Laravel Redis connection sharing: Why does the select method affect other connections?

The influence of Redis connection sharing and select methods under the Laravel framework

When using Redis in the Laravel framework, developers may encounter a problem: the Redis connection obtained through the configuration file will affect the same connection obtained before switching the database using select method. This article analyzes this problem and provides solutions.

Problem description: Suppose the code obtains a Redis connection named 'config1' through Redis::connection('config1') , and its configuration is as follows:

 'config1' => [
    'host' => 'xx',
    'password' => 'xx',
    'port' => 'xx',
    'database' => 2
]

Get the 'config1' connection twice, and perform select(3) on one of the connections to switch to database 3:

 $a = Redis::connection('config1');
$b = Redis::connection('config1');
$b->select(3);
$a->set('test1', 1); // 'test1' writes to database 3, not expected database 2

The result of $a->set('test1', 1) is surprising, because the expected data should be written to database 2. This is because the Redis connection management mechanism of the Laravel framework causes $a and $b to actually refer to the same Redis connection object.

\Illuminate\Support\Facades\Redis facade of the Laravel framework returns redis via getFacadeAccessor method, and redis is implemented by \Illuminate\Redis\RedisManager . The connection method of \Illuminate\Redis\RedisManager will cache the connection after the first parsing, and subsequent calls will directly return the same Redis instance.

Therefore, to avoid this problem, you cannot call Redis::connection() multiple times to get a standalone connection. The solution is to create a new connection instance using Laravel's resolve method:

 $a = app('redis')->connection('config1');
$b = app('redis')->connection('config1');
$b->select(3);
$a->set('test1', 1); // 'test1' will now write to database 2

Use app('redis')->connection('config1') to create a new connection instance every time, avoiding the issue of sharing the same underlying Redis connection and ensuring that each connection has an independent database selection. This solves the problem that select method affects other connections.

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