This webinar will help you understand the differences between multiple replication approaches, the requirements of each strategy, what can be achieved with each of them, and hopefully, you'll be more informed to identify what you really need for your system. During this webinar, you will learn: - How physical replication works in PostgreSQL - How logical replication works in PostgreSQL - Differences between synchronous and asynchronous replication - Advantages, disadvantages, and challenges in multi-master replication - Which replication strategy is more suitable to different use cases

1. Variations on
PostgreSQL Replication
Boriss Mejías
Holistic System Software Engineer
Air Guitar Player
3 February 2021

2. Variations on
PostgreSQL Replication
Boriss Mejías
Solution Architect
Air Guitar Player
3 February 2021

3. Why this Talk?

4. Open Source Music
By Kiko Loureiro
https://gt.kikoloureiro.com/open-source/

6. Heavy Metal has its roots in Blues & Rock
Variations from the roots

7. Heavy Metal has its roots in Blues & Rock
Replication has its roots in Backup & Recovery
Variations from the roots

8. PostgreSQL resilient to crash

9. PostgreSQL resilient to crash

10. PostgreSQL resilient to crash

11. Physical backup

12. Physical backup and recovery

13. Physical streaming replication

14. Physical streaming replication

15. Read replica

16. Is it master or replica?
On master
wacken=# select pg_is_in_recovery();
pg_is_in_recovery
-------------------
f
On replica
wacken=# select pg_is_in_recovery();
pg_is_in_recovery
-------------------
t

17. Can you hear me !?

18. Can you hear me !?
wacken=# select * from pg_stat_replication;
-[ RECORD 1 ]----+------------------------------
pid | 14284
application_name | metal
client_addr | 172.17.0.3
state | streaming
sent_lsn | 0/3049320
write_lsn | 0/3049320
flush_lsn | 0/3049320
replay_lsn | 0/3049320
write_lag | 00:00:00.000628
flush_lag | 00:00:00.001741
replay_lag | 00:00:00.00224
sync_priority | 0
sync_state | async

19. Can you hear me !?
wacken=# select * from pg_stat_replication;
-[ RECORD 1 ]----+------------------------------
pid | 14284
application_name | metal
client_addr | 172.17.0.3
state | streaming
sent_lsn | 0/3049320
write_lsn | 0/3049320
flush_lsn | 0/3049320
replay_lsn | 0/3049320
write_lag | 00:00:00.000628
flush_lag | 00:00:00.001741
replay_lag | 00:00:00.00224
sync_priority | 0
sync_state | async

20. Physical streaming replication

31. Asynchronous replication

32. Asynchronous replication

33. Multiple replicas

34. Read-Writes to the master

35. Read-only to the replicas

36. Horizontal read scalability

37. Robustness

38. Robustness

39. Robustness with two locations

40. Cascading replication

41. Cascading replication

42. Such a fine line between cascading...
wacken is primary
at metal node
primary_conninfo='user=repmgr host=wacken port=5432 application_name=metal'
at power node
primary_conninfo='user=repmgr host=metal port=5432 application_name=rock'

43. Such a fine line between cascading...
wacken is primary
at metal node
primary_conninfo='user=repmgr host=wacken port=5432 application_name=metal'
at power node
primary_conninfo='user=repmgr host=metal port=5432 application_name=rock'

44. Cascading replication

45. Add a witness

46. Automated failover

47. Automated failover – network or node failure

48. Automated failover – network isolation

49. Cascading replication

50. Protect against human error

51. Physical streaming replication

52. Delayed physical streaming replication

53. Reduce data loss

54. Reduce data loss → synchronous replication

55. Reduce data loss → synchronous replication

56. Reduce data loss → synchronous replication

57. Lag really matters now
wacken=# select * from pg_stat_replication;
-[ RECORD 1 ]----+------------------------------
pid | 14284
application_name | metal
client_addr | 172.17.0.3
state | streaming
sent_lsn | 0/3049320
write_lsn | 0/3049320
flush_lsn | 0/3049320
replay_lsn | 0/3049320
write_lag | 00:00:00.000628
flush_lag | 00:00:00.001741
replay_lag | 00:00:00.00224
sync_priority | 1
sync_state | sync

58. Who is replicating
wacken=# select * from pg_stat_replication;
-[ RECORD 1 ]----+------------------------------
pid | 14284
application_name | metal synchronous_standby_names
client_addr | 172.17.0.3
state | streaming
sent_lsn | 0/3049320
write_lsn | 0/3049320
flush_lsn | 0/3049320
replay_lsn | 0/3049320
write_lag | 00:00:00.000628
flush_lag | 00:00:00.001741
replay_lag | 00:00:00.00224
sync_priority | 1
sync_state | sync

