# spring-cloud-kubernetes **Repository Path**: AWenGe/spring-cloud-kubernetes ## Basic Information - **Project Name**: spring-cloud-kubernetes - **Description**: Kubernetes integration with Spring Cloud Discovery Client, Configuration, etc... - **Primary Language**: Unknown - **License**: Apache-2.0 - **Default Branch**: master - **Homepage**: None - **GVP Project**: No ## Statistics - **Stars**: 0 - **Forks**: 1 - **Created**: 2020-04-23 - **Last Updated**: 2020-12-19 ## Categories & Tags **Categories**: Uncategorized **Tags**: None ## README //// DO NOT EDIT THIS FILE. IT WAS GENERATED. Manual changes to this file will be lost when it is generated again. Edit the files in the src/main/asciidoc/ directory instead. //// = Spring Cloud Kubernetes :doctype: book :idprefix: :idseparator: - :toc: left :toclevels: 4 :tabsize: 4 :numbered: :sectanchors: :sectnums: :icons: font :hide-uri-scheme: :docinfo: shared,private :sc-ext: java :project-full-name: Spring Cloud Kubernetes :all: {asterisk}{asterisk} This reference guide covers how to use Spring Cloud Kubernetes. == Why do you need Spring Cloud Kubernetes? Spring Cloud Kubernetes provide Spring Cloud common interface implementations that consume Kubernetes native services. The main objective of the projects provided in this repository is to facilitate the integration of Spring Cloud and Spring Boot applications running inside Kubernetes. == Starters Starters are convenient dependency descriptors you can include in your application. Include a starter to get the dependencies and Spring Boot auto-configuration for a feature set. [cols="a,d"] |=== | Starter | Features | [source,xml] ---- org.springframework.cloud spring-cloud-starter-kubernetes ---- | <> implementation that resolves service names to Kubernetes Services. | [source,xml] ---- org.springframework.cloud spring-cloud-starter-kubernetes-config ---- | Load application properties from Kubernetes <> and <>. <> application properties when a ConfigMap or Secret changes. | [source,xml] ---- org.springframework.cloud spring-cloud-starter-kubernetes-ribbon ---- | <> client-side load balancer with server list obtained from Kubernetes Endpoints. | [source,xml] ---- org.springframework.cloud spring-cloud-starter-kubernetes-all ---- | All Spring Cloud Kubernetes features. |=== == DiscoveryClient for Kubernetes This project provides an implementation of https://github.com/spring-cloud/spring-cloud-commons/blob/master/spring-cloud-commons/src/main/java/org/springframework/cloud/client/discovery/DiscoveryClient.java[Discovery Client] for https://kubernetes.io[Kubernetes]. This client lets you query Kubernetes endpoints (see https://kubernetes.io/docs/user-guide/services/[services]) by name. A service is typically exposed by the Kubernetes API server as a collection of endpoints that represent `http` and `https` addresses and that a client can access from a Spring Boot application running as a pod. This discovery feature is also used by the Spring Cloud Kubernetes Ribbon project to fetch the list of the endpoints defined for an application to be load balanced. This is something that you get for free by adding the following dependency inside your project: ==== [source,xml] ---- org.springframework.cloud spring-cloud-starter-kubernetes ---- ==== To enable loading of the `DiscoveryClient`, add `@EnableDiscoveryClient` to the according configuration or application class, as the following example shows: ==== [source,java] ---- @SpringBootApplication @EnableDiscoveryClient public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } } ---- ==== Then you can inject the client in your code simply by autowiring it, as the following example shows: ==== [source,java] ---- @Autowired private DiscoveryClient discoveryClient; ---- ==== You can choose to enable `DiscoveryClient` from all namespaces by setting the following property in `application.properties`: ==== [source] ---- spring.cloud.kubernetes.discovery.all-namespaces=true ---- ==== If, for any reason, you need to disable the `DiscoveryClient`, you can set the following property in `application.properties`: ==== [source] ---- spring.cloud.kubernetes.discovery.enabled=false ---- ==== Some Spring Cloud components use the `DiscoveryClient` in order to obtain information about the local service instance. For this to work, you need to align the Kubernetes service name with the `spring.application.name` property. NOTE: `spring.application.name` has no effect as far as the name registered for the application within Kubernetes Spring Cloud Kubernetes can also watch the Kubernetes service catalog for changes and update the `DiscoveryClient` implementation accordingly. In order to enable this functionality you need to add `@EnableScheduling` on a configuration class in your application. == Kubernetes native service discovery Kubernetes itself is capable of (server side) service discovery (see: https://kubernetes.io/docs/concepts/services-networking/service/#discovering-services). Using native kubernetes service discovery ensures compatibility with additional tooling, such as Istio (https://istio.io), a service mesh that is capable of load balancing, ribbon, circuit breaker, failover, and much more. The caller service then need only refer to names resolvable in a particular Kubernetes cluster. A simple implementation might use a spring `RestTemplate` that refers to a fully qualified domain name (FQDN), such as `https://{service-name}.{namespace}.svc.