core/src/main/java/io/grpc/internal/ServiceConfigUtil.java - platform/external/grpc-grpc-java - Git at Google

 /*
  * Copyright 2018 The gRPC 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.grpc.internal;

 import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.base.Preconditions.checkState;
 import static com.google.common.base.Verify.verify;

 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.MoreObjects;
 import com.google.common.base.Objects;
 import com.google.common.base.VerifyException;
 import io.grpc.LoadBalancerProvider;
 import io.grpc.LoadBalancerRegistry;
 import io.grpc.NameResolver.ConfigOrError;
 import io.grpc.Status;
 import io.grpc.internal.RetriableStream.Throttle;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.EnumSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import javax.annotation.Nullable;

 /**
  * Helper utility to work with service configs.
  *
  * <p>This class contains helper methods to parse service config JSON values into Java types.
  */
 public final class ServiceConfigUtil {

   private ServiceConfigUtil() {}

   /**
    * Fetches the health-checked service config from service config. {@code null} if can't find one.
    */
   @Nullable
   public static Map<String, ?> getHealthCheckedService(@Nullable  Map<String, ?> serviceConfig) {
     if (serviceConfig == null) {
       return null;
     }

     /* schema as follows
     {
       "healthCheckConfig": {
         // Service name to use in the health-checking request.
         "serviceName": string
       }
     }
     */
     return JsonUtil.getObject(serviceConfig, "healthCheckConfig");
   }

   /**
    * Fetches the health-checked service name from health-checked service config. {@code null} if
    * can't find one.
    */
   @Nullable
   public static String getHealthCheckedServiceName(
       @Nullable Map<String, ?> healthCheckedServiceConfig) {
     if (healthCheckedServiceConfig == null) {
       return null;
     }
     return JsonUtil.getString(healthCheckedServiceConfig, "serviceName");
   }

   @Nullable
   static Throttle getThrottlePolicy(@Nullable Map<String, ?> serviceConfig) {
     if (serviceConfig == null) {
       return null;
     }

     /* schema as follows
     {
       "retryThrottling": {
         // The number of tokens starts at maxTokens. The token_count will always be
         // between 0 and maxTokens.
         //
         // This field is required and must be greater than zero.
         "maxTokens": number,

         // The amount of tokens to add on each successful RPC. Typically this will
         // be some number between 0 and 1, e.g., 0.1.
         //
         // This field is required and must be greater than zero. Up to 3 decimal
         // places are supported.
         "tokenRatio": number
       }
     }
     */

     Map<String, ?> throttling = JsonUtil.getObject(serviceConfig, "retryThrottling");
     if (throttling == null) {
       return null;
     }

     // TODO(dapengzhang0): check if this is null.
     float maxTokens = JsonUtil.getNumber(throttling, "maxTokens").floatValue();
     float tokenRatio = JsonUtil.getNumber(throttling, "tokenRatio").floatValue();
     checkState(maxTokens > 0f, "maxToken should be greater than zero");
     checkState(tokenRatio > 0f, "tokenRatio should be greater than zero");
     return new Throttle(maxTokens, tokenRatio);
   }

   @Nullable
   static Integer getMaxAttemptsFromRetryPolicy(Map<String, ?> retryPolicy) {
     return JsonUtil.getNumberAsInteger(retryPolicy, "maxAttempts");
   }

   @Nullable
   static Long getInitialBackoffNanosFromRetryPolicy(Map<String, ?> retryPolicy) {
     return JsonUtil.getStringAsDuration(retryPolicy, "initialBackoff");
   }

   @Nullable
   static Long getMaxBackoffNanosFromRetryPolicy(Map<String, ?> retryPolicy) {
     return JsonUtil.getStringAsDuration(retryPolicy, "maxBackoff");
   }

   @Nullable
   static Double getBackoffMultiplierFromRetryPolicy(Map<String, ?> retryPolicy) {
     return JsonUtil.getNumber(retryPolicy, "backoffMultiplier");
   }

