| 1 | # GNU MediaGoblin -- federated, autonomous media hosting |
| 2 | # Copyright (C) 2011, 2012 MediaGoblin contributors. See AUTHORS. |
| 3 | # |
| 4 | # This program is free software: you can redistribute it and/or modify |
| 5 | # it under the terms of the GNU Affero General Public License as published by |
| 6 | # the Free Software Foundation, either version 3 of the License, or |
| 7 | # (at your option) any later version. |
| 8 | # |
| 9 | # This program is distributed in the hope that it will be useful, |
| 10 | # but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 11 | # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 12 | # GNU Affero General Public License for more details. |
| 13 | # |
| 14 | # You should have received a copy of the GNU Affero General Public License |
| 15 | # along with this program. If not, see <http://www.gnu.org/licenses/>. |
| 16 | |
| 17 | from mediagoblin.tools.common import simple_printer |
| 18 | from sqlalchemy import Table |
| 19 | |
| 20 | class TableAlreadyExists(Exception): |
| 21 | pass |
| 22 | |
| 23 | |
| 24 | class MigrationManager(object): |
| 25 | """ |
| 26 | Migration handling tool. |
| 27 | |
| 28 | Takes information about a database, lets you update the database |
| 29 | to the latest migrations, etc. |
| 30 | """ |
| 31 | |
| 32 | def __init__(self, name, models, foundations, migration_registry, session, |
| 33 | printer=simple_printer): |
| 34 | """ |
| 35 | Args: |
| 36 | - name: identifier of this section of the database |
| 37 | - session: session we're going to migrate |
| 38 | - migration_registry: where we should find all migrations to |
| 39 | run |
| 40 | """ |
| 41 | self.name = unicode(name) |
| 42 | self.models = models |
| 43 | self.foundations = foundations |
| 44 | self.session = session |
| 45 | self.migration_registry = migration_registry |
| 46 | self._sorted_migrations = None |
| 47 | self.printer = printer |
| 48 | |
| 49 | # For convenience |
| 50 | from mediagoblin.db.models import MigrationData |
| 51 | |
| 52 | self.migration_model = MigrationData |
| 53 | self.migration_table = MigrationData.__table__ |
| 54 | |
| 55 | @property |
| 56 | def sorted_migrations(self): |
| 57 | """ |
| 58 | Sort migrations if necessary and store in self._sorted_migrations |
| 59 | """ |
| 60 | if not self._sorted_migrations: |
| 61 | self._sorted_migrations = sorted( |
| 62 | self.migration_registry.items(), |
| 63 | # sort on the key... the migration number |
| 64 | key=lambda migration_tuple: migration_tuple[0]) |
| 65 | |
| 66 | return self._sorted_migrations |
| 67 | |
| 68 | @property |
| 69 | def migration_data(self): |
| 70 | """ |
| 71 | Get the migration row associated with this object, if any. |
| 72 | """ |
| 73 | return self.session.query( |
| 74 | self.migration_model).filter_by(name=self.name).first() |
| 75 | |
| 76 | @property |
| 77 | def latest_migration(self): |
| 78 | """ |
| 79 | Return a migration number for the latest migration, or 0 if |
| 80 | there are no migrations. |
| 81 | """ |
| 82 | if self.sorted_migrations: |
| 83 | return self.sorted_migrations[-1][0] |
| 84 | else: |
| 85 | # If no migrations have been set, we start at 0. |
| 86 | return 0 |
| 87 | |
| 88 | @property |
| 89 | def database_current_migration(self): |
| 90 | """ |
| 91 | Return the current migration in the database. |
| 92 | """ |
| 93 | # If the table doesn't even exist, return None. |
| 94 | if not self.migration_table.exists(self.session.bind): |
| 95 | return None |
| 96 | |
| 97 | # Also return None if self.migration_data is None. |
