grpc / grpc-java / #20383

/*

 * Copyright 2015 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;

import com.google.common.base.Preconditions;

import java.util.List;

import java.util.Map;

import java.util.concurrent.Executor;

import java.util.concurrent.TimeUnit;

import javax.annotation.Nullable;

/**

 * A builder for {@link ManagedChannel} instances.

 *

 * @param <T> The concrete type of this builder.

 */

  /**

   * Creates a channel with the target's address and port number.

   *

   * <p>Note that there is an open JDK bug on {@link java.net.URI} class parsing an ipv6 scope ID:

   * bugs.openjdk.org/browse/JDK-8199396. This method is exposed to this bug. If you experience an

   * issue, a work-around is to convert the scope ID to its numeric form (e.g. by using

   * Inet6Address.getScopeId()) before calling this method.

   *

   * @see #forTarget(String)

   * @since 1.0.0

   */

  public static ManagedChannelBuilder<?> forAddress(String name, int port) {

  }

  /**

   * Creates a channel with a target string, which can be either an RFC 3986 URI, or an authority

   * string.

   *

   * <p>Example URIs:

   * <ul>

   *   <li>{@code "dns:///foo.googleapis.com:8080"}</li>

   *   <li>{@code "dns:///foo.googleapis.com"}</li>

   *   <li>{@code "dns:///%5B2001:db8:85a3:8d3:1319:8a2e:370:7348%5D:443"}</li>

   *   <li>{@code "dns://8.8.8.8/foo.googleapis.com:8080"}</li>

   *   <li>{@code "dns://8.8.8.8/foo.googleapis.com"}</li>

   *   <li>{@code "zookeeper://zk.example.com:9900/example_service"}</li>

   *   <li>{@code "intent:#Intent;package=com.some.app;action=a;category=c;end;"}</li>

   * </ul>

   *

   * <p>An authority string will be converted to a URI having the scheme of the name resolver with

   * the highest priority (e.g. {@code "dns"}), the empty string as the authority, and

   * {@code target} as its absolute path. We recommend libraries specify {@code target} as a URI

   * instead since they cannot know which NameResolver will be default at runtime.

   * Example authority strings:

   * <ul>

   *   <li>{@code "localhost"}</li>

   *   <li>{@code "127.0.0.1"}</li>

   *   <li>{@code "localhost:8080"}</li>

   *   <li>{@code "foo.googleapis.com:8080"}</li>

   *   <li>{@code "127.0.0.1:8080"}</li>

   *   <li>{@code "[2001:db8:85a3:8d3:1319:8a2e:370:7348]"}</li>

   *   <li>{@code "[2001:db8:85a3:8d3:1319:8a2e:370:7348]:443"}</li>

   * </ul>

   *

   * <p>The URI form of {@code target} is preferred because it is less ambiguous. For example, the

   * target string {@code foo:8080} is a valid authority string with host {@code foo} and port

   * {@code 8080} but it is also a valid RFC 3986 URI with scheme {@code foo} and path {@code 8080}.

   * gRPC prioritizes the URI form, which means {@code foo:8080} will be treated as a URI with

   * scheme {@code foo}. Using {@code dns:///foo:8080} avoids this ambiguity.

   *

   * <p>Note that there is an open JDK bug on {@link java.net.URI} class parsing an ipv6 scope ID:

   * bugs.openjdk.org/browse/JDK-8199396. This method is exposed to this bug. If you experience an

   * issue, a work-around is to convert the scope ID to its numeric form (e.g. by using

   * Inet6Address.getScopeId()) before calling this method.

   * 

   * @since 1.0.0

   */

  public static ManagedChannelBuilder<?> forTarget(String target) {

  }

  /**

   * Execute application code directly in the transport thread. The application must not block under

   * any circumstances.

   *

   * <p>Depending on the underlying transport and the application code, using a direct executor may

   * lead to 10s of µs latency reduction but causes a substantial performance degradation when

   * misused.

   *

   * <p>Calling this method is semantically equivalent to calling {@link #executor(Executor)} and

   * passing in a direct executor. However, this is the preferred way as it may allow the transport

   * to perform special optimizations.

