fix(subscriptions): filter not found recreates polling filter (#78)

ethers.nimble

@@ -15,6 +15,6 @@ requires "stew"
 requires "eth#c482b4c5b658a77cc96b49d4a397aa6d98472ac7"
 
 task test, "Run the test suite":
-  exec "nimble install -d -y"
+  # exec "nimble install -d -y"
   withDir "testmodule":
     exec "nimble test"

ethers/providers/jsonrpc/subscriptions.nim

@@ -1,5 +1,6 @@
 import std/tables
 import std/sequtils
+import std/strutils
 import pkg/chronos
 import pkg/json_rpc/rpcclient
 import ../../basics
@@ -132,16 +133,31 @@ type
   PollingSubscriptions = ref object of JsonRpcSubscriptions
     polling: Future[void]
 
+    # We need to keep around the filters that are used to create log filters on the RPC node
+    # as there might be a time when they need to be recreated as RPC node might prune/forget
+    # about them
+    filters: Table[JsonNode, EventFilter]
+
+    # Used when filters are recreated to translate from the id that user
+    # originally got returned to new filter id
+    subscriptionMapping: Table[JsonNode, JsonNode]
+
 proc new*(_: type JsonRpcSubscriptions,
           client: RpcHttpClient,
           pollingInterval = 4.seconds): JsonRpcSubscriptions =
 
   let subscriptions = PollingSubscriptions(client: client)
 
-  proc getChanges(id: JsonNode): Future[JsonNode] {.async.} =
+  proc getChanges(originalId: JsonNode): Future[JsonNode] {.async.} =
     try:
-      return await subscriptions.client.eth_getFilterChanges(id)
-    except CatchableError:
+      let mappedId = subscriptions.subscriptionMapping[originalId]
+      return await subscriptions.client.eth_getFilterChanges(mappedId)
+    except CatchableError as e:
+      if "filter not found" in e.msg:
+        let filter = subscriptions.filters[originalId]
+        let newId = await subscriptions.client.eth_newFilter(filter)
+        subscriptions.subscriptionMapping[originalId] = newId
+
       return newJArray()
 
   proc poll(id: JsonNode) {.async.} =
@@ -180,6 +196,7 @@ method subscribeBlocks(subscriptions: PollingSubscriptions,
 
   let id = await subscriptions.client.eth_newBlockFilter()
   subscriptions.callbacks[id] = callback
+  subscriptions.subscriptionMapping[id] = id
   return id
 
 method subscribeLogs(subscriptions: PollingSubscriptions,
@@ -194,10 +211,14 @@ method subscribeLogs(subscriptions: PollingSubscriptions,
 
   let id = await subscriptions.client.eth_newFilter(filter)
   subscriptions.callbacks[id] = callback
+  subscriptions.filters[id] = filter
+  subscriptions.subscriptionMapping[id] = id
   return id
 
 method unsubscribe*(subscriptions: PollingSubscriptions,
                    id: JsonNode)
                   {.async.} =
+  discard await subscriptions.client.eth_uninstallFilter(subscriptions.subscriptionMapping[id])
+  subscriptions.filters.del(id)
   subscriptions.callbacks.del(id)
-  discard await subscriptions.client.eth_uninstallFilter(id)
+  subscriptions.subscriptionMapping.del(id)

