SparseCache is identical to TileStache's Disk cache except that it returns 404s for "empty" tiles (with a file size matching the empty_size kwarg).

This may improve performance under some circumstances, as it eliminates the need to transfer additional, duplicate empty files (although it doesn't eliminate the requests for them, nor does it prevent them from being saved to the cache).

• empty_size - size of an empty file (in bytes). 334 bytes (the default value) is the size of an empty, transparent, 24-bit PNG (the default output).

{
  "cache":
  {
    "class": "SparseCache",
    "kwargs": {
      "path": "/tmp/stache",
      "umask": "0000",
      "empty_size": 334
    }
  },
}

LanternCache exposes an additional X-Land-Or-Sea header corresponding to the content of a given tile (determined by its md5sum).

The value will be 1 if by land, 2 if by sea, 0 if by both or indeterminate (i.e. the second tile is not yet present in the cache).

This can be used to conditionally load related tiles (tiles at the next zoom or additional data tiles), reducing the number of requests a client needs to make to display a consistent view.

• land - md5sum of a tile that is entirely "land".
• sea - md5sum of a tile that is entirely "sea".
• second - Name of an alternate layer that should be used to compare md5sums with the primary layer. Its cache configuration should roughly match the LanternCached layer.

{
  "cache":
  {
    "class": "LanternCache",
    "kwargs": {
      "path": "/tmp/stache",
      "umask": "0000",
      "land": "cd37744a985b79ed29bb6269e45da27f",
      "sea": "35f515ac80cd2fb679de95699044ee7b",
      "second": "layer2"
    }
  },
}

Released under the BSD license.