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processor: add log_sampling processor for rate limiting #10732

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processor: add log_sampling processor for rate limiting #10732

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c7166ee
processor: log_sampling: add new processor for rate limiting
niedbalski Aug 14, 2025
3ff1e70
tests: internal: add unit tests for log_sampling processor
niedbalski Aug 14, 2025
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1 change: 1 addition & 0 deletions cmake/plugins_options.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
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1 change: 1 addition & 0 deletions plugins/CMakeLists.txt
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Expand Up @@ -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")
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1 change: 1 addition & 0 deletions plugins/processor_log_sampling/CMakeLists.txt
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@@ -0,0 +1 @@
FLB_PLUGIN(processor_log_sampling "log_sampling.c" "")
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💡 Verification agent

🧩 Analysis chain

Link with libm when needed (pow) to avoid unresolved symbol errors

The implementation calls pow() (see log_sampling.c exponential strategy). On Unix-like systems, that usually requires linking libm. Consider conditionally adding m to deps.

Option A (simple; may fail on non-libm platforms):

-FLB_PLUGIN(processor_log_sampling "log_sampling.c" "")
+FLB_PLUGIN(processor_log_sampling "log_sampling.c" "m")

Option B (portable; detects libm presence):

include(CheckLibraryExists)
check_library_exists(m pow "" HAVE_LIBM)
if(HAVE_LIBM)
  FLB_PLUGIN(processor_log_sampling "log_sampling.c" "m")
else()
  FLB_PLUGIN(processor_log_sampling "log_sampling.c" "")
endif()

To verify current need for libm and pow usage across the tree, run:

🏁 Script executed:

#!/bin/bash
# Find pow() usage and any explicit -lm linkage in CMake files
rg -n "pow\\(" -g '!build' -S
rg -n --glob '!build' '\-lm| target_link_libraries\\([^)]*\\bm\\b' **/CMakeLists.txt

Length of output: 10968

Link libm for processor_log_sampling (pow used in log_sampling.c)

log_sampling.c calls pow() (plugins/processor_log_sampling/log_sampling.c:154). Add libm to the plugin link on platforms that require it.

Files to change:

  • plugins/processor_log_sampling/log_sampling.c — uses pow()
  • plugins/processor_log_sampling/CMakeLists.txt — update plugin linkage

Recommended (portable) change — detect libm and add "m" only when present:

+ include(CheckLibraryExists)
+ check_library_exists(m pow "" HAVE_LIBM)
+ if(HAVE_LIBM)
- FLB_PLUGIN(processor_log_sampling "log_sampling.c" "")
+   FLB_PLUGIN(processor_log_sampling "log_sampling.c" "m")
+ else()
+   FLB_PLUGIN(processor_log_sampling "log_sampling.c" "")
+ endif()

Simpler alternative (may be fine on most Unix-like systems):

-FLB_PLUGIN(processor_log_sampling "log_sampling.c" "")
+FLB_PLUGIN(processor_log_sampling "log_sampling.c" "m")
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
FLB_PLUGIN(processor_log_sampling "log_sampling.c" "")
include(CheckLibraryExists)
check_library_exists(m pow "" HAVE_LIBM)
if(HAVE_LIBM)
FLB_PLUGIN(processor_log_sampling "log_sampling.c" "m")
else()
FLB_PLUGIN(processor_log_sampling "log_sampling.c" "")
endif()

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