diff --git a/README.rst b/README.rst index 3e851363..f752c2ca 100644 --- a/README.rst +++ b/README.rst @@ -110,8 +110,16 @@ For an example file, see ``postgres0.yml``. Regarding settings: - *username*: admin username; user is created during initialization. It will have CREATEDB and CREATEROLE privileges. - *password*: admin password; user is created during initialization. - - *recovery\_conf*: additional configuration settings written to recovery.conf when configuring the follower. - - *parameters*: list of configuration settings for Postgres. Many of these are required for replication to work. + - *recovery\_conf*: additional configuration settings written to recovery.conf when configuring follower. + - *parameters*: list of configuration settings for Postgres. Many of these are required for replication to work. + + - *create_replica_methods*: an ordered list of the create methods for turning a patroni node into a new replica. + "basebackup" is the default method; other methods are assumed to refer to scripts, each of which is configured + as its own config item. + + - *{replica_method}* for each create_replica_method other than basebackup, you would add a configuration section + of the same name. At a minimum, this should include "command" with a full path to the actual script to be + executed. Other configuration parameters will be passed along to the script in the form "parameter=value". Replication Choices ------------------- diff --git a/patroni/postgresql.py b/patroni/postgresql.py index 4cff9d76..c4c710f4 100644 --- a/patroni/postgresql.py +++ b/patroni/postgresql.py @@ -223,25 +223,79 @@ class Postgresql: r = parseurl(leader.conn_url) env = self.write_pgpass(r) - return self.create_replica(r, env) == 0 + ret = self.create_replica(leader, env) == 0 + ret and self.delete_trigger_file() + return ret @staticmethod def build_connstring(conn): - return "host={host} port={port} user={user}".format(**conn) + mconn = "" + for param, val in conn.items(): + mconn = mconn + "{0}={1} ".format(param, val) - def create_replica(self, master_connection, env): - self.set_state('building replica from {host}:{port}'.format(**master_connection)) - connstring = self.build_connstring(master_connection) - cmd = self.config['restore'] - try: - ret = subprocess.call(shlex.split(cmd) + [self.scope, "replica", self.data_dir, connstring], env=env) - self.delete_trigger_file() - except: - logger.exception('Error when creating replica') - ret = 1 - if ret != 0: - self.set_state('failed to build replica from {host}:{port}'.format(**master_connection)) - return ret + return mconn + + def create_replica(self, leader, env): + # create the replica according to the replica_method + # defined by the user. this is a list, so we need to + # loop through all methods the user supplies + connstring = leader.conn_url + # get list of replica methods from config + replica_list = self.config.get('create_replica_method', 'basebackup') + replica_methods = [rm.strip() for rm in replica_list.split(',')] + # go through them in priority order + for replica_method in replica_methods: + # if the method is basebackup, then use the built-in + if replica_method == "basebackup": + ret = self.basebackup(leader, env) + if ret == 0: + # if basebackup succeeds, exit with success + break + else: + # user-defined method; check for configuration + # not required, actually + if replica_method in self.config: + # look to see if the user has supplied a full command path + # if not, use the method name as the command + if "command" in self.config[replica_method]: + cmd = self.config[replica_method]["command"] + else: + cmd = replica_method + + # get the rest of the replica config + method_config = self.config[replica_method].copy() + # remove the command and turn it into a shlex set + del method_config["command"] + # add the default parameters + method_config.update({"scope": self.scope, + "role": "replica", + "datadir": self.data_dir, + "connstring": connstring}) + params = ["--{0}={1}".format(arg, val) for arg, val in method_config.items()] + else: + cmd = replica_method + method_config = {"scope": self.scope, + "role": "replica", + "datadir": self.data_dir, + "connstring": connstring} + + try: + # call script with the full set of parameters + ret = subprocess.call(shlex.split(cmd) + params, env=env) + # if we succeeded, stop + if ret == 0: + break + except Exception as e: + logger.exception('Error creating replica using method {0}: {1}'.format(replica_method, e.str)) + ret = 1 + + # write the recovery.conf + if ret == 0: + ret = self.write_recovery_conf(leader) + return 0 + + # out of methods, return 1 + return 1 def is_leader(self): return not self.query('SELECT pg_is_in_recovery()').fetchone()[0] @@ -539,7 +593,7 @@ recovery_target_timeline = 'latest' """ restore a previously saved postgresql.conf """ try: for f in self.configuration_to_save: - not os.path.isfile(f) and os.path.isfile(f+'.backup') and shutil.copy(f + '.backup', f) + not os.path.isfile(f) and os.path.isfile(f + '.backup') and