From 66e2e94b18013aa4de33d5fb1e9338a541c04597 Mon Sep 17 00:00:00 2001
From: Nate Koenig <nate@openrobotics.org>
Date: Mon, 5 Apr 2021 14:15:22 -0700
Subject: [PATCH 1/2] Support unsubscribing from a topic

Signed-off-by: Nate Koenig <nate@openrobotics.org>
---
 plugins/websocket_server/WebsocketServer.cc | 26 +++++++++++++++++++++
 plugins/websocket_server/WebsocketServer.hh | 11 +++++----
 2 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/plugins/websocket_server/WebsocketServer.cc b/plugins/websocket_server/WebsocketServer.cc
index 6b535543..53271cae 100644
--- a/plugins/websocket_server/WebsocketServer.cc
+++ b/plugins/websocket_server/WebsocketServer.cc
@@ -761,6 +761,32 @@ void WebsocketServer::OnMessage(int _socketId, const std::string &_msg)
           this, std::placeholders::_1,
           std::placeholders::_2, std::placeholders::_3));
   }
+  else if (frameParts[0] == "unsub")
+  {
+    igndbg << "Unsubscribe request for topic[" << frameParts[1] << "]\n";
+    std::map<std::string, std::set<int>>::iterator topicConnectionIter =
+      this->topicConnections.find(frameParts[1]);
+
+    if (topicConnectionIter != this->topicConnections.end())
+    {
+      // Remove from the topic connections map
+      topicConnectionIter->second.extract(_socketId);
+
+      // Only unsubscribe from the Ignition Transport topic if there are no
+      // more websocket connections.
+      if (topicConnectionIter->second.empty())
+      {
+        igndbg << "Unsubscribing from Ignition Transport Topic["
+          << frameParts[1] << "]\n";
+        this->node.Unsubscribe(frameParts[1]);
+      }
+    }
+    else
+    {
+      ignwarn << "The websocket server is not subscribed to topic["
+        << frameParts[1] << "]. Unable to unsubscribe from the topic\n";
+    }
+  }
 }
 
 //////////////////////////////////////////////////
diff --git a/plugins/websocket_server/WebsocketServer.hh b/plugins/websocket_server/WebsocketServer.hh
index 484cdddb..b29046b0 100644
--- a/plugins/websocket_server/WebsocketServer.hh
+++ b/plugins/websocket_server/WebsocketServer.hh
@@ -85,13 +85,14 @@ namespace ignition
     ///     1. "sub": Subscribe to the topic in the `topic_name` component,
     ///     2. "pub": Publish a message from the Ignition Transport topic in
     ///               the `topic_name` component,
-    ///     3. "topics": Get the list of available topics, and
+    ///     3. "topics": Get the list of available topics,
     ///     4. "protos": Get a string containing all the protobuf
-    ///                  definitions.
+    ///                  definitions, and
+    ///     5. "unsub": Unsubscribe from the topic in the `topic_name` component
     ///
-    /// The `topic_name` component is mandatory for the "sub" and "pub"
-    /// operations. If present, it must be the name of an Ignition Transport
-    /// topic.
+    /// The `topic_name` component is mandatory for the "sub", "pub", and
+    /// "unsub" operations. If present, it must be the name of an Ignition
+    /// Transport topic.
     ///
     /// The `message_type` component is mandatory for the "pub" operation. If
     /// present it names the Ignition Message type, such as

From 48a8f48114a0d483e1072039729119c03ad2dc53 Mon Sep 17 00:00:00 2001
From: Nate Koenig <nate@openrobotics.org>
Date: Fri, 9 Apr 2021 10:06:53 -0700
Subject: [PATCH 2/2] extract to erase

Signed-off-by: Nate Koenig <nate@openrobotics.org>
---
 plugins/websocket_server/WebsocketServer.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/plugins/websocket_server/WebsocketServer.cc b/plugins/websocket_server/WebsocketServer.cc
index 53271cae..ce003e41 100644
--- a/plugins/websocket_server/WebsocketServer.cc
+++ b/plugins/websocket_server/WebsocketServer.cc
@@ -770,7 +770,7 @@ void WebsocketServer::OnMessage(int _socketId, const std::string &_msg)
     if (topicConnectionIter != this->topicConnections.end())
     {
       // Remove from the topic connections map
-      topicConnectionIter->second.extract(_socketId);
+      topicConnectionIter->second.erase(_socketId);
 
       // Only unsubscribe from the Ignition Transport topic if there are no
       // more websocket connections.