.. _converter_validation:

Parsing and Validation
----------------------

GeoMesa provides options for dealing with bad input records which can be configured on your converter. For example,
you may want to skip over bad records for some input sources or fail entire files in other cases. The Converter
framework provides a few options that can help control how errors in input data are handled.

Validators
~~~~~~~~~~

At their core, converters transform input streams into SimpleFeatures. Validators provide hooks to validate properties
of those SimpleFeatures before they are written to GeoMesa. For example, you may want to validate that there is a
geometry field and that the geometry is valid.

There are currently three validators available for use with GeoMesa converters:

* ``has-geo`` - Ensure that the SimpleFeature has a geometry and it is non-null
* ``has-dtg`` - Ensure that the SimpleFeature has a date and it is non-null
* ``z-index`` - Ensure the Geometry and Date are within the space/time bounds of GeoMesa Z-Index implementations
  (i.e. Z2, Z3, XZ2, XZ3)

By default the ``has-geo`` and ``has-dtg`` validators are enabled. To enable other validators add this to the options
block of your typesafe converter config:

::

    geomesa.converters.myconverter {
      options {
        validators = ["has-dtg", "has-geo", "z-index"]
      }
    }

Validation can be disabled by setting it to an empty array.

Error Mode
~~~~~~~~~~

There are two types of modes for handling errors:

* ``skip-bad-records``
* ``raise-errors``

``raise-errors`` mode will throw an IOException if bad data is detected based on parsing or validation. This can
be especially useful when first developing and testing a converter definition. ``skip-bad-records`` mode will
still provide debug level logging but will not throw an exception. To configure the
error mode add the following option to your converter's typesafe config:

::

    geomesa.converters.myconverter {
      options {
        error-mode = "raise-errors"
      }
    }


Parse Mode
~~~~~~~~~~

The parse mode option allows you to control whether a file is parsed incrementally or fully before being converted. This
is important when it comes to validation. There are two modes available:

* ``incremental``
* ``batch``

Since converters provide iterators of SimpleFeatures, the default parse mode is ``incremental`` which provides better
performance and less memory overhead. Using ``incremental`` parse mode means that data may be partially ingested into
GeoMesa before an error is raised. In most cases this is appropriate and can be handled by the client code.

Using ``batch`` mode will buffer an entire input stream or file in memory to validate the data which is less performant
and requires more memory. ``batch`` mode does, however, prevent partially ingested data streams. It is unlikely that
you need to use ``batch`` mode in environments where data is properly sanitized.

To configure the parse mode use add an option to your converter's typesafe config:

::

    geomesa.converters.myconverter {
      options {
        parse-mode = "incremental"
      }
    }

Logging
~~~~~~~

To view validation logs you can enable debug level logging on the package ``org.locationtech.geomesa.convert``.

By default, logging will just show the field that failed. To show the entire record, along with the stack trace,
you can set ``options.verbose = true``.

Transactional Considerations
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Most of the datastores that GeoMesa works with (Accumulo, HBase, etc) do not provide transactions. Therefore, streaming
data in and out of a converter and into an ingest pipeline is not transactional. To mimic transactions you can use
a batch parse mode with ``raise-errors`` error mode and likely with the ``z-index`` validator. Note that this may
increase your memory requirements and hurt performance:

::

    geomesa.converters.myconverter {
      options {
        validators = [ "z-index" ]
        parse-mode = "batch"
        error-mode = "raise-errors"
      }
    }

If you need notification of bad input data you may consider using an error mode of ``raise-errors`` with an
incremental parse mode:

::

    geomesa.converters.myconverter {
      options {
        validators = [ "z-index" ]
        parse-mode = "incremental"
        error-mode = "raise-errors"
      }
    }

If you are using a framework such as the GeoMesa Nifi processor, then the file will still be routed to an error
relationship but you may experience partially ingested data. See :doc:`/user/nifi` for more info.