/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF 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
*
* 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.usergrid.persistence.qakka.serialization;
import com.datastax.driver.core.Row;
import com.datastax.driver.core.Statement;
import com.datastax.driver.core.querybuilder.Clause;
import com.datastax.driver.core.querybuilder.QueryBuilder;
import org.apache.usergrid.persistence.qakka.core.CassandraClient;
import org.apache.usergrid.persistence.qakka.serialization.queuemessages.DatabaseQueueMessage;
import org.apache.usergrid.persistence.qakka.serialization.queuemessages.impl.QueueMessageSerializationImpl;
import org.apache.usergrid.persistence.qakka.serialization.sharding.Shard;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.*;
import static org.apache.usergrid.persistence.qakka.serialization.queuemessages.impl.QueueMessageSerializationImpl.*;
public class MultiShardMessageIterator implements Iterator<DatabaseQueueMessage> {
private static final Logger logger = LoggerFactory.getLogger( MultiShardMessageIterator.class );
private final CassandraClient cassandraClient;
private final int PAGE_SIZE = 100;
private final String queueName;
private final String region;
private final DatabaseQueueMessage.Type messageType;
private final Iterator<Shard> shardIterator;
private Iterator<DatabaseQueueMessage> currentIterator;
private Shard currentShard;
private UUID nextStart;
public MultiShardMessageIterator(
final CassandraClient cassandraClient,
final String queueName,
final String region,
final DatabaseQueueMessage.Type messageType,
final Iterator<Shard> shardIterator,
final UUID nextStart) {
this.queueName = queueName;
this.region = region;
this.messageType = messageType;
this.shardIterator = shardIterator;
this.nextStart = nextStart;
this.cassandraClient = cassandraClient;
if (shardIterator == null) {
throw new RuntimeException("shardIterator cannot be null");
}
}
@Override
public boolean hasNext() {
try {
if (shardIterator.hasNext() && currentIterator == null) {
advance();
}
if (shardIterator.hasNext() && !currentIterator.hasNext()) {
advance();
}
if (!shardIterator.hasNext() && (currentIterator == null || !currentIterator.hasNext())) {
advance();
}
return currentIterator == null ? false : currentIterator.hasNext();
} catch ( NoSuchElementException e ) {
return false;
}
}
@Override
public DatabaseQueueMessage next() {
if ( !hasNext() ) {
throw new NoSuchElementException( "No next message exists" );
}
return currentIterator.next();
}
private void advance(){
if (currentShard == null){
currentShard = shardIterator.next();
}
Clause queueNameClause = QueryBuilder.eq( COLUMN_QUEUE_NAME, queueName);
Clause regionClause = QueryBuilder.eq( COLUMN_REGION, region);
Clause shardIdClause = QueryBuilder.eq( COLUMN_SHARD_ID, currentShard.getShardId());
// if we have a pointer from the shard and this is the first seek, init from the pointer's position
if ( currentShard.getPointer() != null && nextStart == null ){
nextStart = currentShard.getPointer();
}
Statement query;
if ( nextStart == null) {
query = QueryBuilder.select().all().from(QueueMessageSerializationImpl.getTableName(messageType))
.where(queueNameClause)
.and(regionClause)
.and(shardIdClause)
.limit(PAGE_SIZE);
} else {
Clause messageIdClause = QueryBuilder.gt( COLUMN_QUEUE_MESSAGE_ID, nextStart);
query = QueryBuilder.select().all().from(QueueMessageSerializationImpl.getTableName(messageType))
.where(queueNameClause)
.and(regionClause)
.and(shardIdClause)
.and(messageIdClause)
.limit(PAGE_SIZE);
}
List<Row> rows = cassandraClient.getQueueMessageSession().execute(query).all();
logger.trace("results {} from query {}", rows.size(), query.toString());
if ( (rows == null || rows.size() == 0) && shardIterator.hasNext()) {
currentShard = shardIterator.next();
advance();
} else {
currentIterator = getIteratorFromRows(rows);
}
}
private Iterator<DatabaseQueueMessage> getIteratorFromRows(List<Row> rows){
List<DatabaseQueueMessage> messages = new ArrayList<>(rows.size());
rows.forEach(row -> {
final String queueName = row.getString( COLUMN_QUEUE_NAME);
final String region = row.getString( COLUMN_REGION);
final long shardId = row.getLong( COLUMN_SHARD_ID);
final UUID queueMessageId = row.getUUID( COLUMN_QUEUE_MESSAGE_ID);
final UUID messageId = row.getUUID( COLUMN_MESSAGE_ID);
final long queuedAt = row.getLong( COLUMN_QUEUED_AT);
final long inflightAt = row.getLong( COLUMN_INFLIGHT_AT);
messages.add(new DatabaseQueueMessage(
messageId, messageType, queueName, region, shardId, queuedAt, inflightAt, queueMessageId));
//queueMessageId is internal to the messages_available and messages_inflight tables
nextStart = queueMessageId;
});
return messages.iterator();
}
public Shard getCurrentShard() {
return currentShard;
}
}