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yacy_search_server/source/net/yacy/peers/Dispatcher.java

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// Dispatcher.java
// ------------------------------
// part of YaCy
// (C) 2009 by Michael Peter Christen; mc@yacy.net
// first published on http://yacy.net
// Frankfurt, Germany, 28.01.2009
//
// $LastChangedDate$
// $LastChangedRevision$
// $LastChangedBy$
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
package net.yacy.peers;
import java.io.IOException;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import net.yacy.cora.document.encoding.ASCII;
import net.yacy.cora.order.Base64Order;
import net.yacy.cora.storage.HandleSet;
import net.yacy.cora.util.ConcurrentLog;
import net.yacy.cora.util.Memory;
import net.yacy.cora.util.SpaceExceededException;
import net.yacy.kelondro.data.word.Word;
import net.yacy.kelondro.data.word.WordReference;
import net.yacy.kelondro.index.RowHandleSet;
import net.yacy.kelondro.rwi.ReferenceContainer;
import net.yacy.kelondro.workflow.WorkflowProcessor;
import net.yacy.kelondro.workflow.WorkflowTask;
import net.yacy.peers.Transmission.Chunk;
import net.yacy.search.Switchboard;
import net.yacy.search.SwitchboardConstants;
import net.yacy.search.index.Segment;
public class Dispatcher implements WorkflowTask<Transmission.Chunk> {
/**
* the dispatcher class accumulates indexContainerCache objects before they are transfered
* to other peers. A dispatcher holds several of such caches to enhance the transmission process.
* Before a RWI is sent, the following process is applied:
* - (1) a number of RWIs are selected and accumulated.
* When they are selected, they are removed from the index
* - (2) the RWI collection is split into a number of partitions according to the vertical DHT.
* - (3) the split RWIs are enqueued as Entry object in the write buffer of the dispatcher
* - (4) more entries may be enqueued to the dispatcher and
* entries with the same primary target are accumulated to the same buffer entry.
* - (5) the largest entries are selected from the dispatcher write buffer and enqueued to the 'next' array
* which means that they are ready for transmission
* - (6) the dispatcher takes some of the entries in the next queue and initiates
* transmission to other peers concurrently. As much transmissions are initiated concurrently
* as the redundancy factor.
* - (7) a transmission thread executes the entry transmission.
* - (8) the transmission thread initiates another transmission in case that it fails
* - (9) when the wanted number of redundant peers have received the entries,
* they are removed from the next queue
* Concurrency in this process:
* 1-3 follow directly and should be synchronous because of the database operation that are used
* 4 is a repeated action of 1-3 and should be done in a busyThread
* 5&6 is a repeated action as (4), but must be executed multiple times of (4) in a busyThread,
* which idle is shorter than the idle time of (4)
* 7&8 this is done concurrently with other transmission threads for the same entry and other entries
* for example, if the redundancy factor is 3 and 2 entries are in the 'next' queue, then 6
* transmissions are running concurrently
* 9 concurrency ends for the transmission, if the wanted number of redundant peers received the entry,
* or the target queue runs out of entries. If the target queue is empty, the transmission is
* called failed. In case of a fail, the RWI fragment is put back into the backend index structure
*/
/**
* A transmission buffer is a write buffer for the rwi objects (indices) that wait to be transmitted.
* The String-key is the primary target as contained in the chunk entry.
