Chaos test stand

[Pavkazzz]

Chaos Test Results

Tested against Docker cluster: 3 PostgreSQL 16 nodes (1 master + 2 replicas),
streaming replication, iptables-based network fault injection.

hasql 0.8.0 (master)

freeze_master -- iptables DROP on master, promote replica, unfreeze

Driver                Writes OK  Write Err   Reads OK   Read Err   Max W ms   Max R ms
---------------------------------------------------------------------------------------
asyncpg                      49          0         49          0      26835          1
aiopg                        50          0         50          0      26450          1
psycopg3                     49          0         49          0      26366          2
aiopg_sa                     50          0         50          0      26364          1
asyncsqlalchemy              49          0         49          0      26720         25

replica_failover -- kill both replicas, restart sequentially

Driver                Writes OK  Write Err   Reads OK   Read Err   Max W ms   Max R ms
---------------------------------------------------------------------------------------
asyncpg                      35          0         34          1          1         23
aiopg                        36          0         36          0          2          1
psycopg3                     36          0         36          0          3          2
aiopg_sa                     36          0         36          0          3          1
asyncsqlalchemy              36          0         35          1         23         25

hasql 0.10.0 (feature/types-and-split)

freeze_master

Driver                Writes OK  Write Err   Reads OK   Read Err   Max W ms   Max R ms
---------------------------------------------------------------------------------------
asyncpg                      49          0         49          0      26684          1
aiopg                        49          0         49          0      26798          1
psycopg3                     49          0         49          0      26743          2
aiopg_sa                     50          0         50          0      26724          1
asyncsqlalchemy              50          0         50          0      26579         25

replica_failover

Driver                Writes OK  Write Err   Reads OK   Read Err   Max W ms   Max R ms
---------------------------------------------------------------------------------------
asyncpg                      35          0         34          1          2         21
aiopg                        36          0         36          0          3          1
psycopg3                     36          0         36          0          3          1
aiopg_sa                     36          0         35          1          2          1
asyncsqlalchemy              36          0         35          1         22         24

Summary

• Zero write errors across all drivers in both versions and both scenarios
• freeze_master: all drivers survive master failover with ~26s blocked write (TCP timeout), reads uninterrupted
• replica_failover: asyncpg-based drivers (asyncpg, asyncsqlalchemy) show 1 transient read error on abrupt replica kill; aiopg and psycopg3 handle it cleanly
• No regressions in 0.10.0 -- behavior is identical to 0.8.0
• Unit tests: 140 passed (0.8.0), 277 passed (0.10.0)