Skip to content

Idle Connection Timeout

Nalix provides a built-in mechanism to automatically detect and disconnect client connections that have been inactive for a specified duration. This is critical for reclaiming resources and protecting against persistent connection exhaustion (Slowloris-style attacks).

Learning Signals

1. The Timing Wheel Mechanism

Instead of using a separate Timer for every connection (which is expensive and causes GC pressure), Nalix uses a Hashed Timing Wheel.

How it Works

  1. Connections are placed into "buckets" on a virtual wheel.
  2. A single background worker "ticks" through these buckets at a fixed interval.
  3. Only connections in the current bucket are checked for idleness.

This ensures that even with 100,000+ concurrent connections, the CPU overhead remains constant and minimal.

graph TD
    subgraph Wheel[Timing Wheel]
        B1[Bucket 1]
        B2[Bucket 2]
        B3[Current Bucket]
        B4[Bucket 4]
    end

    Loop[Background Worker] -->|Tick| B3
    B3 -->|Check| C1[Connection A]
    B3 -->|Check| C2[Connection B]

    C1 -->|Idle > Limit| Disc[Disconnect]
    C2 -->|Still Active| Resch[Reschedule to future bucket]

2. Configuration

Idle timeout is managed via NetworkSocketOptions (to enable/disable) and TimingWheelOptions (to tune the timing).

Method 1: Configuration Files (INI)

The framework's internal Bootstrap automatically loads these settings from .ini files in your executable directory.

network.ini 

; Enable the idle timeout mechanism
EnableTimeout = true

timing.ini 

; The duration in milliseconds before an idle connection is closed
IdleTimeoutMs = 60000

; The precision of the idle check (lower = more precise but higher CPU)
TickDuration = 1000

; Number of buckets in the wheel (higher = fewer collisions)
BucketCount = 512

3. Method 2: Fluent Builder (C#)

If you prefer to configure the server in code, use the Configure<T> methods on the NetworkApplicationBuilder.

using Nalix.Hosting;
using Nalix.Network.Options;

var host = NetworkApplication.CreateBuilder()
    // Enable or disable the mechanism globally
    .Configure<NetworkSocketOptions>(options => 
    {
        options.EnableTimeout = true;
    })
    // Fine-tune the timeout duration
    .Configure<TimingWheelOptions>(options => 
    {
        options.IdleTimeoutMs = 30_000; // Disconnect after 30 seconds of silence
        options.TickDuration = 1000;    // Check once per second
    })
    .BindTcp<MyProtocol>().Bind()
    .Build();

await host.RunAsync();

4. Verifying Idle Disconnection

When the timing wheel disconnects a client, it emits a Debug or Info level log (depending on your logging configuration).

Example Log Output: 

[DEBUG] [NW.TimingWheel] timeout remote=192.168.1.50 idle=30005ms
[INFO]  [NW.TcpListenerBase] close=192.168.1.50

Pro-Tip: TCP Keep-Alive

Idle timeout detects application-level silence. To detect network-level dead sockets (where the client crashed without closing the connection), also ensure KeepAlive is enabled in NetworkSocketOptions.