   @Nullable
   static Long getPerAttemptRecvTimeoutNanosFromRetryPolicy(Map<String, ?> retryPolicy) {
     return JsonUtil.getStringAsDuration(retryPolicy, "perAttemptRecvTimeout");
   }

   private static Set<Status.Code> getListOfStatusCodesAsSet(Map<String, ?> obj, String key) {
     List<?> statuses = JsonUtil.getList(obj, key);
     if (statuses == null) {
       return null;
     }
     return getStatusCodesFromList(statuses);
   }

   private static Set<Status.Code> getStatusCodesFromList(List<?> statuses) {
     EnumSet<Status.Code> codes = EnumSet.noneOf(Status.Code.class);
     for (Object status : statuses) {
       Status.Code code;
       if (status instanceof Double) {
         Double statusD = (Double) status;
         int codeValue = statusD.intValue();
         verify((double) codeValue == statusD, "Status code %s is not integral", status);
         code = Status.fromCodeValue(codeValue).getCode();
         verify(code.value() == statusD.intValue(), "Status code %s is not valid", status);
       } else if (status instanceof String) {
         try {
           code = Status.Code.valueOf((String) status);
         } catch (IllegalArgumentException iae) {
           throw new VerifyException("Status code " + status + " is not valid", iae);
         }
       } else {
         throw new VerifyException(
             "Can not convert status code " + status + " to Status.Code, because its type is "
                 + status.getClass());
       }
       codes.add(code);
     }
     return Collections.unmodifiableSet(codes);
   }

   static Set<Status.Code> getRetryableStatusCodesFromRetryPolicy(Map<String, ?> retryPolicy) {
     String retryableStatusCodesKey = "retryableStatusCodes";
     Set<Status.Code> codes = getListOfStatusCodesAsSet(retryPolicy, retryableStatusCodesKey);
     verify(codes != null, "%s is required in retry policy", retryableStatusCodesKey);
     verify(!codes.contains(Status.Code.OK), "%s must not contain OK", retryableStatusCodesKey);
     return codes;
   }

   @Nullable
   static Integer getMaxAttemptsFromHedgingPolicy(Map<String, ?> hedgingPolicy) {
     return JsonUtil.getNumberAsInteger(hedgingPolicy, "maxAttempts");
   }

   @Nullable
   static Long getHedgingDelayNanosFromHedgingPolicy(Map<String, ?> hedgingPolicy) {
     return JsonUtil.getStringAsDuration(hedgingPolicy, "hedgingDelay");
   }

   static Set<Status.Code> getNonFatalStatusCodesFromHedgingPolicy(Map<String, ?> hedgingPolicy) {
     String nonFatalStatusCodesKey = "nonFatalStatusCodes";
     Set<Status.Code> codes = getListOfStatusCodesAsSet(hedgingPolicy, nonFatalStatusCodesKey);
     if (codes == null) {
       return Collections.unmodifiableSet(EnumSet.noneOf(Status.Code.class));
     }
     verify(!codes.contains(Status.Code.OK), "%s must not contain OK", nonFatalStatusCodesKey);
     return codes;
   }

   @Nullable
   static String getServiceFromName(Map<String, ?> name) {
     return JsonUtil.getString(name, "service");
   }

   @Nullable
   static String getMethodFromName(Map<String, ?> name) {
     return JsonUtil.getString(name, "method");
   }

   @Nullable
   static Map<String, ?> getRetryPolicyFromMethodConfig(Map<String, ?> methodConfig) {
     return JsonUtil.getObject(methodConfig, "retryPolicy");
   }

   @Nullable
   static Map<String, ?> getHedgingPolicyFromMethodConfig(Map<String, ?> methodConfig) {
     return JsonUtil.getObject(methodConfig, "hedgingPolicy");
   }

   @Nullable
   static List<Map<String, ?>> getNameListFromMethodConfig(
       Map<String, ?> methodConfig) {
     return JsonUtil.getListOfObjects(methodConfig, "name");
   }

