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/*
* 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.flink.runtime.state.gemini.engine.vm;
import org.apache.flink.runtime.state.gemini.engine.GRegionContext;
import org.apache.flink.runtime.state.gemini.engine.dbms.GContext;
import org.apache.flink.runtime.state.gemini.engine.filecache.FileCache;
import org.apache.flink.runtime.state.gemini.engine.handler.GeminiEventExecutorGroup;
import org.apache.flink.runtime.state.gemini.engine.page.DataPage;
import org.apache.flink.runtime.state.gemini.engine.page.LogicChainedPage;
import org.apache.flink.runtime.state.gemini.engine.page.PageAddress;
import org.apache.flink.runtime.state.gemini.engine.rm.ReferenceCount.ReleaseType;
import org.apache.flink.shaded.guava18.com.google.common.util.concurrent.ThreadFactoryBuilder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicInteger;
/**
* FetchPolicyImpl.
* aim to reduce the IO access num. for now only support preFetch pages which is belonged to a same logic page.
* non thread safe.
*/
public class FetchPolicyImpl implements FetchPolicy {
private static final Logger LOG = LoggerFactory.getLogger(FetchPolicyImpl.class);
private final DataPageLRU readPageCacheLRU;
private final CacheStats cacheStats;
private final FileCache fileCache;
private final ExecutorService preFetchExecutor;
private final AtomicInteger currentPrefetchingNum = new AtomicInteger(0);
private final int maxPrefchingNum;
public FetchPolicyImpl(
GContext gContext, CacheStats cacheStats, DataPageLRU readPageCacheLRU) {
this.readPageCacheLRU = readPageCacheLRU;
this.cacheStats = cacheStats;
this.fileCache = gContext.getSupervisor().getFileCache();
ThreadFactory namedThreadFactory = new ThreadFactoryBuilder().setNameFormat(
gContext.getGConfiguration().getExcetorPrefixName() + "geminiPrefetch-%d").build();
this.preFetchExecutor = new GeminiEventExecutorGroup(gContext.getGConfiguration().getFlushThreadNum(),
namedThreadFactory,
gContext.getGConfiguration().getFetchThreadSleepTimeNS(), gContext);
this.maxPrefchingNum = gContext.getGConfiguration().getMaxCompactionChainThreshold();
}
void preFetch(LogicChainedPage logicChainedPage, int startIndex, GRegionContext gRegionContext) {
/**
* logicChainedPage and startIndex are pointed to other Pages needed to prefetch.
*/
while (startIndex >= 0 && gRegionContext.getGContext().isDBNormal()) {
PageAddress pageAddress = logicChainedPage.getPageAddress(startIndex);
startIndex--;
if (pageAddress.hasDataPage()) {
continue;
}
//too slow?
if (currentPrefetchingNum.get() > maxPrefchingNum) {
return;
}
FutureDataPage futureDataPageOld = this.readPageCacheLRU.get(pageAddress);
if (futureDataPageOld != null && !futureDataPageOld.isFail()) {
return;
}
currentPrefetchingNum.incrementAndGet();
FutureDataPage futureDataPage = new FutureDataPage(pageAddress.getDataLen());
//readPageCacheLRU is a small cache, and finally we should put this pages to Cache by commit this pages to RegionEvent,
//for now, we have not implement this logic, and depends on compaction to update the Cache.
this.readPageCacheLRU.put(pageAddress, futureDataPage);
//TODO in the future, we should combine the preFetchExecutor and evictExecutor,
//TODO that means when we preFetch some pages,evictHandler will skip these pages.
this.preFetchExecutor.submit(() -> asyncFetch(futureDataPage, pageAddress, gRegionContext));
}
}
private void asyncFetch(FutureDataPage futureDataPage, PageAddress pageAddress, GRegionContext gRegionContext) {
//todo to resuse dataPage need send to Region handler.
try {
DataPage dataPage = this.fileCache.getPage(
pageAddress,
gRegionContext,
gRegionContext.getGContext().getSupervisor().getFlushExecutorGroup().next());
if (!futureDataPage.complete(dataPage)) {
dataPage.delReferenceCount(ReleaseType.Normal);
}
} catch (Exception e) {
futureDataPage.completeExceptionally(e);
} finally {
currentPrefetchingNum.decrementAndGet();
}
}
@Override
public DataPage fetch(
PageAddress pageAddress,
LogicChainedPage logicChainedPage,
int startIndex,
GRegionContext gRegionContext,
boolean prefetch,
boolean doCache) {
//PageAddress can not be updated, so can be as Key.
final FutureDataPage futureDataPage = this.readPageCacheLRU.get(pageAddress);
if (futureDataPage != null) {
if (futureDataPage.isDone()) {
try {
DataPage dataPage = futureDataPage.get();
dataPage.addReferenceCount();
this.cacheStats.addPageCacheLRUHitCount();
return dataPage;
} catch (Exception e) {
//futureDataPage fail. try new.
}
}
}
if (prefetch) {
preFetch(logicChainedPage, startIndex - 1, gRegionContext);
}
DataPage dataPage = this.fileCache.getPage(pageAddress,
gRegionContext,
gRegionContext.getGContext().getSupervisor().getFlushExecutorGroup().next());
if (doCache) {
this.readPageCacheLRU.put(pageAddress, new FutureDataPage(dataPage));
dataPage.addReferenceCount();
}
return dataPage;
}
@Override
public DataPageLRU getDataPageLRU() {
return this.readPageCacheLRU;
}
@Override
public void close() {
this.preFetchExecutor.shutdownNow();
}
}
