NIFI-8437 RecordReader 'Infer Schema' for large records may throw BufferedInputStream error

[adenes]

• increased the mark readLimit in InferSchemaAccessStrategy.getSchema() to Integer.MAX_VALUE
• removed the unnecessary BufferedInputStream wrapping in JsonPathReader.createRecordReader()
• added a new test case to test with 50MB record

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[adenes]

@markap14, indeed, the removal of the BufferedInputStream wrapping in JsonPathReader.createRecordReader() solves the issue (as you suggested on the Jira) because the ContentClaimInputStream doesn't use the readLimit in the mark call. Regardless of this I think it might be worth to increase the readLimit as there's no guarantee that the provided InputStream implementation doesn't takes it into account.
What do you think?

[markap14]

I think we want to keep this at a smaller value. The general contract of InputStream says that when mark is called, the stream must remember at least that many bytes but is free to remember more. As the comment above explains, the general expectation is that the stream will be of type ContentClaimInputStream. In that case, the value passed to mark is ignored because it can always roll back to the beginning of the stream (by re-reading the file under the hood).

But keeping the 10 MB limit (or even a 1 MB limit would probably be okay) means that if the caller does wrap the InputStream in a BufferedInputStream, then we have the chance remember this amount of data. If it's changed to Integer.MAX_VALUE, that bound is basically removed, which can lead to OutOfMemoryError very easily, and that should be avoided at almost any cost as the entire JVM can become defunct.

[adenes]

I see your point and share your concern.
Then I'll revert this change and also remove the newly added test case and keep only the BufferedInputStream wrapping removal.
I also checked all the other references to org.apache.nifi.serialization.SchemaRegistryService#getSchema() and no other BufferedInputStream wrapping occurs, at least not directly before the getSchema() call.

[markap14]

Thanks @adenes! I think the changes look good, except that I'm concerned about changing the argument passed to InputStream.mark. That value is there as a safe-guard, specifically for this situation where an InputStream was wrapped in a BufferedInputStream. We do not want to buffer an unbounded (or bound at Integer.MAX_VALUE) amount of data in BufferedInputStream. We'd rather throw an Exception.

[markap14]

Thanks @adenes all looks good to me. +1 merged to main