rgw_sal_motr, motr_gc: [CORTX-33148] Add MotrGC::GCWorker class

For supporting concurrent IOs MotrGC need to have multiple GCWorker threads.
Introducing GCWorker class and changing the MotrGC interfaces to manage
all the worker threads.

Signed-off-by: Sumedh A. Kulkarni <sumedh.a.kulkarni@seagate.com>

src/rgw/motr/gc/gc.cc

@@ -15,17 +15,44 @@
 
 #include "gc.h"
 
-void *MotrGC::entry() {
-  std::unique_lock<std::mutex> lk(mtx);
-  ldpp_dout(dpp, 10) << __func__ << ": Motr GC started" << dendl;
+void *MotrGC::GCWorker::entry() {
+  // std::unique_lock<std::mutex> lk(lock);
+  // ldpp_dout(dpp, 10) << __func__ << ": Motr GC started" << dendl;
 
-  do {
-    ldpp_dout(dpp, 10) << __func__ << ": In a Motr GC loop." << dendl;
-    cv.wait_for(lk, std::chrono::milliseconds(gc_interval * 10));
-  } while (! stop_signalled);
+  // do {
+  //   ldpp_dout(dpp, 10) << __func__ << ": In a Motr GC loop." << dendl;
+  //   cv.wait_for(lk, std::chrono::milliseconds(gc_interval * 10));
+  // } while (! stop_signalled);
 
-  ldpp_dout(dpp, 0) << __func__ << ": Stop signalled called.#" 
-    << stop_signalled << dendl;
+  // ldpp_dout(dpp, 0) << __func__ << ": Stop signalled called.#" 
+  //   << stop_signalled << dendl;
   return nullptr;
 }
 
+void MotrGC::initialize(CephContext *_cct, rgw::sal::Store* _store) {
+  cct = _cct;
+  store = _store;
+  // fetch num_max_queue from config
+  // create all gc queues in motr index store
+}
+
+void MotrGC::start_processor() {
+  // fetch max_concurrent_io i.e. max_threads to create from config.
+  // start all the gc_worker threads
+}
+
+void MotrGC::stop_processor() {
+  // in case of stop signal,
+  // gracefully shutdown all the gc threads.
+  down_flag = true;
+  for (auto& worker : workers) {
+    worker->stop();
+    worker->join();
+  }
+  workers.clear();
+}
+
+void MotrGC::GCWorker::stop() {
+  std::lock_guard l{lock};
+  cv.notify_all();
+}

src/rgw/motr/gc/gc.h

@@ -20,28 +20,47 @@
 #include "common/Thread.h"
 #include <mutex>
 #include <condition_variable>
+#include <atomic>
 
-class MotrGC : public Thread {
- private: 
-  const DoutPrefixProvider *dpp;
+class MotrGC : public DoutPrefixProvider {
+ private:
+  CephContext *cct;
   rgw::sal::Store *store;
-  std::mutex mtx;
-  std::condition_variable cv;
-  bool stop_signalled = false;
-  uint32_t gc_interval = 60*60;  // default: 24*60*60 sec
-  uint32_t gc_obj_min_wait = 60*60;  // 60*60sec default
+  int max_indices = 0;
+  std::vector<std::string> index_names;
+  std::atomic<bool> down_flag = false;
 
  public:
-  MotrGC(const DoutPrefixProvider *_dpp, rgw::sal::Store* _store) :
-         dpp(_dpp), store(_store) {}
+  class GCWorker : public Thread {
+   private:
+    const DoutPrefixProvider *dpp;
+    CephContext *cct;
+    MotrGC *motr_gc;
+    int worker_id;
+    uint32_t gc_interval = 60*60;  // default: 24*60*60 sec
+    std::mutex lock;
+    std::condition_variable cv;
+   public:
+    GCWorker(const DoutPrefixProvider* _dpp, CephContext *_cct,
+             MotrGC *_motr_gc, int _worker_id)
+      : dpp(_dpp), cct(_cct), motr_gc(_motr_gc), worker_id(_worker_id) {};
 
-  void *entry() override;
+    void *entry() override;
+    void stop();
+  };
+  std::vector<std::unique_ptr<MotrGC::GCWorker>> workers;
 
-  void signal_stop() {
-    std::lock_guard<std::mutex> lk_guard(mtx);
-    stop_signalled = true;
-    cv.notify_all();  
+  MotrGC() : cct(nullptr), store(nullptr) {}
+  ~MotrGC() {
+    stop_processor();
+    finalize();
   }
+
+  void initialize(CephContext *_cct, rgw::sal::Store* _store);
+  void finalize();
+
+  void start_processor();
+  void stop_processor();
 };
 
 #endif

src/rgw/rgw_sal_motr.cc

@@ -1485,24 +1485,23 @@ int MotrStore::initialize(CephContext *cct, const DoutPrefixProvider *dpp) {
   if (use_gc_thread) {
     int rc = create_gc(dpp);
     if (rc != 0)
-      ldpp_dout(dpp, 0) << __func__ << ": Metadata cache init failed " <<
+      ldpp_dout(dpp, 0) << __func__ << ": Failed to Create MotrGC " <<
         "with rc = " << rc << dendl;
   }
   return rc;
 }
 
 int MotrStore::create_gc(const DoutPrefixProvider *dpp) {
   int ret = 0;
-  // [TODO] Create multiple GC threads as per config
-  gc_worker = std::make_unique<MotrGC>(dpp, this);
-  gc_worker->create("motr_gc");
+  motr_gc->initialize(cctx, this);
+  motr_gc->start_processor();
   return ret;
 }
 
 void MotrStore::stop_gc() {
-  if (gc_worker) {
-    gc_worker->signal_stop();
-    gc_worker->join();
+  if (motr_gc) {
+    motr_gc->stop_processor();
+    motr_gc->finalize();
   }
 }
 

src/rgw/rgw_sal_motr.h

@@ -987,7 +987,7 @@ class MotrStore : public Store {
 
     // [TODO] Create vector of gc_workers
     //        size is input from `rgw_gc_max_concurrent_io`
-    std::unique_ptr<MotrGC> gc_worker;
+    std::unique_ptr<MotrGC> motr_gc;
     bool use_gc_thread;
     bool use_cache;