{cluster}.local:{service-port}`. Additionally, you can use Hystrix for: * Circuit breaker implementation on the caller side, by annotating the spring boot application class with `@EnableCircuitBreaker` * Fallback functionality, by annotating the respective method with `@HystrixCommand(fallbackMethod=` == Kubernetes PropertySource implementations The most common approach to configuring your Spring Boot application is to create an `application.properties` or `application.yaml` or an `application-profile.properties` or `application-profile.yaml` file that contains key-value pairs that provide customization values to your application or Spring Boot starters. You can override these properties by specifying system properties or environment variables. [[configmap-propertysource]] === Using a `ConfigMap` `PropertySource` Kubernetes provides a resource named https://kubernetes.io/docs/user-guide/configmap/[`ConfigMap`] to externalize the parameters to pass to your application in the form of key-value pairs or embedded `application.properties` or `application.yaml` files. The link:./spring-cloud-kubernetes-config[Spring Cloud Kubernetes Config] project makes Kubernetes `ConfigMap` instances available during application bootstrapping and triggers hot reloading of beans or Spring context when changes are detected on observed `ConfigMap` instances. The default behavior is to create a `ConfigMapPropertySource` based on a Kubernetes `ConfigMap` that has a `metadata.name` value of either the name of your Spring application (as defined by its `spring.application.name` property) or a custom name defined within the `bootstrap.properties` file under the following key: `spring.cloud.kubernetes.config.name`. However, more advanced configuration is possible where you can use multiple `ConfigMap` instances. The `spring.cloud.kubernetes.config.sources` list makes this possible. For example, you could define the following `ConfigMap` instances: ==== [source,yaml] ---- spring: application: name: cloud-k8s-app cloud: kubernetes: config: name: default-name namespace: default-namespace sources: # Spring Cloud Kubernetes looks up a ConfigMap named c1 in namespace default-namespace - name: c1 # Spring Cloud Kubernetes looks up a ConfigMap named default-name in whatever namespace n2 - namespace: n2 # Spring Cloud Kubernetes looks up a ConfigMap named c3 in namespace n3 - namespace: n3 name: c3 ---- ==== In the preceding example, if `spring.cloud.kubernetes.config.namespace` had not been set, the `ConfigMap` named `c1` would be looked up in the namespace that the application runs. Any matching `ConfigMap` that is found is processed as follows: * Apply individual configuration properties. * Apply as `yaml` the content of any property named `application.yaml`. * Apply as a properties file the content of any property named `application.properties`. The single exception to the aforementioned flow is when the `ConfigMap` contains a *single* key that indicates the file is a YAML or properties file. In that case, the name of the key does NOT have to be `application.yaml` or `application.properties` (it can be anything) and the value of the property is treated correctly. This features facilitates the use case where the `ConfigMap` was created by using something like the following: ==== [source] ---- kubectl create configmap game-config --from-file=/path/to/app-config.yaml ---- ==== Assume that we have a Spring Boot application named `demo` that uses the following properties to read its thread pool configuration. * `pool.size.core` * `pool.size.maximum` This can be externalized to config map in `yaml` format as follows: ==== [source,yaml] ---- kind: ConfigMap apiVersion: v1 metadata: name: demo data: pool.size.core: 1 pool.size.max: 16 ---- ==== Individual properties work fine for most cases. However, sometimes, embedded `yaml` is more convenient. In this case, we use a single property named `application.yaml` to embed our `yaml`, as follows: ==== [source,yaml] ---- kind: ConfigMap apiVersion: v1 metadata: name: demo data: application.yaml: |- pool: size: core: 1 max:16 ---- ==== The following example also works: ==== [source,yaml] ---- kind: ConfigMap apiVersion: v1 metadata: name: demo data: custom-name.yaml: |- pool: size: core: 1 max:16 ---- ==== You can also configure Spring Boot applications differently depending on active profiles that are merged together when the `ConfigMap` is read. You can provide different property values for different profiles by using an `application.properties` or `application.yaml` property, specifying profile-specific values, each in their own document (indicated by the `---` sequence), as follows: ==== [source,yaml] ---- kind: ConfigMap apiVersion: v1 metadata: name: demo data: application.yml: |- greeting: message: Say Hello to the World farewell: message: Say Goodbye --- spring: profiles: development greeting: message: Say Hello to the Developers farewell: message: Say Goodbye to the Developers --- spring: profiles: production greeting: message: Say Hello to the Ops ---- ==== In the preceding case, the configuration loaded into your Spring Application with the `development` profile is as follows: ==== [source,yaml] ---- greeting: message: Say Hello to the Developers farewell: message: Say Goodbye to the Developers ---- ==== However, if the `production` profile is active, the configuration becomes: ==== [source,yaml] ---- greeting: message: Say Hello to the Ops farewell: message: Say Goodbye ---- ==== If both profiles are active, the property that appears last within the `ConfigMap` overwrites any preceding values. Another option is to create a different config map per profile and spring boot will automatically fetch it based on active profiles ==== [source,yaml] ---- kind: ConfigMap apiVersion: v1 metadata: name: demo data: application.yml: |- greeting: message: Say Hello to the World farewell: message: Say Goodbye ---- ==== ==== [source,yaml] ---- kind: ConfigMap apiVersion: v1 metadata: name: demo-development data: application.yml: |- spring: profiles: development greeting: message: Say Hello to the Developers farewell: message: Say Goodbye to the Developers ---- ==== ==== [source,yaml] ---- kind: ConfigMap apiVersion: v1 metadata: name: demo-production data: application.yml: |- spring: profiles: production greeting: message: Say Hello to the Ops farewell: message: Say Goodbye ---- ==== To tell Spring Boot which `profile` should be enabled at bootstrap, you can pass `SPRING_PROFILES_ACTIVE` environment variable. To do so, you can launch your Spring