CGImap

Overview

CGImap is a C++ implementation of some parts of the OpenStreetMap API as an FCGI process. The rails implementation of the "map" call had a few problems with memory - it uses a lot of it and there is a leak which makes it annoying to use in long-running environments, such as the main OSM server.

CGImap attempts to address these memory problems and makes it easier to optimise the queries, something which is also a bit of a pain to do in Rails.

Currently, CGImap implements:

• 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,
• changeset downloads,
• changeset uploads.

Note that changeset metadata isn't the same thing as the changeset download (i.e: osmChange data).

Requirements

CGImap uses a PostgreSQL server for either the APIDB or PGsnapshot backends. A minimum server version of 9.4 is required.

CGImap depends on the following libraries. Versions used during development are in brackets. Other versions may work, but YMMV.

• libxml2 (2.9.3+dfsg1-1ubuntu0.2)
• libpqxx-4.0 (4.0.1+dfsg-3ubuntu2)
• libfcgi (2.4.0-8.3)
• libboost (1.58.0+dfsg-5ubuntu3.1)
• libcrypto++ (5.6.1-9)

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 \
  libboost-dev libboost-regex-dev libboost-program-options-dev \
  libboost-date-time-dev libboost-filesystem-dev \
  libboost-system-dev libboost-locale-dev libmemcached-dev \
  libcrypto++-dev

Note that C++11 is required to build CGImap.

The build system used is GNU Make, using pkg-config to provide some of the flags.

Note that the full set of packages needed from a fresh install (tested with Ubuntu 16.04) - you may already have many or all of these - is:

sudo apt-get install git build-essential automake autoconf libtool

If you want to enable the experimental JSON format, then you'll also need:

sudo apt-get install libyajl-dev

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

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

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

cd openstreetmap-cgimap/
./autogen.sh
./configure
make

You should now have a "./openstreetmap-cgimap" executable in the current directory.

Setup

To run CGImap binary, use the command:

./openstreetmap-cgimap --socket :54321 --backend apidb \
  --dbname openstreetmap

Note: CGImap has to be used with a fastcgi enabled 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 to test. 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_fastcgi_handler. 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.

An example of this can be found in OSM Chef.

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.

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/cgibin.conf. To use this on a Ubuntu-based system you need to copy the cofiguration 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.

Database Permissions

The apidb backend requires permissions to SELECT and CREATE TEMPORARY on the Postgres server. For situations where temporary tables cannot be created there is the --readonly option.

The pgsnapshot backend requires permissions to SELECT and CREATE TEMPORARY on the Postgres server, but will not work in situations where temporary tables cannot be created.

In both cases it is recommended that a separate account is created for CGImap to avoid any possibility of data corruption. Care has been taken programming CGImap but, as with most C++ applications, there is the chance of an exploitable flaw leading to complete pwnage.

Testing

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

sudo apt-get install postgresql postgresql-contrib postgis

And you will need to be able to create databases as your user:

sudo -u postgres createuser -s $USER

Formatting

The CGImap code is formatted using clang-format in a style which is based on the "LLVM style" which ships with clang-format. Note that version 3.6 or later is needed to avoid introducing problems with formatting try-catch blocks. To enable an automatic reformatting option, provide the --with-clang-format option to configure and then reformatting can be done across the whole set of source files by running:

make clang-format

Ideally, this should be done before committing each set of changes.

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.