*/
private Map<String, Transmission.Chunk> transmissionBuffer;
/** the segment backend is used to store the remaining indexContainers in case that the object is closed */
private final Segment segment;
/** the seed database */
private final SeedDB seeds;
/** the log */
private final ConcurrentLog log;
/** transmission process */
private WorkflowProcessor<Transmission.Chunk> indexingTransmissionProcessor;
/** transmission object */
private final Transmission transmission;
/** The Switchboard instance holding the server environment */
private final Switchboard env;
public Dispatcher(
final Switchboard env,
final boolean gzipBody,
final int timeout
) {
this.env = env;
this.transmissionBuffer = new ConcurrentHashMap<String, Transmission.Chunk>();
this.segment = env.index;
this.seeds = env.peers;
this.log = new ConcurrentLog("INDEX-TRANSFER-DISPATCHER");
this.transmission = new Transmission(env, this.log, gzipBody, timeout);
final int concurrentSender = Math.min(8, WorkflowProcessor.availableCPU);
this.indexingTransmissionProcessor = new WorkflowProcessor<Transmission.Chunk>(
"transferDocumentIndex",
"This is the RWI transmission process",
new String[]{"RWI/Cache/Collections"},
this, concurrentSender * 3, null, concurrentSender);
}
public int bufferSize() {
return (this.transmissionBuffer == null) ? 0 : this.transmissionBuffer.size();
}
public int transmissionSize() {
return (this.indexingTransmissionProcessor == null) ? 0 : this.indexingTransmissionProcessor.getQueueSize();
}
/**
* PROCESS(1)
* Select a number of index containers from the RWI index.
* Selected containers are removed from the RWIs (not from Solr, only the DHT references).
* @param hash
* @param limitHash
* @param maxContainerCount
* @param maxtime
* @return
* @throws IOException
*/
private ArrayList<ReferenceContainer<WordReference>> selectContainers(
final byte[] hash,
final byte[] limitHash,
final int maxContainerCount,
final int maxReferenceCount,
final int maxtime) throws IOException {
// prefer file
final ArrayList<ReferenceContainer<WordReference>> containers = selectContainers(hash, limitHash, maxContainerCount, maxReferenceCount, maxtime, false);
// if ram does not provide any result, take from file
//if (containers.isEmpty()) containers = selectContainers(hash, limitHash, maxContainerCount, maxtime, false);
return containers;
}
private ArrayList<ReferenceContainer<WordReference>> selectContainers(
final byte[] hash,
final byte[] limitHash,
final int maxContainerCount,
final int maxReferenceCount,
final int maxtime,
final boolean ram) throws IOException {
final ArrayList<ReferenceContainer<WordReference>> containers = new ArrayList<ReferenceContainer<WordReference>>(maxContainerCount);
final Iterator<ReferenceContainer<WordReference>> indexContainerIterator = this.segment.termIndex() == null ? new ArrayList<ReferenceContainer<WordReference>>().iterator() : this.segment.termIndex().referenceContainerIterator(hash, true, true, ram); // very important that rotation is true here
ReferenceContainer<WordReference> container;
int refcount = 0;
// first select the container
final long timeout = maxtime == Integer.MAX_VALUE ? Long.MAX_VALUE : (maxtime < 0) ? Long.MAX_VALUE : System.currentTimeMillis() + maxtime;
while (
(containers.size() < maxContainerCount) &&
(refcount < maxReferenceCount) &&
(indexContainerIterator.hasNext()) &&
(System.currentTimeMillis() < timeout) &&
((container = indexContainerIterator.next()) != null) &&
((containers.isEmpty()) ||
(Base64Order.enhancedCoder.compare(container.getTermHash(), limitHash) < 0))
) {
if (container.isEmpty()) continue;
if (Word.isPrivate(container.getTermHash())) continue; // exclude private containers
refcount += container.size();
containers.add(container);
}
// then remove the container from the backend
final ArrayList<ReferenceContainer<WordReference>> rc;
if (ram) {
// selection was only from ram, so we have to carefully remove only the selected entries
final HandleSet urlHashes = new RowHandleSet(Word.commonHashLength, Word.commonHashOrder, 0);
Iterator<WordReference> it;
for (final ReferenceContainer<WordReference> c: containers) {
urlHashes.clear();
it = c.entries();
while (it.hasNext()) try { urlHashes.put(it.next().urlhash()); } catch (final SpaceExceededException e) { ConcurrentLog.logException(e); }
if (this.log.isFine()) this.log.fine("selected " + urlHashes.size() + " urls for word '" + ASCII.String(c.getTermHash()) + "'");
if (this.segment.termIndex() != null && !urlHashes.isEmpty()) this.segment.termIndex().remove(c.getTermHash(), urlHashes);
}
rc = containers;
} else {
// selection was from whole index, so we can just delete the whole container
// but to avoid race conditions return the results from the deletes
rc = new ArrayList<ReferenceContainer<WordReference>>(containers.size());
for (final ReferenceContainer<WordReference> c: containers) {
container = this.segment.termIndex() == null ? null : this.segment.termIndex().remove(c.getTermHash()); // be aware this might be null!
