pmtiles

go-whosonfirst-spatial-pmtiles

Go package to implement the whosonfirst/go-whosonfirst-spatial interfaces using a Protomaps .pmtiles database.

Background

A global point-in-polygon service using a static 8GB data file

Documentation

Documentation is incomplete at this time.

This is work in progress

There may be bugs. Notably, as written:

• The underlying spatial queries performed on features derived from PMTiles data are done using in-memory whosonfirst/go-whosonfirst-spatial-sqlite instances.
• The go-whosonfirst-spatial-pmtiles package implements both the whosonfirst/go-whosonfirst-spatial and whosonfirst/go-reader interfaces however in order to support the latter caching must be enabled in the spatial database URI constructor (see below). Caching is necessary to maintain a local cache of features mapped to any given Who's On First ID. This is really only important if you need to to return GeoJSON responses (rather than the default Standard Place Response) or you are using an application derived from go-whosonfirst-spatial-www which tries to load GeoJSON features from itself.
• GeoJSON features for large, administrative areas (states, countries, etc.) are likely to be clipped to the tile boundary that contains them. Likewise because features are cached so a read request for a place with a large surface area (say the United States) will return the geometry for the first tile that contains it. This can lead to bizarre results or potential information leakage or both.
• As is often the case with any kind of caching there are probably still "edge cases" to account for and improvements to implement.
• The following WOF properties are decoded from their MVT encoding: wof:belongsto, wof:supersedes, wof:superseded_by and wof:hierarchy. The first three are core properties in the standard place response definition; the third is an optional property that can be included in a PMTiles database using the -append-spr-property flag in the features tool discussed below. Support for custom decoders are not available yet.
• Alternate geometry files are not supported yet.

Producing a Who's On First -enabled Protomaps tile database

As of this writing producing a Who's On First -enabled Protomaps tile database is a manual two-step process.

Tippecanoe

The first step is to produce a MBTiles database derived from Who's On First data. There are a variety of ways you might accomplish this but as a convenience you can use the features tool which is part of the whosonfirst/go-whosonfirst-tippecanoe package. For example:

$> bin/features \
	-writer-uri 'constant://?val=jsonl://?writer=stdout://' \
	/usr/local/data/sfomuseum-data-whosonfirst/ \
	
	| tippecanoe -P -z 12 -pf -pk -o /usr/local/data/wof.mbtiles

Things to note: The -pf and -pk flags to ensure that no features are dropped and the -z 12 flag to store everything at zoom 12 which is a good trade-off to minimize the number of places to query (ray cast) in any given tile and the total number of tiles to produce and store.

PMTiles

Next, use the pmtiles tool which is part of the protomaps/go-pmtiles package to convert the MBTiles database to a Protomaps PMTiles database:

$> pmtiles /usr/local/data/wof.mbtiles /usr/local/data/wof.pmtiles

Spatial Database URIs

Spatial database URIs for Protomaps PMTiles databases take the form of:

pmtiles://?{QUERY_PARAMETERS}

Query parameters

For example:

pmtiles://?tiles=file:///usr/local/data&database=wof

Example

import (
       _ "github.com/whosonfirst/go-whosonfirst-spatial-pmtiles"
)

import (
       "context"
       "fmt"
       "github.com/paulmach/orb"       
       "github.com/whosonfirst/go-whosonfirst-spatial/database"
)

func main(){

     ctx := context.Background()

     db, _ := database.NewSpatialDatabase(ctx, "pmtiles://?tiles=file:///usr/local/data&database=wof&enable_cache=true")

     lat := 37.621131
     lon := -122.384292
     
     pt := orb.Point{ lon, lat }
     
     spr, _ := db.PointInPolygon(ctx, pt)

     for _, r := range spr.Results(){
     	fmt.Printf("%s %s\n", r.Id(), r.Name())
     }
}

Error handling omitted for the sake of brevity.

