Merge pull request #300 from matrix-org/erikj/store_engine

Split out the schema preparation and update logic into its own module

1 files changed, 395 insertions, 0 deletions

diff --git a/synapse/storage/prepare_database.py b/synapse/storage/prepare_database.py
new file mode 100644
index 0000000000..1ddf55be4d
--- /dev/null
+++ b/synapse/storage/prepare_database.py
@@ -0,0 +1,395 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014, 2015 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import fnmatch
+import imp
+import logging
+import os
+import re
+
+
+logger = logging.getLogger(__name__)
+
+
+# Remember to update this number every time a change is made to database
+# schema files, so the users will be informed on server restarts.
+SCHEMA_VERSION = 24
+
+dir_path = os.path.abspath(os.path.dirname(__file__))
+
+
+def read_schema(path):
+    """ Read the named database schema.
+
+    Args:
+        path: Path of the database schema.
+    Returns:
+        A string containing the database schema.
+    """
+    with open(path) as schema_file:
+        return schema_file.read()
+
+
+class PrepareDatabaseException(Exception):
+    pass
+
+
+class UpgradeDatabaseException(PrepareDatabaseException):
+    pass
+
+
+def prepare_database(db_conn, database_engine):
+    """Prepares a database for usage. Will either create all necessary tables
+    or upgrade from an older schema version.
+    """
+    try:
+        cur = db_conn.cursor()
+        version_info = _get_or_create_schema_state(cur, database_engine)
+
+        if version_info:
+            user_version, delta_files, upgraded = version_info
+            _upgrade_existing_database(
+                cur, user_version, delta_files, upgraded, database_engine
+            )
+        else:
+            _setup_new_database(cur, database_engine)
+
+        # cur.execute("PRAGMA user_version = %d" % (SCHEMA_VERSION,))
+
+        cur.close()
+        db_conn.commit()
+    except:
+        db_conn.rollback()
+        raise
+
+
+def _setup_new_database(cur, database_engine):
+    """Sets up the database by finding a base set of "full schemas" and then
+    applying any necessary deltas.
+
+    The "full_schemas" directory has subdirectories named after versions. This
+    function searches for the highest version less than or equal to
+    `SCHEMA_VERSION` and executes all .sql files in that directory.
+
+    The function will then apply all deltas for all versions after the base
+    version.
+
+    Example directory structure:
+
+        schema/
+            delta/
+                ...
+            full_schemas/
+                3/
+                    test.sql
+                    ...
+                11/
+                    foo.sql
+                    bar.sql
+                ...
+
+    In the example foo.sql and bar.sql would be run, and then any delta files
+    for versions strictly greater than 11.
+    """
+    current_dir = os.path.join(dir_path, "schema", "full_schemas")
+    directory_entries = os.listdir(current_dir)
+
+    valid_dirs = []
+    pattern = re.compile(r"^\d+(\.sql)?$")
+    for filename in directory_entries:
+        match = pattern.match(filename)
+        abs_path = os.path.join(current_dir, filename)
+        if match and os.path.isdir(abs_path):
+            ver = int(match.group(0))
+            if ver <= SCHEMA_VERSION:
+                valid_dirs.append((ver, abs_path))
+        else:
+            logger.warn("Unexpected entry in 'full_schemas': %s", filename)
+
+    if not valid_dirs:
+        raise PrepareDatabaseException(
+            "Could not find a suitable base set of full schemas"
+        )
+
+    max_current_ver, sql_dir = max(valid_dirs, key=lambda x: x[0])
+
+    logger.debug("Initialising schema v%d", max_current_ver)
+
+    directory_entries = os.listdir(sql_dir)
+
+    for filename in fnmatch.filter(directory_entries, "*.sql"):
+        sql_loc = os.path.join(sql_dir, filename)
+        logger.debug("Applying schema %s", sql_loc)
+        executescript(cur, sql_loc)
+
+    cur.execute(
+        database_engine.convert_param_style(
+            "INSERT INTO schema_version (version, upgraded)"
+            " VALUES (?,?)"