   /**
    * Returns the number of nanoseconds of timeout for the given method config.
    *
    * @return duration nanoseconds, or {@code null} if it isn't present.
    */
   @Nullable
   static Long getTimeoutFromMethodConfig(Map<String, ?> methodConfig) {
     return JsonUtil.getStringAsDuration(methodConfig, "timeout");
   }

   @Nullable
   static Boolean getWaitForReadyFromMethodConfig(Map<String, ?> methodConfig) {
     return JsonUtil.getBoolean(methodConfig, "waitForReady");
   }

   @Nullable
   static Integer getMaxRequestMessageBytesFromMethodConfig(Map<String, ?> methodConfig) {
     return JsonUtil.getNumberAsInteger(methodConfig, "maxRequestMessageBytes");
   }

   @Nullable
   static Integer getMaxResponseMessageBytesFromMethodConfig(Map<String, ?> methodConfig) {
     return JsonUtil.getNumberAsInteger(methodConfig, "maxResponseMessageBytes");
   }

   @Nullable
   static List<Map<String, ?>> getMethodConfigFromServiceConfig(
       Map<String, ?> serviceConfig) {
     return JsonUtil.getListOfObjects(serviceConfig, "methodConfig");
   }

   /**
    * Extracts load balancing configs from a service config.
    */
   @VisibleForTesting
   public static List<Map<String, ?>> getLoadBalancingConfigsFromServiceConfig(
       Map<String, ?> serviceConfig) {
     /* schema as follows
     {
       "loadBalancingConfig": [
         {"xds" :
           {
             "childPolicy": [...],
             "fallbackPolicy": [...],
           }
         },
         {"round_robin": {}}
       ],
       "loadBalancingPolicy": "ROUND_ROBIN"  // The deprecated policy key
     }
     */
     List<Map<String, ?>> lbConfigs = new ArrayList<>();
     String loadBalancingConfigKey = "loadBalancingConfig";
     if (serviceConfig.containsKey(loadBalancingConfigKey)) {
       lbConfigs.addAll(JsonUtil.getListOfObjects(
           serviceConfig, loadBalancingConfigKey));
     }
     if (lbConfigs.isEmpty()) {
       // No LoadBalancingConfig found.  Fall back to the deprecated LoadBalancingPolicy
       String policy = JsonUtil.getString(serviceConfig, "loadBalancingPolicy");
       if (policy != null) {
         // Convert the policy to a config, so that the caller can handle them in the same way.
         policy = policy.toLowerCase(Locale.ROOT);
         Map<String, ?> fakeConfig = Collections.singletonMap(policy, Collections.emptyMap());
         lbConfigs.add(fakeConfig);
       }
     }
     return Collections.unmodifiableList(lbConfigs);
   }

   /**
    * Unwrap a LoadBalancingConfig JSON object into a {@link LbConfig}.  The input is a JSON object
    * (map) with exactly one entry, where the key is the policy name and the value is a config object
    * for that policy.
    */
   public static LbConfig unwrapLoadBalancingConfig(Map<String, ?> lbConfig) {
     if (lbConfig.size() != 1) {
       throw new RuntimeException(
           "There are " + lbConfig.size() + " fields in a LoadBalancingConfig object. Exactly one"
           + " is expected. Config=" + lbConfig);
     }
     String key = lbConfig.entrySet().iterator().next().getKey();
     return new LbConfig(key, JsonUtil.getObject(lbConfig, key));
   }

   /**
    * Given a JSON list of LoadBalancingConfigs, and convert it into a list of LbConfig.
    */
   public static List<LbConfig> unwrapLoadBalancingConfigList(List<Map<String, ?>> list) {
     if (list == null) {
       return null;
     }
     ArrayList<LbConfig> result = new ArrayList<>();
     for (Map<String, ?> rawChildPolicy : list) {
       result.add(unwrapLoadBalancingConfig(rawChildPolicy));
     }
     return Collections.unmodifiableList(result);
   }