Tools

query

$> ./bin/query -h
  -alternate-geometry value
    	One or more alternate geometry labels (wof:alt_label) values to filter results by.
  -cessation-date string
    	A valid EDTF date string.
  -custom-placetypes string
    	A JSON-encoded string containing custom placetypes defined using the syntax described in the whosonfirst/go-whosonfirst-placetypes repository.
  -enable-custom-placetypes
    	Enable wof:placetype values that are not explicitly defined in the whosonfirst/go-whosonfirst-placetypes repository.
  -enable-geojson
    	...
  -geometries string
    	Valid options are: all, alt, default. (default "all")
  -inception-date string
    	A valid EDTF date string.
  -is-ceased value
    	One or more existential flags (-1, 0, 1) to filter results by.
  -is-current value
    	One or more existential flags (-1, 0, 1) to filter results by.
  -is-deprecated value
    	One or more existential flags (-1, 0, 1) to filter results by.
  -is-superseded value
    	One or more existential flags (-1, 0, 1) to filter results by.
  -is-superseding value
    	One or more existential flags (-1, 0, 1) to filter results by.
  -is-wof
    	Input data is WOF-flavoured GeoJSON. (Pass a value of '0' or 'false' if you need to index non-WOF documents. (default true)
  -iterator-uri string
    	A valid whosonfirst/go-whosonfirst-iterate/v2 URI. Supported schemes are: directory://, featurecollection://, file://, filelist://, geojsonl://, null://, repo://. (default "repo://")
  -latitude float
    	A valid latitude.
  -longitude float
    	A valid longitude.
  -mode string
    	... (default "cli")
  -placetype value
    	One or more place types to filter results by.
  -properties-reader-uri string
    	A valid whosonfirst/go-reader.Reader URI. Available options are: [fs:// null:// repo:// sqlite:// stdin://]
  -property value
    	One or more Who's On First properties to append to each result.
  -server-uri string
    	... (default "http://localhost:8080")
  -sort-uri value
    	Zero or more whosonfirst/go-whosonfirst-spr/v2/sort URIs.
  -spatial-database-uri string
    	A valid whosonfirst/go-whosonfirst-spatial/data.SpatialDatabase URI. options are: [pmtiles:// sqlite://]
  -verbose
    	Be chatty.

Example

$> ./bin/query \
	-spatial-database-uri 'pmtiles://?tiles=file:///usr/local/data&database=wof' \
	-latitude 37.621131 \
	-longitude -122.384292 \
	-sort-uri name:// \

| jq '.places[]["wof:name"]'

"94128"
"California"
"Earth"
"North America"
"San Francisco International Airport"
"San Mateo"
"United States"

Support for gocloud.dev blob and docstore interfaces

By default this package enables support the gocloud.dev/blob/fileblob and gocloud.dev/docstore/memdocstore packages for reading files from the local filesystem and caching data in memory respectively.

In order to add support for additional implementations you will need to clone the relevant code and add any required import declarations. For example this is how you would support for reading data from an S3 bucket to the query tool using the s3blob package:

package main

import (
       _ "gocloud.dev/blob/s3blob"
)

import (
	_ "github.com/whosonfirst/go-whosonfirst-spatial-pmtiles"
)

import (
	"context"
	"log"

	"github.com/whosonfirst/go-whosonfirst-spatial-pip/app/query"
)

func main() {

	ctx := context.Background()

	logger := log.Default()

	err := query.Run(ctx, logger)

	if err != nil {
		logger.Fatalf("Failed to run PIP application, %v", err)
	}

}

Web interface(s)