shutil.copy(f + '.backup', f) except: logger.exception('unable to restore configuration files from backup') @@ -663,3 +717,29 @@ $$""".format(name, options), name, password, password) except: logger.exception('Could not remove data directory %s', self.data_dir) self.move_data_directory() + + def basebackup(self, leader, env): + # creates a replica data dir using pg_basebackup. + # this is the default, built-in create_replica_method + # tries twice, then returns failure (as 1) + # uses "stream" as the xlog-method to avoid sync issues + master_connection = leader.conn_url + bbfailures = 0 + maxfailures = 2 + ret = 1 + while bbfailures < maxfailures: + try: + ret = subprocess.call(['pg_basebackup', '--pgdata=' + self.data_dir, + '--xlog-method=stream', "--dbname=" + master_connection], env=env) + if ret == 0: + break + + except Exception as e: + logger.error('Error when fetching backup with pg_basebackup: {0}'.format(e)) + + bbfailures += 1 + if bbfailures < maxfailures: + logger.error('Trying again in 5 seconds') + time.sleep(5) + + return ret diff --git a/patroni/scripts/wale_restore.py b/patroni/scripts/wale_restore.py new file mode 100644 index 00000000..fca1f7d8 --- /dev/null +++ b/patroni/scripts/wale_restore.py @@ -0,0 +1,178 @@ +#!/usr/bin/python + +# sample script to clone new replicas using WAL-E restore +# falls back to pg_basebackup if WAL-E restore fails, or if +# WAL-E backup is too far behind +# note that pg_basebackup still expects to use restore from +# WAL-E for transaction logs + +# theoretically should work with SWIFT, but not tested on it + +# arguments are: +# - cluster scope +# - cluster role +# - master connection string +# - number of retries +# - envdir for the WALE env +# - WALE_BACKUP_THRESHOLD_MEGABYTES if WAL amount is above that - use pg_basebackup +# - WALE_BACKUP_THRESHOLD_PERCENTAGE if WAL size exceeds a certain percentage of the + +# this script depends on an envdir defining the S3 bucket (or SWIFT dir),and login +# credentials per WALE Documentation. + +# currently also requires that you configure the restore_command to use wal_e, example: +# recovery_conf: +# restore_command: envdir /etc/wal-e.d/env wal-e wal-fetch "%f" "%p" + +import logging +import os +import psycopg2 +import subprocess +import sys +import argparse + + +if sys.hexversion >= 0x03000000: + long = int + +logger = logging.getLogger(__name__) + + +class WALERestore(object): + + def __init__(self, scope, role, datadir, connstring, env_dir, threshold_mb, threshold_pct, use_iam): + self.scope = scope + self.role = role + self.master_connection = connstring + self.data_dir = datadir + self.wal_e.dir = env_dir + self.wal_e.threshold_mb = threshold_mb + self.wal_e.threshold_pct = threshold_pct + if use_iam == 1: + self.wal_e.iam_string = ' --aws-instance-profile ' + else: + self.wal_e.iam_string = '' + if not os.path.exists(self.wal_e.dir): + self.init_error = True + else: + self.init_error = False + self.wal_e.cmd = 'envdir {0} wal-e {1} '.\ + format(self.wal_e.dir, self.wal_e.iam_string) + + def run(self): + """ creates a new replica using WAL-E """ + ret = self.replica_method() + return ret + + def replica_method(self): + if self.should_use_s3_to_create_replica(): + return self.create_replica_with_s3 + return None + + def should_use_s3_to_create_replica(self): + """ determine whether it makes sense to use S3 and not pg_basebackup """ + if self.init_error: + return False + + threshold_megabytes = self.wal_e.threshold_mb + threshold_backup_size_percentage = self.wal_e.threshold_pct + + try: + latest_backup = subprocess.check_output(self.wal_e.cmd.split() + ['backup-list', '--detail', 'LATEST']) + # name last_modified expanded_size_bytes wal_segment_backup_start wal_segment_offset_backup_start + # wal_segment_backup_stop wal_segment_offset_backup_stop + # base_00000001000000000000007F_00000040 2015-05-18T10:13:25.000Z + # 20310671 00000001000000000000007F 00000040 + # 00000001000000000000007F 00000240 + backup_strings = latest_backup.splitlines() if latest_backup else () + if len(backup_strings) != 2: + return False + + names = backup_strings[0].split() + vals = backup_strings[1].split() + if (len(names) != len(vals)) or (len(names) != 7): + return False + + backup_info = dict(zip(names, vals)) + except subprocess.CalledProcessError as e: + logger.error("could not query wal-e latest backup: {}".format(e)) + return False + + try: + backup_size = backup_info['expanded_size_bytes'] + backup_start_segment = backup_info['wal_segment_backup_start'] + backup_start_offset = backup_info['wal_segment_offset_backup_start'] + except Exception as e: + logger.error("unable to get some of WALE backup parameters: {}".format(e)) + return False + + # WAL filename is XXXXXXXXYYYYYYYY000000ZZ, where X - timeline, Y - LSN logical log file, + # ZZ - 2 high digits of LSN offset. The rest of the offset is the provided decimal offset, + # that we have to convert to hex and 'prepend' to the high offset digits. + + lsn_segment = backup_start_segment[8:16] + # first 