CardanoSolutions · KtorZ · Jan 24, 2022 · Jan 24, 2022 · Jan 24, 2022 · Jan 24, 2022
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -17,13 +17,16 @@ pre: "<b>6. </b>"
 >
 >   A version of `cardano-node@1.33.1` patched with the necessary commits can be found at [CardanoSolutions/cardano-node@1.33.1+local-tx-monitor](https://github.com/CardanoSolutions/cardano-node/releases/tag/1.33.1+local-tx-monitor).
 >
-> - `connectionStatus` in the health object, taking `"connected"` or `"disconnected"` as values to reflect the current connection status with the node. [#154](https://github.com/CardanoSolutions/ogmios/issues/154)
+> - New fields in the health object:
+>   - `connectionStatus` → `"connected"` or `"disconnected"`, to reflect status with the node. [#154](https://github.com/CardanoSolutions/ogmios/issues/154)
+>   - `currentEpoch` → which returns the current known epoch of the linked node [#164](https://github.com/CardanoSolutions/ogmios/issues/164)
+>   - `slotInEpoch` → which returns the relative number of slots elapsed in the current epoch [#164](https://github.com/CardanoSolutions/ogmios/issues/154)
 >
 > - New `ogmios health-check` command, useful to perform simple health check on a running server. For example, to monitor a container via Docker health check mechanism:
 >   ```Dockerfile
 >   HEALTHCHECK --interval=10s --timeout=5s --retries=1 CMD /bin/ogmios health-check
 >   ```
-> - Bumped internal dependencies to Cardano's 1.33.0 eco-system.
+> - Bumped internal dependencies to Cardano's 1.33.* eco-system.
 
 #### Changed
 

diff --git a/clients/TypeScript/packages/client/test/ServerHealth.test.ts b/clients/TypeScript/packages/client/test/ServerHealth.test.ts
@@ -9,8 +9,12 @@ const expectHealth = (obj: any): void => {
       'lastTipUpdate',
       'metrics',
       'startTime',
-      'networkSynchronization'
+      'networkSynchronization',
+      'currentEpoch',
+      'slotInEpoch'
     ]))
+  expect(obj.currentEpoch).not.toBe(null)
+  expect(obj.slotInEra).not.toBe(null)
 }
 
 describe('ServerHealth', () => {

diff --git a/docs/content/getting-started/monitoring.md b/docs/content/getting-started/monitoring.md
@@ -45,7 +45,9 @@ $ curl -H 'Accept: application/json' http://localhost:1337/health
     },
     "networkSynchronization": 0.99,
     "currentEra": "Mary",
-    "connectionStatus": "disconnected"
+    "connectionStatus": "disconnected",
+    "currentEpoch": 164,
+    "slotInEpoch": 324543
 }
 ```
 
@@ -59,6 +61,8 @@ All information are computed at runtime and **not preserved between restarts** (
 | `lastKnownTip`                         | Last known chain tip received from the node (can be `null`)                                                                       |
 | `networkSynchronization`               | A **(nullable)** percentage indicator of how far the server/node is from the network tip. `1` means it is synchronized.           |
 | `currentEra`                           | The **(nullable)** current Cardano era of the underlying node. Useful for state-queries and debugging.                            |
+| `currentEpoch`                         | The **(nullable)** current epoch number known of the underlying node.                                                             |
+| `slotInEpoch`                          | The **(nullable)** relative slot number within the current epoch.                                                                 |
 | `metrics.activeConnections`            | Number of WebSocket connections currently established with the server.                                                            |
 | `metrics.totalConnections`             | Total number of WebSocket connections established with the server since it's started.                                             |
 | `metrics.sessionDurations`             | Some time measures (`min`, `max`, `mean`) of the duration of each sessions, in milliseconds.                                      |

diff --git a/server/src/Ogmios/App/Health.hs b/server/src/Ogmios/App/Health.hs
@@ -57,8 +57,10 @@ import Ogmios.Control.MonadSTM
 import Ogmios.Data.Health
     ( CardanoEra (..)
     , ConnectionStatus (..)
+    , EpochNo (..)
     , Health (..)
     , NetworkSynchronization
+    , SlotInEpoch (..)
