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Broadcasting Events in gRPC from Server to Clients
When creating applications involving multiple clients connecting to a server, it's often necessary to broadcast events to all connected clients. In gRPC, there are several approaches to achieve this.
One option to consider is using a long-polling approach. This involves having clients periodically poll the server for updates. When an event occurs, the server notifies all connected clients, triggering their polling calls to return with the new information.
To implement a long-polling approach in Python, consider the following code (a similar implementation is possible in other languages like Go):
<code class="python"># SERVER class UpdaterServer(UpdaterServicer): def __init__(self): self.condition = threading.Condition() self.updates = [] def post_update(self, update): with self.condition: self.updates.append(updates) self.condition.notify_all() def GetUpdates(self, req, context): with self.condition: while self.updates[req.last_received_update + 1:] == []: self.condition.wait() new_updates = self.updates[req.last_received_update + 1:] response = GetUpdatesResponse() for update in new_updates: response.updates.add().CopyFrom(update) response.update_index = req.last_received_update + len(new_updates) return response # SEPARATE THREAD IN CLIENT request = GetUpdatesRequest() request.last_received_update = -1 while True: stub = UpdaterStub(channel) try: response = stub.GetUpdates(request, timeout=60*10) handle_updates(response.updates) request.last_received_update = response.update_index except grpc.FutureTimeoutError: pass</code>
In this example:
Using a long-polling approach ensures that all connected clients receive broadcast events and provides a reliable way to communicate updates to multiple parties.
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