Multple persistent connections to the same Redis host with different databases: database number changes #1920
Description
Expected behaviour
Redis documentation for the SELECT command says that
New connections always use the database 0
So subsequent SELECT commands on different connections should not change the database number for other connections, even if the database 0 was not explicitly selected.
And if the database for connection was changed for any reason, Redis::getDbNum() method should return database number being used.
Actual behaviour
I have the following script which runs in PHP-FPM:
<?php
$redis0 = new Redis();
$redis0->pconnect('redis', 6379, 0.0, 'redis0');
# No explicit select 0 here
$redis1 = new Redis();
$redis1->pconnect('redis', 6379, 0.0, 'redis1');
$redis1->select(1);
$redis2 = new Redis();
$redis2->pconnect('redis', 6379, 0.0, 'redis2');
$redis2->select(2);
echo $redis0->getDbNum();
$redis0->set('REDIS_0', '0');
echo $redis1->getDbNum();
$redis1->set('REDIS_1', '1');
echo $redis2->getDbNum();
$redis2->set('REDIS_2', '2');On the first and second requests the keys appear in correct databases (MONITOR output from redis-cli):
# Request 1
1611942079.015152 [0 172.18.0.9:45512] "SELECT" "1"
1611942079.016807 [0 172.18.0.9:45514] "SELECT" "2"
1611942079.017168 [0 172.18.0.9:45510] "SET" "REDIS_0" "0"
1611942079.017464 [1 172.18.0.9:45512] "SET" "REDIS_1" "1"
1611942079.017689 [2 172.18.0.9:45514] "SET" "REDIS_2" "2"
1611942219.691163 [2 172.18.0.1:47622] "flushall" # flushall from redis-cli
# Request 1
1611942223.955243 [0 172.18.0.9:45592] "SELECT" "1"
1611942223.955885 [0 172.18.0.9:45594] "SELECT" "2"
1611942223.956078 [0 172.18.0.9:45590] "SET" "REDIS_0" "0"
1611942223.956166 [1 172.18.0.9:45592] "SET" "REDIS_1" "1"
1611942223.956259 [2 172.18.0.9:45594] "SET" "REDIS_2" "2"
Checking the keys in redis-cli:
127.0.0.1:63799> keys *
1) "REDIS_0"
127.0.0.1:63799> select 1
OK
127.0.0.1:63799[1]> keys *
1) "REDIS_1"
127.0.0.1:63799[1]> select 2
OK
127.0.0.1:63799[2]> keys *
1) "REDIS_2"
However, on the third request (without flushall between requests) the "REDIS_0" key appears in the database 2:
1611942329.811933 [2 172.18.0.9:45514] "ECHO" "phpredis:601449b9c6073:1867ae6f"
1611942329.812692 [1 172.18.0.9:45512] "ECHO" "phpredis:601449b9c6586:3eac0768"
1611942329.813386 [1 172.18.0.9:45512] "SELECT" "1"
1611942329.813804 [0 172.18.0.9:45510] "ECHO" "phpredis:601449b9c6a0c:1bb3c7f6"
1611942329.814144 [0 172.18.0.9:45510] "SELECT" "2"
1611942329.814439 [2 172.18.0.9:45514] "SET" "REDIS_0" "0"
1611942329.814647 [1 172.18.0.9:45512] "SET" "REDIS_1" "1"
1611942329.814945 [2 172.18.0.9:45510] "SET" "REDIS_2" "2"
Checking the keys:
127.0.0.1:63799> keys *
1) "REDIS_0"
127.0.0.1:63799> select 1
OK
127.0.0.1:63799[1]> keys *
1) "REDIS_1"
127.0.0.1:63799[1]> select 2
OK
127.0.0.1:63799[2]> keys *
1) "REDIS_2"
2) "REDIS_0"
Meanwhile, during all the requests $redisN->getDbNum(); outputs correct database numbers: 0 1 2.
I'm seeing this behaviour on
- OS: Linux 5.10.9-201.fc33.x86_64 x86_64 (redis docker image)
- PHP: 7.4.13
- Redis: 6.0.8
- phpredis: 5.3.2
I've checked
- There is no similar issue from other users
- Issue isn't fixed in
developbranch - not sure how do I check that