X-Git-Url: https://git.openstreetmap.org./nominatim.git/blobdiff_plain/3475e1dfd6c1ef44b7e2cc046d62a6f50108b6a0..02d357d29e40a8dfe5bc8eb4eac35c3ad3cc0958:/nominatim/db/async_connection.py diff --git a/nominatim/db/async_connection.py b/nominatim/db/async_connection.py index 45e83664..a86c5bdc 100644 --- a/nominatim/db/async_connection.py +++ b/nominatim/db/async_connection.py @@ -6,40 +6,89 @@ """ Database helper functions for the indexer. """ import logging +import select +import time + import psycopg2 from psycopg2.extras import wait_select +# psycopg2 emits different exceptions pre and post 2.8. Detect if the new error +# module is available and adapt the error handling accordingly. +try: + import psycopg2.errors # pylint: disable=no-name-in-module,import-error + __has_psycopg2_errors__ = True +except ImportError: + __has_psycopg2_errors__ = False + LOG = logging.getLogger() +class DeadlockHandler: + """ Context manager that catches deadlock exceptions and calls + the given handler function. All other exceptions are passed on + normally. + """ + + def __init__(self, handler, ignore_sql_errors=False): + self.handler = handler + self.ignore_sql_errors = ignore_sql_errors + + def __enter__(self): + return self + + def __exit__(self, exc_type, exc_value, traceback): + if __has_psycopg2_errors__: + if exc_type == psycopg2.errors.DeadlockDetected: # pylint: disable=E1101 + self.handler() + return True + elif exc_type == psycopg2.extensions.TransactionRollbackError \ + and exc_value.pgcode == '40P01': + self.handler() + return True + + if self.ignore_sql_errors and isinstance(exc_value, psycopg2.Error): + LOG.info("SQL error ignored: %s", exc_value) + return True + + return False + + class DBConnection: """ A single non-blocking database connection. """ - def __init__(self, dsn): + def __init__(self, dsn, cursor_factory=None, ignore_sql_errors=False): self.current_query = None self.current_params = None self.dsn = dsn + self.ignore_sql_errors = ignore_sql_errors self.conn = None self.cursor = None - self.connect() + self.connect(cursor_factory=cursor_factory) - def connect(self): + def close(self): + """ Close all open connections. Does not wait for pending requests. + """ + if self.conn is not None: + self.cursor.close() + self.conn.close() + + self.conn = None + + def connect(self, cursor_factory=None): """ (Re)connect to the database. Creates an asynchronous connection with JIT and parallel processing disabled. If a connection was already open, it is closed and a new connection established. The caller must ensure that no query is pending before reconnecting. """ - if self.conn is not None: - self.cursor.close() - self.conn.close() + self.close() # Use a dict to hand in the parameters because async is a reserved # word in Python3. - self.conn = psycopg2.connect(**{'dsn' : self.dsn, 'async' : True}) + self.conn = psycopg2.connect(**{'dsn': self.dsn, 'async': True}) self.wait() - self.cursor = self.conn.cursor() + self.cursor = self.conn.cursor(cursor_factory=cursor_factory) # Disable JIT and parallel workers as they are known to cause problems. # Update pg_settings instead of using SET because it does not yield # errors on older versions of Postgres where the settings are not @@ -50,23 +99,18 @@ class DBConnection: WHERE name = 'max_parallel_workers_per_gather';""") self.wait() + def _deadlock_handler(self): + LOG.info("Deadlock detected (params = %s), retry.", str(self.current_params)) + self.cursor.execute(self.current_query, self.current_params) + def wait(self): """ Block until any pending operation is done. """ while True: - try: + with DeadlockHandler(self._deadlock_handler, self.ignore_sql_errors): wait_select(self.conn) self.current_query = None return - except psycopg2.extensions.TransactionRollbackError as error: - if error.pgcode == '40P01': - LOG.info("Deadlock detected (params = %s), retry.", - str(self.current_params)) - self.cursor.execute(self.current_query, self.current_params) - else: - raise - except psycopg2.errors.DeadlockDetected: # pylint: disable=E1101 - self.cursor.execute(self.current_query, self.current_params) def perform(self, sql, args=None): """ Send SQL query to the server. Returns immediately without @@ -90,17 +134,82 @@ class DBConnection: if self.current_query is None: return True - try: + with DeadlockHandler(self._deadlock_handler, self.ignore_sql_errors): if self.conn.poll() == psycopg2.extensions.POLL_OK: self.current_query = None return True - except psycopg2.extensions.TransactionRollbackError as error: - if error.pgcode == '40P01': - LOG.info("Deadlock detected (params = %s), retry.", str(self.current_params)) - self.cursor.execute(self.current_query, self.current_params) - else: - raise - except psycopg2.errors.DeadlockDetected: # pylint: disable=E1101 - self.cursor.execute(self.current_query, self.current_params) return False + + +class WorkerPool: + """ A pool of asynchronous database connections. + + The pool may be used as a context manager. + """ + REOPEN_CONNECTIONS_AFTER = 100000 + + def __init__(self, dsn, pool_size, ignore_sql_errors=False): + self.threads = [DBConnection(dsn, ignore_sql_errors=ignore_sql_errors) + for _ in range(pool_size)] + self.free_workers = self._yield_free_worker() + self.wait_time = 0 + + + def finish_all(self): + """ Wait for all connection to finish. + """ + for thread in self.threads: + while not thread.is_done(): + thread.wait() + + self.free_workers = self._yield_free_worker() + + def close(self): + """ Close all connections and clear the pool. + """ + for thread in self.threads: + thread.close() + self.threads = [] + self.free_workers = None + + + def next_free_worker(self): + """ Get the next free connection. + """ + return next(self.free_workers) + + + def _yield_free_worker(self): + ready = self.threads + command_stat = 0 + while True: + for thread in ready: + if thread.is_done(): + command_stat += 1 + yield thread + + if command_stat > self.REOPEN_CONNECTIONS_AFTER: + self._reconnect_threads() + ready = self.threads + command_stat = 0 + else: + tstart = time.time() + _, ready, _ = select.select([], self.threads, []) + self.wait_time += time.time() - tstart + + + def _reconnect_threads(self): + for thread in self.threads: + while not thread.is_done(): + thread.wait() + thread.connect() + + + def __enter__(self): + return self + + + def __exit__(self, exc_type, exc_value, traceback): + self.finish_all() + self.close()