CGImap

Overview

CGImap is a C++ implementation of performance critical parts of the OpenStreetMap API as an FastCGI process.

As CGImap doesn't manage any database schemas and tables on its own, it can only be deployed alongside the openstreetmap-website application to replace selected API endpoints by their performance optimized counterparts. CGImap directly interacts with the APIDB, and completely bypasses the openstreetmap-website Rails application. See the CGImap wiki page for further details.

CGImap implements the following 25 OSM API 0.6 endpoints:

• the "map" API call,
• single node, way and relation fetches,
• multiple node, way and relation fetches,
• the "full" way and relation calls and
• changset metadata downloads, including discussions,
• single node, way and relation history calls,
• single node, way and relation specific version fetches,
• multiple node, way and relation specific version fetches,
• relations for element (node, way, relation),
• ways for node,
• create changeset,
• update changeset,
• close changeset,
• changeset downloads,
• changeset uploads.

Requirements

CGImap uses a PostgreSQL server for the APIDB backend.

If you're running a Debian or Ubuntu system these can be installed using the following command:

sudo apt-get install libxml2-dev libpqxx-dev libfcgi-dev zlib1g-dev libbrotli-dev \
  libboost-program-options-dev libfmt-dev libmemcached-dev libcrypto++-dev libyajl-dev

Note that C++17 is required to build CGImap.

The build system used is cmake.

Note that the full set of packages needed from a fresh install (tested with Ubuntu 20.04 and 22.04) - you may already have many or all of these - is:

sudo apt-get install git build-essential cmake make

To build the system from scratch, first check out the source code (skip this step if you've already got the source):

git clone https://github.com/zerebubuth/openstreetmap-cgimap.git

Then change to the source code directory to configure and build using cmake:

cd openstreetmap-cgimap/
mkdir build
cd build
cmake ..
cmake --build .

You should now have a "./openstreetmap-cgimap" executable in the current directory. For system-wide installation you still need to run:

sudo make install

For historic reasons, CGImap provides a number of shared libraries which were originally intended for reuse by other applications. As there are no real world consumers of these libraries, a static build is used by default. If you want to build with dynamic libraries instead, you can use the following cmake parameters:

cmake .. -DBUILD_SHARED_LIBS=ON

Setup

To run CGImap binary, use the command:

./openstreetmap-cgimap --dbname=openstreetmap --username=user --password=pass \
     --dbport=5432 --socket=:54321 --logfile=/tmp/logfile \
     --daemon --instances=10

Instead of a world-accessible TCP socket 54321, you might want to use 127.0.0.1:54321 to restrict access to the current host, or use plain filename like "--socket mysocket" for a Unix domain socket instead.

CGImap has to be used with a FastCGI enabled HTTP server like lighttpd, apache2 etc. See the instructions below to use CGImap with lighttpd or apache2.

A sample lighttd.conf file is provided, which can be used for testing purposes only. To test CGImap with lighttpd you will need to install lighttpd:

sudo apt-get install lighttpd

Edit the supplied lighttpd.config file to include your CGImap path and run it with the lighttpd like

/usr/sbin/lighttpd -f lighttpd.conf

You can then access the running instance at http://localhost:31337/api/0.6/map?bbox=...

The api.osm.org instance runs CGImap as a daemon and Apache with mod_proxy_fcgi.

Specifying configuration options

Typically you will need to modify the database connection parameters and path to the executable. See ./openstreetmap-cgimap --help for a list of options.

To convert a command line option to an environment variable append CGIMAP_ to the option and capatalize it. For example, the option --dbname becomes the environment variable CGIMAP_DBNAME.

Besides environment variables and command line options, CGImap configuration settings can also be provided in an INI-style config file. Use command line parameter --configfile to define the file location.

Example:

dbname=openstreetmap
host=localhost
username=user
password=pass

#update-host=127.0.0.1
#update-dbname=openstreetmap
#ratelimit=100000

# Expert settings (should be left to their default values in most cases)
# see --help for further details
#
#map-area=10
#disable-api-write=
#max-payload=50000000

Automatic startup as Daemon Service

An init.d script to run CGImap as a daemon is supplied in scripts/cgimap.init. To use it modify the paths and environment variables to suit your installation, copy it to /etc/init.d/cgibin and change the mode to 755, and owner:group to root:root.

For more recent operating systems using systemd instead of init scripts/cgimap.service is provided to run CGImap as a daemon. To use it modify the paths, set environment variables or the settings in the config file, copy it to /etc/systemd/system/cgimap.service. Change the mode to 755, and owner:group to root:root. To enable the service use systemctl enable cgimap and to start the service systemctl start cgimap.

An example of this can be found in OSM Chef.

Configuring Apache as FastCGI proxy

Fcgi programs can be deployed with Apache using mod_fastcgi_handler, mod_fcgid, mod_fastcgi, and on recent versions mod_proxy_fcgi. A sample Apache configuration file that will work in conjunction with CGImap as a daemon is supplied in scripts/cgimap.conf. To use this on a Ubuntu-based system you need to copy the configuration to where Apache will read it and create an api directory:

sudo cp scripts/cgimap.conf /etc/apache2/sites-available/cgimap
sudo chmod 644 /etc/apache2/sites-available/cgimap
sudo chown root:root /etc/apache2/sites-available/cgimap
sudo mkdir /var/www/api
sudo a2ensite cgimap
sudo service apache2 restart

The apache modules mod_proxy and mod_fastcgi_handler must also be enabled.

Docker

This repository includes a Dockerfile, which can be used to build a cgimap image based on Ubuntu 24.04:

docker build -f docker/ubuntu/Dockerfile2404 . -t cgimap

Due to the multi-stage build process, Docker version 17.05 or higher is required. The resulting cgimap image has a total size of about 140MB. openstreetmap-cgimap is built as a static binary.

#213 has additional configuration details on how to use the cgimap image in a complete development environment, which includes the Rails port, a Postgresql DB, lighttpd as reverse proxy, and openstreetmap-cgimap.

Database Permissions

The read only apidb backend requires permissions to SELECT on the Postgres server. Update database connections require additional permissions to INSERT/UPDATE/DELETE data, as well as creating temporary tables.

It is recommended that a separate unix account is used for CGImap to avoid any possibility of data corruption.

Testing

To run the test suite you will need additional packages installed:

sudo apt-get install postgresql-all postgresql-common postgresql-server-dev-all

Tests can be built by using the Debug build type or explicitly setting the BUILD_TESTING: option

cmake .. -DCMAKE_BUILD_TYPE=Debug

or

cmake .. -DBUILD_TESTING=ON

The test suite can then be run using cmake --build . -t test / ctest as normal.

Test cases are executed under pg_virtualenv, i.e. no further steps are needed to create databases as your user.

Acknowledgements

CGImap contains code from and is partly based on the following:

• modosmapi by d40cht and japplebyalis.
• quad_tile.c by TomH.
• GNU CGICC by Stephen F. Booth and Sebastien Diaz.
• libxml++ by The libxml++ development team
• Catch2 by Catch2 Authors
• SJParser by Denis Tikhomirov