59. Who is replicating?
wacken=# select * from pg_stat_replication;
-[ RECORD 1 ]----+------------------------------
pid | 14284
application_name | metal synchronous_standby_names
client_addr | 172.17.0.3
state | streaming
sent_lsn | 0/3049320
write_lsn | 0/3049320
flush_lsn | 0/3049320
replay_lsn | 0/3049320
write_lag | 00:00:00.000628
flush_lag | 00:00:00.001741
replay_lag | 00:00:00.00224
sync_priority | 1
sync_state | sync

60. When is synchronously replicated?
wacken=# select * from pg_stat_replication;
-[ RECORD 1 ]----+------------------------------
pid | 14284
application_name | metal synchronous_standby_names
client_addr | 172.17.0.3
state | streaming
sent_lsn | 0/3049320
write_lsn | 0/3049320 remote_write
flush_lsn | 0/3049320 on
replay_lsn | 0/3049320 remote_apply
write_lag | 00:00:00.000628
flush_lag | 00:00:00.001741
replay_lag | 00:00:00.00224
sync_priority | 1
sync_state | sync

61. Reduce data loss → synchronous replication

62. Reduce data loss → synchronous replication

63. Reduce data loss → synchronous replication

64. When is synchronously replicated?
wacken=# select * from pg_stat_replication;
-[ RECORD 1 ]----+------------------------------
pid | 14284
application_name | metal synchronous_standby_names
client_addr | 172.17.0.3
state | streaming
sent_lsn | 0/3049320
write_lsn | 0/3049320 remote_write
flush_lsn | 0/3049320 on
replay_lsn | 0/3049320 remote_apply
write_lag | 00:00:00.000628
flush_lag | 00:00:00.001741
replay_lag | 00:00:00.00224
sync_priority | 1
sync_state | sync

65. Synchronous standby names

66. Synchronous standby names
synchronous_standby_names = ...
'FIRST 1 (metal, rock, blues)'
'FIRST 2 (rock, blues, metal)'
'ANY 2 (rock, blues, metal)'

67. Different places to be synchronous
synchronous_commit = ...
remote_write
on
remote_apply

68. Different places to be synchronous
synchronous_commit = ...
remote_write
on
remote_apply
local

69. Synchronous when it’s important

70. Synchronous when it’s important
synchronous_standby_names = 'ANY 1 (metal, rock, blues)'
synchronous_commit = local

71. Synchronous when it’s important
synchronous_standby_names = 'ANY 1 (metal, rock, blues)'
synchronous_commit = local
wacken=# SET synchronous_commit = remote_apply;
SET

72. Synchronous when it’s important
synchronous_standby_names = 'ANY 1 (metal, rock, blues)'
synchronous_commit = local
wacken=# SET synchronous_commit = remote_apply;
SET
wacken=# INSERT INTO orders (id, customer, item, quantity)
VALUES (2267709, 666, 'beer', 18);
INSERT 0 1

73. Synchronous when it’s important
synchronous_standby_names = 'ANY 1 (metal, rock, blues)'
synchronous_commit = local
wacken=# SET synchronous_commit = remote_apply;
SET
wacken=# INSERT INTO orders (id, customer, item, quantity)
VALUES (2267709, 666, 'beer', 18);
INSERT 0 1
wacken=# RESET synchronous_commit ;
RESET

74. Synchronous Replication

75. Synchronous Replication - Fragile

76. Synchronous Replication - OK

77. Synchronous Replication – 2 DC

78. Synchronous Replication – 2 DC

79. Synchronous Replication - Robust

80. Dynamic asynchronous / synchronous

81. Dynamic asynchronous / synchronous

82. Intermezzo

84. Physical streaming replication

85. Logical streaming replication

86. Logical streaming replication

87. Logical streaming replication

88. Upgrade major version

89. Upgrade major version and split

90. Upgrade full cluster

91. Upgrade full cluster

92. Upgrade full cluster

93. Upgrade full cluster

94. Upgrade full cluster

95. Progressive Metal

104. Conclusion

106. Open Source Community
It brings us a higher sense of community and
enhances our creativity and possibilities.
So why not take this concept to our art, our
music?
- Kiko Loureiro

107. Variations on
PostgreSQL Replication
Thank you
boriss.mejias@enterprisedb.com
@tchorix