com.linecorp.armeria.client.endpoint.dns.DnsTextEndpointGroup.java Source code

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Here is the source code for com.linecorp.armeria.client.endpoint.dns.DnsTextEndpointGroup.java

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/*
 * Copyright 2018 LINE Corporation
 *
 * LINE Corporation licenses this file to you 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.linecorp.armeria.client.endpoint.dns;

import java.util.List;
import java.util.function.Function;
import java.util.stream.Collectors;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSortedSet;

import com.linecorp.armeria.client.Endpoint;
import com.linecorp.armeria.client.endpoint.DynamicEndpointGroup;
import com.linecorp.armeria.client.retry.Backoff;
import com.linecorp.armeria.common.CommonPools;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufHolder;
import io.netty.channel.EventLoop;
import io.netty.handler.codec.dns.DefaultDnsQuestion;
import io.netty.handler.codec.dns.DnsRawRecord;
import io.netty.handler.codec.dns.DnsRecord;
import io.netty.handler.codec.dns.DnsRecordType;
import io.netty.resolver.dns.DnsServerAddressStreamProvider;

/**
 * {@link DynamicEndpointGroup} which resolves targets using DNS {@code TXT} records. This is useful for
 * environments where service discovery is handled using DNS.
 */
public final class DnsTextEndpointGroup extends DnsEndpointGroup {

    /**
     * Creates a {@link DnsTextEndpointGroup} that schedules queries on a random {@link EventLoop} from
     * {@link CommonPools#workerGroup()}.
     *
     * @param hostname the hostname to query DNS queries for
     * @param mapping the {@link Function} that maps the content of a {@code TXT} record into
     *                an {@link Endpoint}. The {@link Function} is expected to return {@code null}
     *                if the record contains unsupported content.
     */
    public static DnsTextEndpointGroup of(String hostname, Function<byte[], Endpoint> mapping) {
        return new DnsTextEndpointGroupBuilder(hostname, mapping).build();
    }

    private final Function<byte[], Endpoint> mapping;

    DnsTextEndpointGroup(EventLoop eventLoop, int minTtl, int maxTtl,
            DnsServerAddressStreamProvider serverAddressStreamProvider, Backoff backoff, String hostname,
            Function<byte[], Endpoint> mapping) {
        super(eventLoop, minTtl, maxTtl, serverAddressStreamProvider, backoff,
                ImmutableList.of(new DefaultDnsQuestion(hostname, DnsRecordType.TXT)), unused -> {
                });
        this.mapping = mapping;
        start();
    }

    @Override
    ImmutableSortedSet<Endpoint> onDnsRecords(List<DnsRecord> records, int ttl) throws Exception {
        final ImmutableSortedSet.Builder<Endpoint> builder = ImmutableSortedSet.naturalOrder();
        for (DnsRecord r : records) {
            if (!(r instanceof DnsRawRecord) || r.type() != DnsRecordType.TXT) {
                continue;
            }

            final ByteBuf content = ((ByteBufHolder) r).content();
            if (!content.isReadable()) { // Missing length octet
                warnInvalidRecord(DnsRecordType.TXT, content);
                continue;
            }

            content.markReaderIndex();
            final int txtLen = content.readUnsignedByte();
            if (txtLen == 0) { // Empty content
                continue;
            }

            if (content.readableBytes() != txtLen) { // Mismatching number of octets
                content.resetReaderIndex();
                warnInvalidRecord(DnsRecordType.TXT, content);
                continue;
            }

            final byte[] txt = new byte[txtLen];
            content.readBytes(txt);

            final Endpoint endpoint;
            try {
                endpoint = mapping.apply(txt);
            } catch (Exception e) {
                content.resetReaderIndex();
                warnInvalidRecord(DnsRecordType.TXT, content);
                continue;
            }

            if (endpoint != null) {
                if (endpoint.isGroup()) {
                    logger().warn("{} Ignoring group endpoint: {}", logPrefix(), endpoint);
                } else {
                    builder.add(endpoint);
                }
            }
        }

        final ImmutableSortedSet<Endpoint> endpoints = builder.build();
        if (logger().isDebugEnabled()) {
            logger().debug("{} Resolved: {} (TTL: {})", logPrefix(),
                    endpoints.stream().map(Object::toString).collect(Collectors.joining(", ")), ttl);
        }

        return endpoints;
    }
}