libcephfs: add API to get client perf counters

Fixes: http://tracker.ceph.com/issues/71233
Signed-off-by: Venky Shankar <[email protected]>

Author: vshankar

src/client/Client.cc

@@ -17483,6 +17483,23 @@ void Client::set_cap_epoch_barrier(epoch_t e)
   cap_epoch_barrier = e;
 }
 
+int Client::get_perf_counters(bufferlist *outbl) {
+  RWRef_t iref_reader(initialize_state, CLIENT_INITIALIZED);
+  if (!iref_reader.is_state_satisfied()) {
+    return -ENOTCONN;
+  }
+
+  ceph::bufferlist inbl;
+  std::ostringstream err;
+  std::vector<std::string> cmd{
+    "{\"prefix\": \"perf dump\"}",
+    "{\"format\": \"json\"}"
+  };
+
+  ldout(cct, 10) << __func__ << ": perf cmd=" << cmd << dendl;
+  return cct->get_admin_socket()->execute_command(cmd, inbl, err, outbl);
+}
+
 std::vector<std::string> Client::get_tracked_keys() const noexcept
 {
   static constexpr auto as_sv = std::to_array<std::string_view>({

src/client/Client.h

@@ -380,6 +380,8 @@ class Client : public Dispatcher, public md_config_obs_t {
 		     std::vector<std::pair<uint64_t,uint64_t>> *blocks);
   int file_blockdiff_finish(struct scan_state_t *state);
 
+  int get_perf_counters(bufferlist *outbl);
+
   /*
    * Get the next snapshot delta entry.
    *

src/include/cephfs/libcephfs.h

@@ -2285,6 +2285,23 @@ int ceph_get_snap_info(struct ceph_mount_info *cmount,
  * @param snap_info snapshot info struct (fetched via call to ceph_get_snap_info()).
  */
 void ceph_free_snap_info_buffer(struct snap_info *snap_info);
+
+/**
+ * perf counters via libcephfs API.
+ */
+
+/**
+ * Get a json string of performance counters
+ *
+ * @param cmount the ceph mount handle to use.
+ * @param perf_dump buffer holding the perf dump
+ *
+ * Returns 0 success with the performance counters populated in the
+ * passed in perf_dump buffer. Caller is responsible for freeing the
+ * @perf_dump buffer using free().
+ */
+int ceph_get_perf_counters(struct ceph_mount_info *cmount, char **perf_dump);
+
 #ifdef __cplusplus
 }
 #endif

src/libcephfs.cc

@@ -2540,3 +2540,14 @@ extern "C" void ceph_free_snap_info_buffer(struct snap_info *snap_info) {
   }
   free(snap_info->snap_metadata);
 }
+
+extern "C" int ceph_get_perf_counters(struct ceph_mount_info *cmount, char **perf_dump) {
+  bufferlist outbl;
+  int r = cmount->get_client()->get_perf_counters(&outbl);
+  if (r != 0) {
+    return r;
+  }
+
+  do_out_buffer(outbl, perf_dump, NULL);
+  return outbl.length();
+}