server

$> > ./bin/server -h
  -authenticator-uri string
    	A valid sfomuseum/go-http-auth URI. (default "null://")
  -cors-allow-credentials
    	Allow HTTP credentials to be included in CORS requests.
  -cors-origin value
    	One or more hosts to allow CORS requests from; may be a comma-separated list.
  -custom-placetypes string
    	A JSON-encoded string containing custom placetypes defined using the syntax described in the whosonfirst/go-whosonfirst-placetypes repository.
  -enable-cors
    	Enable CORS headers for data-related and API handlers.
  -enable-custom-placetypes
    	Enable wof:placetype values that are not explicitly defined in the whosonfirst/go-whosonfirst-placetypes repository.
  -enable-geojson
    	Enable GeoJSON output for point-in-polygon API calls.
  -enable-gzip
    	Enable gzip-encoding for data-related and API handlers.
  -enable-www
    	Enable the interactive /debug endpoint to query points and display results.
  -is-wof
    	Input data is WOF-flavoured GeoJSON. (Pass a value of '0' or 'false' if you need to index non-WOF documents. (default true)
  -iterator-uri string
    	A valid whosonfirst/go-whosonfirst-iterate/v2 URI. Supported schemes are: directory://, featurecollection://, file://, filelist://, geojsonl://, null://, repo://. (default "repo://")
  -leaflet-enable-draw
    	Enable the Leaflet.Draw plugin.
  -leaflet-enable-fullscreen
    	Enable the Leaflet.Fullscreen plugin.
  -leaflet-enable-hash
    	Enable the Leaflet.Hash plugin. (default true)
  -leaflet-initial-latitude float
    	The initial latitude for map views to use. (default 37.616906)
  -leaflet-initial-longitude float
    	The initial longitude for map views to use. (default -122.386665)
  -leaflet-initial-zoom int
    	The initial zoom level for map views to use. (default 14)
  -leaflet-max-bounds string
    	An optional comma-separated bounding box ({MINX},{MINY},{MAXX},{MAXY}) to set the boundary for map views.
  -leaflet-tile-url string
    	A valid Leaflet 'tileLayer' layer URL. Only necessary if -map-provider is "leaflet".
  -log-timings
    	Emit timing metrics to the application's logger
  -map-provider string
    	The name of the map provider to use. Valid options are: leaflet, protomaps, tangram
  -nextzen-apikey string
    	A valid Nextzen API key. Only necessary if -map-provider is "tangram".
  -nextzen-style-url string
    	A valid URL for loading a Tangram.js style bundle. Only necessary if -map-provider is "tangram". (default "/tangram/refill-style.zip")
  -nextzen-tile-url string
    	A valid Nextzen tile URL template for loading map tiles. Only necessary if -map-provider is "tangram". (default "https://tile.nextzen.org/tilezen/vector/v1/512/all/{z}/{x}/{y}.mvt")
  -path-api string
    	The root URL for all API handlers (default "/api")
  -path-data string
    	The URL for data (GeoJSON) handler (default "/data")
  -path-ping string
    	The URL for the ping (health check) handler (default "/health/ping")
  -path-pip string
    	The URL for the point in polygon web handler (default "/point-in-polygon")
  -path-prefix string
    	Prepend this prefix to all assets (but not HTTP handlers). This is mostly for API Gateway integrations.
  -properties-reader-uri string
    	A valid whosonfirst/go-reader.Reader URI. Available options are: [fs:// null:// pmtiles:// repo:// sqlite:// stdin://]. If the value is {spatial-database-uri} then the value of the '-spatial-database-uri' implements the reader.Reader interface and will be used.
  -protomaps-bucket-uri string
    	The gocloud.dev/blob.Bucket URI where Protomaps tiles are stored. Only necessary if -map-provider is "protomaps" and -protomaps-serve-tiles is true.
  -protomaps-caches-size int
    	The size of the internal Protomaps cache if serving tiles locally. Only necessary if -map-provider is "protomaps" and -protomaps-serve-tiles is true. (default 64)
  -protomaps-database string
    	The name of the Protomaps database to serve tiles from. Only necessary if -map-provider is "protomaps" and -protomaps-serve-tiles is true.
  -protomaps-serve-tiles
    	A boolean flag signaling whether to serve Protomaps tiles locally. Only necessary if -map-provider is "protomaps".
  -protomaps-tile-url string
    	A valid Protomaps .pmtiles URL for loading map tiles. Only necessary if -map-provider is "protomaps". (default "/tiles/")
  -server-uri string
    	A valid aaronland/go-http-server URI. (default "http://localhost:8080")
  -spatial-database-uri string
    	A valid whosonfirst/go-whosonfirst-spatial/data.SpatialDatabase URI. options are: [pmtiles:// sqlite://]
  -tilezen-enable-tilepack
    	Enable to use of Tilezen MBTiles tilepack for tile-serving. Only necessary if -map-provider is "tangram".
  -tilezen-tilepack-path string
    	The path to the Tilezen MBTiles tilepack to use for serving tiles. Only necessary if -map-provider is "tangram" and -tilezen-enable-tilezen is true.
  -verbose
    	Be chatty.