Boot application with an environment variable that you can define it in the PodSpec at the container specification. Deployment resource file, as follows: ==== [source,yaml] ---- apiVersion: apps/v1 kind: Deployment metadata: name: deployment-name labels: app: deployment-name spec: replicas: 1 selector: matchLabels: app: deployment-name template: metadata: labels: app: deployment-name spec: containers: - name: container-name image: your-image env: - name: SPRING_PROFILES_ACTIVE value: "development" ---- ==== NOTE: You should check the security configuration section. To access config maps from inside a pod you need to have the correct Kubernetes service accounts, roles and role bindings. Another option for using `ConfigMap` instances is to mount them into the Pod by running the Spring Cloud Kubernetes application and having Spring Cloud Kubernetes read them from the file system. This behavior is controlled by the `spring.cloud.kubernetes.config.paths` property. You can use it in addition to or instead of the mechanism described earlier. You can specify multiple (exact) file paths in `spring.cloud.kubernetes.config.paths` by using the `,` delimiter. NOTE: You have to provide the full exact path to each property file, because directories are not being recursively parsed. .Properties: [options="header,footer"] |=== | Name | Type | Default | Description | `spring.cloud.kubernetes.config.enabled` | `Boolean` | `true` | Enable ConfigMaps `PropertySource` | `spring.cloud.kubernetes.config.name` | `String` | `${spring.application.name}` | Sets the name of `ConfigMap` to look up | `spring.cloud.kubernetes.config.namespace` | `String` | Client namespace | Sets the Kubernetes namespace where to lookup | `spring.cloud.kubernetes.config.paths` | `List` | `null` | Sets the paths where `ConfigMap` instances are mounted | `spring.cloud.kubernetes.config.enableApi` | `Boolean` | `true` | Enable or disable consuming `ConfigMap` instances through APIs |=== === Secrets PropertySource Kubernetes has the notion of https://kubernetes.io/docs/concepts/configuration/secret/[Secrets] for storing sensitive data such as passwords, OAuth tokens, and so on. This project provides integration with `Secrets` to make secrets accessible by Spring Boot applications. You can explicitly enable or disable This feature by setting the `spring.cloud.kubernetes.secrets.enabled` property. When enabled, the `SecretsPropertySource` looks up Kubernetes for `Secrets` from the following sources: . Reading recursively from secrets mounts . Named after the application (as defined by `spring.application.name`) . Matching some labels *Note:* By default, consuming Secrets through the API (points 2 and 3 above) *is not enabled* for security reasons. The permission 'list' on secrets allows clients to inspect secrets values in the specified namespace. Further, we recommend that containers share secrets through mounted volumes. If you enable consuming Secrets through the API, we recommend that you limit access to Secrets by using an authorization policy, such as RBAC. For more information about risks and best practices when consuming Secrets through the API refer to https://kubernetes.io/docs/concepts/configuration/secret/#best-practices[this doc]. If the secrets are found, their data is made available to the application. Assume that we have a spring boot application named `demo` that uses properties to read its database configuration. We can create a Kubernetes secret by using the following command: ==== [source] ---- kubectl create secret generic db-secret --from-literal=username=user --from-literal=password=p455w0rd ---- ==== The preceding command would create the following secret (which you can see by using `kubectl get secrets db-secret -o yaml`): ==== [source,yaml] ---- apiVersion: v1 data: password: cDQ1NXcwcmQ= username: dXNlcg== kind: Secret metadata: creationTimestamp: 2017-07-04T09:15:57Z name: db-secret namespace: default resourceVersion: "357496" selfLink: /api/v1/namespaces/default/secrets/db-secret uid: 63c89263-6099-11e7-b3da-76d6186905a8 type: Opaque ---- ==== Note that the data contains Base64-encoded versions of the literal provided by the `create` command. Your application can then use this secret -- for example, by exporting the secret's value as environment variables: ==== [source,yaml] ---- apiVersion: v1 kind: Deployment metadata: name: ${project.artifactId} spec: template: spec: containers: - env: - name: DB_USERNAME valueFrom: secretKeyRef: name: db-secret key: username - name: DB_PASSWORD valueFrom: secretKeyRef: name: db-secret key: password ---- ==== You can select the Secrets to consume in a number of ways: . By listing the directories where secrets are mapped: + ==== [source,bash] ---- -Dspring.cloud.kubernetes.secrets.paths=/etc/secrets/db-secret,etc/secrets/postgresql ---- ==== + If you have all the secrets mapped to a common root, you can set them like: + ==== [source,bash] ---- -Dspring.cloud.kubernetes.secrets.paths=/etc/secrets ---- ==== . By setting a named secret: + ==== [source,bash] ---- -Dspring.cloud.kubernetes.secrets.name=db-secret ---- ==== . By defining a list of labels: + ==== [source,bash] ---- -Dspring.cloud.kubernetes.secrets.labels.broker=activemq -Dspring.cloud.kubernetes.secrets.labels.db=postgresql ---- ==== As the case with `ConfigMap`, more advanced configuration is also possible where you can use multiple `Secret` instances. The `spring.cloud.kubernetes.secrets.sources` list makes this possible. For example, you could define the following `Secret` instances: ==== [source,yaml] ---- spring: application: name: cloud-k8s-app cloud: kubernetes: secrets: name: default-name namespace: default-namespace sources: # Spring Cloud Kubernetes looks up a Secret named s1 in namespace default-namespace - name: s1 # Spring Cloud Kubernetes looks up a Secret named default-name in whatever namespace n2 - namespace: n2 # Spring Cloud Kubernetes looks up a Secret named s3 in namespace n3 - namespace: n3 name: s3 ---- ==== In the