     , emptyHealth
     , mkNetworkSynchronization
     , modifyHealth
@@ -79,7 +81,7 @@ import Network.TypedProtocol.Pipelined
 import Ouroboros.Consensus.HardFork.Combinator
     ( HardForkBlock, eraIndexToInt )
 import Ouroboros.Consensus.HardFork.History.Qry
-    ( interpretQuery, slotToWallclock )
+    ( interpretQuery, slotToEpoch', slotToWallclock )
 import Ouroboros.Network.Block
     ( Point (..), Tip (..), genesisPoint, getTipPoint )
 import Ouroboros.Network.NodeToClient
@@ -135,13 +137,19 @@ newHealthCheckClient tr Debouncer{debounce} = do
         { chainSyncClient = mkHealthCheckClient $ \lastKnownTip -> debounce $ do
             tvar <- asks (view typed)
             metrics <- join (Metrics.sample <$> asks (view typed) <*> asks (view typed))
-            (now, Just -> networkSynchronization, Just -> currentEra) <- getNetworkInformation lastKnownTip
+            ( now
+              , Just -> networkSynchronization
+              , (Just -> currentEpoch, Just -> slotInEpoch)
+              , Just -> currentEra
+              ) <- getNetworkInformation lastKnownTip
             health <- modifyHealth tvar $ \h -> h
                 { lastKnownTip
                 , lastTipUpdate = Just now
                 , networkSynchronization
                 , currentEra
                 , metrics
+                , currentEpoch
+                , slotInEpoch
                 , connectionStatus = Connected
                 }
             logWith tr (HealthTick health)
@@ -268,23 +276,23 @@ newTimeInterpreterClient
         , HasType NetworkParameters env
         )
     => m ( LocalStateQueryClient block (Point block) (Ledger.Query block) m ()
-         , Tip block -> m (UTCTime, NetworkSynchronization, CardanoEra)
+         , Tip block -> m (UTCTime, NetworkSynchronization, (EpochNo, SlotInEpoch), CardanoEra)
          )
 newTimeInterpreterClient = do
     notifyTip <- atomically newEmptyTMVar
     getResult <- atomically newEmptyTMVar
     return
         ( LocalStateQueryClient $ clientStIdle
             (atomically $ takeTMVar notifyTip)
-            (\a0 a1 a2 -> atomically $ putTMVar getResult (a0, a1, a2))
+            (\a0 a1 a2 a3 -> atomically $ putTMVar getResult (a0, a1, a2, a3))
         , \tip -> do
             atomically $ putTMVar notifyTip tip
             atomically $ takeTMVar getResult
         )
   where
     clientStIdle
         :: m (Tip block)
-        -> (UTCTime -> NetworkSynchronization -> CardanoEra -> m ())
+        -> (UTCTime -> NetworkSynchronization -> (EpochNo, SlotInEpoch) -> CardanoEra -> m ())
         -> m (LSQ.ClientStIdle block (Point block) (Ledger.Query block) m ())
     clientStIdle getTip notifyResult =
         pure $ LSQ.SendMsgAcquire Nothing $ LSQ.ClientStAcquiring
@@ -296,7 +304,7 @@ newTimeInterpreterClient = do
 
     clientStAcquired
         :: m (Tip block)
-        -> (UTCTime -> NetworkSynchronization -> CardanoEra -> m ())
+        -> (UTCTime -> NetworkSynchronization -> (EpochNo, SlotInEpoch) -> CardanoEra -> m ())
         -> m (LSQ.ClientStAcquired block (Point block) (Ledger.Query block) m ())
     clientStAcquired getTip notifyResult = do
         tip <- getTip
@@ -310,7 +318,7 @@ newTimeInterpreterClient = do
             }
 
     clientStQuerySlotTime
-        :: (UTCTime -> NetworkSynchronization -> CardanoEra -> m ())
+        :: (UTCTime -> NetworkSynchronization -> (EpochNo, SlotInEpoch) -> CardanoEra -> m ())
         -> (Tip block)
         -> m (LSQ.ClientStAcquired block (Point block) (Ledger.Query block) m ())
         -> LSQ.ClientStAcquired block (Point block) (Ledger.Query block) m ()
@@ -321,17 +329,22 @@ newTimeInterpreterClient = do
                 let slot = case tip of
                         TipGenesis -> 0
                         Tip sl _ _ -> sl
-                case interpreter `interpretQuery` slotToWallclock slot of
+                let result = (,)
+                        <$> (interpreter `interpretQuery` slotToWallclock slot)
+                        <*> (interpreter `interpretQuery` slotToEpoch' slot)
+                case result of
                     -- NOTE: This request cannot fail in theory because the tip
                     -- is always known of the interpreter. If that every happens
                     -- because of some weird condition, retrying should do.
