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https://github.com/openvswitch/ovs
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42a49b9601
When a strong reference to a non-root table is ephemeral, the database log can contain inconsistencies. In particular, if the column in question is the only reference to a row, then the row will be created in one logged transaction but the reference to it will not be logged (because it is ephemeral). Thus, any later occurrence of the row later in the log (to modify it, to delete it, or just to reference it) will yield a transaction error and reading the database will abort at that point. This commit fixes the problem by forcing any column with a strong reference to a non-root table to be persistent. The change to ovsdb_schema_from_json() looks bigger than it really is: it just swaps the order of two operations on the schema and updates their comments. Similarly for the update to ovs.db.DbSchema.__init__(). Bug #5144. Reported-by: Sujatha Sumanth <ssumanth@nicira.com> Bug #5149. Reported-by: Ram Jothikumar <rjothikumar@nicira.com>
228 lines
8.8 KiB
Python
228 lines
8.8 KiB
Python
# Copyright (c) 2009, 2010, 2011 Nicira Networks
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at:
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import re
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import sys
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from ovs.db import error
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import ovs.db.parser
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from ovs.db import types
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class DbSchema(object):
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"""Schema for an OVSDB database."""
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def __init__(self, name, version, tables):
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self.name = name
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self.version = version
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self.tables = tables
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# "isRoot" was not part of the original schema definition. Before it
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# was added, there was no support for garbage collection. So, for
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# backward compatibility, if the root set is empty then assume that
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# every table is in the root set.
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if self.__root_set_size() == 0:
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for table in self.tables.itervalues():
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table.is_root = True
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# Validate that all ref_tables refer to the names of tables
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# that exist.
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#
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# Also force certain columns to be persistent, as explained in
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# __check_ref_table(). This requires 'is_root' to be known, so this
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# must follow the loop updating 'is_root' above.
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for table in self.tables.itervalues():
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for column in table.columns.itervalues():
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self.__check_ref_table(column, column.type.key, "key")
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self.__check_ref_table(column, column.type.value, "value")
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def __root_set_size(self):
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"""Returns the number of tables in the schema's root set."""
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n_root = 0
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for table in self.tables.itervalues():
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if table.is_root:
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n_root += 1
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return n_root
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@staticmethod
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def from_json(json):
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parser = ovs.db.parser.Parser(json, "database schema")
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name = parser.get("name", ['id'])
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version = parser.get_optional("version", [unicode])
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parser.get_optional("cksum", [unicode])
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tablesJson = parser.get("tables", [dict])
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parser.finish()
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if (version is not None and
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not re.match('[0-9]+\.[0-9]+\.[0-9]+$', version)):
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raise error.Error("schema version \"%s\" not in format x.y.z"
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% version)
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tables = {}
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for tableName, tableJson in tablesJson.iteritems():
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if tableName.startswith('_'):
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raise error.Error("names beginning with \"_\" are reserved",
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json)
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elif not ovs.db.parser.is_identifier(tableName):
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raise error.Error("name must be a valid id", json)
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tables[tableName] = TableSchema.from_json(tableJson, tableName)
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return DbSchema(name, version, tables)
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def to_json(self):
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# "isRoot" was not part of the original schema definition. Before it
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# was added, there was no support for garbage collection. So, for
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# backward compatibility, if every table is in the root set then do not
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# output "isRoot" in table schemas.
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default_is_root = self.__root_set_size() == len(self.tables)
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tables = {}
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for table in self.tables.itervalues():
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tables[table.name] = table.to_json(default_is_root)
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json = {"name": self.name, "tables": tables}
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if self.version:
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json["version"] = self.version
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return json
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def __check_ref_table(self, column, base, base_name):
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if not base or base.type != types.UuidType or not base.ref_table:
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return
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ref_table = self.tables.get(base.ref_table)
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if not ref_table:
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raise error.Error("column %s %s refers to undefined table %s"
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% (column.name, base_name, base.ref_table),
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tag="syntax error")
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if base.is_strong_ref() and not ref_table.is_root:
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# We cannot allow a strong reference to a non-root table to be
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# ephemeral: if it is the only reference to a row, then replaying
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# the database log from disk will cause the referenced row to be
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# deleted, even though it did exist in memory. If there are
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# references to that row later in the log (to modify it, to delete
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# it, or just to point to it), then this will yield a transaction
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# error.
