com.google.appengine.api.backends.BackendServiceImpl Maven / Gradle / Ivy

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/*
 * Copyright 2021 Google LLC
 *
 * 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
 *
 *     https://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 com.google.appengine.api.backends;

import com.google.appengine.api.utils.SystemProperty;
import com.google.apphosting.api.ApiProxy;
import com.google.apphosting.api.ApiProxy.Environment;
import java.util.Map;

/**
 * The implementation of the Backends API for the production appserver.
 *
 */
class BackendServiceImpl implements BackendService {
  static final String DATACENTER_ATTR_KEY = "com.google.apphosting.api.ApiProxy.datacenter";

  // Keep in sync with java/com/google/apphosting/runtime/ApiProxyImpl.java
  static final String DEFAULT_VERSION_HOSTNAME =
      "com.google.appengine.runtime.default_version_hostname";

  BackendServiceImpl() {
  }

  @Override
  public String getCurrentBackend() {
    return (String) getThreadLocalAttributes().get(BACKEND_ID_ENV_ATTRIBUTE);
  }

  @Override
  public int getCurrentInstance() {
    try {
      return Integer.parseInt((String) getThreadLocalAttributes().get(INSTANCE_ID_ENV_ATTRIBUTE));
    } catch (NumberFormatException e) {
      // no instance configured
      return -1;
    }
  }

  @Override
  public String getBackendAddress(String backendName) {
    if (isProduction()) {
      return backendName + "." + getDefaultVersionHostname();
    } else {
      // running in the dev-appserver, get the local port
      return getDevAppServerLocalAddress(backendName);
    }
  }

  @Override
  public String getBackendAddress(String backendName, int instance) {
    String backendInstance = instance + "." + backendName;
    if (isProduction()) {
      return backendInstance + "." + getDefaultVersionHostname();
    } else {
      // running in the dev-appserver, get the local port
      return getDevAppServerLocalAddress(backendInstance);
    }
  }

  /**
   * Returns the local address in the devappserver given the url-prefix of a
   * backend.
   *
   *  Examples: . for a specific backend instance, or 
   * for the backend without instance specified.
   *
   * @param string The url prefix for the backend
   * @return The local address of that backend
   */
  private String getDevAppServerLocalAddress(String string) {
    @SuppressWarnings("unchecked")
    Map portMap =
        (Map) getThreadLocalAttributes().get(DEVAPPSERVER_PORTMAPPING_KEY);
    Object addr = portMap.get(string);
    if (addr == null) {
      throw new IllegalStateException("Tried to get local address of unknown backend");
    }
    return (String) addr;
  }

  /* @VisibleForTesting */
  static String getDefaultVersionHostname() {
    return (String) getThreadLocalAttributes().get(DEFAULT_VERSION_HOSTNAME);
  }

  private static Map getThreadLocalAttributes() {
    Environment env = ApiProxy.getCurrentEnvironment();
    if (env == null) {
      throw new IllegalStateException(
          "Operation not allowed in a thread that is neither the original request thread "
              + "nor a thread created by ThreadManager");
    }
    Map attr = env.getAttributes();
    if (attr == null) {
      throw new RuntimeException(
          "Local environment is corrupt (thread local attributes map is null)");
    }
    return attr;
  }

  private static boolean isProduction() {
    return SystemProperty.environment.value() == SystemProperty.Environment.Value.Production;
  }
}