if (container != null && !container.isEmpty()) {
if (this.log.isFine()) this.log.fine("selected " + container.size() + " urls for word '" + ASCII.String(c.getTermHash()) + "'");
rc.add(container);
}
}
}
// finished. The caller must take care of the containers and must put them back if not needed
return rc;
}
/**
* PROCESS(2)
* split a list of containers into partitions according to the vertical distribution scheme
* @param containers
* @return a #verticalPartitions list of reference containers, one for each vertical position
* @throws SpaceExceededException
*/
private ReferenceContainer<WordReference>[] splitContainer(final ReferenceContainer<WordReference> container) throws SpaceExceededException {
// init the result vector
final int partitionCount = this.seeds.scheme.verticalPartitions();
// check all entries and split them to the partitions
@SuppressWarnings("unchecked")
final ReferenceContainer<WordReference>[] partitionBuffer = (ReferenceContainer<WordReference>[]) Array.newInstance(ReferenceContainer.class, partitionCount);
// init the new partitions
for (int j = 0; j < partitionBuffer.length; j++) {
partitionBuffer[j] = new ReferenceContainer<WordReference>(Segment.wordReferenceFactory, container.getTermHash(), container.size() / partitionCount);
}
// split the container
final Iterator<WordReference> i = container.entries();
while (i.hasNext()) {
WordReference wordReference = i.next();
if (wordReference == null) continue;
partitionBuffer[this.seeds.scheme.verticalDHTPosition(wordReference.urlhash())].add(wordReference);
}
return partitionBuffer;
}
/**
* PROCESS(3) and PROCESS(4)
* put containers into the write buffer. This needs information about the network,
* because the possible targets are assigned here as well. The indexRepositoryReference
* is the database of references which is needed here because this is the place where
* finally is checked if the reference exists. If the entry does not exist for specific
* entries in the indexContainer, then it is discarded. If it exists, then the entry is
* stored in a cache of the Entry for later transmission to the targets, which means that
* then no additional IO is necessary.
* @param containers a reference containers array, one container for each vertical position
*/
private void enqueueContainersToBuffer(final byte[] wordhash, final ReferenceContainer<WordReference>[] containers) {
assert (containers.length == this.seeds.scheme.verticalPartitions());
if (this.transmissionBuffer == null) return;
List<Seed>[] targets = DHTSelection.selectDHTDistributionTargets(this.seeds, wordhash, 3, this.seeds.redundancy());
assert (targets.length == this.seeds.scheme.verticalPartitions());
assert (targets.length == containers.length);
for (int vertical = 0; vertical < containers.length; vertical++) {
ReferenceContainer<WordReference> verticalContainer = containers[vertical];
if (verticalContainer.isEmpty()) continue;
// extend the transmissionBuffer with entries for each redundant position
for (Seed target: targets[vertical]) {
Transmission.Chunk entry = this.transmissionBuffer.get(target.hash); // if this is not null, the entry is extended here
if (entry == null) entry = transmission.newChunk(target); else {
log.info("extending chunk for peer " + entry.dhtTarget().hash + " containing " + entry.containersSize() + " references with " + verticalContainer.size() + " more entries");
}
try {
entry.add(verticalContainer);
} catch (SpaceExceededException e) {
ConcurrentLog.logException(e);
}
this.transmissionBuffer.put(target.hash, entry);
}
}
}
public boolean selectContainersEnqueueToBuffer(
final byte[] hash,
final byte[] limitHash,
final int maxContainerCount,
final int maxReferenceCount,
final int maxtime) {
if (this.transmissionBuffer == null) return false;
