Merge bd75928227 into 11eaebfd77

codex/erasure/erasure.nim

@@ -85,6 +85,10 @@ type
 
   ErasureError* = object of CodexError
   InsufficientBlocksError* = object of ErasureError
+    # Minimum size, in bytes, that the dataset must have had
+    # for the encoding request to have succeeded with the parameters
+    # provided.
+    minSize*: NBytes
 
 func indexToPos(steps, idx, step: int): int {.inline.} =
   ## Convert an index to a position in the encoded
@@ -240,11 +244,12 @@ proc init*(
   ecK: Natural, ecM: Natural,
   strategy: StrategyType): ?!EncodingParams =
   if ecK > manifest.blocksCount:
-    let exc = newException(InsufficientBlocksError,
-      "Unable to encode manifest, not enough blocks, ecK = " &
+    let exc = (ref InsufficientBlocksError)(
+      msg: "Unable to encode manifest, not enough blocks, ecK = " &
       $ecK &
       ", blocksCount = " &
-      $manifest.blocksCount)
+      $manifest.blocksCount,
+      minSize: ecK.NBytes * manifest.blockSize)
     return failure(exc)
 
   let

codex/rest/api.nim

@@ -461,7 +461,9 @@ proc initPurchasingApi(node: CodexNodeRef, router: var RestRouter) =
           expiry), error:
 
           if error of InsufficientBlocksError:
-            return RestApiResponse.error(Http400, "Insufficient blocks, increased dataset size required")
+            return RestApiResponse.error(Http400,
+            "Dataset too small for erasure parameters, need at least " &
+              $(ref InsufficientBlocksError)(error).minSize.int & " bytes")
 
           return RestApiResponse.error(Http500, error.msg)