   /**
    * Parses and selects a load balancing policy from a non-empty list of raw configs. If selection
    * is successful, the returned ConfigOrError object will include a {@link
    * ServiceConfigUtil.PolicySelection} as its config value.
    */
   public static ConfigOrError selectLbPolicyFromList(
       List<LbConfig> lbConfigs, LoadBalancerRegistry lbRegistry) {
     List<String> policiesTried = new ArrayList<>();
     for (LbConfig lbConfig : lbConfigs) {
       String policy = lbConfig.getPolicyName();
       LoadBalancerProvider provider = lbRegistry.getProvider(policy);
       if (provider == null) {
         policiesTried.add(policy);
       } else {
         if (!policiesTried.isEmpty()) {
           Logger.getLogger(ServiceConfigUtil.class.getName()).log(
               Level.FINEST,
               "{0} specified by Service Config are not available", policiesTried);
         }
         ConfigOrError parsedLbPolicyConfig =
             provider.parseLoadBalancingPolicyConfig(lbConfig.getRawConfigValue());
         if (parsedLbPolicyConfig.getError() != null) {
           return parsedLbPolicyConfig;
         }
         return ConfigOrError.fromConfig(
             new PolicySelection(provider, parsedLbPolicyConfig.getConfig()));
       }
     }
     return ConfigOrError.fromError(
         Status.UNKNOWN.withDescription(
             "None of " + policiesTried + " specified by Service Config are available."));
   }

   /**
    * A LoadBalancingConfig that includes the policy name (the key) and its raw config value (parsed
    * JSON).
    */
   public static final class LbConfig {
     private final String policyName;
     private final Map<String, ?> rawConfigValue;

     public LbConfig(String policyName, Map<String, ?> rawConfigValue) {
       this.policyName = checkNotNull(policyName, "policyName");
       this.rawConfigValue = checkNotNull(rawConfigValue, "rawConfigValue");
     }

     public String getPolicyName() {
       return policyName;
     }

     public Map<String, ?> getRawConfigValue() {
       return rawConfigValue;
     }

     @Override
     public boolean equals(Object o) {
       if (o instanceof LbConfig) {
         LbConfig other = (LbConfig) o;
         return policyName.equals(other.policyName)
             && rawConfigValue.equals(other.rawConfigValue);
       }
       return false;
     }

     @Override
     public int hashCode() {
       return Objects.hashCode(policyName, rawConfigValue);
     }

     @Override
     public String toString() {
       return MoreObjects.toStringHelper(this)
           .add("policyName", policyName)
           .add("rawConfigValue", rawConfigValue)
           .toString();
     }
   }

   public static final class PolicySelection {
     final LoadBalancerProvider provider;
     @Nullable
     final Object config;

     /** Constructs a PolicySelection with selected LB provider and the deeply parsed LB config. */
     public PolicySelection(
         LoadBalancerProvider provider,
         @Nullable Object config) {
       this.provider = checkNotNull(provider, "provider");
       this.config = config;
     }

     public LoadBalancerProvider getProvider() {
       return provider;
     }

     @Nullable
     public Object getConfig() {
       return config;
     }

     @Override
     public boolean equals(Object o) {
       if (this == o) {
         return true;
       }
       if (o == null || getClass() != o.getClass()) {
         return false;
       }
       PolicySelection that = (PolicySelection) o;
       return Objects.equal(provider, that.provider)
           && Objects.equal(config, that.config);
     }

     @Override
     public int hashCode() {
       return Objects.hashCode(provider, config);
     }

