Plugin 'sql' does not support multi workers configuration (Fluent::Plugin::SQLOutput)

[micdobro]

Any reason for not supporting multi worker configuration on output?

Using td-agent 4.3.0 fluentd 1.14.3 (438a82aead488a86180cd484bbc4e7e344a9032b). It looks like all SQL output plugins don't support it at all.

[Watson1978]

The error occurs because SQLOutput does not override multi_workers_ready?, which defaults to false in Fluentd's output plugin base class. Fluentd refuses to start any plugin under a workers configuration unless the plugin explicitly declares multi-worker support.

Technically, out_sql should be able to support multi workers: each worker process would maintain its own ActiveRecord connection pool and perform independent bulk inserts, with no shared local resources between workers. Enabling it is likely as simple as adding def multi_workers_ready?; true; end, but it needs verification — particularly around the fallback path and total DB connection count (pool × number of workers).