Nominatim/docs/admin/Update.md

Updating the Database

There are many different ways to update your Nominatim database. The following section describes how to keep it up-to-date using an online replication service for OpenStreetMap data For a list of other methods to add or update data see the output of nominatim add-data --help.

!!! important If you have configured a flatnode file for the import, then you need to keep this flatnode file around for updates.

Installing the newest version of Pyosmium

The replication process uses Pyosmium to download update data from the server. It is recommended to install Pyosmium via pip. Run (as the same user who will later run the updates):

pip3 install --user osmium

Setting up the update process

Next the update process needs to be initialised. By default Nominatim is configured to update using the global minutely diffs.

If you want a different update source you will need to add some settings to .env. For example, to use the daily country extracts diffs for Ireland from Geofabrik add the following:

# base URL of the replication service
NOMINATIM_REPLICATION_URL="https://download.geofabrik.de/europe/ireland-and-northern-ireland-updates"
# How often upstream publishes diffs (in seconds)
NOMINATIM_REPLICATION_UPDATE_INTERVAL=86400
# How long to sleep if no update found yet (in seconds)
NOMINATIM_REPLICATION_RECHECK_INTERVAL=900

To set up the update process now run the following command:

nominatim replication --init

It outputs the date where updates will start. Recheck that this date is what you expect.

The replication --init command needs to be rerun whenever the replication service is changed.

Updating Nominatim

Nominatim supports different modes how to retrieve the update data from the server. Which one you want to use depends on your exact setup and how often you want to retrieve updates.

These instructions are for using a single source of updates. If you have imported multiple country extracts and want to keep them up-to-date, Advanced installations section contains instructions to set up and update multiple country extracts.

Continuous updates

This is the easiest mode. Simply run the replication command without any parameters:

nominatim replication

The update application keeps running forever and retrieves and applies new updates from the server as they are published.

You can run this command as a simple systemd service. Create a service description like that in /etc/systemd/system/nominatim-updates.service:

[Unit]
Description=Continuous updates of Nominatim

[Service]
WorkingDirectory=/srv/nominatim
ExecStart=nominatim replication
StandardOutput=append:/var/log/nominatim-updates.log
StandardError=append:/var/log/nominatim-updates.error.log
User=nominatim
Group=nominatim
Type=simple

[Install]
WantedBy=multi-user.target

Replace the WorkingDirectory with your project directory. Also adapt user and group names as required.

Now activate the service and start the updates:

sudo systemctl daemon-reload
sudo systemctl enable nominatim-updates
sudo systemctl start nominatim-updates

One-time mode

When the --once parameter is given, then Nominatim will download exactly one batch of updates and then exit. This one-time mode still respects the NOMINATIM_REPLICATION_UPDATE_INTERVAL that you have set. If according to the update interval no new data has been published yet, it will go to sleep until the next expected update and only then attempt to download the next batch.

The one-time mode is particularly useful if you want to run updates continuously but need to schedule other work in between updates. For example, the main service at osm.org uses it, to regularly recompute postcodes -- a process that must not be run while updates are in progress. Its update script looks like this:

#!/bin/bash

# Switch to your project directory.
cd /srv/nominatim

while true; do
  nominatim replication --once
  if [ -f "/srv/nominatim/schedule-maintenance" ]; then
    rm /srv/nominatim/schedule-maintenance
    nominatim refresh --postcodes
  fi
done

A cron job then creates the file /srv/nominatim/schedule-maintenance once per night.

One-time mode with systemd

You can run the one-time mode with a systemd timer & service.

Create a timer description like /etc/systemd/system/nominatim-updates.timer:

[Unit]
Description=Timer to start updates of Nominatim

[Timer]
OnActiveSec=2
OnUnitActiveSec=1min
Unit=nominatim-updates.service

[Install]
WantedBy=multi-user.target

And then a similar service definition: /etc/systemd/system/nominatim-updates.service:

[Unit]
Description=Single updates of Nominatim

[Service]
WorkingDirectory=/srv/nominatim
ExecStart=nominatim replication --once
StandardOutput=append:/var/log/nominatim-updates.log
StandardError=append:/var/log/nominatim-updates.error.log
User=nominatim
Group=nominatim
Type=simple

[Install]
WantedBy=multi-user.target

Replace the WorkingDirectory with your project directory. Also adapt user and group names as required. OnUnitActiveSec defines how often the individual update command is run.

Now activate the service and start the updates:

sudo systemctl daemon-reload
sudo systemctl enable nominatim-updates.timer
sudo systemctl start nominatim-updates.timer

You can stop future data updates, while allowing any current, in-progress update steps to finish, by running sudo systemctl stop nominatim-updates.timer and waiting until nominatim-updates.service isn't running (sudo systemctl is-active nominatim-updates.service). Current output from the update can be seen like above (systemctl status nominatim-updates.service).

Catch-up mode

With the --catch-up parameter, Nominatim will immediately try to download all changes from the server until the database is up-to-date. The catch-up mode still respects the parameter NOMINATIM_REPLICATION_MAX_DIFF. It downloads and applies the changes in appropriate batches until all is done.

The catch-up mode is foremost useful to bring the database up to speed after the initial import. Give that the service usually is not in production at this point, you can temporarily be a bit more generous with the batch size and number of threads you use for the updates by running catch-up like this:

cd /srv/nominatim
NOMINATIM_REPLICATION_MAX_DIFF=5000 nominatim replication --catch-up --threads 15

The catch-up mode is also useful when you want to apply updates at a lower frequency than what the source publishes. You can set up a cron job to run replication catch-up at whatever interval you desire.

!!! hint When running scheduled updates with catch-up, it is a good idea to choose a replication source with an update frequency that is an order of magnitude lower. For example, if you want to update once a day, use an hourly updated source. This makes sure that you don't miss an entire day of updates when the source is unexpectedly late to publish its update.

If you want to use the source with the same update frequency (e.g. a daily
updated source with daily updates), use the
continuous update mode. It ensures to re-request the newest update until it
is published.