server/queue/queue-rabbitmq/src/main/java/org/apache/james/queue/rabbitmq/Enqueuer.java

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package org.apache.james.queue.rabbitmq;

import static com.rabbitmq.client.MessageProperties.PERSISTENT_TEXT_PLAIN;
import static org.apache.james.backends.rabbitmq.Constants.EMPTY_ROUTING_KEY;
import static org.apache.james.queue.api.MailQueue.ENQUEUED_METRIC_NAME_PREFIX;

import java.time.Clock;

import javax.mail.MessagingException;
import javax.mail.internet.MimeMessage;

import org.apache.james.blob.api.Store;
import org.apache.james.blob.mail.MimeMessagePartsId;
import org.apache.james.metrics.api.Metric;
import org.apache.james.metrics.api.MetricFactory;
import org.apache.james.queue.api.MailQueue;
import org.apache.james.queue.rabbitmq.view.api.MailQueueView;
import org.apache.james.queue.rabbitmq.view.cassandra.CassandraMailQueueBrowser;
import org.apache.mailet.Mail;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.github.fge.lambdas.Throwing;
import com.google.common.collect.ImmutableMap;
import com.rabbitmq.client.AMQP;

import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import reactor.rabbitmq.OutboundMessage;
import reactor.rabbitmq.Sender;

class Enqueuer {
    private final MailQueueName name;
    private final Sender sender;
    private final Store<MimeMessage, MimeMessagePartsId> mimeMessageStore;
    private final MailReferenceSerializer mailReferenceSerializer;
    private final Metric enqueueMetric;
    private final MailQueueView mailQueueView;
    private final Clock clock;

    Enqueuer(MailQueueName name, Sender sender, Store<MimeMessage, MimeMessagePartsId> mimeMessageStore,
             MailReferenceSerializer serializer, MetricFactory metricFactory,
             MailQueueView mailQueueView, Clock clock) {
        this.name = name;
        this.sender = sender;
        this.mimeMessageStore = mimeMessageStore;
        this.mailReferenceSerializer = serializer;
        this.mailQueueView = mailQueueView;
        this.clock = clock;
        this.enqueueMetric = metricFactory.generate(ENQUEUED_METRIC_NAME_PREFIX + name.asString());
    }

    void enQueue(Mail mail) throws MailQueue.MailQueueException {
        EnqueueId enqueueId = EnqueueId.generate();
        saveMail(mail)
            .map(partIds -> new MailReference(enqueueId, mail, partIds))
            .flatMap(Throwing.<MailReference, Mono<Void>>function(mailReference -> {
                EnqueuedItem enqueuedItem = toEnqueuedItems(mailReference);
                return Flux.mergeDelayError(2,
                        mailQueueView.storeMail(enqueuedItem),
                        publishReferenceToRabbit(mailReference))
                        .then();
            }).sneakyThrow())
            .thenEmpty(Mono.fromRunnable(enqueueMetric::increment))
            .block();
    }

    Mono<Void> reQueue(CassandraMailQueueBrowser.CassandraMailQueueItemView item) {
        Mail mail = item.getMail();
        return Mono.fromCallable(() -> new MailReference(item.getEnqueuedId(), mail, item.getEnqueuedPartsId()))
            .flatMap(Throwing.function(this::publishReferenceToRabbit).sneakyThrow())
            .then();
    }

    private Mono<MimeMessagePartsId> saveMail(Mail mail) throws MailQueue.MailQueueException {
        try {
            return mimeMessageStore.save(mail.getMessage());
        } catch (MessagingException e) {
            throw new MailQueue.MailQueueException("Error while saving blob", e);
        }
    }

    private Mono<Void> publishReferenceToRabbit(MailReference mailReference) throws MailQueue.MailQueueException {
        AMQP.BasicProperties basicProperties = new AMQP.BasicProperties.Builder()
            .deliveryMode(PERSISTENT_TEXT_PLAIN.getDeliveryMode())
            .priority(PERSISTENT_TEXT_PLAIN.getPriority())
            .contentType(PERSISTENT_TEXT_PLAIN.getContentType())
            .headers(ImmutableMap.of("x-dead-letter-routing-key", EMPTY_ROUTING_KEY))
            .build();

        OutboundMessage data = new OutboundMessage(
            name.toRabbitExchangeName().asString(),
            EMPTY_ROUTING_KEY,
            basicProperties,
            getMailReferenceBytes(mailReference));
        return sender.send(Mono.just(data));
    }

    private EnqueuedItem toEnqueuedItems(MailReference mailReference) {
        return EnqueuedItem.builder()
                .enqueueId(mailReference.getEnqueueId())
                .mailQueueName(name)
                .mail(mailReference.getMail())
                .enqueuedTime(clock.instant())
                .mimeMessagePartsId(mailReference.getPartsId())
                .build();
    }

    private byte[] getMailReferenceBytes(MailReference mailReference) throws MailQueue.MailQueueException {
        try {
            MailReferenceDTO mailDTO = MailReferenceDTO.fromMailReference(mailReference);
            return mailReferenceSerializer.write(mailDTO);
        } catch (JsonProcessingException e) {
            throw new MailQueue.MailQueueException("Unable to serialize message", e);
        }
    }
}