[wiki:Haiti]
----
== Data Migration & Consistency ==

We want to be able to migrate data from Prod to Dev so that Testers / Documenters have real data to play with.

Easy as a 1-off:
{{{
/etc/init.d/apache2 stop
rm -rf /home/haiti/dev/databases
cp -ar /home/haiti/prod/databases /home/haiti/dev
/etc/init.d/apache2 start
}}}

Maintaining this should be possible via [wiki: DataMigration#WebServices Web Services]

Also want to be able to migrate from the current sqlite backend to [wiki:InstallationGuidelinesMySQL MySQL]

We often need to use this same tricks to deal with database consistency issues.

=== CSV ===
Beware DB locks!
 * Don't keep Web2Py shell open longer than necessary
 * Consider goign into Maintenance Mode on the Webserver & disabling the Web2Py cron in {{{/etc/crontab}}}

{{{
cd /home/haiti/web2py
python web2py.py -S prod -M -N
db.export_to_csv_file(open('db.csv','wb'))
Ctrl+D
}}}

Remove reference Tables from CSV file (don't want to import duplicates!)

NB Do CSV file edits in a text editor, not MS Excel (MS Excel makes the dumps unusable!)

NB Be careful of file permissions!
 * All files in the databases folder should be {{{chown www-data:www-data}}}
 * If the 1st run of the model happens in the Python shell, then they will be owned by root...

{{{
cd /home/haiti/web2py
python web2py.py -S dev -M -N
db.import_from_csv_file(open('db.csv','rb'))
db.commit()
Ctrl+D
}}}

==== Changing a Column type in Sqlite live ====
sqlite handles live migrations pretty well, however if there is existing data then a conversion from string to integer can cause problems.
For a development system, the easiest solution is simply to remove all {{{databases/*}}} & restart, however this isn't possible for a live system:
{{{
vim /home/haiti/prod/models/00_db.py
    migrate = True

cd /home/haiti/prod
bzr pull

cd /home/haiti/web2py
python web2py.py -S prod -M

db(db.or_organisation.id > 0).select().export_to_csv_file(open('orgs.csv','wb'))
db.or_organisation.drop()
db.commit()
Ctrl+D

python web2py.py -S prod -M

db.or_organisation.import_from_csv_file(open('orgs.csv','rb'))
db.commit()
Ctrl+D

/etc/init.d/apache2 force-reload

vim /home/haiti/prod/models/00_db.py
    migrate = False
}}}

If the system is being heavily used, need to put up a holding page during this time to prevent data entry.
For switching on maintenance.
{{{
cd /home/haiti
./maintenance.on
}}}
For switching off maintenance.
{{{
cd /home/haiti
./maintenance.off
}}}
==== Changing a set of Lookup Options live ====
We can easily amend the module_resource_opts = {} live in the code (usually models/module.py) however we need to migrate existing data (after backing it up, of course):
{{{
cd /home/haiti/prod
bzr pull

cd /home/haiti/web2py
python web2py.py -S prod -M

db(db.or_organisation.id > 0).select().export_to_csv_file(open('orgs.csv','wb'))
db(db.or_organisation.type == 4).update(type='')
db(db.or_organisation.type == 5).update(type='')
db.commit()
Ctrl+D

/etc/init.d/apache2 force-reload
}}}

If the system is being heavily used, need to put up a holding page during this time to prevent data entry.
For switching on maintenance.
{{{
cd /home/haiti
./maintenance.on
}}}
For switching off maintenance.
{{{
cd /home/haiti
./maintenance.off
}}}
==== Dealing with database corruption ====
 1. We had problems with the or_organisation table - queries wouldn't complete.

The tracebacks included: {{{ValueError: invalid literal for int() with base 10: '01/14/10 1'}}}

By commenting out each field in turn in the model, discovered that this was the timestamp column which included this data.

(Note the file was also {{{chown root:root}}}!)

To fix this we needed to:
 * Delete column from model
{{{
vim /home/haiti/prod/models/05_or.py

resource = 'organisation'
table = module + '_' + resource
db.define_table(table, timestamp, deletion_status,
  # uuidstamp
}}}
 * Export as CSV
{{{
cd /home/haiti/web2py
python web2py.py -S prod -M -N
db.or_organisation.export_to_csv_file(open('prod_orgs.csv','wb'))
Ctrl+D
}}}
 * Drop table
{{{
cd /home/haiti/web2py
python web2py.py -S prod -M -N
db.or_organisation.drop()
db.commit()
Ctrl+D
}}}
 * Rebuild Table
  * Ensuring that table is owned by www-data
   * http://haiti.sahanafoundation.org
 * Reimport from CSV
{{{
cd /home/haiti/web2py
python web2py.py -S prod -M -N
db.or_organisation.import_from_csv_file(open('prod_orgs.csv','rb'))
db.commit()
Ctrl+D
}}}

 2. rms_sms_request table couldn't be recreated

Since this part of the system is under active development, it was necessary to drop the table as part of the [wiki:ReleaseManagement release process].
 * Although normally we can re-populate the tables from their source feeds simply using:
{{{
cd /home/haiti/web2py
python web2py.py -S prod -M -N
feature_class_id = db(db.gis_feature_class.name == 'SMS').select().first().id
db(db.gis_location.feature_class_id == feature_class_id).delete()
db.rms_tweet_request.truncate()
db.rms_sms_request.truncate()
db.commit()
Ctrl+D
}}}

However this didn't complete fully as there was still an associated view file in {{{databases/}}} & hence when model tries to create:
 * {{{SyntaxError: invalid table name: rms_sms_request}}}

To resolve this
=== Web Services ===
Better to avoid locks & do without SSH login

 * Currently needs to be done resource by resource (JOINed tables can be done together as Components of main resource)
  * need to do referenced tables before the tables which refer to them
  * migrate the locations first (using the xml interface), you can later migrate the orgs and offices together (through Component JOIN)
    *  http://localhost:8000/sahana/gis/location/create?format=xml&fetchurl=http://haiti.sahanafoundation.org/prod/gis/location.xml
    *  http://localhost:8000/sahana/pr/person/create?format=xml&fetchurl=http://haiti.sahanafoundation.org/prod/pr/person.xml
    *  http://localhost:8000/sahana/or/organisation/create?format=xml&fetchurl=http://haiti.sahanafoundation.org/prod/or/organisation.xml
     * This should pull in all components, so no need to do:
     *  http://localhost:8000/sahana/or/office/create?format=xml&fetchurl=http://haiti.sahanafoundation.org/prod/or/office.xml
    *  http://localhost:8000/sahana/or/contact/create?format=xml&fetchurl=http://haiti.sahanafoundation.org/prod/or/contact.xml 
 * BluePrintSynchronisation
   * Ideally we want to develop a way of having all tables loaded together into RAM, refs fixed-up & then imported to db together

----
[wiki:Haiti]