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ASF GitHub Bot commented on NIFI-2854: -------------------------------------- Github user olegz commented on a diff in the pull request: https://github.com/apache/nifi/pull/1202#discussion_r88486311 --- Diff: nifi-nar-bundles/nifi-provenance-repository-bundle/nifi-persistent-provenance-repository/src/main/java/org/apache/nifi/provenance/AbstractRecordWriter.java --- @@ -0,0 +1,173 @@ +/* + * 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.nifi.provenance; + +import java.io.File; +import java.io.IOException; +import java.io.OutputStream; +import java.util.concurrent.locks.Lock; +import java.util.concurrent.locks.ReentrantLock; + +import org.apache.nifi.provenance.serialization.RecordWriter; +import org.apache.nifi.provenance.toc.TocWriter; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +public abstract class AbstractRecordWriter implements RecordWriter { + private static final Logger logger = LoggerFactory.getLogger(AbstractRecordWriter.class); + + private final File file; + private final TocWriter tocWriter; + private final Lock lock = new ReentrantLock(); + + private volatile boolean dirty = false; + private volatile boolean closed = false; + + private int recordsWritten = 0; + + public AbstractRecordWriter(final File file, final TocWriter writer) throws IOException { + logger.trace("Creating Record Writer for {}", file); + + this.file = file; + this.tocWriter = writer; + } + + @Override + public synchronized void close() throws IOException { + closed = true; + + logger.trace("Closing Record Writer for {}", file == null ? null : file.getName()); + + lock(); --- End diff -- Wondering what is the purpose of explicit locking when _synchronized_ is used? > Enable repositories to support upgrades and rollback in well defined scenarios > ------------------------------------------------------------------------------ > > Key: NIFI-2854 > URL: https://issues.apache.org/jira/browse/NIFI-2854 > Project: Apache NiFi > Issue Type: Improvement > Components: Core Framework > Reporter: Mark Payne > Assignee: Mark Payne > Fix For: 1.1.0 > > > The flowfile, swapfile, provenance, and content repositories play a very > important roll in NiFi's ability to be safely upgraded and rolled back. We > need to have well documented behaviors, designs, and version adherence so > that users can safely rely on these mechanisms. > Once this is formalized and in place we should update our versioning guidance > to reflect this as well. > The following would be true from NiFi 1.2.0 onward > * No changes to how the repositories are persisted to disk can be made which > will break forward/backward compatibility and specifically this means that > things like the way each is serialized to disk cannot change. > * If changes are made which impact forward or backward compatibility they > should be reserved for major releases only and should include a utility to > help users with pre-existing data convert from some older format to the newer > format. It may not be feasible to have rollback on major releases. > * The content repository should not be changed within a major release cycle > in any way that will harm forward or backward compatibility. > * The flow file repository can change in that new fields can be added to > existing write ahead log record types but no fields can be removed nor can > any new types be added. Once a field is considered required it must remain > required. Changes may only be made across minor version changes - not > incremental. > * Swap File storage should follow very similar rules to the flow file > repository. Adding a schema to the swap file header may allow some variation > there but the variation should only be hints to optimize how they're > processed and not change their behavior otherwise. Changes are only permitted > during minor version releases. > * Provenance repository changes are only permitted during minor version > releases. These changes may include adding or removing fields from existing > event types. If a field is considered required it must always be considered > required. If a field is removed then it must not be a required field and > there must be a sensible default an older version could use if that value is > not found in new data once rolled back. New event types may be added. > Fields or event types not known to older version, if seen after a rollback, > will simply be ignored. -- This message was sent by Atlassian JIRA (v6.3.4#6332)