     @Override
     public String toString() {
       return MoreObjects.toStringHelper(this)
           .add("provider", provider)
           .add("config", config)
           .toString();
     }
   }
 }
	/*
	* Copyright 2018 The gRPC 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.grpc.internal;

	import static com.google.common.base.Preconditions.checkNotNull;
	import static com.google.common.base.Preconditions.checkState;
	import static com.google.common.base.Verify.verify;

	import com.google.common.annotations.VisibleForTesting;
	import com.google.common.base.MoreObjects;
	import com.google.common.base.Objects;
	import com.google.common.base.VerifyException;
	import io.grpc.LoadBalancerProvider;
	import io.grpc.LoadBalancerRegistry;
	import io.grpc.NameResolver.ConfigOrError;
	import io.grpc.Status;
	import io.grpc.internal.RetriableStream.Throttle;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.EnumSet;
	import java.util.List;
	import java.util.Locale;
	import java.util.Map;
	import java.util.Set;
	import java.util.logging.Level;
	import java.util.logging.Logger;
	import javax.annotation.Nullable;

	/**
	* Helper utility to work with service configs.
	*
	* <p>This class contains helper methods to parse service config JSON values into Java types.
	*/
	public final class ServiceConfigUtil {

	private ServiceConfigUtil() {}

	/**
	* Fetches the health-checked service config from service config. {@code null} if can't find one.
	*/
	@Nullable
	public static Map<String, ?> getHealthCheckedService(@Nullable Map<String, ?> serviceConfig) {
	if (serviceConfig == null) {
	return null;
	}

	/* schema as follows
	{
	"healthCheckConfig": {
	// Service name to use in the health-checking request.
	"serviceName": string
	}
	}
	*/
	return JsonUtil.getObject(serviceConfig, "healthCheckConfig");
	}

	/**
	* Fetches the health-checked service name from health-checked service config. {@code null} if
	* can't find one.
	*/
	@Nullable
	public static String getHealthCheckedServiceName(
	@Nullable Map<String, ?> healthCheckedServiceConfig) {
	if (healthCheckedServiceConfig == null) {
	return null;
	}
	return JsonUtil.getString(healthCheckedServiceConfig, "serviceName");
	}

	@Nullable
	static Throttle getThrottlePolicy(@Nullable Map<String, ?> serviceConfig) {
	if (serviceConfig == null) {
	return null;
	}

	/* schema as follows
	{
	"retryThrottling": {
	// The number of tokens starts at maxTokens. The token_count will always be
	// between 0 and maxTokens.
	//
	// This field is required and must be greater than zero.
	"maxTokens": number,

	// The amount of tokens to add on each successful RPC. Typically this will
	// be some number between 0 and 1, e.g., 0.1.
	//
	// This field is required and must be greater than zero. Up to 3 decimal
	// places are supported.
	"tokenRatio": number
	}
	}
	*/

	Map<String, ?> throttling = JsonUtil.getObject(serviceConfig, "retryThrottling");
	if (throttling == null) {
	return null;
	}

	// TODO(dapengzhang0): check if this is null.
	float maxTokens = JsonUtil.getNumber(throttling, "maxTokens").floatValue();
	float tokenRatio = JsonUtil.getNumber(throttling, "tokenRatio").floatValue();
	checkState(maxTokens > 0f, "maxToken should be greater than zero");
	checkState(tokenRatio > 0f, "tokenRatio should be greater than zero");
	return new Throttle(maxTokens, tokenRatio);
	}

	@Nullable
	static Integer getMaxAttemptsFromRetryPolicy(Map<String, ?> retryPolicy) {
	return JsonUtil.getNumberAsInteger(retryPolicy, "maxAttempts");
	}

	@Nullable
	static Long getInitialBackoffNanosFromRetryPolicy(Map<String, ?> retryPolicy) {
	return JsonUtil.getStringAsDuration(retryPolicy, "initialBackoff");
	}

	@Nullable
	static Long getMaxBackoffNanosFromRetryPolicy(Map<String, ?> retryPolicy) {
	return JsonUtil.getStringAsDuration(retryPolicy, "maxBackoff");
	}