| 98 | if self.migration_data is None: |
| 99 | return None |
| 100 | |
| 101 | return self.migration_data.version |
| 102 | |
| 103 | def set_current_migration(self, migration_number=None): |
| 104 | """ |
| 105 | Set the migration in the database to migration_number |
| 106 | (or, the latest available) |
| 107 | """ |
| 108 | self.migration_data.version = migration_number or self.latest_migration |
| 109 | self.session.commit() |
| 110 | |
| 111 | def migrations_to_run(self): |
| 112 | """ |
| 113 | Get a list of migrations to run still, if any. |
| 114 | |
| 115 | Note that this will fail if there's no migration record for |
| 116 | this class! |
| 117 | """ |
| 118 | assert self.database_current_migration is not None |
| 119 | |
| 120 | db_current_migration = self.database_current_migration |
| 121 | |
| 122 | return [ |
| 123 | (migration_number, migration_func) |
| 124 | for migration_number, migration_func in self.sorted_migrations |
| 125 | if migration_number > db_current_migration] |
| 126 | |
| 127 | |
| 128 | def init_tables(self): |
| 129 | """ |
| 130 | Create all tables relative to this package |
| 131 | """ |
| 132 | # sanity check before we proceed, none of these should be created |
| 133 | for model in self.models: |
| 134 | # Maybe in the future just print out a "Yikes!" or something? |
| 135 | if model.__table__.exists(self.session.bind): |
| 136 | raise TableAlreadyExists( |
| 137 | u"Intended to create table '%s' but it already exists" % |
| 138 | model.__table__.name) |
| 139 | |
| 140 | self.migration_model.metadata.create_all( |
| 141 | self.session.bind, |
| 142 | tables=[model.__table__ for model in self.models]) |
| 143 | |
| 144 | def populate_table_foundations(self): |
| 145 | """ |
| 146 | Create the table foundations (default rows) as layed out in FOUNDATIONS |
| 147 | in mediagoblin.db.models |
| 148 | """ |
| 149 | for Model, rows in self.foundations.items(): |
| 150 | self.printer(u' + Laying foundations for %s table\n' % |
| 151 | (Model.__name__)) |
| 152 | for parameters in rows: |
| 153 | new_row = Model(**parameters) |
| 154 | self.session.add(new_row) |
| 155 | |
| 156 | def create_new_migration_record(self): |
| 157 | """ |
| 158 | Create a new migration record for this migration set |
| 159 | """ |
| 160 | migration_record = self.migration_model( |
| 161 | name=self.name, |
| 162 | version=self.latest_migration) |
| 163 | self.session.add(migration_record) |
| 164 | self.session.commit() |
| 165 | |
| 166 | def dry_run(self): |
| 167 | """ |
| 168 | Print out a dry run of what we would have upgraded. |
| 169 | """ |
| 170 | if self.database_current_migration is None: |
| 171 | self.printer( |
| 172 | u'~> Woulda initialized: %s\n' % self.name_for_printing()) |
| 173 | return u'inited' |
| 174 | |
| 175 | migrations_to_run = self.migrations_to_run() |
| 176 | if migrations_to_run: |
| 177 | self.printer( |
| 178 | u'~> Woulda updated %s:\n' % self.name_for_printing()) |
| 179 | |
| 180 | for migration_number, migration_func in migrations_to_run(): |
| 181 | self.printer( |
| 182 | u' + Would update %s, "%s"\n' % ( |
| 183 | migration_number, migration_func.func_name)) |
| 184 | |
| 185 | return u'migrated' |
| 186 | |
| 187 | def name_for_printing(self): |
| 188 | if self.name == u'__main__': |
| 189 | return u"main mediagoblin tables" |
| 190 | else: |
| 191 | return u'plugin "%s"' % self.name |
| 192 | |
| 193 | def init_or_migrate(self): |
| 194 | """ |
| 195 | Initialize the database or migrate if appropriate. |
| 196 | |
