Spurious warnings from AttachmentEventGeneratorListener: Failed to send event DocumentUpdatedEvent to listener

[raphj]

We are randomly seeing such warnings as
[com.xpn.xwiki.internal.event.AttachmentEventGeneratorListener@392cf6c6]
Failed to send event [org.xwiki.bridge.event.DocumentUpdatedEvent@575fb407] to listener.

We need to find the cause and to find out the consequences, and fix this.

Full stack trace:

[org.xwiki.store.UnexpectedException: Failed to get InputStream,
  at org.xwiki.store.legacy.doc.internal.FilesystemAttachmentContent.getContentInputStream(FilesystemAttachmentContent.java:127),
  at com.xpn.xwiki.doc.XWikiAttachment.getContentInputStream(XWikiAttachment.java:924),
  at com.xpn.xwiki.doc.XWikiAttachment.getContentInputStream(XWikiAttachment.java:919),
  at com.xpn.xwiki.doc.XWikiDocument.retrieveDeletedAttachment(XWikiDocument.java:7234),
  at com.xpn.xwiki.doc.XWikiDocument.getAttachmentDiff(XWikiDocument.java:7198),
  at com.xpn.xwiki.internal.event.AttachmentEventGeneratorListener.onDocumentUpdatedEvent(AttachmentEventGeneratorListener.java:139),
  at com.xpn.xwiki.internal.event.AttachmentEventGeneratorListener.onEvent(AttachmentEventGeneratorListener.java:88),
  at org.xwiki.observation.internal.DefaultObservationManager.notify(DefaultObservationManager.java:320),
  at org.xwiki.observation.internal.DefaultObservationManager.notify(DefaultObservationManager.java:285),
  at com.xpn.xwiki.XWiki.afterSave(XWiki.java:2035),
  at com.xpn.xwiki.XWiki.saveDocument(XWiki.java:2123),
  at com.xwiki.confluencepro.internal.DocumentInstanceOutputFilterStream.maybeSaveDocument(DocumentInstanceOutputFilterStream.java:252),
  at com.xwiki.confluencepro.internal.DocumentInstanceOutputFilterStream.endWikiDocumentRevision(DocumentInstanceOutputFilterStream.java:164),
  at jdk.internal.reflect.GeneratedMethodAccessor126.invoke(Unknown Source),
  at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43),
  at java.base/java.lang.reflect.Method.invoke(Method.java:566),
  at org.xwiki.filter.internal.FilterProxy.invoke(FilterProxy.java:90),
  at org.xwiki.filter.internal.CompositeFilter.invoke(CompositeFilter.java:75),
  at com.sun.proxy.$Proxy235.endWikiDocumentRevision(Unknown Source),
  at jdk.internal.reflect.GeneratedMethodAccessor126.invoke(Unknown Source),
  at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43),
  at java.base/java.lang.reflect.Method.invoke(Method.java:566),
  at org.xwiki.filter.internal.FilterProxy.invoke(FilterProxy.java:90),
  at org.xwiki.filter.internal.CompositeFilter.invoke(CompositeFilter.java:75),
  at com.sun.proxy.$Proxy236.endWikiDocumentRevision(Unknown Source),
  at jdk.internal.reflect.GeneratedMethodAccessor126.invoke(Unknown Source),
  at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43),
  at java.base/java.lang.reflect.Method.invoke(Method.java:566),
  at org.xwiki.filter.internal.FilterProxy.invoke(FilterProxy.java:90),
  at org.xwiki.filter.internal.FilterProxy.invoke(FilterProxy.java:63),
  at com.sun.proxy.$Proxy237.endWikiDocumentRevision(Unknown Source),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.readPageRevision(ConfluenceInputFilterStream.java:1353),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.sendRevisions(ConfluenceInputFilterStream.java:1211),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.sendTerminalDoc(ConfluenceInputFilterStream.java:1143),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.readPage(ConfluenceInputFilterStream.java:1111),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.sendPage(ConfluenceInputFilterStream.java:460),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.sendPages(ConfluenceInputFilterStream.java:497),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.readPage(ConfluenceInputFilterStream.java:1114),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.sendPage(ConfluenceInputFilterStream.java:460),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.sendPages(ConfluenceInputFilterStream.java:497),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.readPage(ConfluenceInputFilterStream.java:1114),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.sendPage(ConfluenceInputFilterStream.java:460),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.sendPages(ConfluenceInputFilterStream.java:497),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.readPage(ConfluenceInputFilterStream.java:1114),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.sendPage(ConfluenceInputFilterStream.java:460),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.sendPages(ConfluenceInputFilterStream.java:497),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.readPage(ConfluenceInputFilterStream.java:1114),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.sendPage(ConfluenceInputFilterStream.java:460),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.sendPages(ConfluenceInputFilterStream.java:497),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.sendConfluenceRootSpace(ConfluenceInputFilterStream.java:436),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.readInternal(ConfluenceInputFilterStream.java:346),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.read(ConfluenceInputFilterStream.java:184),
  at org.xwiki.contrib.confluence.filter.internal.input.ConfluenceInputFilterStream.read(ConfluenceInputFilterStream.java:96),
  at org.xwiki.filter.input.AbstractBeanInputFilterStream.read(AbstractBeanInputFilterStream.java:79),
  at org.xwiki.filter.internal.job.FilterStreamConverterJob.runInternal(FilterStreamConverterJob.java:97),
  at org.xwiki.job.AbstractJob.runInContext(AbstractJob.java:246),
  at org.xwiki.job.AbstractJob.run(AbstractJob.java:223),
  at org.xwiki.filter.script.internal.ScriptFilterStreamConverterJob.run(ScriptFilterStreamConverterJob.java:75),
  at com.xwiki.confluencepro.internal.ConfluenceMigrationJob.runInternal(ConfluenceMigrationJob.java:166),
  at org.xwiki.job.AbstractJob.runInContext(AbstractJob.java:246),
  at org.xwiki.job.AbstractJob.run(AbstractJob.java:223),
  at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128),
  at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628),
  at java.base/java.lang.Thread.run(Thread.java:829), Caused by: java.io.FileNotFoundException: /var/lib/xwiki/data/store/file/xwiki/9/3/8e27905808f40e87e635782de034e5/attachments/2/f/986a55f22de5a5a7c24d75e3ac2257/fv1.2.pdf (No such file or directory),
  at java.base/java.io.FileInputStream.open0(Native Method),
  at java.base/java.io.FileInputStream.open(FileInputStream.java:219),
  at java.base/java.io.FileInputStream.<init>(FileInputStream.java:157),
  at org.xwiki.store.legacy.doc.internal.FilesystemAttachmentContent.getContentInputStream(FilesystemAttachmentContent.java:125),  ... 63 more]

[raphj]

See https://jira.xwiki.org/browse/XWIKI-21979