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Application Class Data Sharing (AppCDS)

Application Class Data Sharing (AppCDS) is a JVM feature that maps pre-processed class metadata into shared memory. This eliminates class loading and verification overhead during startup, reducing Helix CLI latency by over 65% (down to sub-100ms).

Performance Comparison​

MetricWithout AppCDSWith AppCDS (helix.jsa)Improvement
JVM Startup Latency~285 ms~92 ms67.7% Faster
Classes Loaded on Init2,450 classesPre-mapped shared archiveZero I/O bottleneck
Memory FootprintSeparate copy per processRead-only shared memory pageShared across workers

1-Step Generation via Helper Script​

Helix includes an automated script that profiles classloading and builds the helix.jsa archive:

./scripts/generate-appcds.sh

Script Execution Flow​

Manual Generation Commands​

If you wish to customize class list profiling:

# Step 1: Dump Class List during representative workload
java -XX:DumpLoadedClassList=helix.lst \
     -jar engine-core/target/engine-core-1.0.0-SNAPSHOT.jar \
     compile --rule examples/rules/fraud-detection.json

# Step 2: Dump the Shared Archive File
java -Xshare:dump \
     -XX:SharedClassListFile=helix.lst \
     -XX:SharedArchiveFile=helix.jsa \
     -jar engine-core/target/engine-core-1.0.0-SNAPSHOT.jar

# Step 3: Run with AppCDS Enabled
java -XX:SharedArchiveFile=helix.jsa \
     -jar engine-core/target/engine-core-1.0.0-SNAPSHOT.jar \
     execute --rule examples/rules/fraud-detection.json \
             --context examples/rules/sample-context.json
Automatic Detection

The ./scripts/start-helix.sh wrapper automatically searches for helix.jsa in the project root. If found, it attaches -XX:SharedArchiveFile=helix.jsa without requiring manual JVM configuration flags.