Advanced Cache Settings

This section describes Mappin’s advanced caching settings that have not been discussed in previous sections.

If you encounter problems with cache settings, the CREATE DEFAULT CONFIG button can be used to re-create a default cache configuration which can solve most issues. Be aware that this will result in losing some overridden settings so you should always go through your configuration afterwards and ensure it is set as desired.

Global Settings

The Global settings section (General tab) looks like this and contains the following settings:

../_images/cache_global_settings.png

Name (read-only)

An internal name used by Mappin.

Meta Buffer Size

The default Meta Buffer Size setting for new layer cache entries.

Warning

a known issue at the time of writing means that specifying a default Meta Buffer Size of 0 may cause Mappin’s admin interface to stop working. See Default Meta Buffer Size of 0 Causes Admin Interface to Stop Working for more information.

Meta Tile Size

The default Meta Tile Size setting for new layer cache entries.

Services

The Services section (General tab) looks like this and contains the following settings:

../_images/cache_services_settings.png

Name (read-only)

The name of each service. At present, only wms is supported.

Supported Projections

This setting lists the projections that Mappin will support when a WMS client requests map tiles. By default it will list the projection configured in the Map module. If you wish other WMS clients (e.g. QGIS) to be served WMS images in other projections from Mappin, list those projections here.

Supported BBox Projections

Similar to Supported Projections - the projections which are advertised in Mappin’s GetCapabilities response.

Caches

Each cached layer will have an entry in the Caches section. Each cache will have settings like these:

../_images/cache_cache_settings.png

Name (read-only)

The name of the cache.

Grids

The grids associated with this cache. This defaults to primary_grid and should not be modified.

Sources

The source for this cache. This defaults to primary_wms:LAYER_NAME and should not be modified.

Meta Buffer Size

The cache’s Meta Buffer Size setting, described fully in the Meta Cache Settings section.

Meta Tile Size

The cache’s Meta Tile Size setting, described fully in the Meta Cache Settings section.

Disable Storage

When checked, means Mappin will use a layer’s associated cache settings to draw and serve it, but will not store the result. This setting is useful for trialling various caching options without needing to clear the layer’s cache each time something is changed.

Grids

Grids defines how Mappin serves maps as tiles. At present only one grid is supported and it’s generated automatically by Mappin based on the settings of the Map module. It has settings like these:

../_images/cache_grid_settings.png

Name (read-only)

The name of the grid. This is always set to primary_grid.

Tile Size

The size in pixels of grid tiles. This setting is taken automatically from the Map module settings and should not be changed here.

Resolutions

The resolutions supported by the grid. This setting is taken automatically from the Map module settings and should not be changed here.

Base

When using British National Grid in the Map module settings, this setting will be BNG_grid, else it will be blank. This setting should not be changed.

Sources

Sources define where Mappin’s cache should fetch map images. These settings have a few user-configurable settings. Each source (usually one) will have settings like these:

../_images/cache_source_settings.png

Name (read-only)

Name of the source. This is always set to primary_wms.

WMS Server URL

This is the URL used by Mappin to access its associated WMS server. If using Mappin as a subscription-based service, this will usually point to a non-internet accessible address such as the one shown below:

http://mapproxy-0.headless:8080/?MAP=%2Fprojects%2Faddresses%2Fcontainer.qgs&DPI=84

If you are using QGIS Server as your WMS server (subscription-based customers will be by default) then you may adjust the DPI parameter passed to QGIS server. This value affects the size of map elements with styles defined in points or mm (not pixels) and defaults to 84 which has been found to result in images looking almost identical to those seen in QGIS desktop GIS.

Aside from the DPI setting, the rest of the WMS Server URL should not be modified.

WMS Response Delay (s)

The number of seconds Mappin’s cache will wait for the WMS server to render a tile. Increasing this value can help if you are seeing errors in map tiles where the WMS server is not rendering tiles fast enough. In these cases you may also want to check out the Performance Tips section which describes how to optimise WMS server performance.

Transparent Image

Whether to support transparent images. Unchecking this option may result in transparency not working as expected and white artefacts appearing in maps.

Supported Projections

The projections supported by the WMS server. This setting is populated automatically and should not be changed here.