This error occurs every-time my Jenkins Master restarts.

Same here.

SEVERE: Unable to read /var/lib/jenkins/global-build-stats.xml
java.io.IOException: Unable to read /var/lib/jenkins/global-build-stats.xml
at hudson.XmlFile.unmarshal(XmlFile.java:165)
at hudson.Plugin.load(Plugin.java:264)
at hudson.plugins.global_build_stats.GlobalBuildStatsPlugin.load(GlobalBuildStatsPlugin.java:97)
at hudson.plugins.global_build_stats.business.GlobalBuildStatsPluginSaver.reloadPlugin(GlobalBuildStatsPluginSaver.java:99)
at hudson.plugins.global_build_stats.business.GlobalBuildStatsBusiness.reloadPlugin(GlobalBuildStatsBusiness.java:395)
at hudson.plugins.global_build_stats.GlobalBuildStatsPlugin$GlobalBuildStatsItemListener.onLoaded(GlobalBuildStatsPlugin.java:152)
at jenkins.model.Jenkins.<init>(Jenkins.java:994)
at hudson.model.Hudson.<init>(Hudson.java:85)
at hudson.model.Hudson.<init>(Hudson.java:81)
at hudson.WebAppMain$3.run(WebAppMain.java:231)
Caused by: com.thoughtworks.xstream.converters.ConversionException: null : null
---- Debugging information ----
cause-exception : java.lang.NullPointerException
cause-message : null
class : hudson.plugins.global_build_stats.GlobalBuildStatsPlugin
required-type : hudson.plugins.global_build_stats.GlobalBuildStatsPlugin
converter-type : hudson.plugins.global_build_stats.xstream.GlobalBuildStatsXStreamConverter
path : /hudson.plugins.global_build_stats.GlobalBuildStatsPlugin
line number : 2
version : not available
-------------------------------
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:79)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1189)
at hudson.util.XStream2.unmarshal(XStream2.java:114)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1173)
at hudson.XmlFile.unmarshal(XmlFile.java:163)
... 9 more
Caused by: java.lang.NullPointerException
at java.util.ArrayList.addAll(ArrayList.java:577)
at hudson.plugins.global_build_stats.model.JobBuildResultSharder.load(JobBuildResultSharder.java:140)
at hudson.plugins.global_build_stats.xstream.migration.AbstractMigrator.readGlobalBuildStatsPOJO(AbstractMigrator.java:35)
at hudson.plugins.global_build_stats.xstream.GlobalBuildStatsXStreamConverter.unmarshal(GlobalBuildStatsXStreamConverter.java:159)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
... 18 more

Hello !

What are your steps to get this NPE, just restart? Because I tried on different Jenkins-Versions (1&2) with Global-Build-Stats 1.4, with restart/safeRestart and could not reproduce :-/.

And could you check on your Jenkins the /jenkins/global-build-stats/jobresults/ directory , if there is a result-xml which contains only "<null/>"? This issue seems related to JENKINS-16475. I will take a look there as well.