informative error message if you try to rewind before min(blockheight)

src/Chainweb/Pact/Backend/RelationalCheckpointer.hs

@@ -124,6 +124,7 @@ initRelationalCheckpointer' bstate sqlenv loggr v cid = do
             _cpRestore = doRestore v cid db
           , _cpSave = doSave db
           , _cpDiscard = doDiscard db
+          , _cpGetEarliestBlock = doGetEarliest db
           , _cpGetLatestBlock = doGetLatest db
           , _cpBeginCheckpointerBatch = doBeginBatch db
           , _cpCommitCheckpointerBatch = doCommitBatch db
@@ -231,6 +232,22 @@ doDiscard dbenv = runBlockEnv dbenv $ do
     --
     commitSavepoint Block
 
+doGetEarliest :: Db logger -> IO (Maybe (BlockHeight, BlockHash))
+doGetEarliest dbenv =
+  runBlockEnv dbenv $ callDb "getEarliestBlock" $ \db -> do
+    r <- qry_ db qtext [RInt, RBlob] >>= mapM go
+    case r of
+      [] -> return Nothing
+      (!o:_) -> return (Just o)
+  where
+    qtext = "SELECT blockheight, hash FROM BlockHistory \
+            \ ORDER BY blockheight ASC LIMIT 1"
+
+    go [SInt hgt, SBlob blob] =
+        let hash = either error id $ runGetEitherS decodeBlockHash blob
+        in return (fromIntegral hgt, hash)
+    go _ = fail "impossible"
+
 doGetLatest :: Db logger -> IO (Maybe (BlockHeight, BlockHash))
 doGetLatest dbenv =
     runBlockEnv dbenv $ callDb "getLatestBlock" $ \db -> do

src/Chainweb/Pact/Backend/Types.hs

@@ -297,6 +297,9 @@ data Checkpointer logger = Checkpointer
       -- ^ commits pending modifications to block, with the given blockhash
     , _cpDiscard :: !(IO ())
       -- ^ discard pending block changes
+    , _cpGetEarliestBlock :: !(IO (Maybe (BlockHeight, BlockHash)))
+      -- ^ get the checkpointer's idea of the earliest block. The block height
+      --   is the height of the block of the block hash.
     , _cpGetLatestBlock :: !(IO (Maybe (BlockHeight, BlockHash)))
       -- ^ get the checkpointer's idea of the latest block. The block height is
       -- is the height of the block of the block hash.

src/Chainweb/Pact/PactService/Checkpointer.hs

@@ -41,10 +41,10 @@ module Chainweb.Pact.PactService.Checkpointer
     -- There are two function for restoring the checkpointer for evaluation of back
     -- code:
     --
-    -- * 'withCheckPointerRewind' and
+    -- * 'withCheckpointerRewind' and
     -- * 'withCurrentCheckpointer'.
     --
-    -- 'withCheckPointerRewind' rewinds the checkpointer to the provided parent
+    -- 'withCheckpointerRewind' rewinds the checkpointer to the provided parent
     -- header. 'withCurrentCheckpointer' evaluates the pact transaction within the
     -- context of the current checkpointer state. Both functions update the value of
     -- '_psParentHeader' at the beginning and the end of each call.
@@ -171,7 +171,7 @@ data WithCheckpointerResult a
 --
 -- This function assumes that '_psParentHeader' has been updated to match the
 -- latest block in the checkpointers. This is guaranteed to be the case after
--- calling any of 'rewindTo', 'syncParentHeader', 'withCheckPointerRewind',
+-- calling any of 'rewindTo', 'syncParentHeader', 'withCheckpointerRewind',
 -- 'withCheckPointerWithoutRewind', or 'withCurrentCheckpointer'.
 --
 -- /NOTE:/
@@ -273,7 +273,7 @@ withCheckpointerRewind rewindLimit p caller act = do
 
 -- | Run a batch of checkpointer operations, possibly involving the evaluation
 -- transactions accross several blocks using more than a single call of
--- 'withCheckPointerRewind' or 'withCurrentCheckpointer', and persist the final
+-- 'withCheckpointerRewind' or 'withCurrentCheckpointer', and persist the final
 -- state. In case of an failure, the checkpointer is reverted to the initial
 -- state.
 --
@@ -308,7 +308,7 @@ withBatchIO runPact act = mask $ \umask -> do
 