preceding example, if `spring.cloud.kubernetes.secrets.namespace` had not been set, the `Secret` named `s1` would be looked up in the namespace that the application runs. .Properties: [options="header,footer"] |=== | Name | Type | Default | Description | `spring.cloud.kubernetes.secrets.enabled` | `Boolean` | `true` | Enable Secrets `PropertySource` | `spring.cloud.kubernetes.secrets.name` | `String` | `${spring.application.name}` | Sets the name of the secret to look up | `spring.cloud.kubernetes.secrets.namespace` | `String` | Client namespace | Sets the Kubernetes namespace where to look up | `spring.cloud.kubernetes.secrets.labels` | `Map` | `null` | Sets the labels used to lookup secrets | `spring.cloud.kubernetes.secrets.paths` | `List` | `null` | Sets the paths where secrets are mounted (example 1) | `spring.cloud.kubernetes.secrets.enableApi` | `Boolean` | `false` | Enables or disables consuming secrets through APIs (examples 2 and 3) |=== Notes: * The `spring.cloud.kubernetes.secrets.labels` property behaves as defined by https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-Configuration-Binding#map-based-binding[Map-based binding]. * The `spring.cloud.kubernetes.secrets.paths` property behaves as defined by https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-Configuration-Binding#collection-based-binding[Collection-based binding]. * Access to secrets through the API may be restricted for security reasons. The preferred way is to mount secrets to the Pod. You can find an example of an application that uses secrets (though it has not been updated to use the new `spring-cloud-kubernetes` project) at https://github.com/fabric8-quickstarts/spring-boot-camel-config[spring-boot-camel-config] === `PropertySource` Reload Some applications may need to detect changes on external property sources and update their internal status to reflect the new configuration. The reload feature of Spring Cloud Kubernetes is able to trigger an application reload when a related `ConfigMap` or `Secret` changes. By default, this feature is disabled. You can enable it by using the `spring.cloud.kubernetes.reload.enabled=true` configuration property (for example, in the `application.properties` file). The following levels of reload are supported (by setting the `spring.cloud.kubernetes.reload.strategy` property): * `refresh` (default): Only configuration beans annotated with `@ConfigurationProperties` or `@RefreshScope` are reloaded. This reload level leverages the refresh feature of Spring Cloud Context. * `restart_context`: the whole Spring `ApplicationContext` is gracefully restarted. Beans are recreated with the new configuration. * `shutdown`: the Spring `ApplicationContext` is shut down to activate a restart of the container. When you use this level, make sure that the lifecycle of all non-daemon threads is bound to the `ApplicationContext` and that a replication controller or replica set is configured to restart the pod. Assuming that the reload feature is enabled with default settings (`refresh` mode), the following bean is refreshed when the config map changes: ==== [java, source] ---- @Configuration @ConfigurationProperties(prefix = "bean") public class MyConfig { private String message = "a message that can be changed live"; // getter and setters } ---- ==== To see that changes effectively happen, you can create another bean that prints the message periodically, as follows ==== [source,java] ---- @Component public class MyBean { @Autowired private MyConfig config; @Scheduled(fixedDelay = 5000) public void hello() { System.out.println("The message is: " + config.getMessage()); } } ---- ==== You can change the message printed by the application by using a `ConfigMap`, as follows: ==== [source,yaml] ---- apiVersion: v1 kind: ConfigMap metadata: name: reload-example data: application.properties: |- bean.message=Hello World! ---- ==== Any change to the property named `bean.message` in the `ConfigMap` associated with the pod is reflected in the output. More generally speaking, changes associated to properties prefixed with the value defined by the `prefix` field of the `@ConfigurationProperties` annotation are detected and reflected in the application. <> is explained earlier in this chapter. The full example is available in https://github.com/fabric8io/spring-cloud-kubernetes/tree/master/spring-cloud-kubernetes-examples/kubernetes-reload-example[`spring-cloud-kubernetes-reload-example`]. The reload feature supports two operating modes: * Event (default): Watches for changes in config maps or secrets by using the Kubernetes API (web socket). Any event produces a re-check on the configuration and, in case of changes, a reload. The `view` role on the service account is required in order to listen for config map changes. A higher level role (such as `edit`) is required for secrets (by default, secrets are not monitored). * Polling: Periodically re-creates the configuration from config maps and secrets to see if it has changed. You can configure the polling period by using the `spring.cloud.kubernetes.reload.period` property and defaults to 15 seconds. It requires the same role as the monitored property source. This means, for example, that using polling on file-mounted secret sources does not require particular privileges. .Properties: [options="header,footer"] |=== | Name | Type | Default | Description | `spring.cloud.kubernetes.reload.enabled` | `Boolean` | `false` | Enables monitoring of property sources and configuration reload | `spring.cloud.kubernetes.reload.monitoring-config-maps` | `Boolean` | `true` | Allow monitoring changes in config maps | `spring.cloud.kubernetes.reload.monitoring-secrets` | `Boolean` | `false` | Allow monitoring changes in secrets | `spring.cloud.kubernetes.reload.strategy` | `Enum` | `refresh` | The strategy to use when firing a reload (`refresh`, `restart_context`, or `shutdown`) | `spring.cloud.kubernetes.reload.mode` | `Enum` | `event` | Specifies how to listen for changes in