The timestamp involed here isn’t the one defined in the schema, it’s the timestamp written on each cell when you apply a mutation (write).
That timestamp is the one returned by WRITETIME(), and visible in sstablemetadata – it’s not visible in the schema directly. Failing to have the proper unit (milliseconds vs microseconds) could certainly cause confusion. From: Venkatesh Arivazhagan Reply-To: "user@cassandra.apache.org" Date: Monday, September 21, 2015 at 1:41 PM To: "user@cassandra.apache.org" Subject: Re: Help with tombstones and compaction Thank you for your reply Jeff! I will switch to Cassandra 2.1.9. Quick follow up question: Does the schema, settings I have setup look alright? My timestamp column's type is blob - I was wondering if this could confuse DTCS? On Sun, Sep 20, 2015 at 3:37 PM, Jeff Jirsa <jeff.ji...@crowdstrike.com> wrote: 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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