如何配置mcrouter使用wch3哈希函数并设置两节点50/50均衡权重？

Got it, let's walk through exactly how to set up mcrouter to use the wch3 hashing function with two nodes split 50/50. I know it's frustrating when the docs don't have explicit examples for less common hash functions, so here's a concrete working config and explanation:

Step 1: Modify Your mcrouter Configuration File #

mcrouter uses JSON-based config files (typically something like mcrouter.json). Here's a complete, valid config that implements what you need:

{
  "pools": {
    "weighted_redis_pool": {
      "servers": [
        {
          "address": "your-first-node:11211",
          "weight": 1
        },
        {
          "address": "your-second-node:11211",
          "weight": 1
        }
      ],
      "hash_function": "wch3",
      "pool_type": "async"
    }
  },
  "route": {
    "type": "PoolRoute",
    "pool": "weighted_redis_pool"
  }
}

Key Config Details Explained #

• "hash_function": "wch3": This line replaces the default ch3 hash with the weighted version (wch3), which is specifically designed to respect node weights when distributing traffic.
• Node Weights: Setting "weight": 1 for both nodes ensures exactly 50/50 traffic distribution. Weights are relative—if you ever wanted to adjust to, say, 70/30, you'd set weights to 7 and 3 respectively.
• pool_type: "async": This is the standard asynchronous pool type for mcrouter, suitable for most production use cases where you want non-blocking operations.
• Route Setup: The PoolRoute type tells mcrouter to route all traffic directly to your configured weighted pool.

Step 2: Validate and Apply the Config #

Before restarting mcrouter, validate your config to catch any syntax errors:

mcrouter --validate-config /path/to/your/mcrouter.json

If validation passes, restart mcrouter to apply the changes (command depends on your init system):

# For systemd-based systems
systemctl restart mcrouter

# For upstart
service mcrouter restart

Quick Verification #

To confirm the hash function and weights are working as expected, you can use mcrouter's built-in stats or test with a set of keys—wch3 should distribute keys evenly between the two nodes given equal weights.

内容的提问来源于stack exchange，提问作者The Georgia