	@Nullable
	static Double getBackoffMultiplierFromRetryPolicy(Map<String, ?> retryPolicy) {
	return JsonUtil.getNumber(retryPolicy, "backoffMultiplier");
	}

	@Nullable
	static Long getPerAttemptRecvTimeoutNanosFromRetryPolicy(Map<String, ?> retryPolicy) {
	return JsonUtil.getStringAsDuration(retryPolicy, "perAttemptRecvTimeout");
	}

	private static Set<Status.Code> getListOfStatusCodesAsSet(Map<String, ?> obj, String key) {
	List<?> statuses = JsonUtil.getList(obj, key);
	if (statuses == null) {
	return null;
	}
	return getStatusCodesFromList(statuses);
	}

	private static Set<Status.Code> getStatusCodesFromList(List<?> statuses) {
	EnumSet<Status.Code> codes = EnumSet.noneOf(Status.Code.class);
	for (Object status : statuses) {
	Status.Code code;
	if (status instanceof Double) {
	Double statusD = (Double) status;
	int codeValue = statusD.intValue();
	verify((double) codeValue == statusD, "Status code %s is not integral", status);
	code = Status.fromCodeValue(codeValue).getCode();
	verify(code.value() == statusD.intValue(), "Status code %s is not valid", status);
	} else if (status instanceof String) {
	try {
	code = Status.Code.valueOf((String) status);
	} catch (IllegalArgumentException iae) {
	throw new VerifyException("Status code " + status + " is not valid", iae);
	}
	} else {
	throw new VerifyException(
	"Can not convert status code " + status + " to Status.Code, because its type is "
	+ status.getClass());
	}
	codes.add(code);
	}
	return Collections.unmodifiableSet(codes);
	}

	static Set<Status.Code> getRetryableStatusCodesFromRetryPolicy(Map<String, ?> retryPolicy) {
	String retryableStatusCodesKey = "retryableStatusCodes";
	Set<Status.Code> codes = getListOfStatusCodesAsSet(retryPolicy, retryableStatusCodesKey);
	verify(codes != null, "%s is required in retry policy", retryableStatusCodesKey);
	verify(!codes.contains(Status.Code.OK), "%s must not contain OK", retryableStatusCodesKey);
	return codes;
	}

	@Nullable
	static Integer getMaxAttemptsFromHedgingPolicy(Map<String, ?> hedgingPolicy) {
	return JsonUtil.getNumberAsInteger(hedgingPolicy, "maxAttempts");
	}

	@Nullable
	static Long getHedgingDelayNanosFromHedgingPolicy(Map<String, ?> hedgingPolicy) {
	return JsonUtil.getStringAsDuration(hedgingPolicy, "hedgingDelay");
	}

	static Set<Status.Code> getNonFatalStatusCodesFromHedgingPolicy(Map<String, ?> hedgingPolicy) {
	String nonFatalStatusCodesKey = "nonFatalStatusCodes";
	Set<Status.Code> codes = getListOfStatusCodesAsSet(hedgingPolicy, nonFatalStatusCodesKey);
	if (codes == null) {
	return Collections.unmodifiableSet(EnumSet.noneOf(Status.Code.class));
	}
	verify(!codes.contains(Status.Code.OK), "%s must not contain OK", nonFatalStatusCodesKey);
	return codes;
	}

	@Nullable
	static String getServiceFromName(Map<String, ?> name) {
	return JsonUtil.getString(name, "service");
	}

	@Nullable
	static String getMethodFromName(Map<String, ?> name) {
	return JsonUtil.getString(name, "method");
	}

	@Nullable
	static Map<String, ?> getRetryPolicyFromMethodConfig(Map<String, ?> methodConfig) {
	return JsonUtil.getObject(methodConfig, "retryPolicy");
	}

	@Nullable
	static Map<String, ?> getHedgingPolicyFromMethodConfig(Map<String, ?> methodConfig) {
	return JsonUtil.getObject(methodConfig, "hedgingPolicy");
	}

