scray.hdfs.io.index.format.sequence.RawValueFileReader.scala Maven / Gradle / Ivy
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scray adapter to write BLOBs to HDFS
// See the LICENCE.txt file distributed with this work for additional
// information regarding copyright ownership.
//
// 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 scray.hdfs.io.index.format.sequence
import org.apache.hadoop.io.SequenceFile
import org.apache.hadoop.fs.Path
import org.apache.hadoop.fs.FileSystem
import org.apache.hadoop.conf.Configuration
import org.apache.hadoop.io.SequenceFile.Reader
import scray.hdfs.io.index.format.sequence.types.IndexValue
import org.apache.hadoop.io.Text
import com.typesafe.scalalogging.LazyLogging
import scray.hdfs.io.index.format.sequence.mapping.SequenceKeyValuePair
import org.apache.hadoop.io.Writable
import scray.hdfs.io.index.format.sequence.mapping.SequneceValue
class RawValueFileReader[+DATAKEY <: Writable, +DATAVALUE <: Writable](path: String, hdfsConf: Configuration, fs: Option[FileSystem], val outMapping: SequneceValue[DATAKEY, DATAVALUE]) extends LazyLogging {
if(getClass.getClassLoader == null) {
hdfsConf.setClassLoader(getClass.getClassLoader)
}
logger.trace(s"Try to read from path ${path}")
hdfsConf.set("dfs.client.use.datanode.hostname", "true")
val reader: SequenceFile.Reader = new SequenceFile.Reader(hdfsConf, Reader.file(new Path(path)), Reader.bufferSize(4096));
val key = outMapping.getDataKey("", 1)
val idxEntry = outMapping.getDataValue("".getBytes)
// Store state to
private var hasNextWasCalled = false
private var hasNextValue = false
def this(path: String, outMapping: SequneceValue[DATAKEY, DATAVALUE]) = {
this(path, new Configuration, None, outMapping)
}
/**
* Check if more elements exists
*/
def hasNext: Boolean = synchronized {
if (!hasNextWasCalled) { // Has next reads data from fs. For this reason we store the state
hasNextValue = reader.next(key, idxEntry)
hasNextWasCalled = true
hasNextValue
} else {
hasNextValue
}
}
/**
* Return next IndexValue element.
* If no element exists return None
*/
def next(): Option[DATAVALUE] = {
// return read data or request new data
if (hasNextWasCalled) {
if (hasNextValue) {
hasNextWasCalled = false
hasNextValue = false
Some(idxEntry)
} else {
None
}
} else {
hasNext
next
}
}
def close: Unit = {
reader.close()
}
}
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