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https://issues.apache.org/jira/browse/CASSANDRA-6574?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13868917#comment-13868917
]
Jonathan Ellis commented on CASSANDRA-6574:
-------------------------------------------
I bet it's just skipping entries from sstables that have been compacted and are
no longer relevant. You could add a debug line here if you want to be sure:
{code}
public Future<Pair<KeyCacheKey, RowIndexEntry>>
deserialize(DataInputStream input, ColumnFamilyStore cfs) throws IOException
{
ByteBuffer key = ByteBufferUtil.readWithLength(input);
int generation = input.readInt();
SSTableReader reader = findDesc(generation, cfs.getSSTables());
boolean promotedIndexes = input.readBoolean();
if (reader == null)
{
if (promotedIndexes)
RowIndexEntry.serializer.skip(input,
Descriptor.Version.CURRENT);
return null;
}
RowIndexEntry entry = promotedIndexes
? RowIndexEntry.serializer.deserialize(input,
reader.descriptor.version)
:
reader.getPosition(reader.partitioner.decorateKey(key), Operator.EQ, false);
return Futures.immediateFuture(Pair.create(new
KeyCacheKey(reader.descriptor, key), entry));
}
{code}
> key cache shrinks on restart
> ----------------------------
>
> Key: CASSANDRA-6574
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6574
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Environment: 1.2.12 + patches
> Reporter: Chris Burroughs
> Attachments: key-cache-entries.png
>
>
> During a rolling restart the key number of entries the number of entries in
> the key cache is shrinking. That is far fewer entries are loaded than are
> saved. This has obvious bad consequences for post restart performance.
> {noformat}
> key_cache_size_in_mb: 48
> key_cache_save_period: 900
> # Number of keys from the key cache to save
> # Disabled by default, meaning all keys are going to be saved
> # key_cache_keys_to_save: 100
> row_cache_size_in_mb: 256
> row_cache_save_period: 300
> row_cache_keys_to_save: 50000
> row_cache_provider: SerializingCacheProvider
> saved_caches_directory: /home/cassandra/shared/saved_caches
> {noformat}
> Same log lines:
> {noformat}
> INFO [CompactionExecutor:24543] 2014-01-11 11:35:47,783 AutoSavingCache.java
> (line 289) Saved KeyCache (398028 items) in 1252 ms
> *** RESTART ***
> INFO [main] 2014-01-11 11:44:59,608 AutoSavingCache.java (line 140) reading
> saved cache /home/cassandra/shared/saved_caches/ks-cf1-KeyCache-b.db
> INFO [main] 2014-01-11 11:45:00,509 AutoSavingCache.java (line 140) reading
> saved cache /home/cassandra/shared/saved_caches/ks-cf2-RowCache-b.db
> INFO [main] 2014-01-11 12:02:48,675 ColumnFamilyStore.java (line 452)
> completed loading (1068166 ms; 50000 keys) row cache for ks.cf2
> INFO [main] 2014-01-11 12:02:48,769 CassandraDaemon.java (line 291)
> completed pre-loading (67760 keys) key cache.
> INFO [main] 2014-01-11 12:02:48,769 CassandraDaemon.java (line 294)
> completed pre-loading (50000 keys) row cache.
> INFO [CompactionExecutor:1] 2014-01-11 12:02:49,133 AutoSavingCache.java
> (line 289) Saved RowCache (50000 items) in 266 ms
> INFO [CompactionExecutor:2] 2014-01-11 12:02:49,575 AutoSavingCache.java
> (line 289) Saved KeyCache (67760 items) in 707 ms
> {noformat}
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