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ASF GitHub Bot logged work on HDDS-1512: ---------------------------------------- Author: ASF GitHub Bot Created on: 20/May/19 04:04 Start Date: 20/May/19 04:04 Worklog Time Spent: 10m Work Description: arp7 commented on pull request #810: HDDS-1512. Implement DoubleBuffer in OzoneManager. URL: https://github.com/apache/hadoop/pull/810#discussion_r285419063 ########## File path: hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/ratis/OzoneManagerDoubleBuffer.java ########## @@ -0,0 +1,212 @@ +/** + * 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 + * <p> + * http://www.apache.org/licenses/LICENSE-2.0 + * <p> + * 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.hadoop.ozone.om.ratis; + +import java.io.IOException; +import java.util.Iterator; +import java.util.Queue; +import java.util.concurrent.ConcurrentLinkedQueue; +import java.util.concurrent.atomic.AtomicLong; + +import edu.umd.cs.findbugs.annotations.SuppressFBWarnings; +import org.apache.hadoop.ozone.om.OMMetadataManager; +import org.apache.hadoop.ozone.om.ratis.helpers.DoubleBufferEntry; +import org.apache.hadoop.ozone.om.response.OMClientResponse; +import org.apache.hadoop.util.Daemon; +import org.apache.hadoop.util.ExitUtil; +import org.apache.hadoop.utils.db.BatchOperation; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * A double-buffer for OM requests. + */ +public class OzoneManagerDoubleBuffer { + + private static final Logger LOG = + LoggerFactory.getLogger(OzoneManagerDoubleBuffer.class.getName()); + + private TransactionBuffer currentBuffer; + private TransactionBuffer readyBuffer; + private Daemon daemon; + private volatile boolean syncToDB; + private final OMMetadataManager omMetadataManager; + private AtomicLong flushedTransactionCount = new AtomicLong(0); + private AtomicLong flushIterations = new AtomicLong(0); + + public OzoneManagerDoubleBuffer(OMMetadataManager omMetadataManager) { + this.currentBuffer = new TransactionBuffer(); + this.readyBuffer = new TransactionBuffer(); + this.omMetadataManager = omMetadataManager; + + // Daemon thread which runs in back ground and flushes transactions to DB. + daemon = new Daemon(this::flushTransactions); + daemon.start(); + + } + + /** + * Runs in a background thread and batches the transaction in currentBuffer + * and commit to DB. + */ + private void flushTransactions() { + while(true) { + if (canFlush()) { + syncToDB = true; + setReadyBuffer(); + final BatchOperation batchOperation = omMetadataManager.getStore() + .initBatchOperation(); + + readyBuffer.iterator().forEachRemaining((entry) -> { + try { + entry.getResponse().addToRocksDBBatch(omMetadataManager, + batchOperation); + } catch (IOException ex) { + // During Adding to RocksDB batch entry got an exception. + // We should terminate the OM. + String message = "During flush to DB encountered error " + + ex.getMessage(); + ExitUtil.terminate(1, message); + } + }); + + try { + omMetadataManager.getStore().commitBatchOperation(batchOperation); + } catch (IOException ex) { + // During flush to rocksdb got an exception. + // We should terminate the OM. + String message = "During flush to DB encountered error " + + ex.getMessage(); + ExitUtil.terminate(1, message); + } + + int flushedTransactionsSize = readyBuffer.size(); + flushedTransactionCount.addAndGet(flushedTransactionsSize); + flushIterations.incrementAndGet(); + + LOG.info("Sync Iteration {} flushed transactions in this iteration{}", Review comment: Agreed, this should be a debug log. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org Issue Time Tracking ------------------- Worklog Id: (was: 244786) Time Spent: 4h 10m (was: 4h) > Implement DoubleBuffer in OzoneManager > -------------------------------------- > > Key: HDDS-1512 > URL: https://issues.apache.org/jira/browse/HDDS-1512 > Project: Hadoop Distributed Data Store > Issue Type: Sub-task > Components: Ozone Manager > Reporter: Bharat Viswanadham > Assignee: Bharat Viswanadham > Priority: Major > Labels: pull-request-available > Time Spent: 4h 10m > Remaining Estimate: 0h > > This Jira is created to implement DoubleBuffer in OzoneManager to flush > transactions to OM DB. > > h2. Flushing Transactions to RocksDB: > We propose using an implementation similar to the HDFS EditsDoubleBuffer. We > shall flush RocksDB transactions in batches, instead of current way of using > rocksdb.put() after every operation. At a given time only one batch will be > outstanding for flush while newer transactions are accumulated in memory to > be flushed later. > > In DoubleBuffer it will have 2 buffers one is currentBuffer, and the other is > readyBuffer. We add entry to current buffer, and we check if another flush > call is outstanding. If not, we flush to disk Otherwise we add entries to > otherBuffer while sync is happening. > > In this if sync is happening, we shall add new requests to other buffer and > when we can sync we use *RocksDB batch commit to sync to disk, instead of > rocksdb put.* > > Note: If flush to disk is failed on any OM, we shall terminate the > OzoneManager, so that OM DB’s will not diverge. Flush failure should be > considered as catastrophic failure. > > Scope of this Jira is to add DoubleBuffer implementation, integrating to > current OM will be done in further jira's. > -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org