+        ),
+        (max_current_ver, False,)
+    )
+
+    _upgrade_existing_database(
+        cur,
+        current_version=max_current_ver,
+        applied_delta_files=[],
+        upgraded=False,
+        database_engine=database_engine,
+    )
+
+
+def _upgrade_existing_database(cur, current_version, applied_delta_files,
+                               upgraded, database_engine):
+    """Upgrades an existing database.
+
+    Delta files can either be SQL stored in *.sql files, or python modules
+    in *.py.
+
+    There can be multiple delta files per version. Synapse will keep track of
+    which delta files have been applied, and will apply any that haven't been
+    even if there has been no version bump. This is useful for development
+    where orthogonal schema changes may happen on separate branches.
+
+    Different delta files for the same version *must* be orthogonal and give
+    the same result when applied in any order. No guarantees are made on the
+    order of execution of these scripts.
+
+    This is a no-op of current_version == SCHEMA_VERSION.
+
+    Example directory structure:
+
+        schema/
+            delta/
+                11/
+                    foo.sql
+                    ...
+                12/
+                    foo.sql
+                    bar.py
+                ...
+            full_schemas/
+                ...
+
+    In the example, if current_version is 11, then foo.sql will be run if and
+    only if `upgraded` is True. Then `foo.sql` and `bar.py` would be run in
+    some arbitrary order.
+
+    Args:
+        cur (Cursor)
+        current_version (int): The current version of the schema.
+        applied_delta_files (list): A list of deltas that have already been
+            applied.
+        upgraded (bool): Whether the current version was generated by having
+            applied deltas or from full schema file. If `True` the function
+            will never apply delta files for the given `current_version`, since
+            the current_version wasn't generated by applying those delta files.
+    """
+
+    if current_version > SCHEMA_VERSION:
+        raise ValueError(
+            "Cannot use this database as it is too " +
+            "new for the server to understand"
+        )
+
+    start_ver = current_version
+    if not upgraded:
+        start_ver += 1
+
+    logger.debug("applied_delta_files: %s", applied_delta_files)
+
+    for v in range(start_ver, SCHEMA_VERSION + 1):
+        logger.debug("Upgrading schema to v%d", v)
+
+        delta_dir = os.path.join(dir_path, "schema", "delta", str(v))
+
+        try:
+            directory_entries = os.listdir(delta_dir)
+        except OSError:
+            logger.exception("Could not open delta dir for version %d", v)
+            raise UpgradeDatabaseException(
+                "Could not open delta dir for version %d" % (v,)
+            )
+
+        directory_entries.sort()
+        for file_name in directory_entries:
+            relative_path = os.path.join(str(v), file_name)
+            logger.debug("Found file: %s", relative_path)
+            if relative_path in applied_delta_files:
+                continue
+
+            absolute_path = os.path.join(
+                dir_path, "schema", "delta", relative_path,
+            )
+            root_name, ext = os.path.splitext(file_name)
+            if ext == ".py":
+                # This is a python upgrade module. We need to import into some
+                # package and then execute its `run_upgrade` function.
+                module_name = "synapse.storage.v%d_%s" % (
+                    v, root_name
+                )
+                with open(absolute_path) as python_file:
+                    module = imp.load_source(
+                        module_name, absolute_path, python_file
+                    )
+                logger.debug("Running script %s", relative_path)
+                module.run_upgrade(cur, database_engine)
+            elif ext == ".pyc":
+                # Sometimes .pyc files turn up anyway even though we've
+                # disabled their generation; e.g. from distribution package
+                # installers. Silently skip it
+                pass
+            elif ext == ".sql":
+                # A plain old .sql file, just read and execute it
+                logger.debug("Applying schema %s", relative_path)
+                executescript(cur, absolute_path)
+            else:
+                # Not a valid delta file.
