Snapshot manifest block added to prometheus (#232)

Co-authored-by: adria0.eth <5526331+adria0@users.noreply.github.com>

crates/ethcore/sync/src/api.rs

@@ -406,6 +406,11 @@ impl PrometheusMetrics for EthSync {
 
         let restoration = self.eth_handler.snapshot_service.restoration_status();
         let creation = self.eth_handler.snapshot_service.creation_status();
+        let (manifest_block_num, _) = self
+            .eth_handler
+            .snapshot_service
+            .manifest_block()
+            .unwrap_or((0, H256::zero()));
 
         prometheus_gauge(
             r,
@@ -427,6 +432,12 @@ impl PrometheusMetrics for EthSync {
                 0
             },
         );
+        prometheus_gauge(
+            r,
+            "snapshot_manifest_block",
+            "First block number of the present snapshot",
+            manifest_block_num as i64,
+        );
     }
 }
 

crates/ethcore/sync/src/tests/snapshot.rs

@@ -89,6 +89,12 @@ impl SnapshotService for TestSnapshotService {
         self.manifest.as_ref().cloned()
     }
 
+    fn manifest_block(&self) -> Option<(u64, H256)> {
+        self.manifest
+            .as_ref()
+            .map(|manifest| (manifest.block_number, manifest.block_hash))
+    }
+
     fn supported_versions(&self) -> Option<(u64, u64)> {
         Some((1, 2))
     }