	@Nullable
	static List<Map<String, ?>> getNameListFromMethodConfig(
	Map<String, ?> methodConfig) {
	return JsonUtil.getListOfObjects(methodConfig, "name");
	}

	/**
	* Returns the number of nanoseconds of timeout for the given method config.
	*
	* @return duration nanoseconds, or {@code null} if it isn't present.
	*/
	@Nullable
	static Long getTimeoutFromMethodConfig(Map<String, ?> methodConfig) {
	return JsonUtil.getStringAsDuration(methodConfig, "timeout");
	}

	@Nullable
	static Boolean getWaitForReadyFromMethodConfig(Map<String, ?> methodConfig) {
	return JsonUtil.getBoolean(methodConfig, "waitForReady");
	}

	@Nullable
	static Integer getMaxRequestMessageBytesFromMethodConfig(Map<String, ?> methodConfig) {
	return JsonUtil.getNumberAsInteger(methodConfig, "maxRequestMessageBytes");
	}

	@Nullable
	static Integer getMaxResponseMessageBytesFromMethodConfig(Map<String, ?> methodConfig) {
	return JsonUtil.getNumberAsInteger(methodConfig, "maxResponseMessageBytes");
	}

	@Nullable
	static List<Map<String, ?>> getMethodConfigFromServiceConfig(
	Map<String, ?> serviceConfig) {
	return JsonUtil.getListOfObjects(serviceConfig, "methodConfig");
	}

	/**
	* Extracts load balancing configs from a service config.
	*/
	@VisibleForTesting
	public static List<Map<String, ?>> getLoadBalancingConfigsFromServiceConfig(
	Map<String, ?> serviceConfig) {
	/* schema as follows
	{
	"loadBalancingConfig": [
	{"xds" :
	{
	"childPolicy": [...],
	"fallbackPolicy": [...],
	}
	},
	{"round_robin": {}}
	],
	"loadBalancingPolicy": "ROUND_ROBIN" // The deprecated policy key
	}
	*/
	List<Map<String, ?>> lbConfigs = new ArrayList<>();
	String loadBalancingConfigKey = "loadBalancingConfig";
	if (serviceConfig.containsKey(loadBalancingConfigKey)) {
	lbConfigs.addAll(JsonUtil.getListOfObjects(
	serviceConfig, loadBalancingConfigKey));
	}
	if (lbConfigs.isEmpty()) {
	// No LoadBalancingConfig found. Fall back to the deprecated LoadBalancingPolicy
	String policy = JsonUtil.getString(serviceConfig, "loadBalancingPolicy");
	if (policy != null) {
	// Convert the policy to a config, so that the caller can handle them in the same way.
	policy = policy.toLowerCase(Locale.ROOT);
	Map<String, ?> fakeConfig = Collections.singletonMap(policy, Collections.emptyMap());
	lbConfigs.add(fakeConfig);
	}
	}
	return Collections.unmodifiableList(lbConfigs);
	}

	/**
	* Unwrap a LoadBalancingConfig JSON object into a {@link LbConfig}. The input is a JSON object
	* (map) with exactly one entry, where the key is the policy name and the value is a config object
	* for that policy.
	*/
	public static LbConfig unwrapLoadBalancingConfig(Map<String, ?> lbConfig) {
	if (lbConfig.size() != 1) {
	throw new RuntimeException(
	"There are " + lbConfig.size() + " fields in a LoadBalancingConfig object. Exactly one"
	+ " is expected. Config=" + lbConfig);
	}
	String key = lbConfig.entrySet().iterator().next().getKey();
	return new LbConfig(key, JsonUtil.getObject(lbConfig, key));
	}

	/**
	* Given a JSON list of LoadBalancingConfigs, and convert it into a list of LbConfig.
	*/
	public static List<LbConfig> unwrapLoadBalancingConfigList(List<Map<String, ?>> list) {
	if (list == null) {
	return null;
	}
	ArrayList<LbConfig> result = new ArrayList<>();
	for (Map<String, ?> rawChildPolicy : list) {
	result.add(unwrapLoadBalancingConfig(rawChildPolicy));
	}
	return Collections.unmodifiableList(result);
	}

