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/*
 * 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 org.apache.ratis.thirdparty.io.grpc;

import org.apache.ratis.thirdparty.com.google.common.base.Preconditions;
import org.apache.ratis.thirdparty.io.grpc.ManagedChannelProvider.ProviderNotFoundException;

/**
 * Provider of servers for transport agnostic consumption.
 *
 * 

Implementations can be automatically discovered by gRPC via Java's SPI mechanism. For * automatic discovery, the implementation must have a zero-argument constructor and include * a resource named {@code META-INF/services/org.apache.ratis.thirdparty.io.grpc.ServerProvider} in their JAR. The * file's contents should be the implementation's class name. * *

Implementations should not throw. If they do, it may interrupt class loading. If * exceptions may reasonably occur for implementation-specific reasons, implementations should * generally handle the exception gracefully and return {@code false} from {@link #isAvailable()}. */ @Internal public abstract class ServerProvider { /** * Returns the ClassLoader-wide default server. * * @throws ProviderNotFoundException if no provider is available */ public static ServerProvider provider() { ServerProvider provider = ServerRegistry.getDefaultRegistry().provider(); if (provider == null) { throw new ProviderNotFoundException("No functional server found. " + "Try adding a dependency on the grpc-netty or grpc-netty-shaded artifact"); } return provider; } /** * Whether this provider is available for use, taking the current environment into consideration. * If {@code false}, no other methods are safe to be called. */ protected abstract boolean isAvailable(); /** * A priority, from 0 to 10 that this provider should be used, taking the current environment into * consideration. 5 should be considered the default, and then tweaked based on environment * detection. A priority of 0 does not imply that the provider wouldn't work; just that it should * be last in line. */ protected abstract int priority(); /** * Creates a new builder with the given port. */ protected abstract ServerBuilder builderForPort(int port); /** * Creates a new builder with the given port and credentials. Returns an error-string result if * unable to understand the credentials. */ protected NewServerBuilderResult newServerBuilderForPort(int port, ServerCredentials creds) { return NewServerBuilderResult.error("ServerCredentials are unsupported"); } public static final class NewServerBuilderResult { private final ServerBuilder serverBuilder; private final String error; private NewServerBuilderResult(ServerBuilder serverBuilder, String error) { this.serverBuilder = serverBuilder; this.error = error; } public static NewServerBuilderResult serverBuilder(ServerBuilder builder) { return new NewServerBuilderResult(Preconditions.checkNotNull(builder), null); } public static NewServerBuilderResult error(String error) { return new NewServerBuilderResult(null, Preconditions.checkNotNull(error)); } public ServerBuilder getServerBuilder() { return serverBuilder; } public String getError() { return error; } } }





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