Serhii Nesterov created NIFI-11971:
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Summary: FlowFile content is corrupted across the whole NiFi
instance throughout ProcessSession::write with omitting writing any byte to
OutputStream
Key: NIFI-11971
URL: https://issues.apache.org/jira/browse/NIFI-11971
Project: Apache NiFi
Issue Type: Bug
Affects Versions: 1.23.1, 1.23.0
Reporter: Serhii Nesterov
One of the scenarios for ProcessSession::write was broken after recent code
refactoring within the following pull request:
[https://github.com/apache/nifi/pull/7363/files]
The issue is located in StandardContentClaimWriteCache.java in the write(final
ContentClaim claim) method that returns an OutputStream used in the
OutputStreamCallback interface to let NiFi processors write flowfile content
through the ProcessSession::write method.
If a processor calls session.write but does not write any data to the output
stream, then none of the write methods in the OutputStream is invoked, hence
the length of the content claim is not recomputed which means the length will
have the default value that is equal to -1. Because of the latest refactoring
changes that are based on creating a new content claim on each
ProcessSession::write invocation the following formula gives the wrong result:
previous offset + previous length = new offset.
For example, if the previous offset was 1000 and nothing was written to the
stream (length is -1), then 1000 + (-1) will give us 999 which means that the
offset is shifted back by one, hence the next content will have an extra
character from the previous content at the beginning and will lose the last
character at the end, and all other FlowFiles anywhere in NiFi will be
corrupted by this defect until the NiFi instance is restarted.
The following steps can be taken to reproduce the issue (critical in our
commercial project):
* Create an empty text file (“a.txt”);
* Create a text file with any text (“b.txt”);
* Package these files into a .zip archive;
* Put it into a file system on Azure Cloud (we use ADLS Gen2);
* Read the zip file and unpack it content on the NiFi Canvas using
FetchAzureDataLakeStorage and UnpackContent processors;
* Start a flow with the GenerateFlowFile processor. See the results. The empty
file must be extracted before the non-empty file, otherwise the issue won’t
reproduce. You’ll see that the second FlowFile content will be corrupted – the
first character is an unreadable character from the zip archive (last character
of the content with zip) fetched with FetchAzureDataLakeStorage and the last
character will be lost. Starting from this point, NiFi cannot be used at all
because any other processors will lead to FlowFile content corruption across
the entire NiFi instance due to the shifted offset.
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