Example

$> bin/server \
	-spatial-database-uri 'pmtiles://?tiles=file:///usr/local/data&database=wof' \
	-enable-www \
	-map-provider tangram \
	-nextzen-apikey {NEXTZEN_APIKEY}

2022/12/16 14:19:51 Register /data/ handler
2022/12/16 14:19:51 Register /api/point-in-polygon handler
2022/12/16 14:19:51 time to index paths (0) 3.471µs
2022/12/16 14:19:51 finished indexing in 231µs
2022/12/16 14:19:51 Prune tile cache older that 2022-12-16 14:14:51.570246 -0800 PST m=-299.955191662
2022/12/16 14:19:51 Register /point-in-polygon handler
2022/12/16 14:19:51 Register / handler
2022/12/16 14:19:51 Listening on http://localhost:8080

When you visit http://localhost:8080 in your web browser you should see something like this:

If you don't need, or want, to expose a user-facing interface simply remove the -enable-www, -map-provider and -nextzen-apikey flags. For example:

$> ./bin/server \
	-spatial-database-uri 'pmtiles://?tiles=file:///usr/local/data&database=wof'

2022/11/26 09:57:03 Register /data/ handler
2022/11/26 09:57:03 Register /api/point-in-polygon handler
2022/11/26 09:57:03 Listening on http://localhost:8080
2022/11/26 09:57:03 time to index paths (0) 83.545µs
2022/11/26 09:57:03 finished indexing in 618.003µs

And then:

$> curl -s http://localhost:8080/api/point-in-polygon \
	-d '{"latitude": 37.621131, "longitude": -122.384292}' \

| jq '.places[]["wof:name"]'

"Earth"
"United States"
"San Francisco International Airport"
"California"
"North America"
"San Mateo"
"94128"

If you have created your Protomaps database with custom properties and want to be able to access them via the API you will need to ensure that your spatial-database-uri flag has a "enable-cache=true" query parameter and that you assign the value of "{spatial-database-uri}" to the properties-reader-uri flag. For example:

$> ./bin/server \
	-spatial-database-uri 'pmtiles://?tiles=file:///usr/local/data&database=wof&enable-cache=true' \
	-properties-reader-uri '{spatial-database-uri}'

By default, results are returned as a list of "standard places response" (SPR) elements. You can also return results as a GeoJSON FeatureCollection by passing the -enable-geojson flag to the server and including a format=geojson query parameter with requests. For example:

$> bin/server \
	-spatial-database-uri 'pmtiles://?tiles=file:///usr/local/data&database=wof'
	-enable-geojson

However, and this important to note: Geometries are cropped to the boundaries of the first tile that the feature they are associated with. That is to say not only are geometries cropped to the boundaries of a tile but they are cached locally so, for example, the "geometry" for the United States would be the first tile that contained it untile the local cache expires. For example:

If you really need to geometry for a given feature you should fetch it directly from https://data.whosonfirst.org/geojson/{ID} or some other equivalent data source.

