[GitHub] nifi pull request #1542: NIFI-3523: Ensure that if we are unable to read Pro...

[olegz <gi...@git.apache.org>]

Github user olegz commented on a diff in the pull request:

    https://github.com/apache/nifi/pull/1542#discussion_r103749486
  
    --- Diff: nifi-nar-bundles/nifi-provenance-repository-bundle/nifi-persistent-provenance-repository/src/main/java/org/apache/nifi/provenance/serialization/CompressableRecordReader.java ---
    @@ -283,7 +283,20 @@ public StandardProvenanceEventRecord nextRecord() throws IOException {
             }
     
             if (isData()) {
    -            return nextRecord(dis, serializationVersion);
    +            while (true) {
    +                try {
    +                    return nextRecord(dis, serializationVersion);
    +                } catch (final IOException ioe) {
    +                    throw ioe;
    +                } catch (final Exception e) {
    +                    // This would only happen if a bug were to exist such that an 'invalid' event were written
    +                    // out. For example an Event that has no FlowFile UUID. While there is in fact an underlying
    +                    // cause that would need to be sorted out in this case, the Provenance Repository should be
    +                    // resilient enough to handle this. Otherwise, we end up throwing an Exception, which may
    +                    // prevent iterating over additional events in the repository.
    +                    logger.error("Failed to read Provenance Event from " + filename + "; will skip this event and continue reading subsequent events", e);
    +                }
    +            }
    --- End diff --
    
    Perhaps a style preference, but IMHO it would look better like this:
    ```
    StandardProvenanceEventRecord record = null;
     do {
            try {
                 record = nextRecord(dis, serializationVersion);
            } catch (IOException e) {
                        // . . .
            } catch (Exception e) {
                        // . . .
            }
    } while (record == null);
    return record;
    ```
    First, it avoids the ```while(true)``` which essentially relies on the hope that something in the loop will eventually break it.
    Second it follows the general pattern of reading (e.g., from InputStream) used in Reader implementations.


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