   *

   * @return this

   * @since 1.0.0

   */

  public abstract T directExecutor();

  /**

   * Set the default executor for callbacks. This is used for async and future stub callbacks, but

   * can be overridden by {@link CallOptions#withExecutor} and {@code stub.withExecutor()}. Blocking

   * stubs specify a per-RPC executor. This is also used for {@link

   * ManagedChannel#notifyWhenStateChanged}.

   *

   * <p>It's an optional parameter. If the user has not provided an executor when the channel is

   * built, the builder will use a static cached thread pool.

   *

   * <p>The channel won't take ownership of the given executor. It's caller's responsibility to

   * shut down the executor when it's desired.

   *

   * @return this

   * @since 1.0.0

   */

  public abstract T executor(Executor executor);

  /**

   * Provides a custom executor that will be used for operations that block or are expensive, to

   * avoid blocking asynchronous code paths. For example, DNS queries and OAuth token fetching over

   * HTTP could use this executor.

   *

   * <p>It's an optional parameter. If the user has not provided an executor when the channel is

   * built, the builder will use a static cached thread pool.

   *

   * <p>The channel won't take ownership of the given executor. It's caller's responsibility to shut

   * down the executor when it's desired.

   *

   * @return this

   * @throws UnsupportedOperationException if unsupported

   * @since 1.25.0

   */

  public T offloadExecutor(Executor executor) {

  }

  /**

   * Adds interceptors that will be called before the channel performs its real work. This is

   * functionally equivalent to using {@link ClientInterceptors#intercept(Channel, List)}, but while

   * still having access to the original {@code ManagedChannel}. Interceptors run in the reverse

   * order in which they are added, just as with consecutive calls to {@code

   * ClientInterceptors.intercept()}.

   *

   * @return this

   * @since 1.0.0

   */

  public abstract T intercept(List<ClientInterceptor> interceptors);

  /**

   * Adds interceptors that will be called before the channel performs its real work. This is

   * functionally equivalent to using {@link ClientInterceptors#intercept(Channel,

   * ClientInterceptor...)}, but while still having access to the original {@code ManagedChannel}.

   * Interceptors run in the reverse order in which they are added, just as with consecutive calls

   * to {@code ClientInterceptors.intercept()}.

   *

   * @return this

   * @since 1.0.0

   */

  public abstract T intercept(ClientInterceptor... interceptors);

  /**

   * Internal-only: Adds a factory that will construct an interceptor based on the channel's target.

   * This can be used to work around nameResolverFactory() changing the target string.

   */

  @Internal

  protected T interceptWithTarget(InterceptorFactory factory) {

  }

  /** Internal-only. */

  @Internal

  protected interface InterceptorFactory {

    ClientInterceptor newInterceptor(String target);

  }

  /**

   * Adds a {@link ClientTransportFilter}. The order of filters being added is the order they will

   * be executed

   *

   * @return this

   * @since 1.60.0

   */

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/10652")

  public T addTransportFilter(ClientTransportFilter filter) {

  }

  /**

   * Provides a custom {@code User-Agent} for the application.

   *

   * <p>It's an optional parameter. The library will provide a user agent independent of this

   * option. If provided, the given agent will prepend the library's user agent information.

   *

   * @return this

   * @since 1.0.0

   */

  public abstract T userAgent(String userAgent);

  /**

   * Overrides the authority used with TLS and HTTP virtual hosting. It does not change what host is

   * actually connected to. Is commonly in the form {@code host:port}.

   *

   * <p>If the channel builder overrides authority, any authority override from name resolution

   * result (via {@link EquivalentAddressGroup#ATTR_AUTHORITY_OVERRIDE}) will be discarded.

   *

   * <p>This method is intended for testing, but may safely be used outside of tests as an

   * alternative to DNS overrides.

   *

   * @return this

   * @since 1.0.0

   */

  public abstract T overrideAuthority(String authority);

  /**

   * Use of a plaintext connection to the server. By default a secure connection mechanism

   * such as TLS will be used.

