Maps/OSM Database Legacy

= OSM Database =
The Maps OSM database is an important piece of the infrastructure, it's a PostgreSQL database that hosts the data source for tile generation and the Geoshapes service.
The OSM Database needs two processes that are fundamental in order to keep it available with the most updated data from OSM: initial import and replication.
== Initial Importing of OSM data into PostgreSQL database ==
This process needs to be done in all clusters available, one at a time.
=== When you need to do initial import? ===
The following scenarios require a fresh install of the OSM database:
* First setup of the cluster
* Any upgrades or maintenance that require deleting the PostgreSQL data folder, for example:
** OS migration T198622
** Disk space in critical condition because of OSM replication
* OSM replication is disabled for a long time range and the database is outdated
** Depending on the server condition, is safer to re-import OSM data instead of roll replication, because it can overload Tilerator and increase significantly the CPU usage
=== Importing ===
==== Checklist ====
# Create a Phab task to track this work. Example.
# Depool the maps master. 
# Isolate the maps master from the rest of the cluster. Example.
# Disable Tilerator in puppet. Example.
# Delete postgres data, recreate the empty DB.
# Run `osm-initial-import` script to reimport data from OSM, needs root access.
# Re-enable replication
# Repool the maps master
# Re-init all slaves (cookbook)
# Re-enable tilerator
==== Depooling the maps master ====
From the puppetmaster, depooling maps1004 in eqiad: 
sudo confctl select "dc=eqiad,cluster=maps,service=kartotherian,name=maps1004.eqiad.wmnet" set/pooled=no
sudo confctl select "dc=eqiad,cluster=maps,service=kartotherian-ssl,name=maps1004.eqiad.wmnet" set/pooled=no
==== Re-creating an empty Postgres DB ====
Simply remove the database and let puppet handle the rest:
rm -rf /srv/postgresql/9.6/main/* && run-puppet-agent && service postgresql restart
==== Re-creating Postgres DB from backup ====
* Use the postgres resync cookbook
==== The initial-import-script ====
Initial data load of OSM into postgresql is done by running /usr/local/bin/osm-initial-import on the postgresql master node. This command can take over 12 hours or more, so running in screen or tmux is advised. 
osm-initial-import \
 -d <date_of_import> \
 -s <state_file_url> \
 -x webproxy.eqiad.wmnet:8080
* date_of_import: find the latest dump at https://planet.osm.org/pbf/. Example: 160530. Do NOT use "latest", as that might change at any moment.
* state_file_url: The URL to the state file corresponding to the dump, find the correct one at http://planet.openstreetmap.org/replication/ (the state file must be older than the dump). Example: http://planet.openstreetmap.org/replication/day/000/001/355.state.txt.
==== Troubleshouting ====
* If the slave initialization timeouts in puppet, it needs to be run manually:
service postgresql@9.6-main stop
rm -rf /srv/postgresql/9.6/main
sudo -u postgres /usr/bin/pg_basebackup -X stream -D /srv/postgresql/9.6/main -h <maps_master fqdn> -U replication -w
# Run puppet to make sure recovery.conf file is created
service postgresql@9.6-main start
== OSM replication ==
In order to keep the OSM Database updated, we use imposm. This tool periodically fetches data from OSM servers and applies the requested changesets in the PostgreSQL database. When it's complete, the replication script will trigger a request to Tilerator, sending a list of tiles that needs to be regenerated.
== Monitoring ==
You can monitor PostgreSQL activities of the Maps clusters in the following dashboards:
* General PostgreSQL metrics from prometheus postgres exporter
* OSM sync lag: eqiad, codfw