+                logger.warn(
+                    "Found directory entry that did not end in .py or"
+                    " .sql: %s",
+                    relative_path,
+                )
+                continue
+
+            # Mark as done.
+            cur.execute(
+                database_engine.convert_param_style(
+                    "INSERT INTO applied_schema_deltas (version, file)"
+                    " VALUES (?,?)",
+                ),
+                (v, relative_path)
+            )
+
+            cur.execute("DELETE FROM schema_version")
+            cur.execute(
+                database_engine.convert_param_style(
+                    "INSERT INTO schema_version (version, upgraded)"
+                    " VALUES (?,?)",
+                ),
+                (v, True)
+            )
+
+
+def get_statements(f):
+    statement_buffer = ""
+    in_comment = False  # If we're in a /* ... */ style comment
+
+    for line in f:
+        line = line.strip()
+
+        if in_comment:
+            # Check if this line contains an end to the comment
+            comments = line.split("*/", 1)
+            if len(comments) == 1:
+                continue
+            line = comments[1]
+            in_comment = False
+
+        # Remove inline block comments
+        line = re.sub(r"/\*.*\*/", " ", line)
+
+        # Does this line start a comment?
+        comments = line.split("/*", 1)
+        if len(comments) > 1:
+            line = comments[0]
+            in_comment = True
+
+        # Deal with line comments
+        line = line.split("--", 1)[0]
+        line = line.split("//", 1)[0]
+
+        # Find *all* semicolons. We need to treat first and last entry
+        # specially.
+        statements = line.split(";")
+
+        # We must prepend statement_buffer to the first statement
+        first_statement = "%s %s" % (
+            statement_buffer.strip(),
+            statements[0].strip()
+        )
+        statements[0] = first_statement
+
+        # Every entry, except the last, is a full statement
+        for statement in statements[:-1]:
+            yield statement.strip()
+
+        # The last entry did *not* end in a semicolon, so we store it for the
+        # next semicolon we find
+        statement_buffer = statements[-1].strip()
+
+
+def executescript(txn, schema_path):
+    with open(schema_path, 'r') as f:
+        for statement in get_statements(f):
+            txn.execute(statement)
+
+
+def _get_or_create_schema_state(txn, database_engine):
+    # Bluntly try creating the schema_version tables.
+    schema_path = os.path.join(
+        dir_path, "schema", "schema_version.sql",
+    )
+    executescript(txn, schema_path)
+
+    txn.execute("SELECT version, upgraded FROM schema_version")
+    row = txn.fetchone()
+    current_version = int(row[0]) if row else None
+    upgraded = bool(row[1]) if row else None
+
+    if current_version:
+        txn.execute(
+            database_engine.convert_param_style(
+                "SELECT file FROM applied_schema_deltas WHERE version >= ?"
+            ),
+            (current_version,)
+        )
+        applied_deltas = [d for d, in txn.fetchall()]
+        return current_version, applied_deltas, upgraded
+
+    return None
+
+
+def prepare_sqlite3_database(db_conn):
+    """This function should be called before `prepare_database` on sqlite3
+    databases.
+
+    Since we changed the way we store the current schema version and handle
+    updates to schemas, we need a way to upgrade from the old method to the
+    new. This only affects sqlite databases since they were the only ones
+    supported at the time.
+    """
+    with db_conn:
+        schema_path = os.path.join(
+            dir_path, "schema", "schema_version.sql",
+        )
+        create_schema = read_schema(schema_path)
+        db_conn.executescript(create_schema)
+
+        c = db_conn.execute("SELECT * FROM schema_version")
+        rows = c.fetchall()
+        c.close()
+
+        if not rows:
+            c = db_conn.execute("PRAGMA user_version")
+            row = c.fetchone()
+            c.close()
+
+            if row and row[0]:
+                db_conn.execute(
+                    "REPLACE INTO schema_version (version, upgraded)"
+                    " VALUES (?,?)",
+                    (row[0], False)
+                )