patroni.postgresql.rewind module

class patroni.postgresql.rewind.REWIND_STATUS(value)

Bases: enum.IntEnum

An enumeration.

CHECK = 2
CHECKPOINT = 1
FAILED = 6
INITIAL = 0
NEED = 3
NOT_NEED = 4
SUCCESS = 5
class patroni.postgresql.rewind.Rewind(postgresql: patroni.postgresql.Postgresql)

Bases: object

__checkpoint(task: patroni.async_executor.CriticalTask, wakeup: Callable[[], Any])None
__init__(postgresql: patroni.postgresql.Postgresql)None

Initialize self. See help(type(self)) for accurate signature.

_archive_ready_wals()None

Try to archive WALs that have .ready files just in case archive_mode was not set to ‘always’ before promote, while after it the WALs were recycled on the promoted replica. With this we prevent the entire loss of such WALs and the consequent old leader’s start failure.

_buid_archiver_command(command: str, wal_filename: str)str

Replace placeholders in the given archiver command’s template. Applicable for archive_command and restore_command. Can also be used for archive_cleanup_command and recovery_end_command, however %r value is always set to 000000010000000000000001.

_check_timeline_and_lsn(leader: Union[patroni.dcs.Leader, patroni.dcs.RemoteMember])None
_conn_kwargs(member: Union[patroni.dcs.Leader, patroni.dcs.RemoteMember], auth: Dict[str, Any]) → Dict[str, Any]
_fetch_missing_wal(restore_command: str, wal_filename: str)bool
_find_missing_wal(data: bytes) → Optional[str]
_get_checkpoint_end(timeline: int, lsn: int)int

The checkpoint record size in WAL depends on postgres major version and platform (memory alignment). Hence, the only reliable way to figure out where it ends, read the record from file with the help of pg_waldump and parse the output. We are trying to read two records, and expect that it will fail to read the second one: pg_waldump: fatal: error in WAL record at 0/182E220: invalid record length at 0/182E298: wanted 24, got 0 The error message contains information about LSN of the next record, which is exactly where checkpoint ends.

_get_local_timeline_lsn() → Tuple[Optional[bool], Optional[int], Optional[int]]
_get_local_timeline_lsn_from_controldata() → Tuple[Optional[bool], Optional[int], Optional[int]]
static _log_primary_history(history: List[Tuple[int, int, str]], i: int)None
_maybe_clean_pg_replslot()None

Clean pg_replslot directory if pg version is less then 11 (pg_rewind deletes $PGDATA/pg_replslot content only since pg11).

property can_rewind

check if pg_rewind executable is there and that pg_controldata indicates we have either wal_log_hints or checksums turned on

property can_rewind_or_reinitialize_allowed
static check_leader_has_run_checkpoint(conn_kwargs: Dict[str, Any]) → Optional[str]
static check_leader_is_not_in_recovery(conn_kwargs: Dict[str, Any]) → Optional[bool]
checkpoint_after_promote()bool
cleanup_archive_status()None
static configuration_allows_rewind(data: Dict[str, str])bool
property enabled
ensure_checkpoint_after_promote(wakeup: Callable[[], Any])None

After promote issue a CHECKPOINT from a new thread and asynchronously check the result. In case if CHECKPOINT failed, just check that timeline in pg_control was updated.

ensure_clean_shutdown() → Optional[bool]
execute(leader: Union[patroni.dcs.Leader, patroni.dcs.RemoteMember]) → Optional[bool]
property executed
property failed
property is_needed
pg_rewind(r: Dict[str, Any])bool
read_postmaster_opts() → Dict[str, str]

returns the list of option names/values from postgres.opts, Empty dict if read failed or no file

reset_state()None
rewind_or_reinitialize_needed_and_possible(leader: Optional[Union[patroni.dcs.Leader, patroni.dcs.RemoteMember]])bool
property should_remove_data_directory_on_diverged_timelines
single_user_mode(communicate: Optional[Dict[str, Any]] = None, options: Optional[Dict[str, str]] = None) → Optional[int]

run a given command in a single-user mode. If the command is empty - then just start and stop

trigger_check_diverged_lsn()None