Solving the Delay Issue with WebSocket over SSL on Amazon's ELB
Solving the Delay Issue with WebSocket over SSL on Amazon’s ELB
Over the last few years, the use of WebSocket protocol over SSL (WSS) has gained immense popularity among data scientists and software engineers. This protocol is instrumental in developing real-time, bi-directional communication between the server and the client. However, when using Amazon’s Elastic Load Balancer (ELB), you might encounter delay issues with WebSocket over SSL. This blog post aims to provide an in-depth analysis of this problem and guide you through potential solutions.
What is Amazon’s ELB and WebSocket over SSL?
Before we delve into the delay issue, let’s provide some context for those who are not familiar with the concepts of Amazon’s ELB and WebSocket over SSL.
Amazon’s Elastic Load Balancer (ELB) is a load balancing service for AWS deployments. It automatically distributes incoming application traffic across multiple targets, such as Amazon EC2 instances.
WebSocket over SSL, or WSS, is a communication protocol providing full-duplex communication channels over a single TCP connection. It is an advanced technology making it possible to open interactive communication sessions between the user’s browser and a server, securing data with SSL encryption.
The Delay Issue with WebSocket Over SSL on Amazon’s ELB
When using WebSocket over SSL on Amazon’s ELB, you might experience a delay in the communication. This delay can be problematic in real-time applications where a few seconds can make a significant difference.
The delay issue primarily occurs because of the ‘idle timeout’ setting on the ELB. It is a mechanism to close connections that are idle for a specific period. In Amazon ELB, the default idle timeout value is 60 seconds. If the WebSocket connection stays idle longer than the idle timeout period, ELB closes the connection.
How to Solve the Delay Issue
Now that we understand the problem, let’s discuss how to solve this delay issue.
1. Adjust the Idle Timeout
The most straightforward solution is to increase the idle timeout value on the ELB. It can be set to any value between 1 and 3600 seconds (1 hour). However, keep in mind that setting a very high value may lead to resource exhaustion if there are a large number of idle connections.
aws elbv2 modify-load-balancer-attributes --load-balancer-arn your-load-balancer-arn --attributes Key=idle_timeout.timeout_seconds,Value=3600
2. Implement Heartbeat Messages
Another common solution is to maintain the connection’s active status by sending ‘heartbeat’ messages. A heartbeat message is a small packet of data sent periodically to keep the connection alive. You can implement this either on the server-side or client-side depending on your application’s requirements.
// Client-side JavaScript example
setInterval(function() {
if (socket.readyState === WebSocket.OPEN) {
socket.send('heartbeat');
}
}, 50000); // send heartbeat every 50 seconds
3. Use Application-Level Keepalive
If you don’t have control over the client-side or want to avoid modifying the ELB settings, you can use application-level keepalive. It involves sending a small payload from the server to the client at regular intervals to keep the connection active.
// Server-side JavaScript example
setInterval(function() {
if (socket.readyState === WebSocket.OPEN) {
socket.send('keepalive');
}
}, 50000); // send keepalive every 50 seconds
Conclusion
When using WebSocket over SSL on Amazon’s ELB, it is crucial to understand and manage the idle timeout setting to prevent unwanted delays. By adjusting the idle timeout, implementing heartbeat messages, or using application-level keepalive, you can ensure smooth, real-time communication in your applications.
Remember, each solution has its pros and cons, and the choice depends on your application’s specific needs and constraints. As data scientists and software engineers, the key is to understand these trade-offs and make informed decisions.
Happy coding!
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