AWS

Lambda

It is possible to deploy the server tool as a Lambda function, reading from a Protomaps database hosted in an S3 bucket. The Lambda function does not need any special permissions beyond the ability to read files in the S3 bucket you've chosen.

In the "configuration" section you'll need to assign the following variables in the "Environment variables" sub-menu:

Under the hood the value of the ?tiles= query parameter in the -spatial-database-uri (or WHOSONFIRST_SPATIAL_DATABASE_URI) flag is just a gocloud.dev/blob URI so data can be read from any source that implements that package's Blob interfaces. The default supported URIs are file:// for reading data from the local filesystem and s3:// and s3blob:// for reading data from an S3 bucket. The difference between s3:// and s3blob:// is that the latter allows AWS credentials to be defined as a query parameter. For example:

s3blob://{S3_BUCKET}?region={AWS_REGION}&prefix={PREFIX}&credentials={CREDENTIALS}

A concrete example, reading data from an S3 bucket called example in a folder called tiles/ in the AWS us-east-1 region, specifying an AWS credentials profile called example would be:

s3blob://example?region=us-east-1&prefix=tiles/&credentials=example

Unfortunately, because the URI contains its own query parameters, it needs to be URL-encoded before it is included in the final -spatial-database-uri URI. Putting it altogether we end up with this:

pmtiles://?tiles=s3blob%3A%2F%2Fexample%3Fregion%3Dus-east-1%26prefix%3Dtiles%2F%26credentials%3Dexample&database=example

You can also specify any of the other flags that the server tool accepts. The rules for assigning a command line flag as a environment variable are:

• Replace all - characters with _ characters.
• Prepend the string whosonfirst_ to the variable name.
• Upper-case the new string. For example the -leaflet-initial-zoom becomes WHOSONFIRST_LEAFLET_INITIAL_ZOOM.

In the "Generation configuration" sub-menu change the default timeout to something between 10-30 seconds (or more) depending on your specific use case.

That should be all you need to do. You can test the set up by running the function and passing an empty message ({}). Nothing will happen but the function will exit without any errors.

API Gateway

The use of API Gateway works but it's honestly easier to use a Lambda Function URL in conjunction with the awslabs/aws-lambda-web-adapter.

Create a new "REST" API. For the sake of this example we'll call it Architecture (to match the container and Lambda function described above).

• Create a new "Resource" and configure it "as proxy resource".
• Delete the ANY method that will be automatically associated with the newly created resource (it will be labeled {proxy+}.
• Create a new GET on the resource and set the "Integration type" to be Lambda Function and associate the Lambda function you've just created above with the resource.
• Create a new POST on the resource and set the "Integration type" to be Lambda Function and associate the Lambda function you've just created above with the resource.
• Create a new GET method on the root / resource. Configure the "Integration type" to be a "Lambda function" and check the "Use Lambda Proxy integration" button. Associate the Lambda function you've just created above with the resource.
• One the method is created click the "Method response" tab and add a new "Response Body" for HTTP 200 status response. The "Content type" should be text/html and the "Model" should be Empty.
• Create a new "Deployment stage". For the sake of this example we'll call it architecture to match the WHOSONFIRST_PATH_PREFIX environment variable in the Lambda function, described above.
• Deploy the API.

Once deployed the server tool will be available at a URL like {PREFIX}.execute-api.us-east-1.amazonaws.com/architecture. For example:

• https://{PREFIX}.execute-api.us-east-1.amazonaws.com/architecture/
• https://{PREFIX}.execute-api.us-east-1.amazonaws.com/architecture/point-in-polygon/

See also

• https://github.com/whosonfirst/go-whosonfirst-spatial
• https://github.com/whosonfirst/go-whosonfirst-spatial-sqlite
• https://github.com/whosonfirst/go-whosonfirst-spatial-www
• https://github.com/whosonfirst/go-whosonfirst-tippecanoe
• https://github.com/protomaps/go-pmtiles
• https://github.com/felt/tippecanoe