Is your feature request related to a problem? Please describe.
When writing an input plugin using flb_plugin_proxy (e.g. via fluent-bit-go), there is no way to emit metrics events. The proxy input collect callback in src/flb_plugin_proxy.c unconditionally calls flb_input_log_append(), so all data produced by proxy input plugins is treated as logs regardless of its actual type.
Describe the solution you'd like
Proxy input plugins should be able to declare an event_type and have the collect callback dispatch to the appropriate append function (flb_input_metrics_append(), flb_input_trace_append(), etc.) accordingly — mirroring how output proxy plugins already work:
// src/flb_plugin_proxy.c — output side already does this
if (def->event_type == 0) {
out->event_type = FLB_OUTPUT_LOGS;
} else {
out->event_type = def->event_type;
}Concretely, this would require:
- Using the event_type field in the proxy input plugin definition struct.
- Modifying flb_proxy_input_cb_collect() to call the correct append function based on that field.
- Exposing the metrics/trace append APIs through fluent-bit-go (and other language SDKs).
Describe alternatives you've considered
The only current alternative is to rewrite the plugin as a native C input plugin, which defeats the purpose of the proxy/SDK layer. Native plugins like in_opentelemetry already call flb_input_metrics_append() directly, but that API is not accessible to proxy plugins.
Additional context
The goal is to write a Go input plugin that collects metrics and forwards them as FLB_INPUT_METRICS events so they can be routed through a metrics pipeline to a metrics-aware output. Today this is impossible via the proxy layer — proxy input plugins can only feed the logs pipeline.
Is your feature request related to a problem? Please describe.
When writing an input plugin using flb_plugin_proxy (e.g. via fluent-bit-go), there is no way to emit metrics events. The proxy input collect callback in src/flb_plugin_proxy.c unconditionally calls flb_input_log_append(), so all data produced by proxy input plugins is treated as logs regardless of its actual type.
Describe the solution you'd like
Proxy input plugins should be able to declare an event_type and have the collect callback dispatch to the appropriate append function (flb_input_metrics_append(), flb_input_trace_append(), etc.) accordingly — mirroring how output proxy plugins already work:
Concretely, this would require:
Describe alternatives you've considered
The only current alternative is to rewrite the plugin as a native C input plugin, which defeats the purpose of the proxy/SDK layer. Native plugins like in_opentelemetry already call flb_input_metrics_append() directly, but that API is not accessible to proxy plugins.
Additional context
The goal is to write a Go input plugin that collects metrics and forwards them as FLB_INPUT_METRICS events so they can be routed through a metrics pipeline to a metrics-aware output. Today this is impossible via the proxy layer — proxy input plugins can only feed the logs pipeline.