Tamas Palfy created NIFI-9203:
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Summary: Improve GrokReader to be able to handle complex Grok
expressions
Key: NIFI-9203
URL: https://issues.apache.org/jira/browse/NIFI-9203
Project: Apache NiFi
Issue Type: Bug
Reporter: Tamas Palfy
The current {{GrokReader}} implementation cannot handle complex expressions
like in the following scenario:
Suppose we have a custom Grok pattern file:
{code}
SYSLOGBASE_ISO8601 %{TIMESTAMP_ISO8601:timestamp} (?:%{SYSLOGFACILITY}
)?%{SYSLOGHOST:logsource} %{SYSLOGPROG}:
LINE_1 %{SYSLOGBASE}%{GREEDYDATA:message}
LINE_2 %{SYSLOGBASE_ISO8601}%{GREEDYDATA:message}
LINE (?:%{LINE_1}|%{LINE_2})
{code}
If we set the Grok expression to:
{code:}
%LINE
{code}
the service will fail for 2 reasons:
# LINE_1 and LINE_2 define the same labels. The service will try to create a
schema by adding fields for all labels encountered. This leads to duplicate
fields in the schema which is not allowed.
# When the used Grok library reads a record based on a complex expression it
returns an array as a value as the complex expression can have multiple
matches. NiFi in turn tries to handle it as a byte array.
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