server/sources/extlite.py
author Aurelien Campeas <aurelien.campeas@logilab.fr>
Fri, 09 Jan 2009 16:56:51 +0100
changeset 383 66804d97b919
parent 257 4c7d3af7e94d
child 983 cf1caf460081
child 1137 9ce0ac82f94f
permissions -rw-r--r--
[FAQ] debugging selectors : a new faq entry

"""provide an abstract class for external sources using a sqlite database helper

:organization: Logilab
:copyright: 2007-2008 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
"""
__docformat__ = "restructuredtext en"


import time
import threading
from os.path import join, exists

from cubicweb import server
from cubicweb.server.sqlutils import sqlexec, SQLAdapterMixIn
from cubicweb.server.sources import AbstractSource, native
from cubicweb.server.sources.rql2sql import SQLGenerator

def timeout_acquire(lock, timeout):
    while not lock.acquire(False):
        time.sleep(0.2)
        timeout -= 0.2
        if timeout <= 0:
            raise RuntimeError("svn source is busy, can't acquire connection lock")
        
class ConnectionWrapper(object):
    def __init__(self, source=None):
        self.source = source
        self._cnx = None

    @property
    def cnx(self):
        if self._cnx is None:
            timeout_acquire(self.source._cnxlock, 5)
            self._cnx = self.source._sqlcnx
        return self._cnx
    
    def commit(self):
        if self._cnx is not None:
            self._cnx.commit()
        
    def rollback(self):
        if self._cnx is not None:
            self._cnx.rollback()
        
    def cursor(self):
        return self.cnx.cursor()

    
class SQLiteAbstractSource(AbstractSource):
    """an abstract class for external sources using a sqlite database helper
    """
    sqlgen_class = SQLGenerator
    @classmethod
    def set_nonsystem_types(cls):
        # those entities are only in this source, we don't want them in the
        # system source
        for etype in cls.support_entities:
            native.NONSYSTEM_ETYPES.add(etype)
        for rtype in cls.support_relations:
            native.NONSYSTEM_RELATIONS.add(rtype)
        
    options = (
        ('helper-db-path',
         {'type' : 'string',
          'default': None,
          'help': 'path to the sqlite database file used to do queries on the \
repository.',
          'inputlevel': 2,
          }),
    )
            
    def __init__(self, repo, appschema, source_config, *args, **kwargs):
        # the helper db is used to easy querying and will store everything but
        # actual file content 
        dbpath = source_config.get('helper-db-path')
        if dbpath is None:
            dbpath = join(repo.config.appdatahome,
                          '%(uri)s.sqlite' % source_config)
        self.dbpath = dbpath
        self.sqladapter = SQLAdapterMixIn({'db-driver': 'sqlite',
                                           'db-name': dbpath})
        # those attributes have to be initialized before ancestor's __init__
        # which will call set_schema
        self._need_sql_create = not exists(dbpath)
        self._need_full_import = self._need_sql_create
        AbstractSource.__init__(self, repo, appschema, source_config,
                                *args, **kwargs)
        # sql database can only be accessed by one connection at a time, and a
        # connection can only be used by the thread which created it so:
        # * create the connection when needed
        # * use a lock to be sure only one connection is used
        self._cnxlock = threading.Lock()
        
    @property
    def _sqlcnx(self):
        # XXX: sqlite connections can only be used in the same thread, so
        #      create a new one each time necessary. If it appears to be time
        #      consuming, find another way
        return self.sqladapter.get_connection()

    def _is_schema_complete(self):
        for etype in self.support_entities:
            if not etype in self.schema:
                self.warning('not ready to generate %s database, %s support missing from schema',
                             self.uri, etype)
                return False
        for rtype in self.support_relations:
            if not rtype in self.schema:
                self.warning('not ready to generate %s database, %s support missing from schema',
                             self.uri, rtype)
                return False
        return True

    def _create_database(self):
        from yams.schema2sql import eschema2sql, rschema2sql
        from cubicweb.toolsutils import restrict_perms_to_user
        self.warning('initializing sqlite database for %s source' % self.uri)
        cnx = self._sqlcnx
        cu = cnx.cursor()
        schema = self.schema
        for etype in self.support_entities:
            eschema = schema.eschema(etype)
            createsqls = eschema2sql(self.sqladapter.dbhelper, eschema,
                                     skip_relations=('data',))
            sqlexec(createsqls, cu, withpb=False)
        for rtype in self.support_relations:
            rschema = schema.rschema(rtype)
            if not rschema.inlined:
                sqlexec(rschema2sql(rschema), cu, withpb=False)
        cnx.commit()
        cnx.close()
        self._need_sql_create = False
        if self.repo.config['uid']:
            from logilab.common.shellutils import chown
            # database file must be owned by the uid of the server process
            self.warning('set %s as owner of the database file',
                         self.repo.config['uid'])
            chown(self.dbpath, self.repo.config['uid'])
        restrict_perms_to_user(self.dbpath, self.info)
        
