Fix Relay API: handle messages on previously subscribed topics (#413)

tests/v2/test_jsonrpc_waku.nim

@@ -153,6 +153,23 @@ procSuite "Waku v2 JSON-RPC API":
     let client = newRpcHttpClient()
     await client.connect("127.0.0.1", rpcPort)
 
+    # First see if we can retrieve messages published on the default topic (node is already subscribed)
+    await node2.publish(defaultTopic, message)
+
+    await sleepAsync(2000.millis)
+
+    var messages = await client.get_waku_v2_relay_v1_messages(defaultTopic)
+
+    check:
+      messages.len == 1
+      messages[0].contentTopic == contentTopic
+      messages[0].payload == payload
+    
+    # Ensure that read messages are cleared from cache
+    messages = await client.get_waku_v2_relay_v1_messages(pubSubTopic)  
+    check:
+      messages.len == 0
+
     # Now try to subscribe using API
 
     var response = await client.post_waku_v2_relay_v1_subscriptions(@[pubSubTopic])
@@ -168,7 +185,7 @@ procSuite "Waku v2 JSON-RPC API":
 
     await sleepAsync(2000.millis)
     
-    var messages = await client.get_waku_v2_relay_v1_messages(pubSubTopic)
+    messages = await client.get_waku_v2_relay_v1_messages(pubSubTopic)
 
     check:
       messages.len == 1

waku/v2/node/jsonrpc/relay_api.nim

@@ -17,7 +17,7 @@ const maxCache* = 100 # Max number of messages cached per topic @TODO make this
 proc installRelayApiHandlers*(node: WakuNode, rpcsrv: RpcServer, topicCache: TopicCache) =
   
   proc topicHandler(topic: string, data: seq[byte]) {.async.} =
-    trace "Topic handler triggered"
+    trace "Topic handler triggered", topic=topic
     let msg = WakuMessage.init(data)
     if msg.isOk():
       # Add message to current cache
@@ -38,6 +38,16 @@ proc installRelayApiHandlers*(node: WakuNode, rpcsrv: RpcServer, topicCache: Top
     else:
       debug "WakuMessage received but failed to decode", msg=msg, topic=topic
       # @TODO handle message decode failure
+  
+  ## Node may already be subscribed to some topics when Relay API handlers are installed. Let's add these
+  for topic in PubSub(node.wakuRelay).topics.keys:
+    debug "Adding API topic handler for existing subscription", topic=topic
+
+    node.subscribe(topic, topicHandler)      
+    
+    # Create message cache for this topic
+    debug "MessageCache for topic", topic=topic
+    topicCache[topic] = @[]
 
   ## Relay API version 1 definitions
   
@@ -73,10 +83,12 @@ proc installRelayApiHandlers*(node: WakuNode, rpcsrv: RpcServer, topicCache: Top
 
     # Subscribe to all requested topics
     for topic in topics:
-      node.subscribe(topic, topicHandler)      
+      # Only subscribe to topics for which we have no subscribed topic handlers yet
-      # Create message cache for this topic
+      if not topicCache.hasKey(topic):
-      debug "MessageCache for topic", topic=topic
+        node.subscribe(topic, topicHandler)
-      topicCache[topic] = @[]
+        # Create message cache for this topic
+        trace "MessageCache for topic", topic=topic
+        topicCache[topic] = @[]
     
     # Successfully subscribed to all requested topics
     return true

waku/v2/node/wakunode2.nim

@@ -30,6 +30,9 @@ logScope:
 # Default clientId
 const clientId* = "Nimbus Waku v2 node"
 
+# Default topic
+const defaultTopic = "/waku/2/default-waku/proto"
+
 # key and crypto modules different
 type
   KeyPair* = crypto.KeyPair
@@ -361,7 +364,7 @@ proc mountRelay*(node: WakuNode, topics: seq[string] = newSeq[string](), rlnRela
       await node.subscriptions.notify(topic, msg.value())
       waku_node_messages.inc(labelValues = ["relay"])
 
-  node.wakuRelay.subscribe("/waku/2/default-waku/proto", relayHandler)
+  node.wakuRelay.subscribe(defaultTopic, relayHandler)
 
   for topic in topics:
     proc handler(topic: string, data: seq[byte]) {.async, gcsafe.} =