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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
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package org.apache.cassandra.db.view;
import java.util.*;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.locks.Lock;
import com.google.common.util.concurrent.Striped;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.cassandra.config.CFMetaData;
import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.config.ViewDefinition;
import org.apache.cassandra.db.*;
import org.apache.cassandra.db.partitions.*;
import org.apache.cassandra.repair.SystemDistributedKeyspace;
import org.apache.cassandra.service.StorageService;
/**
* Manages {@link View}'s for a single {@link ColumnFamilyStore}. All of the views for that table are created when this
* manager is initialized.
*
* The main purposes of the manager are to provide a single location for updates to be vetted to see whether they update
* any views {@link #updatesAffectView(Collection, boolean)}, provide locks to prevent multiple
* updates from creating incoherent updates in the view {@link #acquireLockFor(int)}, and
* to affect change on the view.
*
* TODO: I think we can get rid of that class. For addition/removal of view by names, we could move it Keyspace. And we
* not sure it's even worth keeping viewsByName as none of the related operation are performance sensitive so we could
* find the view by iterating over the CFStore.viewManager directly.
* For the lock, it could move to Keyspace too, but I don't remmenber why it has to be at the keyspace level and if it
* can be at the table level, maybe that's where it should be.
*/
public class ViewManager
{
private static final Logger logger = LoggerFactory.getLogger(ViewManager.class);
private static final Striped LOCKS = Striped.lazyWeakLock(DatabaseDescriptor.getConcurrentViewWriters() * 1024);
private static final boolean enableCoordinatorBatchlog = Boolean.getBoolean("cassandra.mv_enable_coordinator_batchlog");
private final ConcurrentMap viewsByName = new ConcurrentHashMap<>();
private final ConcurrentMap viewsByBaseTable = new ConcurrentHashMap<>();
private final Keyspace keyspace;
public ViewManager(Keyspace keyspace)
{
this.keyspace = keyspace;
}
public boolean updatesAffectView(Collection mutations, boolean coordinatorBatchlog)
{
if (!enableCoordinatorBatchlog && coordinatorBatchlog)
return false;
for (IMutation mutation : mutations)
{
for (PartitionUpdate update : mutation.getPartitionUpdates())
{
assert keyspace.getName().equals(update.metadata().ksName);
if (coordinatorBatchlog && keyspace.getReplicationStrategy().getReplicationFactor() == 1)
continue;
if (!forTable(update.metadata()).updatedViews(update).isEmpty())
return true;
}
}
return false;
}
private Iterable allViews()
{
return viewsByName.values();
}
public void update(String viewName)
{
View view = viewsByName.get(viewName);
assert view != null : "When updating a view, it should already be in the ViewManager";
view.build();
// We provide the new definition from the base metadata
Optional viewDefinition = keyspace.getMetadata().views.get(viewName);
assert viewDefinition.isPresent() : "When updating a view, it should still be in the Keyspaces views";
view.updateDefinition(viewDefinition.get());
}
public void reload()
{
Map newViewsByName = new HashMap<>();
for (ViewDefinition definition : keyspace.getMetadata().views)
{
newViewsByName.put(definition.viewName, definition);
}
for (String viewName : viewsByName.keySet())
{
if (!newViewsByName.containsKey(viewName))
removeView(viewName);
}
for (Map.Entry entry : newViewsByName.entrySet())
{
if (!viewsByName.containsKey(entry.getKey()))
addView(entry.getValue());
}
// Building views involves updating view build status in the system_distributed
// keyspace and therefore it requires ring information. This check prevents builds
// being submitted when Keyspaces are initialized during CassandraDaemon::setup as
// that happens before StorageService & gossip are initialized. After SS has been
// init'd we schedule builds for *all* views anyway, so this doesn't have any effect
// on startup. It does mean however, that builds will not be triggered if gossip is
// disabled via JMX or nodetool as that sets SS to an uninitialized state.
if (!StorageService.instance.isInitialized())
{
logger.info("Not submitting build tasks for views in keyspace {} as " +
"storage service is not initialized", keyspace.getName());
return;
}
for (View view : allViews())
{
view.build();
// We provide the new definition from the base metadata
view.updateDefinition(newViewsByName.get(view.name));
}
}
public void addView(ViewDefinition definition)
{
// Skip if the base table doesn't exist due to schema propagation issues, see CASSANDRA-13737
if (!keyspace.hasColumnFamilyStore(definition.baseTableId))
{
logger.warn("Not adding view {} because the base table {} is unknown",
definition.viewName,
definition.baseTableId);
return;
}
View view = new View(definition, keyspace.getColumnFamilyStore(definition.baseTableId));
forTable(view.getDefinition().baseTableMetadata()).add(view);
viewsByName.put(definition.viewName, view);
}
public void removeView(String name)
{
View view = viewsByName.remove(name);
if (view == null)
return;
forTable(view.getDefinition().baseTableMetadata()).removeByName(name);
SystemKeyspace.setViewRemoved(keyspace.getName(), view.name);
SystemDistributedKeyspace.setViewRemoved(keyspace.getName(), view.name);
}
public View getByName(String name)
{
return viewsByName.get(name);
}
public void buildAllViews()
{
for (View view : allViews())
view.build();
}
public TableViews forTable(CFMetaData metadata)
{
UUID baseId = metadata.cfId;
TableViews views = viewsByBaseTable.get(baseId);
if (views == null)
{
views = new TableViews(metadata);
TableViews previous = viewsByBaseTable.putIfAbsent(baseId, views);
if (previous != null)
views = previous;
}
return views;
}
public static Lock acquireLockFor(int keyAndCfidHash)
{
Lock lock = LOCKS.get(keyAndCfidHash);
if (lock.tryLock())
return lock;
return null;
}
}