Upstream weight allocation is incorrect

[renshunhang]

I have configured an upstream, node1: 60 node2: 40. When I send 200 requests concurrently within 1 second, the traffic distribution between node1 and node2 is nearly 1:1. However, when I send 200 requests sequentially with a 1-second interval between each request, the traffic ratio is close to 3:2. Why is that?

[dosubot[bot]]

The discrepancy you're observing in traffic distribution between concurrent and sequential requests could be influenced by several factors related to how APISIX handles load balancing.

1. Load Balancing Algorithm: APISIX supports multiple load balancing algorithms, including weighted round-robin, least connections, EWMA, and consistent hashing. The weighted round-robin algorithm should distribute requests based on the specified weights, but concurrent requests might not adhere strictly to the weights due to the nature of concurrent processing and network conditions ^[1].

2. Concurrency Effects: When requests are sent concurrently, network latency, server response times, and connection handling can affect how requests are distributed. The load balancer might not have enough time to adjust the distribution perfectly according to weights, leading to a more even distribution.

3. Sequential Requests: When requests are sent sequentially, the load balancer has more time to process each request according to the specified weights, resulting in a distribution closer to the expected 3:2 ratio.

4. Configuration Parameters: Ensure that the weight attribute is correctly set for each node and that the balancer.algorithm is configured to use weighted round-robin if that is your intended algorithm ^[1].

These factors can contribute to the observed differences in traffic distribution. Adjusting configurations or testing under different network conditions might help achieve more consistent results.

To continue talking to Dosu, mention @dosu.

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