List<ReferenceContainer<WordReference>> selectedContainerCache;
try {
selectedContainerCache = selectContainers(hash, limitHash, maxContainerCount, maxReferenceCount, maxtime);
} catch (final IOException e) {
this.log.severe("selectContainersEnqueueToBuffer: selectedContainer failed", e);
return false;
}
this.log.info("selectContainersEnqueueToBuffer: selectedContainerCache was filled with " + selectedContainerCache.size() + " entries");
if (selectedContainerCache == null || selectedContainerCache.isEmpty()) {
this.log.info("selectContainersEnqueueToBuffer: selectedContainerCache is empty, cannot do anything here.");
return false;
}
// check all entries and split them to the partitions
try {
for (final ReferenceContainer<WordReference> container: selectedContainerCache) {
// init the new partitions
final ReferenceContainer<WordReference>[] partitionBuffer = splitContainer(container);
enqueueContainersToBuffer(container.getTermHash(), partitionBuffer);
}
} catch (final SpaceExceededException e) {
this.log.severe("splitContainer: splitContainers failed because of too low RAM", e);
return false;
}
this.log.info("selectContainersEnqueueToBuffer: splitContainerCache enqueued to the write buffer array which has now " + this.transmissionBuffer.size() + " entries.");
return true;
}
/**
* PROCESS(5)
* take the largest container from the write buffer and put it into the 'next' array,
* where it waits to be processed.
* This method returns true if a container was dequeued, false if not
*/
public boolean dequeueContainer() {
if (this.transmissionBuffer == null) return false;
if (this.indexingTransmissionProcessor.getQueueSize() > this.indexingTransmissionProcessor.getMaxConcurrency()) return false;
String maxtarget = null;
int maxsize = -1;
for (final Map.Entry<String, Transmission.Chunk> chunk: this.transmissionBuffer.entrySet()) {
if (chunk.getValue().containersSize() > maxsize) {
maxsize = chunk.getValue().containersSize();
maxtarget = chunk.getKey();
}
}
if (maxsize < 0) return false;
final Transmission.Chunk chunk = this.transmissionBuffer.remove(maxtarget);
this.indexingTransmissionProcessor.enQueue(chunk);
return true;
}
@Override
public Chunk process(final Transmission.Chunk chunk) throws Exception {
return transferDocumentIndex(chunk);
}
/**
* Transfer job implementation
*/
private Transmission.Chunk transferDocumentIndex(final Transmission.Chunk chunk) {
// try to keep the system healthy; sleep as long as System load is too high
while (Protocol.metadataRetrievalRunning.get() > 0) try {Thread.sleep(1000);} catch (InterruptedException e) {break;}
// we must test this here again
while (Memory.getSystemLoadAverage() > this.env.getConfigFloat(SwitchboardConstants.INDEX_DIST_LOADPREREQ, 2.0f)) try {Thread.sleep(10000);} catch (InterruptedException e) {break;}
// do the transmission
final boolean success = chunk.transmit();
if (success) return chunk;
this.log.info("STORE: Chunk " + chunk.dhtTarget().getName() + " does not respond or accept the dht index, putting back index to backend");
chunk.restore();
return null;
}
public void close() {
// removes all entries from the dispatcher and puts them back to a RAMRI
if (this.indexingTransmissionProcessor != null) this.indexingTransmissionProcessor.shutdown();
if (this.transmissionBuffer != null) {
outerLoop: for (final Map.Entry<String, Transmission.Chunk> e : this.transmissionBuffer.entrySet()) {
for (final ReferenceContainer<WordReference> i : e.getValue()) try {
this.segment.storeRWI(i);
} catch (final Exception e1) {
ConcurrentLog.logException(e1);
break outerLoop;
}
}
this.transmissionBuffer.clear();
}
this.transmissionBuffer = null;
if (this.indexingTransmissionProcessor != null) {
this.indexingTransmissionProcessor.clear();
}
this.indexingTransmissionProcessor = null;
}
}