Optimize JacksonPersister#hydrateFromBytes

atlasdb-client/src/main/java/com/palantir/atlasdb/persister/JacksonPersister.java

@@ -19,7 +19,10 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.base.Throwables;
 import com.palantir.atlasdb.persist.api.ReusablePersister;
+import java.io.ByteArrayInputStream;
 import java.io.IOException;
+import java.io.StringReader;
+import java.nio.charset.StandardCharsets;
 
 /**
  * A {@link ReusablePersister} that uses an {@link ObjectMapper} to serialize and deserialize objects
@@ -38,7 +41,14 @@ public JacksonPersister(Class<T> typeRef, ObjectMapper mapper) {
     @Override
     public final T hydrateFromBytes(byte[] input) {
         try {
-            return mapper.readValue(input, typeRef);
+            if (input.length <= 8192 && mapper.getFactory().canUseCharArrays()) {
+                // Optimize to avoid allocation of heap ByteBuffer via InputStreamReader.
+                // Remove after upgrade to Jackson 2.16.
+                // see: https://github.com/FasterXML/jackson-core/pull/1081
+                // and https://github.com/FasterXML/jackson-benchmarks/pull/9
+                return mapper.readValue(new StringReader(new String(input, StandardCharsets.UTF_8)), typeRef);
+            }
+            return mapper.readValue(new ByteArrayInputStream(input), typeRef);
         } catch (IOException e) {
             throw Throwables.propagate(e);
         }

changelog/@unreleased/pr-6750.v2.yml

@@ -0,0 +1,8 @@
+type: improvement
+improvement:
+  description: |-
+    Optimize to avoid allocation of heap ByteBuffer via InputStreamReader. Remove after upgrade to Jackson 2.16.
+
+    see: https://github.com/FasterXML/jackson-core/pull/1081 and https://github.com/FasterXML/jackson-benchmarks/pull/9
+  links:
+  - https://github.com/palantir/atlasdb/pull/6750