Commit addressing several issues around this branch. Major changes to wal_e_restore script. Updated postgres0.yml to show example options.

patroni/postgresql.py

@@ -189,7 +189,7 @@ class Postgresql:
         r = parseurl(leader.conn_url)
 
         env = self.write_pgpass(r)
-        ret = self.create_replica(r, env) == 0
+        ret = self.create_replica(leader, env) == 0
         ret and self.delete_trigger_file()
         return ret
 
@@ -201,11 +201,11 @@ class Postgresql:
 
         return mconn
 
-    def create_replica(self, master_connection, env):
+    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 = self.build_connstring(master_connection)
+        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(',')]
@@ -213,7 +213,7 @@ class Postgresql:
         for replica_method in replica_methods:
             # if the method is basebackup, then use the built-in
             if replica_method == "basebackup":
-                ret = self.basebackup(connstring, env)
+                ret = self.basebackup(leader, env)
                 if ret == 0:
                     # if basebackup succeeds, exit with success
                     return 0
@@ -236,8 +236,14 @@ class Postgresql:
                     method_config.update({"scope": self.scope,
                                           "role": "replica",
                                           "datadir": self.data_dir,
-                                          "connstring": self.connstring})
+                                          "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
@@ -249,6 +255,10 @@ class Postgresql:
                     logger.exception('Error creating replica using method {0}: {1}'.format(replica_method, e.str))
                     ret = 1
 
+        # write the recovery.conf
+        if ret == 0:
+            self.write_recovery_conf(leader)
+
         # out of methods, return 1
         return 1
 
@@ -667,17 +677,18 @@ recovery_target_timeline = 'latest'
             logger.exception('Could not remove data directory %s', self.data_dir)
             self.move_data_directory()
 
-    def basebackup(self, master_connection, env):
+    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', '-R', '--pgdata=' + self.data_dir,
+                ret = subprocess.call(['pg_basebackup', '--pgdata=' + self.data_dir,
                                        '--xlog-method=stream', "--dbname=" + master_connection], env=env)
                 if ret == 0:
                     break

patroni/scripts/wale_restore.py

@@ -0,0 +1,227 @@
+#!/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
+
+# 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.
+
+# DO NOT USE with additional restore_commands; this script writes the restore command
+
+#   latest backup size
+import logging
+import os
+import psycopg2
+import subprocess
+import sys
+import argparse
+
+
+if sys.hexversion >= 0x03000000:
+    long = int
+
+logger = logging.getLogger(__name__)
+
+
+class Restore(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 = ''
+
+    def setup(self):
+        pass
+
+    def replica_method(self):
+        return self.create_replica_with_pg_basebackup
+
+    def replica_fallback_method(self):
+        return None
+
+    def run(self):
+        """ creates a new replica using either pg_basebackup or WAL-E """
+        method_fn = self.replica_method()
+        ret = method_fn() if method_fn else 1
+        if ret != 0 and self.replica_fallback_method() is not None:
+            ret = (self.replica_fallback_method())()
+        return ret
+
+    def create_replica_with_pg_basebackup(self):
+        try:
+            ret = subprocess.call(['pg_basebackup', '-R', '-D', '-x',
+                                   self.data_dir, '--host=' + self.master_connection['host'],
+                                   '--port=' + str(self.master_connection['port']),
+                                   '-U', self.master_connection['user']])
+        except Exception as e:
+            logger.error('Error when fetching backup with pg_basebackup: {0}'.format(e))
+            return 1
+        return ret
+
+
+class WALERestore(Restore):
+
+    def __init__(scope, role, datadir, connstring, env_dir, threshold_mb, threshold_pct, use_iam):
+        super(WALERestore, self).__init__(scope, role, datadir, connstring, env_dir, threshold_mb, threshold_pct, use_iam)
+        # check the environment variables
+        self.init_error = False
+
+    def setup(self):
+        # check that we actually have an envdir
+        if not os.path.exists(self.wal_e.dir):
+            self.init_error = True
+        else:
+            self.wal_e.cmd = 'envdir {0} wal-e {1} '.\
+                format(self.wal_e.dir, self.wal_e.iam_string)
+
+    def replica_method(self):
+        if self.should_use_s3_to_create_replica():
+            return self.create_replica_with_s3
+        return None
+
+    def replica_fallback_method(self):
+        return self.create_replica_with_pg_basebackup
+
+    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 write_recovery_conf_wale(self):
+        restore_cmd = '{0} wal_fetch "%f" "%p"'.format(self.wal_e.cmd)
+        with open(os.path.join(self.data_dir, 'recovery.conf'), 'w') as f:
+            f.write("""standby_mode = 'on'
+recovery_target_timeline = 'latest'
+""")
+            f.write("""primary_conninfo = '{}'\n""".format(self.master_connection))
+            f.write("""restore_command = '{}'\n""".format(restore_cmd))
+        return 0
+                    
+    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
+        
+        # if success, we need to write a recovery.conf for wal-e
+        # this doesn't work because we need data from main
+        #if ret == 0:
+            #ret = self.write_recovery_conf_wale()
+        
+        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)
+        restore.setup()
+        ret = restore.run()
+        if ret == 0:
+            break
+    
+    sys.exit(ret)

postgres0.yml

@@ -34,10 +34,6 @@ postgresql:
   data_dir: data/postgresql0
   maximum_lag_on_failover: 1048576 # 1 megabyte in bytes
   use_slots: True
-  pgpass: /tmp/pgpass0
-  pg_rewind:
-    username: postgres
-    password: zalando
   pg_hba:
   - host all all 0.0.0.0/0 md5
   - hostssl all all 0.0.0.0/0 md5
@@ -46,16 +42,20 @@ postgresql:
     password: rep-pass
     network:  127.0.0.1/32
   superuser:
-    username: postgres
     password: zalando
   admin:
     username: admin
     password: admin
-  wal_e:
-    env_dir: /home/postgres/etc/wal-e.d/env
-    threshold_megabytes: 10240
-    threshold_backup_size_percentage: 30
   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: /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
   parameters:
@@ -67,4 +67,3 @@ postgresql:
     archive_timeout: 1800s
     max_replication_slots: 5
     hot_standby: "on"
-    wal_log_hints: "on"

postgres1.yml

@@ -34,10 +34,6 @@ postgresql:
   data_dir: data/postgresql1
   maximum_lag_on_failover: 1048576 # 1 megabyte in bytes
   use_slots: True
-  pgpass: /tmp/pgpass1
-  pg_rewind:
-    username: postgres
-    password: zalando
   pg_hba:
   - host all all 0.0.0.0/0 md5
   - hostssl all all 0.0.0.0/0 md5
@@ -46,18 +42,24 @@ postgresql:
     password: rep-pass
     network: 127.0.0.1/32
   superuser:
-    user: postgres
     password: zalando
   admin:
     username: admin
     password: admin
+  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: /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
   #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
-  create_replica_method: basebackup
   parameters:
     archive_mode: "on"
     wal_level: hot_standby
@@ -67,4 +69,3 @@ postgresql:
     archive_timeout: 1800s
     max_replication_slots: 5
     hot_standby: "on"
-    wal_log_hints: "on"