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https://issues.apache.org/jira/browse/NIFI-9203?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tamas Palfy updated NIFI-9203:
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Status: Patch Available (was: In Progress)
> 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
> Assignee: Tamas Palfy
> Priority: Major
> Time Spent: 10m
> Remaining Estimate: 0h
>
> 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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