Failed to retrieve the document that contains the Task Object with id

[raphj]

During a Confluence migration, a user is seeing a lot of these issues:

Failed to retrieve the document that contains the Task Object with id [{}]: ERROR: duplicate key value violates unique constraint "xwikidoc_pkey"
Detail: Key (xwd_id)\\u003d(-4458494136633945569) already exists.

(with varying ids)

Unfortunately, I haven't managed to reproduce the issue yet. I don't have a stack trace because of #131

[trrenty]

This was caused by the following piece of code:

application-task/application-task-default/src/main/java/com/xwiki/task/internal/TaskMacroUpdateEventListener.java

Lines 141 to 150 in 6f3b57a

	// If not in fold event, process the last remaining document.
	if (lastFoldDocumentReference != null) {
	try {
	updateTaskPages(context.getWiki().getDocument(lastFoldDocumentReference, context), context);
	} catch (XWikiException e) {
	logger.warn(EXCEPTION_DOCUMENT_RETRIEVAL, lastFoldDocumentReference, e);
	} finally {
	lastFoldDocumentReference = null;
	}
	}

The code was added as part of this optimization issue #114 . Migrating a document with multiple versions, each version containing task macros, would slow down the migration significantly. This was because each version of the document would be processed by the task listeners. The proposed solution tried to detect when the context is a migration and only process the last revision of a document. This was done by making the listener stateful which causes problems in concurrent environments.

To reproduce the issue, one should do the following:

1. Run a migration of some pages that contain task macros
2. During the execution of the migration, edit and save a arbitrary page on the wiki

The save should be done when the revisions of a page are processed, thus, the higher the number of revisions, the higher the chance to reproduce the issue.

For now, I fixed the issue partially. It can still reproduce if the Admin configures multiple "notSkippedFoldEvents" in the administration section of the Task App AND runs multiple processes that trigger the aforementioned fold events at the same time. I created another issue for that #160 . A solution that would fix that as well is more complicated and requires more time.