osm_update.md

Update mechanism methods

This module uses external module "lfs" (package lua-filesystem in centos 7 repo).

This module uses shared dict ngx.shared.osm_last_update to cache:

• current update mechanism state: enabled or disabled
• mtime for flag file per map

You need to set in nginx configuration file:

lua_shared_dict osm_last_update 8k;

init_worker_by_lua_block {
    local lfs = require "lfs"
}

You can change default module configuration after import:

local osm_update = require 'osm_update'
osm_update.FLAGFILE = '/path/to/flag-file' -- default: '/var/lib/mod_tile/planet-import-complete
osm_update.EXPTIME = 600 -- default 3600

get_state

syntax: osm_update.get_state()

Returns current update mechanism state: true if it's enabled; false or nil if it's disabled.

enable

syntax: osm_update.enable()

Enables osm_update mechanism.

safe_enable

syntax: osm_update.safe_enable()

Enables osm_update mechanism only if current state is nil (is not set).

disable

syntax: osm_update.disable()

Disables osm_update mechanism.

get_list

syntax: osm_update.get_list()

Returns list of all cached items.

is_outdated

syntax: is_outdated = osm_update.is_outdated(metafilename, map, offset)

Checks if metatile file is outdated.

Implements mod_tile-like logic: if modification time of metatile file (metafilename) older than modification time of /var/lib/mod_tile/planet-import-complete (FLAGFILE), mark metatile file as outdated and rerender it.

Uses nginx shared dict to cache mtime of flagfilename per map name (does not need to read this file on every request).

Offset is the optional argument (int, default value is 0). This value will be subtracted from FLAGFILE modification time. Can be useful if some metatiles must be updated with some delay:

-- update metatiles for 18 zoom 30 days after new database was imported
if z == 18 then
  local is_outdated = osm_update.is_outdated('/var/lib/mod_tile/mapname/16/0/0/0/0/0.meta', 'mapname', 30 * 24 * 60 * 60)
end

get_last_update

syntax: time = osm_update.get_last_update(map)

Get last update time stored in nginx shared memory cache for given map.

get_mtime

syntax: mtime = osm_update.get_mtime(filepath)

Get modification time of file. If file does not exist, returns nil.

is_file_newer

syntax: is_newer = osm_update.is_file_newer(filepath1, filepath12)

Compare modification time of two files. Returns true if file1 newer than file2.