property sources (`event` or `polling`) | `spring.cloud.kubernetes.reload.period` | `Duration`| `15s` | The period for verifying changes when using the `polling` strategy |=== Notes: * You should not use properties under `spring.cloud.kubernetes.reload` in config maps or secrets. Changing such properties at runtime may lead to unexpected results. * Deleting a property or the whole config map does not restore the original state of the beans when you use the `refresh` level. == Ribbon Discovery in Kubernetes Spring Cloud client applications that call a microservice should be interested on relying on a client load-balancing feature in order to automatically discover at which endpoint(s) it can reach a given service. This mechanism has been implemented within the https://github.com/spring-cloud/spring-cloud-kubernetes/tree/master/spring-cloud-kubernetes-ribbon[spring-cloud-kubernetes-ribbon] project, where a Kubernetes client populates a https://github.com/Netflix/ribbon[Ribbon] `ServerList` that contains information about such endpoints. The implementation is part of the following starter that you can use by adding its dependency to your pom file: ==== [source,xml] ---- org.springframework.cloud spring-cloud-starter-kubernetes-ribbon ${latest.version} ---- ==== When the list of the endpoints is populated, the Kubernetes client searches the registered endpoints that live in the current namespace or project by matching the service name defined in the Ribbon Client annotation, as follows: ==== [source,java] ---- @RibbonClient(name = "name-service") ---- ==== You can configure Ribbon's behavior by providing properties in your `application.properties` (through your application's dedicated `ConfigMap`) by using the following format: `.ribbon.`, where: * `` corresponds to the service name you access over Ribbon, as configured by using the `@RibbonClient` annotation (such as `name-service` in the preceding example). * `` is one of the Ribbon configuration keys defined by https://github.com/Netflix/ribbon/blob/master/ribbon-core/src/main/java/com/netflix/client/config/CommonClientConfigKey.java[Ribbon's `CommonClientConfigKey` class]. Additionally, the `spring-cloud-kubernetes-ribbon` project defines two additional configuration keys to further control how Ribbon interacts with Kubernetes. In particular, if an endpoint defines multiple ports, the default behavior is to use the first one found. To select more specifically which port to use in a multi-port service, you can use the `PortName` key. If you want to specify in which Kubernetes namespace the target service should be looked up, you can use the `KubernetesNamespace` key, remembering in both instances to prefix these keys with your service name and `ribbon` prefix, as specified earlier. .Spring Cloud Kubernetes Ribbon Configuration |=== |Property Key |Type |Default Value |spring.cloud.kubernetes.ribbon.enabled |boolean |true |spring.cloud.kubernetes.ribbon.mode |`KubernetesRibbonMode` |POD |spring.cloud.kubernetes.ribbon.cluster-domain |string |cluster.local |=== * `spring.cloud.kubernetes.ribbon.mode` supports `POD` and `SERVICE` modes. ** The POD mode is to achieve load balancing by obtaining the Pod IP address of Kubernetes and using Ribbon. POD mode uses the load balancing of the Ribbon Does not support Kubernetes load balancing, The traffic policy of `Istio` is not supported. ** the `SERVICE` mode is directly based on the `service name` of the Ribbon. Get The Kubernetes service is concatenated into `service-name.{namespace}.svc.{cluster.domain}:{port}` such as: `demo1.default.svc.cluster.local:8080`. the `SERVICE` mode uses load balancing of the Kubernetes service to support Istio's traffic policy. * `spring.cloud.kubernetes.ribbon.cluster-domain` Set the custom Kubernetes cluster domain suffix. The default value is: 'cluster.local' The following examples use this module for ribbon discovery: * link:./spring-cloud-kubernetes-examples/kubernetes-circuitbreaker-ribbon-example[Spring Cloud Circuitbreaker and Ribbon] * https://github.com/fabric8-quickstarts/spring-boot-ribbon[fabric8-quickstarts - Spring Boot - Ribbon] * https://github.com/fabric8io/kubeflix/tree/master/examples/loanbroker/bank[Kubeflix - LoanBroker - Bank] NOTE: You can disable the Ribbon discovery client by setting the `spring.cloud.kubernetes.ribbon.enabled=false` key within the application properties file. == Kubernetes Ecosystem Awareness All of the features described earlier in this guide work equally well, regardless of whether your application is running inside Kubernetes. This is really helpful for development and troubleshooting. From a development point of view, this lets you start your Spring Boot application and debug one of the modules that is part of this project. You need not deploy it in Kubernetes, as the code of the project relies on the https://github.com/fabric8io/kubernetes-client[Fabric8 Kubernetes Java client], which is a fluent DSL that can communicate by using `http` protocol to the REST API of the Kubernetes Server. To disable the integration with Kubernetes you can set `spring.cloud.kubernetes.enabled` to `false`. Please be aware that when `spring-cloud-kubernetes-config` is on the classpath, `spring.cloud.kubernetes.enabled` should be set in `bootstrap.{properties|yml}` (or the profile specific one) otherwise it should be in `application.{properties|yml}` (or the profile specific one). Also note that these properties: `spring.cloud.kubernetes.config.enabled` and `spring.cloud.kubernetes.secrets.enabled` only take effect when set in `bootstrap.