: xxxxx
    server: https://api.mydomain.com.bd:port
  name: kubernetes
contexts:
- context:
    cluster: kubernetes
    user: kubernetes-super
  name: kubernetes-super@kubernetes
current-context: kubernetes-super@kubernetes
kind: Config
preferences: {}
users:
- name: kubernetes-super
  user:
    client-certificate-data: xxxxx
    client-key-data: xxxxx

完整堆栈追踪 #

at java.base/java.io.FileInputStream.open0(Native Method)
    at java.base/java.io.FileInputStream.open(FileInputStream.java:213)
    at java.base/java.io.FileInputStream.<init>(FileInputStream.java:152)
    at java.base/java.io.FileInputStream.<init>(FileInputStream.java:106)
    at io.kubernetes.client.util.Config.fromConfig(Config.java:80)
    at com.mua.testservice.k8s.K8sService.readConfigFromFile(K8sService.java:39)
    at com.mua.testservice.k8s.K8sService.readPods(K8sService.java:47)
    at com.mua.testservice.k8s.K8sService$$FastClassBySpringCGLIB$$f7a2349d.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:793)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:763)
    at org.springframework.aop.framework.adapter.AfterReturningAdviceInterceptor.invoke(AfterReturningAdviceInterceptor.java:57)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:763)
    at org.springframework.aop.framework.adapter.MethodBeforeAdviceInterceptor.invoke(MethodBeforeAdviceInterceptor.java:58)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:763)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:97)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:763)
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:708)
    at com.mua.testservice.k8s.K8sService$$EnhancerBySpringCGLIB$$305cd403.readPods(<generated>)
    at com.mua.testCliRun.run(CliRun.java:25)
    at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:768)
    at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:752)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:314)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1303)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1292)
    at com.mua.testK8sExpApplication.main(K8sExpApplication.java:10)

使用的依赖 #

<dependency>
    <groupId>io.kubernetes</groupId>
    <artifactId>client-java</artifactId>
    <version>15.0.1</version>
</dependency>

解决方案 #

错误原因 #

io.kubernetes.client.util.Config.fromConfig(String)方法的参数是文件路径字符串，而非YAML内容字符串。你传入已读取的YAML内容后，方法会将该字符串当作文件路径尝试读取，导致找不到文件抛出异常。

修复方法 #

方法一：直接传入文件路径

无需自行读取文件内容，直接将文件路径传给fromConfig方法：

private ApiClient readConfigFromFile(String filePath) throws IOException {
    return Config.fromConfig(filePath);
}

方法二：将字符串转为InputStream传入

如果必须先读取文件内容为字符串，可将其转为InputStream后调用重载方法：

import java.io.ByteArrayInputStream;
import java.nio.charset.StandardCharsets;
// ...
private ApiClient readConfigFromFile(String filePath) throws IOException {
    String yamlContent = new String(Files.readAllBytes(Paths.get(filePath)));
    try (InputStream inputStream = new ByteArrayInputStream(yamlContent.getBytes(StandardCharsets.UTF_8))) {
        return Config.fromConfig(inputStream);
    }
}

方法三：用YAML解析器直接解析为Config对象

使用客户端自带的YAML工具类将字符串解析为Config对象，再构建ApiClient：

import io.kubernetes.client.util.Yaml;
// ...
private ApiClient readConfigFromFile(String filePath) throws IOException {
    String yamlContent = new String(Files.readAllBytes(Paths.get(filePath)));
    Config config = Yaml.load(yamlContent, Config.class);
    return Config.fromConfig(config);
}

内容的提问来源于stack exchange，提问作者Maifee Ul Asad