Brandon DeVries created NIFI-2159:
-------------------------------------

             Summary: Fingerprint not detecting flow.xml differences
                 Key: NIFI-2159
                 URL: https://issues.apache.org/jira/browse/NIFI-2159
             Project: Apache NiFi
          Issue Type: Bug
    Affects Versions: 0.6.1
            Reporter: Brandon DeVries
            Priority: Critical
             Fix For: 0.7.0


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\[1\]:

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

To:

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

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

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

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 \[2\]:

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


\[1\] 
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



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