{properties|yml}` === Kubernetes Profile Autoconfiguration When the application runs as a pod inside Kubernetes, a Spring profile named `kubernetes` automatically gets activated. This lets you customize the configuration, to define beans that are applied when the Spring Boot application is deployed within the Kubernetes platform (for example, different development and production configuration). === Istio Awareness When you include the `spring-cloud-kubernetes-istio` module in the application classpath, a new profile is added to the application, provided the application is running inside a Kubernetes Cluster with https://istio.io[Istio] installed. You can then use spring `@Profile("istio")` annotations in your Beans and `@Configuration` classes. The Istio awareness module uses `me.snowdrop:istio-client` to interact with Istio APIs, letting us discover traffic rules, circuit breakers, and so on, making it easy for our Spring Boot applications to consume this data to dynamically configure themselves according to the environment. == Pod Health Indicator Spring Boot uses https://github.com/spring-projects/spring-boot/blob/master/spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/health/HealthEndpoint.java[`HealthIndicator`] to expose info about the health of an application. That makes it really useful for exposing health-related information to the user and makes it a good fit for use as https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-probes/[readiness probes]. The Kubernetes health indicator (which is part of the core module) exposes the following info: * Pod name, IP address, namespace, service account, node name, and its IP address * A flag that indicates whether the Spring Boot application is internal or external to Kubernetes == Leader Election == Security Configurations Inside Kubernetes === Namespace Most of the components provided in this project need to know the namespace. For Kubernetes (1.3+), the namespace is made available to the pod as part of the service account secret and is automatically detected by the client. For earlier versions, it needs to be specified as an environment variable to the pod. A quick way to do this is as follows: ==== [source] ---- env: - name: "KUBERNETES_NAMESPACE" valueFrom: fieldRef: fieldPath: "metadata.namespace" ---- ==== === Service Account For distributions of Kubernetes that support more fine-grained role-based access within the cluster, you need to make sure a pod that runs with `spring-cloud-kubernetes` has access to the Kubernetes API. For any service accounts you assign to a deployment or pod, you need to make sure they have the correct roles. Depending on the requirements, you'll need `get`, `list` and `watch` permission on the following resources: .Kubernetes Resource Permissions |=== |Dependency | Resources |spring-cloud-starter-kubernetes |pods, services, endpoints |spring-cloud-starter-kubernetes-config |configmaps, secrets |spring-cloud-starter-kubernetes-ribbon |pods, services, endpoints |=== For development purposes, you can add `cluster-reader` permissions to your `default` service account. On a production system you'll likely want to provide more granular permissions. The following Role and RoleBinding are an example for namespaced permissions for the `default` account: ==== [source,yaml] ---- kind: Role apiVersion: rbac.authorization.k8s.io/v1 metadata: namespace: YOUR-NAME-SPACE name: namespace-reader rules: - apiGroups: ["", "extensions", "apps"] resources: ["configmaps", "pods", "services", "endpoints", "secrets"] verbs: ["get", "list", "watch"] --- kind: RoleBinding apiVersion: rbac.authorization.k8s.io/v1 metadata: name: namespace-reader-binding namespace: YOUR-NAME-SPACE subjects: - kind: ServiceAccount name: default apiGroup: "" roleRef: kind: Role name: namespace-reader apiGroup: "" ---- ==== == Service Registry Implementation In Kubernetes service registration is controlled by the platform, the application itself does not control registration as it may do in other platforms. For this reason using `spring.cloud.service-registry.auto-registration.enabled` or setting `@EnableDiscoveryClient(autoRegister=false)` will have no effect in Spring Cloud Kubernetes. == Examples Spring Cloud Kubernetes tries to make it transparent for your applications to consume Kubernetes Native Services by following the Spring Cloud interfaces. In your applications, you need to add the `spring-cloud-kubernetes-discovery` dependency to your classpath and remove any other dependency that contains a `DiscoveryClient` implementation (that is, a Eureka discovery client). The same applies for `PropertySourceLocator`, where you need to add to the classpath the `spring-cloud-kubernetes-config` and remove any other dependency that contains a `PropertySourceLocator` implementation (that is, a configuration server client). The following projects highlight the usage of these dependencies and demonstrate how you can use these libraries from any Spring Boot application: * https://github.com/spring-cloud/spring-cloud-kubernetes/tree/master/spring-cloud-kubernetes-examples[Spring Cloud Kubernetes Examples]: the ones located inside this repository. * Spring Cloud Kubernetes Full Example: Minions and Boss ** https://github.com/salaboy/spring-cloud-k8s-minion[Minion] ** https://github.com/salaboy/spring-cloud-k8s-boss[Boss] * Spring Cloud Kubernetes Full Example: https://github.com/salaboy/s1p_docs[SpringOne Platform Tickets Service] * https://github.com/salaboy/s1p_gateway[Spring Cloud Gateway with Spring Cloud Kubernetes Discovery and Config] * https://github.com/salaboy/showcase-admin-tool[Spring Boot Admin with Spring Cloud Kubernetes Discovery and Config] == Other Resources This section lists other resources, such as presentations (slides) and videos about Spring Cloud Kubernetes. * https://salaboy.com/2018/09/27/the-s1p-experience/[S1P Spring Cloud on PKS] * https://salaboy.com/2018/07/18/ljc-july-18-spring-cloud-docker-k8s/[Spring Cloud, Docker, Kubernetes -> London Java Community July 2018] Please feel free to submit other resources through pull requests to https://github.com/spring-cloud/spring-cloud-kubernetes[this repository]. == Configuration properties To see the list of all Sleuth related configuration properties please check link:appendix.html[the Appendix page]. == Building :jdkversion: 1.7 === Basic Compile and Test To build the source you will need to install JDK {jdkversion}. Spring