Merge #36196

36196: storage: debug page for RocksDB tickers/histograms r=tbg a=ajkr

Set up a debug page at "/_status/enginestats/<node_id>" that contains
values of all RocksDB ticker stats and histograms. It is also included
in debug zip.

A portion of the debug page (including both tickers and histograms)
looks like this:

![tickershistograms](https://user-images.githubusercontent.com/4780362/55138005-aa88ab00-50ef-11e9-83d6-cc335cc10e6e.png)

The debug zip file contains a JSON file named "debug/nodes/<node_id>/enginestats" with all the tickers/histograms, and looks like this:

```
{
  "stats": [
    {
      "storeId": 1,
      "tickersAndHistograms": {
        "tickers": {
          "rocksdb.blobdb.blob.file.bytes.read": "0",
...
          "rocksdb.write.wal": "296"
        },
        "histograms": {
          "rocksdb.blobdb.blob.file.read.micros": {
            "mean": 0,
            "p50": 0,
            "p95": 0,
            "p99": 0,
            "max": 0,
            "count": "0",
            "sum": "0"
          },
...
          "rocksdb.write.raw.block.micros": {
            "mean": 1.8235294117647058,
            "p50": 0.6071428571428571,
            "p95": 10.749999999999993,
            "p99": 12,
            "max": 12,
            "count": "17",
            "sum": "31"
          }
        }
      }
    }
  ]
}
```

Release Note: None

Co-authored-by: Andrew Kryczka <andrew.kryczka2@gmail.com>

Author: craig[bot]

c-deps/libroach/batch.cc

@@ -557,6 +557,8 @@ DBIterator* DBBatch::NewIter(DBIterOptions iter_options) {
 
 DBStatus DBBatch::GetStats(DBStatsResult* stats) { return FmtStatus("unsupported"); }
 
+DBStatus DBBatch::GetTickersAndHistograms(DBTickersAndHistogramsResult* stats) { return FmtStatus("unsupported"); }
+
 DBString DBBatch::GetCompactionStats() { return ToDBString("unsupported"); }
 
 DBStatus DBBatch::GetEnvStats(DBEnvStatsResult* stats) { return FmtStatus("unsupported"); }
@@ -654,6 +656,8 @@ DBIterator* DBWriteOnlyBatch::NewIter(DBIterOptions) { return NULL; }
 
 DBStatus DBWriteOnlyBatch::GetStats(DBStatsResult* stats) { return FmtStatus("unsupported"); }
 
+DBStatus DBWriteOnlyBatch::GetTickersAndHistograms(DBTickersAndHistogramsResult* stats) { return FmtStatus("unsupported"); }
+
 DBString DBWriteOnlyBatch::GetCompactionStats() { return ToDBString("unsupported"); }
 
 DBStatus DBWriteOnlyBatch::GetEnvStats(DBEnvStatsResult* stats) { return FmtStatus("unsupported"); }

c-deps/libroach/batch.h

@@ -40,6 +40,7 @@ struct DBBatch : public DBEngine {
   virtual DBStatus Get(DBKey key, DBString* value);
   virtual DBIterator* NewIter(DBIterOptions);
   virtual DBStatus GetStats(DBStatsResult* stats);
+  virtual DBStatus GetTickersAndHistograms(DBTickersAndHistogramsResult* stats);
   virtual DBString GetCompactionStats();
   virtual DBStatus GetEnvStats(DBEnvStatsResult* stats);
   virtual DBStatus GetEncryptionRegistries(DBEncryptionRegistries* result);
@@ -72,6 +73,7 @@ struct DBWriteOnlyBatch : public DBEngine {
   virtual DBStatus Get(DBKey key, DBString* value);
   virtual DBIterator* NewIter(DBIterOptions);
   virtual DBStatus GetStats(DBStatsResult* stats);
+  virtual DBStatus GetTickersAndHistograms(DBTickersAndHistogramsResult* stats);
   virtual DBString GetCompactionStats();
   virtual DBString GetEnvStats(DBEnvStatsResult* stats);
   virtual DBStatus GetEncryptionRegistries(DBEncryptionRegistries* result);

c-deps/libroach/db.cc

@@ -658,6 +658,17 @@ DBStatus DBPartialMergeOne(DBSlice existing, DBSlice update, DBString* new_value
 // write them to the provided DBStatsResult instance.
 DBStatus DBGetStats(DBEngine* db, DBStatsResult* stats) { return db->GetStats(stats); }
 
+// `DBGetTickersAndHistograms` retrieves maps of all RocksDB tickers and histograms.
+// It differs from `DBGetStats` by getting _every_ ticker and histogram, and by not
+// getting anything else (DB properties, for example).
+//
+// In addition to freeing the `DBString`s in the result, the caller is also
+// responsible for freeing `DBTickersAndHistogramsResult::tickers` and
+// `DBTickersAndHistogramsResult::histograms`.
+DBStatus DBGetTickersAndHistograms(DBEngine* db, DBTickersAndHistogramsResult* stats) {
+  return db->GetTickersAndHistograms(stats);
+}
+
 DBString DBGetCompactionStats(DBEngine* db) { return db->GetCompactionStats(); }
 
 DBStatus DBGetEnvStats(DBEngine* db, DBEnvStatsResult* stats) { return db->GetEnvStats(stats); }

c-deps/libroach/engine.cc

@@ -219,6 +219,50 @@ DBStatus DBImpl::GetStats(DBStatsResult* stats) {
   return kSuccess;
 }
 