2 characters of the result are 0x and the last one is L + lsn_offset = hex((long(backup_start_segment[16:32], 16) << 24) + long(backup_start_offset))[2:-1] + + # construct the LSN from the segment and offset + backup_start_lsn = '{}/{}'.format(lsn_segment, lsn_offset) + + conn = None + cursor = None + diff_in_bytes = long(backup_size) + try: + # get the difference in bytes between the current WAL location and the backup start offset + conn = psycopg2.connect(self.master_connection) + conn.autocommit = True + cursor = conn.cursor() + cursor.execute("SELECT pg_xlog_location_diff(pg_current_xlog_location(), %s)", (backup_start_lsn,)) + diff_in_bytes = long(cursor.fetchone()[0]) + except psycopg2.Error as e: + logger.error('could not determine difference with the master location: {}'.format(e)) + return False + finally: + cursor and cursor.close() + conn and conn.close() + + # if the size of the accumulated WAL segments is more than a certan percentage of the backup size + # or exceeds the pre-determined size - pg_basebackup is chosen instead. + return (diff_in_bytes < long(threshold_megabytes) * 1048576) and\ + (diff_in_bytes < long(backup_size) * float(threshold_backup_size_percentage) / 100) + + def create_replica_with_s3(self): + if self.init_error: + return 1 + # if we're set up, restore the replica using fetch latest + try: + ret = subprocess.call(self.wal_e.cmd + ' backup-fetch {} LATEST'.format(self.data_dir)) + except Exception as e: + logger.error('Error when fetching backup with WAL-E: {0}'.format(e)) + return 1 + + return ret + + +if __name__ == '__main__': + + parser = argparse.ArgumentParser(description='Script to image replicas using WAL-E') + parser.add_argument('--scope', required=True) + parser.add_argument('--role', required=False) + parser.add_argument('--datadir', required=True) + parser.add_argument('--connstring', required=True) + parser.add_argument('--retries', type=int, default=1) + parser.add_argument('--envdir', required=True) + parser.add_argument('--threshold_megabytes', type=int, default=10240) + parser.add_argument('--threshold_backup_size_percentage', type=int, default=30) + parser.add_argument('--use_iam', type=int, default=0) + args = parser.parse_args() + + # retry cloning in a loop + for retry in range(0, args.retries + 1): + restore = WALERestore(scope=args.scope, datadir=args.datadir, connstring=args.constring, + env_dir=args.env_dir, threshold_mb=args.threshold_megabytes, + threshold_pct=args.threshold_backup_size_percentage) + ret = restore.run() + if ret == 0: + break + + sys.exit(ret) diff --git a/postgres0.yml b/postgres0.yml index 2ef74276..ae3646cf 100644 --- a/postgres0.yml +++ b/postgres0.yml @@ -68,13 +68,18 @@ postgresql: admin: username: admin password: admin - wal_e: - env_dir: /home/postgres/etc/wal-e.d/env - threshold_megabytes: 10240 - threshold_backup_size_percentage: 30 - restore: patroni/scripts/restore.py + create_replica_method: basebackup +# commented-out example for wal-e provisioning + #create_replica_method: wal_e, basebackup + #wal_e: + #command: /patroni/scripts/wale_restore.py + #env_dir: /etc/wal-e.d/env + #threshold_megabytes: 10240 + #threshold_backup_size_percentage: 30 + #retries: 2 + #use_iam: 1 #recovery_conf: - #restore_command: cp ../wal_archive/%f %p + #restore_command: envdir /etc/wal-e.d/env wal-e wal-fetch "%f" "%p" parameters: archive_mode: "on" wal_level: hot_standby diff --git a/postgres1.yml b/postgres1.yml index 2d28ccaa..d96df08c 100644 --- a/postgres1.yml +++ b/postgres1.yml @@ -68,13 +68,17 @@ postgresql: admin: username: admin password: admin +# commented-out example for wal-e provisioning + #create_replica_method: wal_e, basebackup + #wal_e: + #command: /patroni/scripts/wale_restore.py + #env_dir: /home/postgres/etc/wal-e.d/env + #threshold_megabytes: 10240 + #threshold_backup_size_percentage: 30 + #retries: 2 + #use_iam: 1 #recovery_conf: - #restore_command: cp ../wal_archive/%f %p - wal_e: - env_dir: /home/postgres/etc/wal-e.d/env - threshold_megabytes: 10240 - threshold_backup_size_percentage: 30 - restore: patroni/scripts/restore.py + #restore_command: envdir /etc/wal-e.d/env wal-e wal-fetch "%f" "%p" parameters: archive_mode: "on" wal_level: hot_standby diff --git a/tests/test_postgresql.py b/tests/test_postgresql.py index 3e8caf47..1eabcf8d 100644 --- a/tests/test_postgresql.py +++ b/tests/test_postgresql.py @@ -273,9 +273,13 @@ class TestPostgresql(unittest.TestCase): self.assertTrue(self.p.can_rewind) self.p.controldata = tmp + @patch('time.sleep', Mock()) def test_create_replica(self): self.p.delete_trigger_file = Mock(side_effect=OSError()) - self.assertEquals(self.p.create_replica({'host': '', 'port': '', 'user': ''}, ''), 1) + with patch('subprocess.call', Mock(side_effect=[1, 0])): + self.assertEquals(self.p.create_replica(self.leader, ''), 0) + with patch('subprocess.call', Mock(side_effect=[Exception(), 0])): + self.assertEquals(self.p.create_replica(self.leader, ''), 0) def test_create_connection_users(self): cfg = self.p.config