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mod_wmts_wrapper

This module is designed as a wrapper around Apache modules like mod_redirect that only serve tiles via REST requests.

Right now it only works with mod_reproject.

What it does

mod_wmts_wrapper does a few things:

  • Converts KvP WMTS requests into REST, returning errors if necessary.
  • Returns WMTS errors for problems with REST WMTS requests (i.e., non-existent layer)
  • Integrates with mod_reproject so that it can handle layers that have a TIME parameter.
  • Adds additional error handling to mod_reproject (i.e., tile out of bounds)

Build/Install

Dependencies

For the Apache modules, edit the Makefile.lcl file in the src directory and run make install

Jansson can be installed in CentOS 7 with yum install jansson-devel

Time/Date Handling

mod_wmts_wrapper can rewrite mod_reproject and mod_mrf configrations on the fly so that mod_reproject uses the correct URL for a requested date.

In order to use this, you need to modify the string used in the reproject configuration file specified by the Reproject_ConfigurationFiles, IndexFile, DataFile, and Redirect directives.

mod_reproject

You will have a line like this in your Apache config:

Reproject_ConfigurationFiles source.config reproj.config

in the reproj.config file you'll need to have a line like this:

SourcePath /endpoint/layer/style/${date}/tilematrixset/

mod_wmts_wrapper will then use the date from the current request to fill in the ${date} field in the source URL that mod_reproject uses.

mod_mrf

You will have a line like this in your Apache config:

MRF_ConfigurationFile mrf.config

in the mrf.config file you'll need a line like this:

IndexFile /endpoint/layer/style/tilematrixset/${filename}.idx

and either this:

DataFile /endpoint/layer/style/tilematrixset/${filename}.pjg

or this:

Redirect /outside/${filename}.pjg

Configuration

mod_reproject_wrapper has four directives, each to be placed in a <Directory> block in your Apache config.

WMTSWrapperRole String

This indicates what "role" a particular directory plays in your WMTS REST request. Roles are:

  • root
  • layer
  • style
  • tilematrixset

This configuration allows the module to correctly handle errors.

WMTSWrapperEnableTime (On|Off)

Indicates whether or not mod_wmts_wrapper should handled TIME REST and KvP requests. Should be placed in the same <Directory> block as WMTSWrapperRole layer.

WMTSWrapperMimeType String

Set the MIME type for the tiles to be served by this endpoint.

WMTSWrapperTimeLookupUri String

Set the URI of the time lookup service mod_wmts_wrapper should use for layers that involve a TIME dimension (see time_service).

WMTSWrapperEnableYearDir (On|Off)

If turned on, the wrapper module will look for a year substitution string in the path to the IDX file. Use ${YYYY} where the year should be inserted into the IDX path.

Example: IndexFile /var/www/html/mrf_endpoint/date_test_year_dir/default/tms/${YYYY}/${filename}.idx

WMTSWrapperDateServiceKeys (String, can be multiple)

The OnEarth date service can accept additional keys (can be used to separate layers by projection or endpoint).

Keys listed here will be appended to the date service request in order.

So, if configured like this:

WMTSWrapperDateServiceKeys geographic best

The date service query will add the following parameters to the date service request for each tile request:

/date-service?layer=layer&key1=geographic&key2=best

Note that this configuration option works per layer.

Example config (starred entries are mod_reproject configuration directives):

<Directory /usr/share/onearth/demo/wmts-webmerc/>
        WMTSWrapperRole root
</Directory>

<Directory /usr/share/onearth/demo/wmts-webmerc/blue_marble>
        WMTSWrapperRole layer
        WMTSWrapperEnableTime on
</Directory>

<Directory /usr/share/onearth/demo/wmts-webmerc/blue_marble/default>
        WMTSWrapperRole style
</Directory>

<Directory /usr/share/onearth/demo/wmts-webmerc/blue_marble/default/GoogleMapsCompatible_Level7>
        WMTSWrapperRole tilematrixset
        WMTSWrapperMimeType "image/png"
        WMTSWrapperTimeLookupUri "/time_lookup"
        Reproject_RegExp GoogleMapsCompatible_Level7/\d{1,2}/\d{1,3}/\d{1,3}.(png|jpeg|jpg)
        Reproject_ConfigurationFiles /usr/share/onearth/demo/wmts-webmerc/blue_marble/default/GoogleMapsCompatible_Level7/blue_marble_source.config /usr/share/onearth/demo/wmts-webmerc/blue_marble/default/GoogleMapsCompatible_Level7/blue_marble_reproject.config
        WMTSWrapperDateServiceKeys geographic best
</Directory>