1 // Copyright 2022 gRPC authors.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 //     http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 
15 #ifndef GRPC_SRC_CORE_LIB_DEBUG_EVENT_LOG_H
16 #define GRPC_SRC_CORE_LIB_DEBUG_EVENT_LOG_H
17 
18 #include <grpc/support/port_platform.h>
19 
20 #include <stdint.h>
21 
22 #include <atomic>
23 #include <string>
24 #include <vector>
25 
26 #include "absl/base/thread_annotations.h"
27 #include "absl/strings/string_view.h"
28 #include "absl/types/span.h"
29 
30 #include "src/core/lib/gpr/time_precise.h"
31 #include "src/core/lib/gprpp/per_cpu.h"
32 #include "src/core/lib/gprpp/sync.h"
33 
34 namespace grpc_core {
35 
36 // Debug utility to collect a burst of events and then later log them as a
37 // detailed sequence.
38 // Collects (timestamp, counter-name, delta) and gives back a csv with
39 // timestamps and accumulated values for each counter in separate columns.
40 class EventLog {
41  public:
42   EventLog() = default;
43   ~EventLog();
44 
45   EventLog(const EventLog&) = delete;
46   EventLog& operator=(const EventLog&) = delete;
47 
48   void BeginCollection();
49   std::string EndCollectionAndReportCsv(
50       absl::Span<const absl::string_view> columns);
51 
Append(absl::string_view event,int64_t delta)52   static void Append(absl::string_view event, int64_t delta) {
53     EventLog* log = g_instance_.load(std::memory_order_acquire);
54     if (log == nullptr) return;
55     log->AppendInternal(event, delta);
56   }
57 
58  private:
59   struct Entry {
60     gpr_cycle_counter when;
61     absl::string_view event;
62     int64_t delta;
63   };
64 
65   struct Fragment {
66     Mutex mu;
67     std::vector<Entry> entries ABSL_GUARDED_BY(mu);
68   };
69 
70   void AppendInternal(absl::string_view event, int64_t delta);
71   std::vector<Entry> EndCollection(
72       absl::Span<const absl::string_view> wanted_events);
73 
74   PerCpu<Fragment> fragments_{PerCpuOptions().SetCpusPerShard(2)};
75   gpr_cycle_counter collection_begin_;
76   static std::atomic<EventLog*> g_instance_;
77 };
78 
79 }  // namespace grpc_core
80 
81 #endif  // GRPC_SRC_CORE_LIB_DEBUG_EVENT_LOG_H
82