   *

   * <p>Should only be used for testing or for APIs where the use of such API or the data

   * exchanged is not sensitive.

   *

   * <p>This assumes prior knowledge that the target of this channel is using plaintext.  It will

   * not perform HTTP/1.1 upgrades.

   *

   * @return this

   * @throws IllegalStateException if ChannelCredentials were provided when constructing the builder

   * @throws UnsupportedOperationException if plaintext mode is not supported.

   * @since 1.11.0

   */

  public T usePlaintext() {

  }

  /**

   * Makes the client use TLS. Note: this is enabled by default.

   *

   * <p>It is recommended to use the {@link ChannelCredentials} API

   * instead of this method.

   *

   * @return this

   * @throws IllegalStateException if ChannelCredentials were provided when constructing the builder

   * @throws UnsupportedOperationException if transport security is not supported.

   * @since 1.9.0

   */

  public T useTransportSecurity() {

  }

  /**

   * Provides a custom {@link NameResolver.Factory} for the channel. If this method is not called,

   * the builder will try the providers registered in the default {@link NameResolverRegistry} for

   * the given target.

   *

   * <p>This method should rarely be used, as name resolvers should provide a {@code

   * NameResolverProvider} and users rely on service loading to find implementations in the class

   * path. That allows application's configuration to easily choose the name resolver via the

   * 'target' string passed to {@link ManagedChannelBuilder#forTarget(String)}.

   *

   * @return this

   * @since 1.0.0

   * @deprecated Most usages should use a globally-registered {@link NameResolverProvider} instead,

   *     with either the SPI mechanism or {@link NameResolverRegistry#register}. Replacements for

   *     all use-cases are not necessarily available yet. See

   *     <a href="https://github.com/grpc/grpc-java/issues/7133">#7133</a>.

   */

  @Deprecated

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1770")

  public abstract T nameResolverFactory(NameResolver.Factory resolverFactory);

  /**

   * Sets the default load-balancing policy that will be used if the service config doesn't specify

   * one.  If not set, the default will be the "pick_first" policy.

   *

   * <p>Policy implementations are looked up in the

   * {@link LoadBalancerRegistry#getDefaultRegistry default LoadBalancerRegistry}.

   *

   * <p>This method is implemented by all stock channel builders that are shipped with gRPC, but may

   * not be implemented by custom channel builders, in which case this method will throw.

   *

   * @return this

   * @since 1.18.0

   */

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1771")

  public T defaultLoadBalancingPolicy(String policy) {

  }

  /**

   * Set the decompression registry for use in the channel. This is an advanced API call and

   * shouldn't be used unless you are using custom message encoding. The default supported

   * decompressors are in {@link DecompressorRegistry#getDefaultInstance}.

   *

   * @return this

   * @since 1.0.0

   */

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1704")

  public abstract T decompressorRegistry(DecompressorRegistry registry);

  /**

   * Set the compression registry for use in the channel.  This is an advanced API call and

   * shouldn't be used unless you are using custom message encoding.   The default supported

   * compressors are in {@link CompressorRegistry#getDefaultInstance}.

   *

   * @return this

   * @since 1.0.0

   */

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1704")

  public abstract T compressorRegistry(CompressorRegistry registry);

  /**

   * Set the duration without ongoing RPCs before going to idle mode.

   *

   * <p>In idle mode the channel shuts down all connections, the NameResolver and the

   * LoadBalancer. A new RPC would take the channel out of idle mode. A channel starts in idle mode.

   * Defaults to 30 minutes.

   *

   * <p>This is an advisory option. Do not rely on any specific behavior related to this option.

   *

   * @return this

   * @since 1.0.0

   */

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/2022")

  public abstract T idleTimeout(long value, TimeUnit unit);

  /**

   * Sets the maximum message size allowed to be received on the channel. If not called,

   * defaults to 4 MiB. The default provides protection to clients who haven't considered the

   * possibility of receiving large messages while trying to be large enough to not be hit in normal

   * usage.

   *

   * <p>This method is advisory, and implementations may decide to not enforce this.  Currently,

   * the only known transport to not enforce this is {@code InProcessTransport}.

