NIFI-8183 TailFile intermittently creates records with ascii NULL after rollover #4792

adenes · 2021-01-31T20:35:32Z

TailFile processor configured to an NFS mount reads unexpected NUL characters after a file had been rolled over.
Fixed by adding the NUL check to the part where the rolled over file is being read.

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tpalfy · 2021-02-01T10:32:58Z

...dle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/TailFile.java

-                    try (final InputStream fis = new FileInputStream(firstFile);
-                            final CheckedInputStream in = new CheckedInputStream(fis, new CRC32())) {
-                        StreamUtils.copy(in, new NullOutputStream(), position);
+                    try (final FileInputStream fis = new FileInputStream(firstFile)) {


I think we don't need readLines here because we already processed to content up to this point.

Thanks @tpalfy , I have updated the change according to your comment. I also extracted a couple of repeating lines from the readLines() method.

Lehel44 · 2021-02-02T10:16:21Z

...dle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/TailFile.java

@@ -1184,7 +1191,15 @@ private boolean recoverRolledFiles(final ProcessContext context, final ProcessSe
                            // This is the same file that we were reading when we shutdown. Start reading from this point on.
                            rolledOffFiles.remove(0);
                            FlowFile flowFile = session.create();
-                            flowFile = session.importFrom(in, flowFile);
+                            try {


Would you extract this nested try block to a separate method?

Thanks @Lehel44 for the suggestion.
Although I agree that the method gets more and more complicated but I tried to extract these lines to a separate method and unless I do a bigger refactor it doesn't really simplify things.
My biggest concern with it that the new method needs 5 parameters (ProcessContext context, ProcessSession session, List<File> rolledOffFiles, File file, FileInputStream fis) and there's no good way to check whether the FileInputStream belongs to the given File.

It'd be definitely worth to do a bigger refactor on this method, but I'd suggest doing it in a separate PR.

markap14 · 2021-02-03T15:07:27Z

...dle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/TailFile.java

@@ -1184,7 +1191,15 @@ private boolean recoverRolledFiles(final ProcessContext context, final ProcessSe
                            // This is the same file that we were reading when we shutdown. Start reading from this point on.
                            rolledOffFiles.remove(0);
                            FlowFile flowFile = session.create();
-                            flowFile = session.importFrom(in, flowFile);
+                            try {
+                                ByteArrayOutputStream out = new ByteArrayOutputStream();


This approach is going to buffer everything that gets read into the ByteArrayOutputStream. This could potentially be a huge amount of data. We want to be sure that we don't buffer that up. Instead, I would recommend an approach like:

try (final OutputStream out = session.write(flowFile)) { readLines(fis.getChannel(), ByteBuffer.allocate(65536), out, new CRC32(), reReadOnNul, true); }

This allows us to write directly to the content repository instead of buffering the data in a ByteArrayOutputStream.

oh, wow, I wasn't aware of this version of session.write. I was also a bit concerned about the buffering, thanks, will update the PR

Pushed a new commit: I got rid of the BAOS, but used session.write(FlowFile, OutputStreamCallback) because we need the updated FF later.

markap14

Thanks @adenes all looks good to me except for the buffering of data into ByteArrayOutputStream (commented more inline). Otherwise I'm a +1. Thanks!

…er rollover

…er rollover Remove readLines() usage when reading already processed chunk

…er rollover Remove buffering, use write(FlowFile, OutputStreamCallback) instead

markap14 · 2021-02-03T18:08:08Z

Thanks for the update @adenes LGTM +1 will merge to main.

…er rollover This closes apache#4792. Signed-off-by: Mark Payne <markap14@hotmail.com>

adenes force-pushed the nfs_tailfile_rollover_nul_2 branch from a8ec6c4 to 643eb6d Compare January 31, 2021 20:44

tpalfy requested changes Feb 1, 2021

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Lehel44 reviewed Feb 2, 2021

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markap14 reviewed Feb 3, 2021

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markap14 requested changes Feb 3, 2021

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adenes added 2 commits February 3, 2021 16:38

NIFI-8183 TailFile intermittently creates records with ascii NULL aft…

a0fd9b6

…er rollover

NIFI-8183 TailFile intermittently creates records with ascii NULL aft…

08330c2

…er rollover Remove readLines() usage when reading already processed chunk

adenes force-pushed the nfs_tailfile_rollover_nul_2 branch from a18a272 to 4a9bc9a Compare February 3, 2021 15:45

NIFI-8183 TailFile intermittently creates records with ascii NULL aft…

2bbbd4b

…er rollover Remove buffering, use write(FlowFile, OutputStreamCallback) instead

adenes force-pushed the nfs_tailfile_rollover_nul_2 branch from 4a9bc9a to 2bbbd4b Compare February 3, 2021 17:05

markap14 closed this in c1f88ec Feb 3, 2021

driesva pushed a commit to driesva/nifi that referenced this pull request Mar 19, 2021

NIFI-8183 TailFile intermittently creates records with ascii NULL aft…

dc02d63

…er rollover This closes apache#4792. Signed-off-by: Mark Payne <markap14@hotmail.com>

krisztina-zsihovszki pushed a commit to krisztina-zsihovszki/nifi that referenced this pull request Jun 28, 2022

NIFI-8183 TailFile intermittently creates records with ascii NULL aft…

054ce5d

…er rollover This closes apache#4792. Signed-off-by: Mark Payne <markap14@hotmail.com>

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NIFI-8183 TailFile intermittently creates records with ascii NULL after rollover #4792

NIFI-8183 TailFile intermittently creates records with ascii NULL after rollover #4792

adenes commented Jan 31, 2021

tpalfy Feb 1, 2021

adenes Feb 1, 2021

Lehel44 Feb 2, 2021

adenes Feb 3, 2021

markap14 Feb 3, 2021

adenes Feb 3, 2021

adenes Feb 3, 2021

markap14 left a comment

markap14 commented Feb 3, 2021

NIFI-8183 TailFile intermittently creates records with ascii NULL after rollover #4792

NIFI-8183 TailFile intermittently creates records with ascii NULL after rollover #4792

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adenes commented Jan 31, 2021

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