| 197 | Returns information about whether or not we initialized |
| 198 | ('inited'), migrated ('migrated'), or did nothing (None) |
| 199 | """ |
| 200 | assure_migrations_table_setup(self.session) |
| 201 | |
| 202 | # Find out what migration number, if any, this database data is at, |
| 203 | # and what the latest is. |
| 204 | migration_number = self.database_current_migration |
| 205 | |
| 206 | # Is this our first time? Is there even a table entry for |
| 207 | # this identifier? |
| 208 | # If so: |
| 209 | # - create all tables |
| 210 | # - create record in migrations registry |
| 211 | # - print / inform the user |
| 212 | # - return 'inited' |
| 213 | if migration_number is None: |
| 214 | self.printer(u"-> Initializing %s... " % self.name_for_printing()) |
| 215 | |
| 216 | self.init_tables() |
| 217 | # auto-set at latest migration number |
| 218 | self.create_new_migration_record() |
| 219 | self.printer(u"done.\n") |
| 220 | self.populate_table_foundations() |
| 221 | self.set_current_migration() |
| 222 | return u'inited' |
| 223 | |
| 224 | # Run migrations, if appropriate. |
| 225 | migrations_to_run = self.migrations_to_run() |
| 226 | if migrations_to_run: |
| 227 | self.printer( |
| 228 | u'-> Updating %s:\n' % self.name_for_printing()) |
| 229 | for migration_number, migration_func in migrations_to_run: |
| 230 | self.printer( |
| 231 | u' + Running migration %s, "%s"... ' % ( |
| 232 | migration_number, migration_func.func_name)) |
| 233 | migration_func(self.session) |
| 234 | self.set_current_migration(migration_number) |
| 235 | self.printer('done.\n') |
| 236 | |
| 237 | return u'migrated' |
| 238 | |
| 239 | # Otherwise return None. Well it would do this anyway, but |
| 240 | # for clarity... ;) |
| 241 | return None |
| 242 | |
| 243 | |
| 244 | class RegisterMigration(object): |
| 245 | """ |
| 246 | Tool for registering migrations |
| 247 | |
| 248 | Call like: |
| 249 | |
| 250 | @RegisterMigration(33) |
| 251 | def update_dwarves(database): |
| 252 | [...] |
| 253 | |
| 254 | This will register your migration with the default migration |
| 255 | registry. Alternately, to specify a very specific |
| 256 | migration_registry, you can pass in that as the second argument. |
| 257 | |
| 258 | Note, the number of your migration should NEVER be 0 or less than |
| 259 | 0. 0 is the default "no migrations" state! |
| 260 | """ |
| 261 | def __init__(self, migration_number, migration_registry): |
| 262 | assert migration_number > 0, "Migration number must be > 0!" |
| 263 | assert migration_number not in migration_registry, \ |
| 264 | "Duplicate migration numbers detected! That's not allowed!" |
| 265 | |
| 266 | self.migration_number = migration_number |
| 267 | self.migration_registry = migration_registry |
| 268 | |
| 269 | def __call__(self, migration): |
| 270 | self.migration_registry[self.migration_number] = migration |
| 271 | return migration |
| 272 | |
| 273 | |
| 274 | def assure_migrations_table_setup(db): |
| 275 | """ |
| 276 | Make sure the migrations table is set up in the database. |
| 277 | """ |
| 278 | from mediagoblin.db.models import MigrationData |
| 279 | |
| 280 | if not MigrationData.__table__.exists(db.bind): |
| 281 | MigrationData.metadata.create_all( |
| 282 | db.bind, tables=[MigrationData.__table__]) |
| 283 | |
| 284 | |
| 285 | def inspect_table(metadata, table_name): |
| 286 | """Simple helper to get a ref to an already existing table""" |
| 287 | return Table(table_name, metadata, autoload=True, |
| 288 | autoload_with=metadata.bind) |