   *

   * @param bytes the maximum number of bytes a single message can be.

   * @return this

   * @throws IllegalArgumentException if bytes is negative.

   * @since 1.1.0

   */

  public T maxInboundMessageSize(int bytes) {

    // intentional noop rather than throw, this method is only advisory.

  }

  /**

   * Sets the maximum size of metadata allowed to be received. {@code Integer.MAX_VALUE} disables

   * the enforcement. The default is implementation-dependent, but is not generally less than 8 KiB

   * and may be unlimited.

   *

   * <p>This is cumulative size of the metadata. The precise calculation is

   * implementation-dependent, but implementations are encouraged to follow the calculation used for

   * <a href="http://httpwg.org/specs/rfc7540.html#rfc.section.6.5.2">

   * HTTP/2's SETTINGS_MAX_HEADER_LIST_SIZE</a>. It sums the bytes from each entry's key and value,

   * plus 32 bytes of overhead per entry.

   *

   * @param bytes the maximum size of received metadata

   * @return this

   * @throws IllegalArgumentException if bytes is non-positive

   * @since 1.17.0

   */

  public T maxInboundMetadataSize(int bytes) {

    // intentional noop rather than throw, this method is only advisory.

  }

  /**

   * Sets the time without read activity before sending a keepalive ping. An unreasonably small

   * value might be increased, and {@code Long.MAX_VALUE} nano seconds or an unreasonably large

   * value will disable keepalive. Defaults to infinite.

   *

   * <p>Clients must receive permission from the service owner before enabling this option.

   * Keepalives can increase the load on services and are commonly "invisible" making it hard to

   * notice when they are causing excessive load. Clients are strongly encouraged to use only as

   * small of a value as necessary.

   *

   * <p>When the channel implementation supports TCP_USER_TIMEOUT, enabling keepalive will also

   * enable TCP_USER_TIMEOUT for the connection. This requires <em>all</em> sent packets to receive

   * a TCP acknowledgement before the keepalive timeout. The keepalive time is not used for

   * TCP_USER_TIMEOUT, except as a signal to enable the feature. grpc-netty supports

   * TCP_USER_TIMEOUT on Linux platforms supported by netty-transport-native-epoll.

   *

   * @throws UnsupportedOperationException if unsupported

   * @see <a href="https://github.com/grpc/proposal/blob/master/A8-client-side-keepalive.md">gRFC A8

   *     Client-side Keepalive</a>

   * @see <a href="https://github.com/grpc/proposal/blob/master/A18-tcp-user-timeout.md">gRFC A18

   *     TCP User Timeout</a>

   * @since 1.7.0

   */

  public T keepAliveTime(long keepAliveTime, TimeUnit timeUnit) {

  }

  /**

   * Sets the time waiting for read activity after sending a keepalive ping. If the time expires

   * without any read activity on the connection, the connection is considered dead. An unreasonably

   * small value might be increased. Defaults to 20 seconds.

   *

   * <p>This value should be at least multiple times the RTT to allow for lost packets.

   *

   * @throws UnsupportedOperationException if unsupported

   * @see <a href="https://github.com/grpc/proposal/blob/master/A8-client-side-keepalive.md">gRFC A8

   *     Client-side Keepalive</a>

   * @see <a href="https://github.com/grpc/proposal/blob/master/A18-tcp-user-timeout.md">gRFC A18

   *     TCP User Timeout</a>

   * @since 1.7.0

   */

  public T keepAliveTimeout(long keepAliveTimeout, TimeUnit timeUnit) {

  }

  /**

   * Sets whether keepalive will be performed when there are no outstanding RPC on a connection.

   * Defaults to {@code false}.

   *

   * <p>Clients must receive permission from the service owner before enabling this option.

   * Keepalives on unused connections can easilly accidentally consume a considerable amount of

   * bandwidth and CPU. {@link ManagedChannelBuilder#idleTimeout idleTimeout()} should generally be

   * used instead of this option.

