Diagnosing Reproducible Build Issues
When checking Reproducible Build, you may find that the current build output is not the same as the reference:
$ mvn -Papache-release clean verify -Dgpg.skip artifact:compare [INFO] Scanning for projects... ... [INFO] --- maven-artifact-plugin:3.5.3:buildinfo (default-cli) @ doxia-module-markdown --- [INFO] Saved aggregate info on build to /tmp/doxia-1.9.1/doxia-modules/doxia-module-markdown/target/doxia-module-markdown-1.9.1.buildinfo [INFO] Checking against reference build from central... Downloading from central: https://repo.maven.apache.org/maven2/org/apache/maven/doxia/doxia-module-markdown/1.9.1/doxia-module-markdown-1.9.1.buildinfo [WARNING] Reference buildinfo file not found: it will be generated from downloaded reference artifacts [INFO] Reference build java.version: 1.8 (from MANIFEST.MF Build-Jdk-Spec) [INFO] Reference build java.version: 1.8 (from MANIFEST.MF Build-Jdk-Spec) [ERROR] Current build java.version: 1.7 (from MANIFEST.MF Build-Jdk-Spec) [INFO] Reference build os.name: Unix (from pom.properties newline) [INFO] Minimal buildinfo generated from downloaded artifacts: /tmp/doxia-1.9.1/target/reference/doxia-module-markdown-1.9.1.buildinfo [WARNING] size mismatch doxia-logging-api-1.9.1.jar: investigate with diffoscope target/reference/doxia-logging-api-1.9.1.jar doxia-logging-api/target/doxia-logging-api-1.9.1.jar ... [WARNING] size mismatch doxia-module-markdown-1.9.1.jar: investigate with diffoscope target/reference/doxia-module-markdown-1.9.1.jar doxia-modules/doxia-module-markdown/target/doxia-module-markdown-1.9.1.jar [WARNING] Reproducible Build output summary: 39 files ok, 18 different [WARNING] see diff target/reference/doxia-module-markdown-1.9.1.buildinfo doxia-modules/doxia-module-markdown/target/doxia-module-markdown-1.9.1.buildinfo [WARNING] see also https://maven.apache.org/guides/mini/guide-reproducible-builds.html [INFO] Reproducible Build output comparison saved to /tmp/doxia-1.9.1/doxia-modules/doxia-module-markdown/target/doxia-module-markdown-1.9.1.buildcompare [INFO] Aggregate buildcompare copied to /tmp/doxia-1.9.1/target/doxia-1.9.1.buildcompare ...
Multiple interesting parts are available:
- the summary:
[WARNING] Reproducible Build output summary: 39 files ok, 18 different - key information on reference build environment:
[INFO] Reference build java.version: 1.8 (from MANIFEST.MF Build-Jdk-Spec)[INFO] Reference build os.name: Unix (from pom.properties newline)
which are the key requirements (JDK major version and Operating System) for the build environment to reproduce the reference build - eventual mismatch with current build environment:
[ERROR] Current build java.version: 1.7 (from MANIFEST.MF Build-Jdk-Spec) - on each artifact different from reference, a command is provided to investigate differences using diffoscope tool, a diff tool working inside archives (jar, zip, tar, ...):
