processor: add log_sampling processor for rate limiting

Add new processor for log sampling with three window strategies:
- Fixed window: samples first N logs per time window
- Sliding window: maintains rolling rate limit
- Exponential decay: reduces sampling rate over time

Signed-off-by: Jorge Niedbalski <[email protected]>

Author: niedbalski

cmake/plugins_options.cmake

@@ -70,6 +70,7 @@ DEFINE_OPTION(FLB_IN_EBPF                     "Enable Linux eBPF input plugin"
 # ==========
 DEFINE_OPTION(FLB_PROCESSOR_CONTENT_MODIFIER  "Enable content modifier processor"            ON)
 DEFINE_OPTION(FLB_PROCESSOR_LABELS            "Enable metrics label manipulation processor"  ON)
+DEFINE_OPTION(FLB_PROCESSOR_LOG_SAMPLING      "Enable log sampling processor"                ON)
 DEFINE_OPTION(FLB_PROCESSOR_METRICS_SELECTOR  "Enable metrics selector processor"            ON)
 DEFINE_OPTION(FLB_PROCESSOR_OPENTELEMETRY_ENVELOPE "Enable OpenTelemetry envelope processor" ON)
 DEFINE_OPTION(FLB_PROCESSOR_SQL               "Enable SQL processor"                         ON)

plugins/CMakeLists.txt

@@ -345,6 +345,7 @@ REGISTER_IN_PLUGIN("in_random")
 # ==========
 REGISTER_PROCESSOR_PLUGIN("processor_content_modifier")
 REGISTER_PROCESSOR_PLUGIN("processor_labels")
+REGISTER_PROCESSOR_PLUGIN("processor_log_sampling")
 REGISTER_PROCESSOR_PLUGIN("processor_metrics_selector")
 REGISTER_PROCESSOR_PLUGIN("processor_opentelemetry_envelope")
 REGISTER_PROCESSOR_PLUGIN("processor_sampling")

plugins/processor_log_sampling/CMakeLists.txt

@@ -0,0 +1 @@
+FLB_PLUGIN(processor_log_sampling "log_sampling.c" "")