	/**
	* Parses and selects a load balancing policy from a non-empty list of raw configs. If selection
	* is successful, the returned ConfigOrError object will include a {@link
	* ServiceConfigUtil.PolicySelection} as its config value.
	*/
	public static ConfigOrError selectLbPolicyFromList(
	List<LbConfig> lbConfigs, LoadBalancerRegistry lbRegistry) {
	List<String> policiesTried = new ArrayList<>();
	for (LbConfig lbConfig : lbConfigs) {
	String policy = lbConfig.getPolicyName();
	LoadBalancerProvider provider = lbRegistry.getProvider(policy);
	if (provider == null) {
	policiesTried.add(policy);
	} else {
	if (!policiesTried.isEmpty()) {
	Logger.getLogger(ServiceConfigUtil.class.getName()).log(
	Level.FINEST,
	"{0} specified by Service Config are not available", policiesTried);
	}
	ConfigOrError parsedLbPolicyConfig =
	provider.parseLoadBalancingPolicyConfig(lbConfig.getRawConfigValue());
	if (parsedLbPolicyConfig.getError() != null) {
	return parsedLbPolicyConfig;
	}
	return ConfigOrError.fromConfig(
	new PolicySelection(provider, parsedLbPolicyConfig.getConfig()));
	}
	}
	return ConfigOrError.fromError(
	Status.UNKNOWN.withDescription(
	"None of " + policiesTried + " specified by Service Config are available."));
	}

	/**
	* A LoadBalancingConfig that includes the policy name (the key) and its raw config value (parsed
	* JSON).
	*/
	public static final class LbConfig {
	private final String policyName;
	private final Map<String, ?> rawConfigValue;

	public LbConfig(String policyName, Map<String, ?> rawConfigValue) {
	this.policyName = checkNotNull(policyName, "policyName");
	this.rawConfigValue = checkNotNull(rawConfigValue, "rawConfigValue");
	}

	public String getPolicyName() {
	return policyName;
	}

	public Map<String, ?> getRawConfigValue() {
	return rawConfigValue;
	}

	@Override
	public boolean equals(Object o) {
	if (o instanceof LbConfig) {
	LbConfig other = (LbConfig) o;
	return policyName.equals(other.policyName)
	&& rawConfigValue.equals(other.rawConfigValue);
	}
	return false;
	}

	@Override
	public int hashCode() {
	return Objects.hashCode(policyName, rawConfigValue);
	}

	@Override
	public String toString() {
	return MoreObjects.toStringHelper(this)
	.add("policyName", policyName)
	.add("rawConfigValue", rawConfigValue)
	.toString();
	}
	}

	public static final class PolicySelection {
	final LoadBalancerProvider provider;
	@Nullable
	final Object config;

	/** Constructs a PolicySelection with selected LB provider and the deeply parsed LB config. */
	public PolicySelection(
	LoadBalancerProvider provider,
	@Nullable Object config) {
	this.provider = checkNotNull(provider, "provider");
	this.config = config;
	}

	public LoadBalancerProvider getProvider() {
	return provider;
	}

	@Nullable
	public Object getConfig() {
	return config;
	}

	@Override
	public boolean equals(Object o) {
	if (this == o) {
	return true;
	}
	if (o == null \|\| getClass() != o.getClass()) {
	return false;
	}
	PolicySelection that = (PolicySelection) o;
	return Objects.equal(provider, that.provider)
	&& Objects.equal(config, that.config);
	}

	@Override
	public int hashCode() {
	return Objects.hashCode(provider, config);
	}

	@Override
	public String toString() {
	return MoreObjects.toStringHelper(this)
	.add("provider", provider)
	.add("config", config)
	.toString();
	}
	}
	}