Add Kubrnetes DiscoveryClient

discovery-client/src/main/java/io/micronaut/discovery/kubernetes/KubernetesDiscoveryClient.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright 2018 original authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.micronaut.discovery.kubernetes;
+
+import io.micronaut.context.annotation.Requires;
+import io.micronaut.core.util.StringUtils;
+import io.micronaut.discovery.DiscoveryClient;
+import io.micronaut.discovery.ServiceInstance;
+import io.reactivex.Flowable;
+
+import javax.inject.Singleton;
+import java.io.IOException;
+import java.net.URI;
+import java.util.*;
+
+/**
+ * A {@link DiscoveryClient} implementation for Kubernetes. Kubernetes uses environment variables so no API calls is required
+ *
+ * @author graemerocher
+ * @since 1.0
+ */
+@Singleton
+@Requires(env = "KUBERNETES_SERVICE_HOST")
+public class KubernetesDiscoveryClient implements DiscoveryClient {
+
+    private static final String HOST_SUFFIX = "_SERVICE_HOST";
+    private static final String PORT_SUFFIX = "_SERVICE_PORT";
+    private static final String HTTPS_PORT_SUFFIX = "_SERVICE_PORT_HTTPS";
+
+    @Override
+    public Flowable<List<ServiceInstance>> getInstances(String serviceId) {
+
+        Map<String, String> environment = resolveEnvironment();
+
+        String envName = serviceId.toUpperCase(Locale.ENGLISH).replace('-', '_');
+        String host = environment.get(envName + HOST_SUFFIX);
+        if(StringUtils.isNotEmpty(host)) {
+            String port = environment.get(envName + HTTPS_PORT_SUFFIX);
+            if(StringUtils.isNotEmpty(port)) {
+                return singleService(serviceId, host, port, true);
+            }
+            else {
+                port = environment.get(envName + PORT_SUFFIX);
+                if(StringUtils.isNotEmpty(port)) {
+                    return singleService(serviceId, host, port, false);
+                }
+            }
+        }
+        return Flowable.just(Collections.emptyList());
+    }
+
+    @Override
+    public Flowable<List<String>> getServiceIds() {
+        List<String> services = new ArrayList<>();
+
+        Map<String, String> environment = resolveEnvironment();
+        for (String envName : environment.keySet()) {
+            if(envName.endsWith(HOST_SUFFIX)) {
+                String serviceId = envName.substring(0, envName.length() - HOST_SUFFIX.length());
+
+                services.add( serviceId.toLowerCase(Locale.ENGLISH).replace('_','-'));
+            }
+        }
+
+        return Flowable.just(services);
+    }
+
+    @Override
+    public String getDescription() {
+        return "kubernetes";
+    }
+
+    @Override
+    public void close() throws IOException {
+        // no-op
+    }
+
+    /**
+     * Resolves the environment variables
+     *
+     * @return The environment variables
+     */
+    @SuppressWarnings("WeakerAccess")
+    protected Map<String, String> resolveEnvironment() {
+        return System.getenv();
+    }
+
+    private Flowable<List<ServiceInstance>> singleService(String serviceId, String host, String port, boolean secure) {
+        return Flowable.just(
+                Collections.singletonList(
+                        ServiceInstance.builder(
+                                serviceId,
+                                URI.create((secure ? "https://" : "http://") + host + ":" + port)
+                        ).build()
+
+                )
+        );
+    }
+}

discovery-client/src/test/groovy/io/micronaut/discovery/kubernetes/KubernetesDiscoveryClientSpec.groovy

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2018 original authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.micronaut.discovery.kubernetes
+
+import spock.lang.Specification
+
+/**
+ * @author graemerocher
+ * @since 1.0
+ */
+class KubernetesDiscoveryClientSpec extends Specification {
+
+    void "test kubernetes discovery client"() {
+        given:
+        KubernetesDiscoveryClient client = new KubernetesDiscoveryClient() {
+            @Override
+            protected Map<String, String> resolveEnvironment() {
+                [
+                        "FOO_BAR_SERVICE_HOST":"foobar",
+                        "FOO_BAR_SERVICE_PORT":"8080",
+                        "FOO_SERVICE_PORT_HTTPS":"8443",
+                        "FOO_SERVICE_HOST":"foo"
+                ]
+            }
+        }
+
+        expect:
+        client.getServiceIds().blockingFirst() == ['foo-bar', 'foo']
+        client.getInstances('foo-bar').blockingFirst()[0].id == 'foo-bar'
+        client.getInstances('foo-bar').blockingFirst()[0].getURI() == URI.create("http://foobar:8080")
+        client.getInstances('foo').blockingFirst()[0].id == 'foo'
+        client.getInstances('foo').blockingFirst()[0].getURI() == URI.create("https://foo:8443")
+
+    }
+}