Cloud uses Maven for most build-related activities, and you should be able to get off the ground quite quickly by cloning the project you are interested in and typing ---- $ ./mvnw install ---- NOTE: You can also install Maven (>=3.3.3) yourself and run the `mvn` command in place of `./mvnw` in the examples below. If you do that you also might need to add `-P spring` if your local Maven settings do not contain repository declarations for spring pre-release artifacts. NOTE: Be aware that you might need to increase the amount of memory available to Maven by setting a `MAVEN_OPTS` environment variable with a value like `-Xmx512m -XX:MaxPermSize=128m`. We try to cover this in the `.mvn` configuration, so if you find you have to do it to make a build succeed, please raise a ticket to get the settings added to source control. For hints on how to build the project look in `.travis.yml` if there is one. There should be a "script" and maybe "install" command. Also look at the "services" section to see if any services need to be running locally (e.g. mongo or rabbit). Ignore the git-related bits that you might find in "before_install" since they're related to setting git credentials and you already have those. The projects that require middleware generally include a `docker-compose.yml`, so consider using https://docs.docker.com/compose/[Docker Compose] to run the middeware servers in Docker containers. See the README in the https://github.com/spring-cloud-samples/scripts[scripts demo repository] for specific instructions about the common cases of mongo, rabbit and redis. NOTE: If all else fails, build with the command from `.travis.yml` (usually `./mvnw install`). === Documentation The spring-cloud-build module has a "docs" profile, and if you switch that on it will try to build asciidoc sources from `src/main/asciidoc`. As part of that process it will look for a `README.adoc` and process it by loading all the includes, but not parsing or rendering it, just copying it to `${main.basedir}` (defaults to `${basedir}`, i.e. the root of the project). If there are any changes in the README it will then show up after a Maven build as a modified file in the correct place. Just commit it and push the change. === Working with the code If you don't have an IDE preference we would recommend that you use https://www.springsource.com/developer/sts[Spring Tools Suite] or https://eclipse.org[Eclipse] when working with the code. We use the https://eclipse.org/m2e/[m2eclipse] eclipse plugin for maven support. Other IDEs and tools should also work without issue as long as they use Maven 3.3.3 or better. ==== Importing into eclipse with m2eclipse We recommend the https://eclipse.org/m2e/[m2eclipse] eclipse plugin when working with eclipse. If you don't already have m2eclipse installed it is available from the "eclipse marketplace". NOTE: Older versions of m2e do not support Maven 3.3, so once the projects are imported into Eclipse you will also need to tell m2eclipse to use the right profile for the projects. If you see many different errors related to the POMs in the projects, check that you have an up to date installation. If you can't upgrade m2e, add the "spring" profile to your `settings.xml`. Alternatively you can copy the repository settings from the "spring" profile of the parent pom into your `settings.xml`. ==== Importing into eclipse without m2eclipse If you prefer not to use m2eclipse you can generate eclipse project metadata using the following command: [indent=0] ---- $ ./mvnw eclipse:eclipse ---- The generated eclipse projects can be imported by selecting `import existing projects` from the `file` menu. == Contributing :spring-cloud-build-branch: master Spring Cloud is released under the non-restrictive Apache 2.0 license, and follows a very standard Github development process, using Github tracker for issues and merging pull requests into master. If you want to contribute even something trivial please do not hesitate, but follow the guidelines below. === Sign the Contributor License Agreement Before we accept a non-trivial patch or pull request we will need you to sign the https://cla.pivotal.io/sign/spring[Contributor License Agreement]. Signing the contributor's agreement does not grant anyone commit rights to the main repository, but it does mean that we can accept your contributions, and you will get an author credit if we do. Active contributors might be asked to join the core team, and given the ability to merge pull requests. === Code of Conduct This project adheres to the Contributor Covenant https://github.com/spring-cloud/spring-cloud-build/blob/master/docs/src/main/asciidoc/code-of-conduct.adoc[code of conduct]. By participating, you are expected to uphold this code. Please report unacceptable behavior to spring-code-of-conduct@pivotal.io. === Code Conventions and Housekeeping None of these is essential for a pull request, but they will all help. They can also be added after the original pull request but before a merge. * Use the Spring Framework code format conventions. If you use Eclipse you can import formatter settings using the `eclipse-code-formatter.xml` file from the https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/spring-cloud-dependencies-parent/eclipse-code-formatter.xml[Spring Cloud Build] project. If using IntelliJ, you can use the https://plugins.jetbrains.com/plugin/6546[Eclipse Code Formatter Plugin] to import the same file. * Make sure all new `.java` files to have a simple Javadoc class comment with at least an `@author` tag identifying you, and preferably at least a paragraph on what the class is for. * Add the ASF license header comment to all new `.java` files (copy from existing files in the project) * Add yourself as an `@author` to the .java files that you modify substantially (more than cosmetic changes). * Add some Javadocs and, if you change the namespace, some XSD doc elements. * A few unit tests would help a lot as well -- someone has to do it. * If no-one else is