Add a metric to track the number of managed files per column family i…

…n RocksDb (#19214)

We don't add more detailed level to control the cardinality of the
metrics.

Manually tested in local cluster:

<img width="1971" alt="Screenshot 2024-09-04 at 3 11 22 PM"
src="https://github.com/user-attachments/assets/968bb0ac-321f-4749-bc13-e5f852c93ea1">

## Description 

Describe the changes or additions included in this PR.

## Test plan 

How did you test the new or updated feature?

---

## Release notes

Check each box that your changes affect. If none of the boxes relate to
your changes, release notes aren't required.

For each box you select, include information after the relevant heading
that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] Indexer: 
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK:
- [ ] REST API:

crates/typed-store/src/metrics.rs

@@ -77,6 +77,7 @@ impl SamplingInterval {
 pub struct ColumnFamilyMetrics {
     pub rocksdb_total_sst_files_size: IntGaugeVec,
     pub rocksdb_total_blob_files_size: IntGaugeVec,
+    pub rocksdb_total_num_files: IntGaugeVec,
     pub rocksdb_current_size_active_mem_tables: IntGaugeVec,
     pub rocksdb_size_all_mem_tables: IntGaugeVec,
     pub rocksdb_num_snapshots: IntGaugeVec,
@@ -116,6 +117,13 @@ impl ColumnFamilyMetrics {
                 registry,
             )
             .unwrap(),
+            rocksdb_total_num_files: register_int_gauge_vec_with_registry!(
+                "rocksdb_total_num_files",
+                "Total number of files used in the column family",
+                &["cf_name"],
+                registry,
+            )
+            .unwrap(),
             rocksdb_current_size_active_mem_tables: register_int_gauge_vec_with_registry!(
                 "rocksdb_current_size_active_mem_tables",
                 "The current approximate size of active memtable (bytes).",

crates/typed-store/src/rocks/mod.rs

@@ -21,6 +21,7 @@ use bincode::Options;
 use collectable::TryExtend;
 use itertools::Itertools;
 use prometheus::{Histogram, HistogramTimer};
+use rocksdb::properties::num_files_at_level;
 use rocksdb::{
     checkpoint::Checkpoint, BlockBasedOptions, BottommostLevelCompaction, Cache, CompactOptions,
     DBPinnableSlice, LiveFile, OptimisticTransactionDB, SnapshotWithThreadMode,
@@ -911,7 +912,7 @@ impl<K, V> DBMap<K, V> {
     fn get_int_property(
         rocksdb: &RocksDB,
         cf: &impl AsColumnFamilyRef,
-        property_name: &'static std::ffi::CStr,
+        property_name: &std::ffi::CStr,
     ) -> Result<i64, TypedStoreError> {
         match rocksdb.property_int_value_cf(cf, property_name) {
             Ok(Some(value)) => Ok(value.try_into().unwrap()),
@@ -992,6 +993,19 @@ impl<K, V> DBMap<K, V> {
                 Self::get_int_property(rocksdb, &cf, ROCKSDB_PROPERTY_TOTAL_BLOB_FILES_SIZE)
                     .unwrap_or(METRICS_ERROR),
             );
+        // 7 is the default number of levels in RocksDB. If we ever change the number of levels using `set_num_levels`,
+        // we need to update here as well. Note that there isn't an API to query the DB to get the number of levels (yet).
+        let total_num_files: i64 = (0..=6)
+            .map(|level| {
+                Self::get_int_property(rocksdb, &cf, &num_files_at_level(level))
+                    .unwrap_or(METRICS_ERROR)
+            })
+            .sum();
+        db_metrics
+            .cf_metrics
+            .rocksdb_total_num_files
+            .with_label_values(&[cf_name])
+            .set(total_num_files);
         db_metrics
             .cf_metrics
             .rocksdb_current_size_active_mem_tables