 -- | Run a batch of checkpointer operations, possibly involving the evaluation
 -- transactions accross several blocks using more than a single call of
--- 'withCheckPointerRewind' or 'withCurrentCheckpointer', and discard the final
+-- 'withCheckpointerRewind' or 'withCurrentCheckpointer', and discard the final
 -- state at the end.
 --
 withDiscardedBatch :: PactServiceM logger tbl a -> PactServiceM logger tbl a
@@ -645,11 +645,19 @@ failOnTooLowRequestedHeight
     -> Maybe RewindLimit
     -> BlockHeader
     -> PactServiceM logger tbl ()
-failOnTooLowRequestedHeight parent (Just limit) lastHeader
-    | parentHeight + 1 + limitHeight < lastHeight = -- need to stick with addition because Word64
-        throwM $ RewindLimitExceeded limit parentHeight lastHeight parent
-  where
-    limitHeight = BlockHeight $ _rewindLimit limit
-    parentHeight = _blockHeight parent
-    lastHeight = _blockHeight lastHeader
+failOnTooLowRequestedHeight parent (Just limit) lastHeader = do
+  let limitHeight = BlockHeight $ _rewindLimit limit
+  let parentHeight = _blockHeight parent
+  let lastHeight = _blockHeight lastHeader
+  when (parentHeight + 1 + limitHeight < lastHeight) $ do -- need to stick with addition because Word64
+    throwM $ RewindLimitExceeded limit parentHeight lastHeight parent
+
+  cp <- getCheckpointer
+  mEarliestBlock <- liftIO $ _cpGetEarliestBlock cp
+  case mEarliestBlock of
+    Nothing -> error ""
+    Just (minBlockHeight, _) -> do
+      when (parentHeight < minBlockHeight) $ do
+        throwM $ RewindPastMinBlockHeight parentHeight parent minBlockHeight
+
 failOnTooLowRequestedHeight _ _ _ = return ()

src/Chainweb/Pact/PactService/ExecBlock.hs

@@ -102,8 +102,8 @@ setParentHeader msg ph@(ParentHeader bh) = do
 -- /NOTE:/
 --
 -- Any call of this function must occur within a dedicated call to
--- 'withChwithCheckpointerRewind', 'withCurrentCheckpointer' or
--- 'withCheckPointerWithoutRewind'.
+-- 'withCheckpointerRewind', 'withCurrentCheckpointer' or
+-- 'withCheckpointerWithoutRewind'.
 --
 execBlock
     :: (CanReadablePayloadCas tbl, Logger logger)

src/Chainweb/Pact/Service/Types.hs

@@ -202,6 +202,14 @@ data PactException
       , _rewindExceededTarget :: !BlockHeader
           -- ^ target header
       }
+  | RewindPastMinBlockHeight
+      { _rewindPastMinParentHeight :: !BlockHeight
+        -- ^ parent block height
+      , _rewindPastMinParentHeader :: !BlockHeader
+        -- ^ parent block header
+      , _rewindPastMinMinBlockHeight :: !BlockHeight
+        -- ^ min block height @SELECT MIN(blockheight) FROM BlockHistory@
+      }
   | BlockHeaderLookupFailure !Text
   | BuyGasFailure !GasPurchaseFailure
   | MempoolFillFailure !Text
@@ -230,6 +238,11 @@ instance J.Encode PactException where
     , "_rewindExceededForkHeight" J..= J.Aeson @Int (fromIntegral $ _rewindExceededForkHeight o)
     , "_rewindExceededTarget" J..= J.encodeWithAeson (_rewindExceededTarget o)
     ]
+  build o@(RewindPastMinBlockHeight{}) = tagged "RewindPastMinBlockHeight" $ J.object
+    [ "_rewindPastMinParentHeight" J..= J.Aeson @Int (fromIntegral $ _rewindPastMinParentHeight o)
+    , "_rewindPastMinParentHeader" J..= J.encodeWithAeson (_rewindPastMinParentHeader o)
+    , "_rewindPastMinMinBlockHeight" J..= J.Aeson @Int (fromIntegral $ _rewindPastMinMinBlockHeight o)
+    ]
   build (BlockHeaderLookupFailure msg) = tagged "BlockHeaderLookupFailure" msg
   build (BuyGasFailure failure) = tagged "BuyGasFailure" failure
   build (MempoolFillFailure msg) = tagged "MempoolFillFailure" msg

src/Chainweb/Pact/Types.hs

@@ -668,7 +668,6 @@ execPactServiceM
 execPactServiceM st env act
     = execStateT (runReaderT (_unPactServiceM act) env) st
 
-
 getCheckpointer :: PactServiceM logger tbl (Checkpointer logger)
 getCheckpointer = view psCheckpointer