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From Jeff Jirsa <jeff.ji...@crowdstrike.com>
Subject Re: Help with tombstones and compaction
Date Sun, 20 Sep 2015 22:37:39 GMT
2.1.4 is getting pretty old. There’s a DTCS deletion tweak in 2.1.5 ( https://issues.apache.org/jira/browse/CASSANDRA-8359
) that may help you.

2.1.5 and 2.1.6 have some memory leak issues in DTCS, so go to 2.1.7 or newer (probably 2.1.9
unless you have a compelling reason not to go to 2.1.9)


From:  Venkatesh Arivazhagan
Reply-To:  "user@cassandra.apache.org"
Date:  Sunday, September 20, 2015 at 2:48 PM
To:  "user@cassandra.apache.org"
Subject:  Help with tombstones and compaction

Hi Guys,

I have a Cassandra 2.1.4 cluster with 14 nodes. I am using it primarily for storing time series
data collected via KairosDB.
The default TTL for data inserted into the column family named data_points is 12hrs. I have
also set the gc_grace_seconds to 12 hrs.
In-spite of this my disk space keeps on increasing and it looks like tombstones are never
dropped.

It looks like compactions are happening on a regular basis. The SSTable count does not seem
outrageous either. It is constantly between ~10 to ~22.

Am I doing anything wrong? Is there a way to mitigate this?

Attached:
* DESC output for my keyspace
* Disk usage graph
* LiveSSTable Count graph

--------------------------------------------------------------------------------------------------------------------------

CREATE KEYSPACE kairosdb WITH replication = {'class': 'SimpleStrategy', 'replication_factor':
'3'}  AND durable_writes = true;

CREATE TABLE kairosdb.data_points (
    key blob,
    column1 blob,
    value blob,
    PRIMARY KEY (key, column1)
) WITH COMPACT STORAGE
    AND CLUSTERING ORDER BY (column1 ASC)
    AND bloom_filter_fp_chance = 0.01
    AND caching = '{"keys":"ALL", "rows_per_partition":"NONE"}'
    AND comment = ''
    AND compaction = {'max_sstable_age_days': '365', 'base_time_seconds': '3600', 'max_threshold':
'32', 'timestamp_resolution': 'MILLISECONDS', 'enabled': 'true', 'tombstone_compaction_interval':
'1', 'min_threshold': '4', 'tombstone_threshold': '.1', 'class': 'org.apache.cassandra.db.compaction.DateTieredCompactionStrategy'}
    AND compression = {'sstable_compression': 'org.apache.cassandra.io.compress.LZ4Compressor'}
    AND dclocal_read_repair_chance = 0.1
    AND default_time_to_live = 43200
    AND gc_grace_seconds = 43200
    AND max_index_interval = 2048
    AND memtable_flush_period_in_ms = 0
    AND min_index_interval = 128
    AND read_repair_chance = 0.1
    AND speculative_retry = 'NONE';

CREATE TABLE kairosdb.row_key_index (
    key blob,
    column1 blob,
    value blob,
    PRIMARY KEY (key, column1)
) WITH COMPACT STORAGE
    AND CLUSTERING ORDER BY (column1 ASC)
    AND bloom_filter_fp_chance = 0.01
    AND caching = '{"keys":"ALL", "rows_per_partition":"NONE"}'
    AND comment = ''
    AND compaction = {'min_threshold': '4', 'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy',
'max_threshold': '32'}
    AND compression = {'sstable_compression': 'org.apache.cassandra.io.compress.LZ4Compressor'}
    AND dclocal_read_repair_chance = 0.1
    AND default_time_to_live = 0
    AND gc_grace_seconds = 43200
    AND max_index_interval = 2048
    AND memtable_flush_period_in_ms = 0
    AND min_index_interval = 128
    AND read_repair_chance = 0.1
    AND speculative_retry = 'NONE';

CREATE TABLE kairosdb.string_index (
    key blob,
    column1 text,
    value blob,
    PRIMARY KEY (key, column1)
) WITH COMPACT STORAGE
    AND CLUSTERING ORDER BY (column1 ASC)
    AND bloom_filter_fp_chance = 0.01
    AND caching = '{"keys":"ALL", "rows_per_partition":"NONE"}'
    AND comment = ''
    AND compaction = {'min_threshold': '4', 'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy',
'max_threshold': '32'}
    AND compression = {'sstable_compression': 'org.apache.cassandra.io.compress.LZ4Compressor'}
    AND dclocal_read_repair_chance = 0.1
    AND default_time_to_live = 0
    AND gc_grace_seconds = 43200
    AND max_index_interval = 2048
    AND memtable_flush_period_in_ms = 0
    AND min_index_interval = 128
    AND read_repair_chance = 0.1
    AND speculative_retry = 'NONE';
--------------------------------------------------------------------------------------------------------------------------


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