    def set_schema(self, schema):
        super(SQLiteAbstractSource, self).set_schema(schema)
        if self._need_sql_create and self._is_schema_complete():
            self._create_database()
        self.rqlsqlgen = self.sqlgen_class(schema, self.sqladapter.dbhelper)
                
    def get_connection(self):
        return ConnectionWrapper(self)

    def check_connection(self, cnx):
        """check connection validity, return None if the connection is still valid
        else a new connection (called when the pool using the given connection is
        being attached to a session)

        always return the connection to reset eventually cached cursor
        """
        return cnx

    def pool_reset(self, cnx):
        """the pool using the given connection is being reseted from its current
        attached session: release the connection lock if the connection wrapper
        has a connection set
        """
        if cnx._cnx is not None:
            try:
                cnx._cnx.close()
                cnx._cnx = None
            finally:
                self._cnxlock.release()
        
    def syntax_tree_search(self, session, union,
                           args=None, cachekey=None, varmap=None, debug=0):
        """return result from this source for a rql query (actually from a rql 
        syntax tree and a solution dictionary mapping each used variable to a 
        possible type). If cachekey is given, the query necessary to fetch the
        results (but not the results themselves) may be cached using this key.
        """
        if self._need_sql_create:
            return []
        sql, query_args = self.rqlsqlgen.generate(union, args)
        if server.DEBUG:
            print self.uri, 'SOURCE RQL', union.as_string()
            print 'GENERATED SQL', sql
        args = self.sqladapter.merge_args(args, query_args)
        cursor = session.pool[self.uri]
        cursor.execute(sql, args)
        return self.sqladapter.process_result(cursor) 

    def local_add_entity(self, session, entity):
        """insert the entity in the local database.

        This is not provided as add_entity implementation since usually source
        don't want to simply do this, so let raise NotImplementedError and the
        source implementor may use this method if necessary
        """
        cu = session.pool[self.uri]
        attrs = self.sqladapter.preprocess_entity(entity)
        sql = self.sqladapter.sqlgen.insert(str(entity.e_schema), attrs)
        cu.execute(sql, attrs)
        
    def add_entity(self, session, entity):
        """add a new entity to the source"""
        raise NotImplementedError()

    def local_update_entity(self, session, entity):
        """update an entity in the source

        This is not provided as update_entity implementation since usually
        source don't want to simply do this, so let raise NotImplementedError
        and the source implementor may use this method if necessary
        """
        cu = session.pool[self.uri]
        attrs = self.sqladapter.preprocess_entity(entity)
        sql = self.sqladapter.sqlgen.update(str(entity.e_schema), attrs, ['eid'])
        cu.execute(sql, attrs)
        
    def update_entity(self, session, entity):
        """update an entity in the source"""
        raise NotImplementedError()
        
    def delete_entity(self, session, etype, eid):
        """delete an entity from the source

        this is not deleting a file in the svn but deleting entities from the
        source. Main usage is to delete repository content when a Repository
        entity is deleted.
        """
        sqlcursor = session.pool[self.uri]        
        attrs = {'eid': eid}
        sql = self.sqladapter.sqlgen.delete(etype, attrs)
        sqlcursor.execute(sql, attrs)
    
    def delete_relation(self, session, subject, rtype, object):
        """delete a relation from the source"""
        rschema = self.schema.rschema(rtype)
        if rschema.inlined:
            if subject in session.query_data('pendingeids', ()):
                return
            etype = session.describe(subject)[0]
            sql = 'UPDATE %s SET %s=NULL WHERE eid=%%(eid)s' % (etype, rtype)
            attrs = {'eid' : subject}
        else:
            attrs = {'eid_from': subject, 'eid_to': object}
            sql = self.sqladapter.sqlgen.delete('%s_relation' % rtype, attrs)
        sqlcursor = session.pool[self.uri]        
        sqlcursor.execute(sql, attrs)