   *

   * @throws UnsupportedOperationException if unsupported

   * @see #keepAliveTime(long, TimeUnit)

   * @see <a href="https://github.com/grpc/proposal/blob/master/A8-client-side-keepalive.md">gRFC A8

   *     Client-side Keepalive</a>

   * @since 1.7.0

   */

  public T keepAliveWithoutCalls(boolean enable) {

  }

  /**

   * Sets the maximum number of retry attempts that may be configured by the service config. If the

   * service config specifies a larger value it will be reduced to this value.  Setting this number

   * to zero is not effectively the same as {@code disableRetry()} because the former does not

   * disable

   * <a

   * href="https://github.com/grpc/proposal/blob/master/A6-client-retries.md#transparent-retries">

   * transparent retry</a>.

   *

   * <p>This method may not work as expected for the current release because retry is not fully

   * implemented yet.

   *

   * @return this

   * @since 1.11.0

   */

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/3982")

  public T maxRetryAttempts(int maxRetryAttempts) {

  }

  /**

   * Sets the maximum number of hedged attempts that may be configured by the service config. If the

   * service config specifies a larger value it will be reduced to this value.

   *

   * <p>This method may not work as expected for the current release because retry is not fully

   * implemented yet.

   *

   * @return this

   * @since 1.11.0

   */

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/3982")

  public T maxHedgedAttempts(int maxHedgedAttempts) {

  }

  /**

   * Sets the retry buffer size in bytes. If the buffer limit is exceeded, no RPC

   * could retry at the moment, and in hedging case all hedges but one of the same RPC will cancel.

   * The implementation may only estimate the buffer size being used rather than count the

   * exact physical memory allocated. The method does not have any effect if retry is disabled by

   * the client.

   *

   * <p>This method may not work as expected for the current release because retry is not fully

   * implemented yet.

   *

   * @return this

   * @since 1.10.0

   */

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/3982")

  public T retryBufferSize(long bytes) {

  }

  /**

   * Sets the per RPC buffer limit in bytes used for retry. The RPC is not retriable if its buffer

   * limit is exceeded. The implementation may only estimate the buffer size being used rather than

   * count the exact physical memory allocated. It does not have any effect if retry is disabled by

   * the client.

   *

   * <p>This method may not work as expected for the current release because retry is not fully

   * implemented yet.

   *

   * @return this

   * @since 1.10.0

   */

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/3982")

  public T perRpcBufferLimit(long bytes) {

  }

  /**

   * Disables the retry and hedging subsystem provided by the gRPC library. This is designed for the

   * case when users have their own retry implementation and want to avoid their own retry taking

   * place simultaneously with the gRPC library layer retry.

   *

   * @return this

   * @since 1.11.0

   */

  public T disableRetry() {

  }

  /**

   * Enables the retry and hedging subsystem which will use

   * <a href="https://github.com/grpc/proposal/blob/master/A6-client-retries.md#integration-with-service-config">

   * per-method configuration</a>. If a method is unconfigured, it will be limited to

   * transparent retries, which are safe for non-idempotent RPCs. Service config is ideally provided

   * by the name resolver, but may also be specified via {@link #defaultServiceConfig}.

   *

   * @return this

   * @since 1.11.0

   */

  public T enableRetry() {

  }

  /**

   * Sets the BinaryLog object that this channel should log to. The channel does not take

   * ownership of the object, and users are responsible for calling {@link BinaryLog#close()}.

   *

   * @param binaryLog the object to provide logging.

   * @return this

   * @since 1.13.0

   */

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/4017")

  public T setBinaryLog(BinaryLog binaryLog) {

  }

  /**

   * Sets the maximum number of channel trace events to keep in the tracer for each channel or

   * subchannel. If set to 0, channel tracing is effectively disabled.

   *

   * @return this

   * @since 1.13.0

   */

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/4471")

  public T maxTraceEvents(int maxTraceEvents) {

  }

  /**

   * Sets the proxy detector to be used in addresses name resolution. If <code>null</code> is passed

   * the default proxy detector will be used.  For how proxies work in gRPC, please refer to the

   * documentation on {@link ProxyDetector}.