+// `GetTickersAndHistograms` retrieves maps of all RocksDB tickers and histograms.
+// It differs from `GetStats` by getting _every_ ticker and histogram, and by not
+// getting anything else (DB properties, for example).
+//
+// In addition to freeing the `DBString`s in the result, the caller is also
+// responsible for freeing `DBTickersAndHistogramsResult::tickers` and
+// `DBTickersAndHistogramsResult::histograms`.
+DBStatus DBImpl::GetTickersAndHistograms(DBTickersAndHistogramsResult* stats) {
+  const rocksdb::Options& opts = rep->GetOptions();
+  const std::shared_ptr<rocksdb::Statistics>& s = opts.statistics;
+  stats->tickers_len = rocksdb::TickersNameMap.size();
+  // We malloc the result so it can be deallocated by the caller using free().
+  stats->tickers = static_cast<TickerInfo*>(
+      malloc(stats->tickers_len * sizeof(TickerInfo)));
+  if (stats->tickers == nullptr) {
+    return FmtStatus("malloc failed");
+  }
+  for (size_t i = 0; i < stats->tickers_len; ++i) {
+    stats->tickers[i].name = ToDBString(rocksdb::TickersNameMap[i].second);
+    stats->tickers[i].value = s->getTickerCount(static_cast<uint32_t>(i));
+  }
+
+  stats->histograms_len = rocksdb::HistogramsNameMap.size();
+  // We malloc the result so it can be deallocated by the caller using free().
+  stats->histograms = static_cast<HistogramInfo*>(
+      malloc(stats->histograms_len * sizeof(HistogramInfo)));
+  if (stats->histograms == nullptr) {
+    return FmtStatus("malloc failed");
+  }
+  for (size_t i = 0; i < stats->histograms_len; ++i) {
+    stats->histograms[i].name = ToDBString(rocksdb::HistogramsNameMap[i].second);
+    rocksdb::HistogramData data;
+    s->histogramData(static_cast<uint32_t>(i), &data);
+    stats->histograms[i].mean = data.average;
+    stats->histograms[i].p50 = data.median;
+    stats->histograms[i].p95 = data.percentile95;
+    stats->histograms[i].p99 = data.percentile99;
+    stats->histograms[i].max = data.max;
+    stats->histograms[i].count = data.count;
+    stats->histograms[i].sum = data.sum;
+  }
+  return kSuccess;
+}
+
 DBString DBImpl::GetCompactionStats() {
   std::string tmp;
   rep->GetProperty("rocksdb.cfstats-no-file-histogram", &tmp);

c-deps/libroach/engine.h

@@ -41,6 +41,7 @@ struct DBEngine {
   virtual DBStatus Get(DBKey key, DBString* value) = 0;
   virtual DBIterator* NewIter(DBIterOptions) = 0;
   virtual DBStatus GetStats(DBStatsResult* stats) = 0;
+  virtual DBStatus GetTickersAndHistograms(DBTickersAndHistogramsResult* stats) = 0;
   virtual DBString GetCompactionStats() = 0;
   virtual DBString GetEnvStats(DBEnvStatsResult* stats) = 0;
   virtual DBStatus GetEncryptionRegistries(DBEncryptionRegistries* result) = 0;
@@ -89,6 +90,7 @@ struct DBImpl : public DBEngine {
   virtual DBStatus Get(DBKey key, DBString* value);
   virtual DBIterator* NewIter(DBIterOptions);
   virtual DBStatus GetStats(DBStatsResult* stats);
+  virtual DBStatus GetTickersAndHistograms(DBTickersAndHistogramsResult* stats);
   virtual DBString GetCompactionStats();
   virtual DBStatus GetEnvStats(DBEnvStatsResult* stats);
   virtual DBStatus GetEncryptionRegistries(DBEncryptionRegistries* result);

c-deps/libroach/include/libroach.h

@@ -350,6 +350,29 @@ typedef struct {
   int64_t pending_compaction_bytes_estimate;
 } DBStatsResult;
 
+typedef struct {
+  DBString name;
+  uint64_t value;
+} TickerInfo;
+
+typedef struct {
+  DBString name;
+  double mean;
+  double p50;
+  double p95;
+  double p99;
+  double max;
+  uint64_t count;
+  uint64_t sum;
+} HistogramInfo;
+
+typedef struct {
+  TickerInfo* tickers;
+  size_t tickers_len;
+  HistogramInfo* histograms;
+  size_t histograms_len;
+} DBTickersAndHistogramsResult;
+
 // DBEnvStatsResult contains Env stats (filesystem layer).
 typedef struct {
   // Basic file encryption stats:
@@ -375,6 +398,7 @@ typedef struct {
 } DBEncryptionRegistries;
 
 DBStatus DBGetStats(DBEngine* db, DBStatsResult* stats);
+DBStatus DBGetTickersAndHistograms(DBEngine* db, DBTickersAndHistogramsResult* stats);
 DBString DBGetCompactionStats(DBEngine* db);
 DBStatus DBGetEnvStats(DBEngine* db, DBEnvStatsResult* stats);
 DBStatus DBGetEncryptionRegistries(DBEngine* db, DBEncryptionRegistries* result);