[NIFI-2159] Fingerprint not detecting flow.xml differences

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 0.6.1
• Fix Version/s: 1.0.0, 0.7.0, 1.0.0-Beta
• Flags: Important
• Assignee: Mark Payne
• Reporter: Brandon Rhys DeVries
• Created: 01/Jul/16 12:14
• Updated: 04/Aug/16 21:29
• Resolved: 06/Jul/16 21:13

Description

We have very occasionally observed situations where the flow.xml across a cluster was able to become inconsistent, resulting in unexpected behavior. While investigating, the following issue was found. While we are not 100% that this problem is the one we were looking for, it is definitely an issue...

Within the FingerprintFactory, the text values from <relationship> tags were always being appended to the fingerprint as a default value of "NO_VALUE" regardless of whether or not they actually contained a value. This can manifest as two different flow.xml files being considered the same when they have the same number of relationship tags, even though those tags contain different values. Here is a suggested fix:

Change the following in FingerprintFactory.java[1]:

final List<Element> sortedRelationshipElems = sortElements(relationshipElems, getConnectionRelationshipsComparator());
for (final Element relationshipElem : sortedRelationshipElems) {
        addConnectionRelationshipFingerprint(builder, relationshipElem);
}

To:

for (int i = 0;i<relationshipElems.getLength();i++) {
       builder.append(getValue(relationshipElems.item(i),"NO_VALUE"));
}

The following unit test will show that the value of the relationship is now being used in the fingerprint:

@Test
public void testResourceValueInFingerprint() throws IOException{
       final String fp1 = fingerprinter.createFingerprint(getResourceBytes("/nifi/fingerprint/flow1a.xml"),null);
       assertEquals(3,StringUtils.countMatches(fp1,"success"));
}

Additionally, the <name> tag isn't being included in the fingerprint either. While the following solution has not been tested, it is possible that this could be fixed by adding the following line to the addConnectionFingerprint() method [2]:

appendFirstValue(builder, DomUtils.getChildNodesByTagName(connectionElem, "name"));

[1] https://github.com/apache/nifi/blob/270944ec692e12c221cdff202bdab56309dfcfd7/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/fingerprint/FingerprintFactory.java#L861-864
[2] https://github.com/apache/nifi/blob/270944ec692e12c221cdff202bdab56309dfcfd7/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/fingerprint/FingerprintFactory.java#L857

Issue Links

• links to: GitHub Pull Request #612