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column.persistent = True
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class IdlSchema(DbSchema):
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def __init__(self, name, version, tables, idlPrefix, idlHeader):
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DbSchema.__init__(self, name, version, tables)
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self.idlPrefix = idlPrefix
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self.idlHeader = idlHeader
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@staticmethod
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def from_json(json):
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parser = ovs.db.parser.Parser(json, "IDL schema")
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idlPrefix = parser.get("idlPrefix", [unicode])
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idlHeader = parser.get("idlHeader", [unicode])
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subjson = dict(json)
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del subjson["idlPrefix"]
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del subjson["idlHeader"]
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schema = DbSchema.from_json(subjson)
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return IdlSchema(schema.name, schema.version, schema.tables,
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idlPrefix, idlHeader)
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class TableSchema(object):
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def __init__(self, name, columns, mutable=True, max_rows=sys.maxint,
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is_root=True):
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self.name = name
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self.columns = columns
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self.mutable = mutable
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self.max_rows = max_rows
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self.is_root = is_root
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@staticmethod
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def from_json(json, name):
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parser = ovs.db.parser.Parser(json, "table schema for table %s" % name)
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columnsJson = parser.get("columns", [dict])
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mutable = parser.get_optional("mutable", [bool], True)
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max_rows = parser.get_optional("maxRows", [int])
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is_root = parser.get_optional("isRoot", [bool], False)
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parser.finish()
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if max_rows == None:
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max_rows = sys.maxint
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elif max_rows <= 0:
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raise error.Error("maxRows must be at least 1", json)
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if not columnsJson:
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raise error.Error("table must have at least one column", json)
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columns = {}
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for columnName, columnJson in columnsJson.iteritems():
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if columnName.startswith('_'):
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raise error.Error("names beginning with \"_\" are reserved",
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json)
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elif not ovs.db.parser.is_identifier(columnName):
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raise error.Error("name must be a valid id", json)
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columns[columnName] = ColumnSchema.from_json(columnJson,
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columnName)
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return TableSchema(name, columns, mutable, max_rows, is_root)
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def to_json(self, default_is_root=False):
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"""Returns this table schema serialized into JSON.
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The "isRoot" member is included in the JSON only if its value would
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differ from 'default_is_root'. Ordinarily 'default_is_root' should be
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false, because ordinarily a table would be not be part of the root set
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if its "isRoot" member is omitted. However, garbage collection was not
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orginally included in OVSDB, so in older schemas that do not include
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any "isRoot" members, every table is implicitly part of the root set.
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To serialize such a schema in a way that can be read by older OVSDB
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tools, specify 'default_is_root' as True.
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"""
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json = {}
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if not self.mutable:
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json["mutable"] = False
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if default_is_root != self.is_root:
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json["isRoot"] = self.is_root
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json["columns"] = columns = {}
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for column in self.columns.itervalues():
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if not column.name.startswith("_"):
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columns[column.name] = column.to_json()
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if self.max_rows != sys.maxint:
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json["maxRows"] = self.max_rows
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return json
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class ColumnSchema(object):
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def __init__(self, name, mutable, persistent, type):
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self.name = name
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self.mutable = mutable
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self.persistent = persistent
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self.type = type
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@staticmethod
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def from_json(json, name):
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parser = ovs.db.parser.Parser(json, "schema for column %s" % name)
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mutable = parser.get_optional("mutable", [bool], True)
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ephemeral = parser.get_optional("ephemeral", [bool], False)
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type = types.Type.from_json(parser.get("type", [dict, unicode]))
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parser.finish()
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return ColumnSchema(name, mutable, not ephemeral, type)
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def to_json(self):
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json = {"type": self.type.to_json()}
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if not self.mutable:
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json["mutable"] = False
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if not self.persistent:
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json["ephemeral"] = True
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return json
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