Darrel Schneider created GEODE-9772:
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Summary: RedisString should consistently use a DeltaInfo for all
write ops that update a RedisString
Key: GEODE-9772
URL: https://issues.apache.org/jira/browse/GEODE-9772
Project: Geode
Issue Type: Improvement
Components: redis
Reporter: Darrel Schneider
Currently RedisString generates a DeltaInfo instance when it does an "append"
to an existing RedisString. But for all the other write ops on RedisString the
implementation does not generate a DeltaInfo instance. This causes the entire
RedisString instance to be serialized to the secondary. But the ops that do
this tend to change the entire string (for example "set" get rid of the old
value of the string and adds a brand new value). But even for these types of
ops being consistent about generating a DeltaInfo has the following benefits:
1. the memory usage on the region will be consistent between the primary and
secondary because the value will be stored in the same form on both of them.
Understand that for value classes that implement the Delta interface (which all
RedisData classes do) the primary will always store the value in deserialized
form. But it gets stored on the secondary in serialized from until a value
arrives on the secondary that is just the delta bytes. By generating a
DeltaInfo instance the secondary will receive data bytes.
2. By keeping the values stored in the region in object form it causes updates
to not produce "old garbage". What happens when a DeltaInfo is sent is that it
modifies in place an object that is already in the JVM heap memory. But without
a DeltaInfo a whole new value is created and the old value becomes garbage.
That old value may have already been promoted to the older generation and now
the JVM may have to do more work to get it garbage collected. It is best if
object die young (sad but true).
RedisString has a number of ops that do not use generate a DeltaInfo. But they
could easily be changed to just generate a DeltaInfo that contains a byte array
that is the new value of the RedisString. This would even work for "setrange"
and "setbit" but those could be further optimized to only add a subset of the
bytes to the DeltaInfo along with an index.
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