simply copy paste provided command likediffoscope target/reference/doxia-logging-api-1.9.1.jar doxia-logging-api/target/doxia-logging-api-1.9.1.jarand you'll see where differences are:$ diffoscope target/reference/doxia-logging-api-1.9.1.jar doxia-logging-api/target/doxia-logging-api-1.9.1.jar --- target/reference/doxia-logging-api-1.9.1.jar +++ doxia-logging-api/target/doxia-logging-api-1.9.1.jar ├── zipinfo /dev/stdin │ @@ -1,8 +1,8 @@ │ -Zip file size: 11516 bytes, number of entries: 19 │ +Zip file size: 11497 bytes, number of entries: 19 │ -rw-r--r-- 2.0 unx 337 b- defN 20-Feb-13 21:11 META-INF/MANIFEST.MF │ drwxr-xr-x 2.0 unx 0 b- stor 20-Feb-13 21:11 META-INF/ │ drwxr-xr-x 2.0 unx 0 b- stor 20-Feb-13 21:11 org/ │ drwxr-xr-x 2.0 unx 0 b- stor 20-Feb-13 21:11 org/apache/ │ drwxr-xr-x 2.0 unx 0 b- stor 20-Feb-13 21:11 org/apache/maven/ │ drwxr-xr-x 2.0 unx 0 b- stor 20-Feb-13 21:11 org/apache/maven/doxia/ │ drwxr-xr-x 2.0 unx 0 b- stor 20-Feb-13 21:11 org/apache/maven/doxia/logging/ │ @@ -11,11 +11,11 @@ │ drwxr-xr-x 2.0 unx 0 b- stor 20-Feb-13 21:11 META-INF/maven/org.apache.maven.doxia/doxia-logging-api/ │ -rw-r--r-- 2.0 unx 1641 b- defN 20-Feb-13 21:11 META-INF/DEPENDENCIES │ -rw-r--r-- 2.0 unx 11358 b- defN 20-Feb-13 21:11 META-INF/LICENSE │ -rw-r--r-- 2.0 unx 177 b- defN 20-Feb-13 21:11 META-INF/NOTICE │ -rw-r--r-- 2.0 unx 716 b- defN 20-Feb-13 21:11 org/apache/maven/doxia/logging/Log.class │ -rw-r--r-- 2.0 unx 198 b- defN 20-Feb-13 21:11 org/apache/maven/doxia/logging/LogEnabled.class │ -rw-r--r-- 2.0 unx 2840 b- defN 20-Feb-13 21:11 org/apache/maven/doxia/logging/PlexusLoggerWrapper.class │ --rw-r--r-- 2.0 unx 4208 b- defN 20-Feb-13 21:11 org/apache/maven/doxia/logging/SystemStreamLog.class │ +-rw-r--r-- 2.0 unx 4192 b- defN 20-Feb-13 21:11 org/apache/maven/doxia/logging/SystemStreamLog.class │ -rw-r--r-- 2.0 unx 1539 b- defN 20-Feb-13 21:11 META-INF/maven/org.apache.maven.doxia/doxia-logging-api/pom.xml │ -rw-r--r-- 2.0 unx 74 b- defN 20-Feb-13 21:11 META-INF/maven/org.apache.maven.doxia/doxia-logging-api/pom.properties │ -19 files, 23088 bytes uncompressed, 8842 bytes compressed: 61.7% │ +19 files, 23072 bytes uncompressed, 8823 bytes compressed: 61.8% ├── META-INF/MANIFEST.MF │ @@ -1,10 +1,10 @@ │ Manifest-Version: 1.0 │ +Implementation-Vendor: The Apache Software Foundation │ Implementation-Title: Doxia :: Logging API │ Implementation-Version: 1.9.1 │ +Build-Jdk-Spec: 1.7 │ Specification-Vendor: The Apache Software Foundation │ -Specification-Title: Doxia :: Logging API │ -Build-Jdk-Spec: 1.8 │ Created-By: Maven Jar Plugin 3.2.0 │ +Specification-Title: Doxia :: Logging API │ Specification-Version: 1.9 │ -Implementation-Vendor: The Apache Software Foundation ├── org/apache/maven/doxia/logging/PlexusLoggerWrapper.class ...
In this example, reference build was done with JDK 8 (see │ -Build-Jdk-Spec: 1.8), but the current build was done with JDK 7 (see │ +Build-Jdk-Spec: 1.7): this explains both difference in content of META-INF/MANIFEST.MF of every .jar file, but also of some bytecode in .class files.
When general environment issues have been fixed, for each remaining issue, you'll have to find which Maven plugin generated the content and see if there is an update of the plugin that generates reproducible output: see the plugins table of the /guides/mini/guide-reproducible-builds.html for an initial list.