Add more eth1 metrics (#728)

* Add metrics for junk eth1 votes

* Add eth1 cache metrics

beacon_node/beacon_chain/src/eth1_chain.rs

@@ -1,3 +1,4 @@
+use crate::metrics;
 use eth1::{Config as Eth1Config, Eth1Block, Service as HttpService};
 use eth2_hashing::hash;
 use exit_future::Exit;
@@ -351,6 +352,8 @@ impl<T: EthSpec, S: Store<T>> Eth1ChainBackend<T> for CachingEth1Backend<T, S> {
 fn random_eth1_data() -> Eth1Data {
     let mut rng = rand::thread_rng();
 
+    metrics::inc_counter(&metrics::JUNK_ETH1_VOTES);
+
     macro_rules! rand_bytes {
         ($num_bytes: expr) => {{
             let mut arr = [0_u8; $num_bytes];

beacon_node/beacon_chain/src/metrics.rs

@@ -153,6 +153,12 @@ lazy_static! {
     pub static ref CHECKPOINT_CACHE_MISSES: Result<IntCounter> =
         try_create_int_counter("beacon_checkpoint_cache_misses_total", "Count of times checkpoint cache fulfils request");
 
+    /*
+     * Eth1
+     */
+    pub static ref JUNK_ETH1_VOTES: Result<IntCounter> =
+        try_create_int_counter("beacon_eth1_junk_votes", "Count of times we have voted junk for eth1 dat");
+
     /*
      * Chain Head
      */