Reduce heap usage in Zip archiver to prevent OutOfMemoryError in CI builds #390
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The previous threshold of 100000000 (100MB) divided by number of threads was causing OutOfMemoryError issues when creating zip archives, particularly in environments with limited heap space like CI systems. The ByteArrayOutputStream used internally can grow up to 2x the threshold before switching to disk-based storage, leading to excessive memory consumption. Reducing to 10000000 (10MB) reduces memory pressure while still maintaining reasonable performance. For typical builds with 4 threads, this means: - Before: 25MB per stream (potentially 50MB+ with buffer doubling) - After: 2.5MB per stream (potentially 5MB+ with buffer doubling) This change addresses the heap space errors reported in apache/maven CI builds. Co-authored-by: slachiewicz <6705942+slachiewicz@users.noreply.github.com>
Cap individual buffer allocations to 16MB to prevent excessive memory usage. The previous implementation allowed buffers to double indefinitely, which could lead to very large single allocations (32MB, 64MB, 128MB, etc.) that contribute to heap exhaustion. With this cap, when more than 16MB of data needs to be stored, the ByteArrayOutputStream will create multiple 16MB buffers instead of one giant buffer. This spreads the memory allocation across multiple smaller chunks and prevents heap fragmentation issues. Combined with the reduced threshold in ConcurrentJarCreator, this provides defense-in-depth against OutOfMemoryError during zip archive creation. Co-authored-by: slachiewicz <6705942+slachiewicz@users.noreply.github.com>
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October 5, 2025 12:51
slachiewicz
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Oct 5, 2025
slawekjaranowski
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Oct 6, 2025
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Problem
The Zip archiver was causing
OutOfMemoryErrorin CI builds with limited heap space, particularly affecting projects like apache/maven. The error occurred during archive creation:Root Cause
The
ConcurrentJarCreatorwas using an aggressive 100MB memory threshold divided by thread count for managing in-memory buffers. TheByteArrayOutputStreamimplementation would double its buffer size as needed (1MB → 2MB → 4MB → 8MB → 16MB → 32MB → ...), which could lead to very large single allocations before the threshold would trigger switching to disk-based storage.For a typical 4-thread build:
Solution
This PR implements two complementary changes to reduce memory pressure:
1. Reduced Memory Threshold (10x reduction)
Changed the threshold in
ConcurrentJarCreatorfrom 100MB to 10MB:2. Buffer Size Cap
Added a 16MB maximum buffer size in
ByteArrayOutputStreamto prevent unbounded growth:When more than 16MB of data needs to be stored, multiple 16MB buffers are created instead of one giant buffer, preventing heap fragmentation and excessive single allocations.
Impact
Memory Usage (4 threads):
Performance:
Testing
Fixes heap space errors reported in https://github.com/apache/maven/actions/runs/18203002937/job/51826915272 and related CI builds.
Original prompt
This section details on the original issue you should resolve
<issue_title>Heap usage by Zip archiver</issue_title>
<issue_description>We need an investigate heap usage be Zip archiver, in
ConcurrentJarCreatorthere is a buffer about 100MB used ...plexus-archiver/src/main/java/org/codehaus/plexus/archiver/zip/ConcurrentJarCreator.java
Line 117 in 7ed88ad
reference:
Comments on the Issue (you are @copilot in this section)
@slachiewicz also visible in apache/maven project (main branch) CI