Blocks leak and inflight for pending blocks (#315)

* attach `wait` to handle fut

* fix crash when can't find a CID and timeout hits

the exception was not raised, thus a Nil was returned that was
than wrapped in an option, leading to crash.


Signed-off-by: Csaba Kiraly <csaba.kiraly@gmail.com>

* add inFlight flag

* adding pending blocks tests

Signed-off-by: Csaba Kiraly <csaba.kiraly@gmail.com>
Co-authored-by: Csaba Kiraly <csaba.kiraly@gmail.com>

codex/blockexchange/engine/pendingblocks.nim

@@ -27,27 +27,37 @@ const
   DefaultBlockTimeout* = 10.minutes
 
 type
+  BlockReq* = object
+    handle*: Future[Block]
+    inFlight*: bool
+
   PendingBlocksManager* = ref object of RootObj
-    blocks*: Table[Cid, Future[Block]] # pending Block requests
+    blocks*: Table[Cid, BlockReq] # pending Block requests
 
 proc getWantHandle*(
   p: PendingBlocksManager,
   cid: Cid,
-  timeout = DefaultBlockTimeout): Future[Block] {.async.} =
+  timeout = DefaultBlockTimeout,
+  inFlight = false): Future[Block] {.async.} =
   ## Add an event for a block
   ##
 
-  if cid notin p.blocks:
-     p.blocks[cid] = newFuture[Block]().wait(timeout)
-     trace "Adding pending future for block", cid
-
   try:
-    return await p.blocks[cid]
+    if cid notin p.blocks:
+      p.blocks[cid] = BlockReq(
+        handle: newFuture[Block]("pendingBlocks.getWantHandle"),
+        inFlight: inFlight)
+
+      trace "Adding pending future for block", cid
+
+    return await p.blocks[cid].handle.wait(timeout)
   except CancelledError as exc:
     trace "Blocks cancelled", exc = exc.msg, cid
     raise exc
   except CatchableError as exc:
     trace "Pending WANT failed or expired", exc = exc.msg
+    # no need to cancel, it is already cancelled by wait()
+    raise exc
   finally:
     p.blocks.del(cid)
 
@@ -59,12 +69,22 @@ proc resolve*(
 
   for blk in blocks:
     # resolve any pending blocks
-    if blk.cid in p.blocks:
-      p.blocks.withValue(blk.cid, pending):
-        if not pending[].finished:
-          trace "Resolving block", cid = $blk.cid
-          pending[].complete(blk)
-          p.blocks.del(blk.cid)
+    p.blocks.withValue(blk.cid, pending):
+      if not pending[].handle.completed:
+        trace "Resolving block", cid = blk.cid
+        pending[].handle.complete(blk)
+
+proc setInFlight*(
+  p: PendingBlocksManager,
+  cid: Cid) =
+  p.blocks.withValue(cid, pending):
+    pending[].inFlight = true
+
+proc isInFlight*(
+  p: PendingBlocksManager,
+  cid: Cid): bool =
+  p.blocks.withValue(cid, pending):
+    result = pending[].inFlight
 
 proc pending*(
   p: PendingBlocksManager,
@@ -80,11 +100,10 @@ iterator wantList*(p: PendingBlocksManager): Cid =
 
 iterator wantHandles*(p: PendingBlocksManager): Future[Block] =
   for v in p.blocks.values:
-    yield v
+    yield v.handle
 
 func len*(p: PendingBlocksManager): int =
   p.blocks.len
 
 func new*(T: type PendingBlocksManager): T =
-  T(
-    blocks: initTable[Cid, Future[Block]]())
+  T()

tests/codex/blockexchange/testpendingblocks.nim

@@ -0,0 +1,80 @@
+import std/sequtils
+import std/algorithm
+
+import pkg/chronos
+import pkg/asynctest
+import pkg/libp2p
+import pkg/stew/byteutils
+
+import pkg/codex/blocktype as bt
+import pkg/codex/blockexchange
+
+import ../examples
+
+suite "Pending Blocks":
+  test "Should add want handle":
+    let
+      pendingBlocks = PendingBlocksManager.new()
+      blk = bt.Block.new("Hello".toBytes).tryGet
+      handle = pendingBlocks.getWantHandle(blk.cid)
+
+    check pendingBlocks.pending(blk.cid)
+
+  test "Should resolve want handle":
+    let
+      pendingBlocks = PendingBlocksManager.new()
+      blk = bt.Block.new("Hello".toBytes).tryGet
+      handle = pendingBlocks.getWantHandle(blk.cid)
+
+    check blk.cid in pendingBlocks
+    pendingBlocks.resolve(@[blk])
+    check (await handle) == blk
+    check blk.cid notin pendingBlocks
+
+  test "Should cancel want handle":
+    let
+      pendingBlocks = PendingBlocksManager.new()
+      blk = bt.Block.new("Hello".toBytes).tryGet
+      handle = pendingBlocks.getWantHandle(blk.cid)
+
+    check blk.cid in pendingBlocks
+    await handle.cancelAndWait()
+    check blk.cid notin pendingBlocks
+
+  test "Should expire want handle":
+    let
+      pendingBlocks = PendingBlocksManager.new()
+      blk = bt.Block.new("Hello".toBytes).tryGet
+      handle = pendingBlocks.getWantHandle(blk.cid, 1.millis)
+
+    check blk.cid in pendingBlocks
+
+    await sleepAsync(10.millis)
+    expect AsyncTimeoutError:
+      discard await handle
+
+    check blk.cid notin pendingBlocks
+
+  test "Should get wants list":
+    let
+      pendingBlocks = PendingBlocksManager.new()
+      blks = (0..9).mapIt( bt.Block.new(("Hello " & $it).toBytes).tryGet )
+      handles = blks.mapIt( pendingBlocks.getWantHandle( it.cid ) )
+
+    check:
+      blks.mapIt( $it.cid ).sorted(cmp[string]) ==
+      toSeq(pendingBlocks.wantList).mapIt( $it ).sorted(cmp[string])
+
+  test "Should get want handles list":
+    let
+      pendingBlocks = PendingBlocksManager.new()
+      blks = (0..9).mapIt( bt.Block.new(("Hello " & $it).toBytes).tryGet )
+      handles = blks.mapIt( pendingBlocks.getWantHandle( it.cid ) )
+      wantHandles = toSeq(pendingBlocks.wantHandles)
+
+    check wantHandles.len == handles.len
+    pendingBlocks.resolve(blks)
+
+    check:
+      (await allFinished(wantHandles)).mapIt( $it.read.cid ).sorted(cmp[string]) ==
+      (await allFinished(handles)).mapIt( $it.read.cid ).sorted(cmp[string])

tests/codex/testblockexchange.nim

@@ -3,5 +3,6 @@ import ./blockexchange/testnetwork
 import ./blockexchange/testpeerctxstore
 import ./blockexchange/testdiscovery
 import ./blockexchange/testprotobuf
+import ./blockexchange/testpendingblocks
 
 {.warning[UnusedImport]: off.}