Michael Semb Wever created CASSANDRA-21699:
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Summary: InMemoryTrie reads the row overhead property for its size
limit
Key: CASSANDRA-21699
URL: https://issues.apache.org/jira/browse/CASSANDRA-21699
Project: Apache Cassandra
Issue Type: Bug
Components: Local/Memtable
Reporter: Michael Semb Wever
{{InMemoryTrie}} reads {{cassandra.memtable.row_overhead_size}} for its
allocated size threshold:
{code:java}
int limitInMB = CassandraRelevantProperties.MEMTABLE_OVERHEAD_SIZE.getInt(2048
* 10 / 11);
if (limitInMB < 1 || limitInMB > 2047)
throw new AssertionError(...);
{code}
That property is a byte count that {{SkipListMemtable}} reads for its per-row
overhead, and the trie reads the same value as a megabyte count, so one
property drives two unrelated settings. An operator who tunes the row overhead
moves the trie threshold as well, and a row overhead above 2047 makes the class
initialiser throw an {{AssertionError}}.
{{SimulationRunner}} shows the effect in the tree: it sets the property to 100
for the row overhead, which cuts the trie threshold from 1861MB to 100MB, so a
simulated trie memtable reports that it reached its limit after a twentieth of
the memory the default allows.
{{CassandraRelevantProperties}} already declares {{MEMTABLE_TRIE_SIZE_LIMIT}}
({{cassandra.trie_size_limit_mb}}), and no code reads it. The patch reads that
property instead, and names it in the range message. The default threshold does
not change. The static block becomes a package-private method, so a test can
read the threshold more than once.
Patch:
[mck/upstream/trie-size-limit-property/5.0|https://github.com/thelastpickle/cassandra/tree/mck/upstream/trie-size-limit-property/5.0]
Provenance:
[eb272c8458|https://github.com/datastax/cassandra/commit/eb272c8458390d6e3bbbb557c62cf68b9967f04c]
by [~mike_tr_adamson]. That commit makes the same property change and also
lowers the default threshold to 1GB, which this patch leaves out, because the
default belongs to a separate discussion. That commit carries no test; this
patch adds one.
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