using your branch, please rebase it against the current master (or other target branch in the main project). * When writing a commit message please follow https://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html[these conventions], if you are fixing an existing issue please add `Fixes gh-XXXX` at the end of the commit message (where XXXX is the issue number). === Checkstyle Spring Cloud Build comes with a set of checkstyle rules. You can find them in the `spring-cloud-build-tools` module. The most notable files under the module are: .spring-cloud-build-tools/ ---- └── src    ├── checkstyle    │   └── checkstyle-suppressions.xml <3>    └── main    └── resources    ├── checkstyle-header.txt <2>    └── checkstyle.xml <1> ---- <1> Default Checkstyle rules <2> File header setup <3> Default suppression rules ==== Checkstyle configuration Checkstyle rules are *disabled by default*. To add checkstyle to your project just define the following properties and plugins. .pom.xml ---- true <1> true <2> true <3> <4> io.spring.javaformat spring-javaformat-maven-plugin <5> org.apache.maven.plugins maven-checkstyle-plugin <5> org.apache.maven.plugins maven-checkstyle-plugin ---- <1> Fails the build upon Checkstyle errors <2> Fails the build upon Checkstyle violations <3> Checkstyle analyzes also the test sources <4> Add the Spring Java Format plugin that will reformat your code to pass most of the Checkstyle formatting rules <5> Add checkstyle plugin to your build and reporting phases If you need to suppress some rules (e.g. line length needs to be longer), then it's enough for you to define a file under `${project.root}/src/checkstyle/checkstyle-suppressions.xml` with your suppressions. Example: .projectRoot/src/checkstyle/checkstyle-suppresions.xml ---- ---- It's advisable to copy the `${spring-cloud-build.rootFolder}/.editorconfig` and `${spring-cloud-build.rootFolder}/.springformat` to your project. That way, some default formatting rules will be applied. You can do so by running this script: ```bash $ curl https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/.editorconfig -o .editorconfig $ touch .springformat ``` === IDE setup ==== Intellij IDEA In order to setup Intellij you should import our coding conventions, inspection profiles and set up the checkstyle plugin. The following files can be found in the https://github.com/spring-cloud/spring-cloud-build/tree/master/spring-cloud-build-tools[Spring Cloud Build] project. .spring-cloud-build-tools/ ---- └── src    ├── checkstyle    │   └── checkstyle-suppressions.xml <3>    └── main    └── resources    ├── checkstyle-header.txt <2>    ├── checkstyle.xml <1>    └── intellij       ├── Intellij_Project_Defaults.xml <4>       └── Intellij_Spring_Boot_Java_Conventions.xml <5> ---- <1> Default Checkstyle rules <2> File header setup <3> Default suppression rules <4> Project defaults for Intellij that apply most of Checkstyle rules <5> Project style conventions for Intellij that apply most of Checkstyle rules .Code style image::https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/{spring-cloud-build-branch}/docs/src/main/asciidoc/images/intellij-code-style.png[Code style] Go to `File` -> `Settings` -> `Editor` -> `Code style`. There click on the icon next to the `Scheme` section. There, click on the `Import Scheme` value and pick the `Intellij IDEA code style XML` option. Import the `spring-cloud-build-tools/src/main/resources/intellij/Intellij_Spring_Boot_Java_Conventions.xml` file. .Inspection profiles image::https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/{spring-cloud-build-branch}/docs/src/main/asciidoc/images/intellij-inspections.png[Code style] Go to `File` -> `Settings` -> `Editor` -> `Inspections`. There click on the icon next to the `Profile` section. There, click on the `Import Profile` and import the `spring-cloud-build-tools/src/main/resources/intellij/Intellij_Project_Defaults.xml` file. .Checkstyle To have Intellij work with Checkstyle, you have to install the `Checkstyle` plugin. It's advisable to also install the `Assertions2Assertj` to automatically convert the JUnit assertions image::https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/{spring-cloud-build-branch}/docs/src/main/asciidoc/images/intellij-checkstyle.png[Checkstyle] Go to `File` -> `Settings` -> `Other settings` -> `Checkstyle`. There click on the `+` icon in the `Configuration file` section. There, you'll have to define where the checkstyle rules should be picked from. In the image above, we've picked the rules from the cloned Spring Cloud Build repository. However, you can point to the Spring Cloud Build's GitHub repository (e.g. for the `checkstyle.xml` : `https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/spring-cloud-build-tools/src/main/resources/checkstyle.xml`). We need to provide the following variables: - `checkstyle.header.file` - please point it to the Spring Cloud Build's, `spring-cloud-build-tools/src/main/resources/checkstyle-header.txt` file either in your cloned repo or via the `https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/spring-cloud-build-tools/src/main/resources/checkstyle-header.txt` URL. - `checkstyle.suppressions.file` - default suppressions. Please point it to the Spring Cloud Build's, `spring-cloud-build-tools/src/checkstyle/checkstyle-suppressions.xml` file either in your cloned repo or via the `https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/spring-cloud-build-tools/src/checkstyle/checkstyle-suppressions.xml` URL. - `checkstyle.additional.suppressions.file` - this variable corresponds to suppressions in your local project. E.g. you're working on `spring-cloud-contract`. Then point to the `project-root/src/checkstyle/checkstyle-suppressions.xml` folder. Example for `spring-cloud-contract` would be: `/home/username/spring-cloud-contract/src/checkstyle/checkstyle-suppressions.xml`. IMPORTANT: Remember to set the `Scan Scope` to `All sources` since we apply checkstyle rules for production and test sources.