/**
* Copyright (c) 2013 Mark S. Kolich
* http://mark.koli.ch
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following
* conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
package com.kolich.havalo.io.managers;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.google.common.cache.RemovalListener;
import com.google.common.cache.RemovalNotification;
import com.kolich.havalo.entities.types.HavaloUUID;
import com.kolich.havalo.entities.types.Repository;
import com.kolich.havalo.exceptions.repositories.RepositoryFlushException;
public final class RepositoryCacheRemovalListener
implements RemovalListener<HavaloUUID,Repository> {
// http://code.google.com/p/guava-libraries/wiki/CachesExplained#Eviction
// Warning: removal listener operations are executed
// __synchronously__ by default, and since cache maintenance is
// normally performed during normal cache operations, expensive
// removal listeners can slow down normal cache function!
private static final Logger logger__ =
LoggerFactory.getLogger(RepositoryCacheRemovalListener.class);
private final RepositoryMetaWriter metaWriter_;
public RepositoryCacheRemovalListener(final RepositoryMetaWriter metaWriter) {
metaWriter_ = metaWriter;
}
@Override
public void onRemoval(final RemovalNotification<HavaloUUID,Repository> removed) {
Repository repo = null;
try {
// The repo that was "evicted" could be null if it was
// garbage collected between the time it was evicted
// and this listener was called. This should _not_
// happen given that we've asked the Cache to maintain
// _STRONG_ references to the keys and values in the
// cache, but we should check just in case.
if((repo = removed.getValue()) != null) {
// If the repository directory has been deleted (invalidated),
// we should not attempt to flush the meta data for it
// to disk -- the underlying repository has been deleted.
if(repo.getFile().exists()) {
// Queue the repository to be flushed to disk.
metaWriter_.queue(repo);
} else {
logger__.debug("Not flushing repo meta " +
"data, underlying repo directory is " +
"missing (id=" + repo.getKey() + ", " +
"file=" + repo.getFile().getCanonicalPath() +
") -- was probably for a deleted repository.");
}
} else {
// Should really _not_ happen based on the notes
// provided above.
throw new RepositoryFlushException("Could not " +
"flush NULL repository -- was perhaps " +
"already GC'ed?");
}
} catch (Exception e) {
logger__.error("Failed miserably to flush repository " +
"(id=" + ((repo != null) ? repo.getRepoId() : "NULL") +
") -- could be trouble!", e);
}
}
}