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MarkLogic Connector for Hadoop MapReduce
/*
* Copyright 2003-2019 MarkLogic Corporation
*
* 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 com.marklogic.mapreduce;
import java.io.IOException;
import java.util.ArrayList;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.DefaultStringifier;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.OutputCommitter;
import org.apache.hadoop.mapreduce.OutputFormat;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import com.marklogic.mapreduce.utilities.InternalUtilities;
import com.marklogic.mapreduce.utilities.TextArrayWritable;
import com.marklogic.xcc.AdhocQuery;
import com.marklogic.xcc.ContentSource;
import com.marklogic.xcc.RequestOptions;
import com.marklogic.xcc.ResultItem;
import com.marklogic.xcc.ResultSequence;
import com.marklogic.xcc.Session;
import com.marklogic.xcc.exceptions.RequestException;
import com.marklogic.xcc.exceptions.ServerConnectionException;
/**
* MarkLogic-based OutputFormat superclass. Use the provided subclasses, such
* as {@link PropertyOutputFormat} to configure your job.
*
* @author jchen
*/
public abstract class MarkLogicOutputFormat
extends OutputFormat
implements MarkLogicConstants, Configurable {
public static final Log LOG =
LogFactory.getLog(MarkLogicOutputFormat.class);
static final String DIRECTORY_TEMPLATE = "{dir}";
static final String DELETE_DIRECTORY_TEMPLATE =
"xdmp:directory-delete(\"" + DIRECTORY_TEMPLATE + "\")";
static final String CHECK_DIRECTORY_EXIST_TEMPLATE =
"exists(xdmp:directory(\"" + DIRECTORY_TEMPLATE +
"\", \"infinity\"))";
static final String DIRECTORY_CREATE_QUERY =
"import module namespace hadoop = " +
"\"http://marklogic.com/xdmp/hadoop\" at \"/MarkLogic/hadoop.xqy\";\n"+
"hadoop:get-directory-creation()";
public static final String HOSTS_QUERY = "import module namespace hadoop = "
+ "\"http://marklogic.com/xdmp/hadoop\" at \"/MarkLogic/hadoop.xqy\";\n"
+ "let $f := "
+ " fn:function-lookup(xs:QName('hadoop:get-host-names'),0)\n"
+ "let $f2 := "
+ " fn:function-lookup(xs:QName('hadoop:get-replica-host-names'),0)\n"
+ "return if (exists($f2)) then $f2() else \n"
+ " if(exists($f)) then $f() else\n"
+ " for $i at $p in hadoop:get-forest-host-map()"
+ " where $p mod 2 eq 0 "
+ " return $i";
static final String MANUAL_DIRECTORY_MODE = "manual";
protected Configuration conf;
@Override
public void checkOutputSpecs(JobContext context) throws IOException,
InterruptedException {
String[] hosts = conf.getStrings(OUTPUT_HOST);
if (hosts == null || hosts.length == 0) {
throw new IllegalStateException(OUTPUT_HOST +
" is not specified.");
}
for (int i = 0; i < hosts.length; i++) {
try {
ContentSource cs = InternalUtilities.getOutputContentSource(conf,
hosts[i]);
checkOutputSpecs(conf, cs);
return;
}
catch (Exception ex) {
if (ex.getCause() instanceof ServerConnectionException) {
LOG.warn("Unable to connect to " + hosts[i]
+ " to query destination information");
continue;
} else {
throw new IOException(ex);
}
}
}
// No usable output hostname found at this point
throw new IOException("Unable to query destination information,"
+ " no usable hostname found");
}
@Override
public OutputCommitter getOutputCommitter(TaskAttemptContext context)
throws IOException, InterruptedException {
return new OutputCommitter() {
public void abortTask(TaskAttemptContext taskContext) { }
public void commitTask(TaskAttemptContext taskContext) { }
public boolean needsTaskCommit(TaskAttemptContext taskContext) {
return false;
}
public void setupJob(JobContext jobContext) { }
public void setupTask(TaskAttemptContext taskContext) { }
};
}
@Override
public Configuration getConf() {
return conf;
}
@Override
public void setConf(Configuration conf) {
this.conf = conf;
}
protected TextArrayWritable getHosts(Configuration conf) throws IOException {
String forestHost = conf.get(OUTPUT_FOREST_HOST);
if (forestHost != null) {
// Restores the object from the configuration.
TextArrayWritable hosts = DefaultStringifier.load(conf,
OUTPUT_FOREST_HOST, TextArrayWritable.class);
return hosts;
} else {
throw new IOException("Forest host map not found");
}
}
protected TextArrayWritable queryHosts(ContentSource cs)
throws IOException {
return queryHosts(cs, null, null);
}
// Query for a list a hosts, replacing any host name matching hostName
// with outputHost
protected TextArrayWritable queryHosts(ContentSource cs, String matchHost,
String replaceHost)
throws IOException {
Session session = null;
ResultSequence result = null;
try {
session = cs.newSession();
AdhocQuery query = session.newAdhocQuery(HOSTS_QUERY);
// query hosts
RequestOptions options = new RequestOptions();
options.setDefaultXQueryVersion("1.0-ml");
query.setOptions(options);
result = session.submitRequest(query);
ArrayList hosts = new ArrayList();
while (result.hasNext()) {
ResultItem item = result.next();
String host = item.asString();
if (matchHost != null && host.equals(matchHost)) {
hosts.add(new Text(replaceHost));
} else {
hosts.add(new Text(host));
}
}
if (hosts.isEmpty()) {
throw new IOException("Target database has no forests attached: "
+ "check forests in database");
}
return new TextArrayWritable(hosts.toArray(new Text[hosts.size()]));
} catch (RequestException e) {
LOG.error(e.getMessage(), e);
throw new IOException(e);
} finally {
if (result != null) {
result.close();
}
if (session != null) {
session.close();
}
}
}
public abstract void checkOutputSpecs(Configuration conf, ContentSource cs)
throws IOException;
}