                     Left{} ->
                         pure (clientStQuerySlotTime notifyResult tip continue)
-                    Right (slotTime, _) -> do
+                    Right ((slotTime, _), (epochNo, SlotInEpoch -> slotInEpoch)) -> do
                         NetworkParameters{systemStart} <- asks (view typed)
                         now <- getCurrentTime
                         let networkSync = mkNetworkSynchronization systemStart now slotTime
-                        pure (clientStQueryCurrentEra (notifyResult now networkSync) continue)
+                        pure $ clientStQueryCurrentEra
+                            (notifyResult now networkSync (epochNo, slotInEpoch))
+                            continue
             }
 
     clientStQueryCurrentEra

diff --git a/server/src/Ogmios/Data/Health.hs b/server/src/Ogmios/Data/Health.hs
@@ -4,6 +4,7 @@
 
 {-# LANGUAGE DeriveAnyClass #-}
 {-# LANGUAGE DerivingVia #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE UndecidableInstances #-}
 
 module Ogmios.Data.Health
@@ -12,6 +13,8 @@ module Ogmios.Data.Health
     , CardanoEra (..)
     , ConnectionStatus (..)
     , Tip (..)
+    , SlotInEpoch (..)
+    , EpochNo (..)
     , emptyHealth
     , modifyHealth
       -- ** NetworkSynchronization
@@ -28,6 +31,8 @@ import Ogmios.Control.MonadSTM
 import Ogmios.Data.Metrics
     ( Metrics, emptyMetrics )
 
+import Cardano.Slotting.Slot
+    ( EpochNo (..) )
 import Data.Aeson
     ( ToJSON (..), genericToEncoding )
 import Data.ByteString.Builder.Scientific
@@ -77,6 +82,10 @@ data Health block = Health
     -- ^ Application metrics measured at regular interval.
     , connectionStatus :: !ConnectionStatus
     -- ^ State of the connectino with the underlying node.
+    , currentEpoch :: !(Maybe EpochNo)
+    -- ^ Current known epoch number
+    , slotInEpoch :: !(Maybe SlotInEpoch)
+    -- ^ Relative slot number within the epoch
     } deriving stock (Generic, Eq, Show)
 
 instance ToJSON (Tip block) => ToJSON (Health block) where
@@ -91,6 +100,8 @@ emptyHealth startTime = Health
     , currentEra = empty
     , metrics = emptyMetrics
     , connectionStatus = Disconnected
+    , currentEpoch = empty
+    , slotInEpoch = empty
     }
 
 modifyHealth
@@ -105,6 +116,10 @@ modifyHealth tvar fn =
         health <- fn <$> readTVar tvar
         health <$ writeTVar tvar health
 
+newtype SlotInEpoch = SlotInEpoch
+    { getSlotInEpoch :: Word64
+    } deriving stock (Generic, Eq, Show)
+      deriving newtype (ToJSON)
 
 -- | Captures how far is our underlying node from the network, in percentage.
 -- This is calculated using:

diff --git a/server/test/unit/Ogmios/Data/HealthSpec.hs b/server/test/unit/Ogmios/Data/HealthSpec.hs
@@ -52,6 +52,8 @@ spec = parallel $ do
             currentEra health `shouldBe` Nothing
             metrics health `shouldBe` emptyMetrics
             connectionStatus health `shouldBe` Disconnected
+            currentEpoch health `shouldBe` Nothing
+            slotInEpoch health `shouldBe` Nothing
 
     context "NetworkSynchronization" $ do
         let matrix =