testmodule/providers/jsonrpc/rpc_mock.nim

@@ -0,0 +1,50 @@
+import ../../examples
+import ../../../ethers/provider
+import ../../../ethers/providers/jsonrpc/conversions
+
+import std/tables
+import pkg/stew/byteutils
+import pkg/json_rpc/rpcserver except `%`, `%*`
+import pkg/json_rpc/errors
+
+
+type MockRpcHttpServer* = ref object
+  filters*: Table[string, bool]
+  newFilterCounter*: int
+  srv: RpcHttpServer
+
+proc new*(_: type MockRpcHttpServer): MockRpcHttpServer =
+  MockRpcHttpServer(filters: initTable[string, bool](), newFilterCounter: 0, srv: newRpcHttpServer(["127.0.0.1:0"]))
+
+proc invalidateFilter*(server: MockRpcHttpServer, id: string) =
+  server.filters[id] = false
+
+proc start*(server: MockRpcHttpServer) =
+  server.srv.router.rpc("eth_newFilter") do(filter: EventFilter) -> string:
+    let filterId = "0x" & (array[16, byte].example).toHex
+    server.filters[filterId] = true
+    server.newFilterCounter += 1
+    return filterId
+
+  server.srv.router.rpc("eth_getFilterChanges") do(id: string) -> seq[string]:
+    if(not hasKey(server.filters, id) or not server.filters[id]):
+      raise (ref ApplicationError)(code: -32000, msg: "filter not found")
+
+    return @[]
+
+  server.srv.router.rpc("eth_uninstallFilter") do(id: string) -> bool:
+    if(not hasKey(server.filters, id)):
+      raise (ref ApplicationError)(code: -32000, msg: "filter not found")
+
+    server.filters.del(id)
+    return true
+
+  server.srv.start()
+
+proc stop*(server: MockRpcHttpServer) {.async.} =
+  await server.srv.stop()
+  await server.srv.closeWait()
+
+
+proc localAddress*(server: MockRpcHttpServer): seq[TransportAddress] =
+  return server.srv.localAddress()

testmodule/providers/jsonrpc/testJsonRpcSubscriptions.nim

@@ -1,9 +1,15 @@
 import std/json
+import std/sequtils
 import pkg/asynctest
+import pkg/serde
 import pkg/json_rpc/rpcclient
+import pkg/json_rpc/rpcserver
 import ethers/provider
 import ethers/providers/jsonrpc/subscriptions
 
+import ../../examples
+import ./rpc_mock
+
 suite "JsonRpcSubscriptions":
 
   test "can be instantiated with an http client":
@@ -89,3 +95,62 @@ suite "HTTP polling subscriptions":
     await client.close()
 
   subscriptionTests(subscriptions, client)
+
+suite "HTTP polling subscriptions - filter not found":
+
+  var subscriptions: JsonRpcSubscriptions
+  var client: RpcHttpClient
+  var mockServer: MockRpcHttpServer
+
+  setup:
+    mockServer = MockRpcHttpServer.new()
+    mockServer.start()
+
+    client = newRpcHttpClient()
+    await client.connect("http://" & $mockServer.localAddress()[0])
+
+    subscriptions = JsonRpcSubscriptions.new(client,
+                                             pollingInterval = 15.millis)
+    subscriptions.start()
+
+  teardown:
+    await subscriptions.close()
+    await client.close()
+    await mockServer.stop()
+
+  test "filter not found error recreates filter":
+    let filter = EventFilter(address: Address.example, topics: @[array[32, byte].example])
+    let emptyHandler = proc(log: Log) = discard
+
+    check mockServer.newFilterCounter == 0
+    let jsonId = await subscriptions.subscribeLogs(filter, emptyHandler)
+    let id = string.fromJson(jsonId).tryGet
+    check mockServer.newFilterCounter == 1
+
+    await sleepAsync(50.millis)
+    mockServer.invalidateFilter(id)
+    await sleepAsync(50.millis)
+    check mockServer.newFilterCounter == 2
+
+  test "recreated filter can be still unsubscribed using the original id":
+    let filter = EventFilter(address: Address.example, topics: @[array[32, byte].example])
+    let emptyHandler = proc(log: Log) = discard
+
+    check mockServer.newFilterCounter == 0
+    let jsonId = await subscriptions.subscribeLogs(filter, emptyHandler)
+    let id = string.fromJson(jsonId).tryGet
+    check mockServer.newFilterCounter == 1
+
+    await sleepAsync(50.millis)
+    mockServer.invalidateFilter(id)
+    check eventually mockServer.newFilterCounter == 2
+    check mockServer.filters[id] == false
+    check mockServer.filters.len() == 2
+    await subscriptions.unsubscribe(jsonId)
+    check mockServer.filters.len() == 1
+
+    # invalidateFilter sets the filter's value to false which will return the "filter not found"
+    # unsubscribing will actually delete the key from filters table
+    # hence after unsubscribing the only key left in the table should be the original id
+    for key in mockServer.filters.keys():
+      check key == id