   *

   * @return this

   * @since 1.19.0

   */

  public T proxyDetector(ProxyDetector proxyDetector) {

  }

  /**

   * Provides a service config to the channel. The channel will use the default service config when

   * the name resolver provides no service config or if the channel disables lookup service config

   * from name resolver (see {@link #disableServiceConfigLookUp()}). The argument

   * {@code serviceConfig} is a nested map representing a Json object in the most natural way:

   *

   *        <table border="1">

   *          <tr>

   *            <td>Json entry</td><td>Java Type</td>

   *          </tr>

   *          <tr>

   *            <td>object</td><td>{@link Map}</td>

   *          </tr>

   *          <tr>

   *            <td>array</td><td>{@link List}</td>

   *          </tr>

   *          <tr>

   *            <td>string</td><td>{@link String}</td>

   *          </tr>

   *          <tr>

   *            <td>number</td><td>{@link Double}</td>

   *          </tr>

   *          <tr>

   *            <td>boolean</td><td>{@link Boolean}</td>

   *          </tr>

   *          <tr>

   *            <td>null</td><td>{@code null}</td>

   *          </tr>

   *        </table>

   *

   * <p>If null is passed, then there will be no default service config.

   *

   * <p>Your preferred JSON parser may not produce results in the format expected. For such cases,

   * you can convert its output. For example, if your parser produces Integers and other Numbers

   * in addition to Double:

   *

   * <pre>{@code @SuppressWarnings("unchecked")

   * private static Object convertNumbers(Object o) {

   *   if (o instanceof Map) {

   *     ((Map) o).replaceAll((k,v) -> convertNumbers(v));

   *   } else if (o instanceof List) {

   *     ((List) o).replaceAll(YourClass::convertNumbers);

   *   } else if (o instanceof Number && !(o instanceof Double)) {

   *     o = ((Number) o).doubleValue();

   *   }

   *   return o;

   * }}</pre>

   *

   * @return this

   * @throws IllegalArgumentException When the given serviceConfig is invalid or the current version

   *         of grpc library can not parse it gracefully. The state of the builder is unchanged if

   *         an exception is thrown.

   * @since 1.20.0

   */

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/5189")

  public T defaultServiceConfig(@Nullable Map<String, ?> serviceConfig) {

  }

  /**

   * Disables service config look-up from the naming system, which is enabled by default.

   *

   * @return this

   * @since 1.20.0

   */

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/5189")

  public T disableServiceConfigLookUp() {

  }

  /**

   * Adds a {@link MetricSink} for channel to use for configuring and recording metrics.

   *

   * @return this

   * @since 1.64.0

   */

  @Internal

  protected T addMetricSink(MetricSink metricSink) {

  }

  /**

   * Provides a "custom" argument for the {@link NameResolver}, if applicable, replacing any 'value'

   * previously provided for 'key'.

   *

   * <p>NB: If the selected {@link NameResolver} does not understand 'key', or target URI resolution

   * isn't needed at all, your custom argument will be silently ignored.

   *

   * <p>See {@link NameResolver.Args#getArg(NameResolver.Args.Key)} for more.

   *

   * @param key identifies the argument in a type-safe manner

   * @param value the argument itself

   * @return this

   */

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1770")

  public <X> T setNameResolverArg(NameResolver.Args.Key<X> key, X value) {

  }

  /**

   * Sets a configurator that will be applied to all internal child channels created by this

   * channel.

   *

   * <p>This allows injecting universal configuration (like interceptors)

   * into auxiliary channels created by gRPC infrastructure, such as xDS control plane connections.

   *

   * @param channelConfigurator the configurator to apply.

   * @return this

   * @since 1.83.0

   */

  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/12574")

  public T childChannelConfigurator(ChannelConfigurator channelConfigurator) {

  }

  /**

   * Builds a channel using the given parameters.

   *

   * @since 1.0.0

   */

  public abstract ManagedChannel build();

  /**

   * Returns the correctly typed version of the builder.

   */

  private T thisT() {

    @SuppressWarnings("unchecked")

  }

}