EventTracker cleanup

Summary:
1. **Fix member initializer order** (`EventTracker.cpp/.h`): Reorder the member initializer list and declarations so `sampler_` is initialized before `preQueueCallback_` and `postQueueCallback_`, matching the C++ rule that members are initialized in declaration order (avoids compiler warnings and potential undefined behavior if there were dependencies between them).

  2. **Remove dead includes** (`CacheAdmin.cpp`, `BUCK`): Remove unused `#include` of `LoggerEventSink.h` and `LunaSampler.h` from `CacheAdmin.cpp`  and their corresponding BUCK deps.

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Oncall Short Name: cachelib

Differential Revision: D96831625

fbshipit-source-id: 6abbe2420b768c50fb75d0430d5801116caf0cb9

Author: pbhandar2

cachelib/common/EventTracker.cpp

@@ -22,10 +22,10 @@ namespace cachelib {
 EventTracker::EventTracker(Config&& config)
     : eventInfoQueue_(config.queueSize),
       eventSink_(std::move(config.eventSink)),
-      preQueueCallback_(std::move(config.preQueueCallback)),
-      postQueueCallback_(std::move(config.postQueueCallback)),
       sampler_(config.sampler ? std::move(config.sampler)
-                              : std::make_unique<FurcHashSampler>(0)) {
+                              : std::make_unique<FurcHashSampler>(0)),
+      preQueueCallback_(std::move(config.preQueueCallback)),
+      postQueueCallback_(std::move(config.postQueueCallback)) {
   validateConfig();
   backgroundThread_ = std::thread([this]() { runBackgroundThread(); });
 }

cachelib/common/EventTracker.h

@@ -90,6 +90,12 @@ class EventTracker {
     uint32_t queueSize = 0;
     std::unique_ptr<EventSink> eventSink = nullptr;
 
+    // Optional custom sampler.
+    // If provided, this sampler will be used to determine whether a key
+    // should be sampled. If not provided, a default FurcHashSampler is
+    // created with sampling rate 0 (disabled).
+    std::unique_ptr<SamplerInterface> sampler = nullptr;
+
     // Callback invoked before queuing the event (in the caller's thread).
     // Use this for processing non-owning data (e.g., payload StringPiece)
     // that may not be valid by the time the background thread processes it.
@@ -99,12 +105,6 @@ class EventTracker {
     // Use this for processing owned data (e.g., parsing the key string)
     // to avoid adding latency to the hot path.
     std::function<void(EventInfo&)> postQueueCallback = nullptr;
-
-    // Optional custom sampler.
-    // If provided, this sampler will be used to determine whether a key
-    // should be sampled. If not provided, a default FurcHashSampler is
-    // created with sampling rate 0 (disabled).
-    std::unique_ptr<SamplerInterface> sampler = nullptr;
   };
 
   explicit EventTracker(Config&& config);
@@ -135,9 +135,9 @@ class EventTracker {
   folly::MPMCQueue<EventInfo> eventInfoQueue_;
 
   std::unique_ptr<EventSink> eventSink_;
+  std::unique_ptr<SamplerInterface> sampler_;
   std::function<void(EventInfo&)> preQueueCallback_;
   std::function<void(EventInfo&)> postQueueCallback_;
-  std::unique_ptr<SamplerInterface> sampler_;
 
   AtomicCounter recordCount_{0};
   AtomicCounter sampleAttemptCount_{0};