Request help: Correspondence between matched rules and upstreams within one route

[Ben0625]

Request:

Set just one route and the path is "/test".
Set correspondence between many matched rules and upstreams. For example:

if args_id == 1, choose upstream A
if args_id == 2, choose upstream B
if args_id == 3, choose upstream C
......

For now, if I have 10 correspondence, I have to create 10 routes with the same path "/test". Then set one correspondence for each route.
I check traffic-split plugin, it works well for 2 upstreams, but it doesn't seem to match more than 2 correspondence.

Is it possible to set just one route and have multiple correspondence as Request describes?

[spacewander]

You can write your own plugin like traffic-split.

Look like the rules in traffic-split is an array, so you can use it with multiple upstream but not just for 2.

[Firstsawyou]

You can try the traffic-split plug-in. Here is an example of configuration:

curl http://127.0.0.1:9080/apisix/admin/routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -d '
{
    "uri": "/hello",
    "plugins": {
        "traffic-split": {
            "rules": [
                {
                    "match": [
                        {
                            "vars": [
                                ["http_id","==","1"]
                            ]
                        }
                    ],
                    "weighted_upstreams": [
                        {
                            "upstream": {
                                "name": "upstream_A",
                                "type": "roundrobin",
                                "nodes": {
                                    "127.0.0.1:1981":1
                                }
                            },
                            "weight": 3
                        }
                    ]
                },
                {
                    "match": [
                        {
                            "vars": [
                                ["http_id","==","2"]
                            ]
                        }
                    ],
                    "weighted_upstreams": [
                        {
                            "upstream": {
                                "name": "upstream_B",
                                "type": "roundrobin",
                                "nodes": {
                                    "127.0.0.1:1982":1
                                }
                            },
                            "weight": 3
                        }
                    ]
                }
            ]
        }
    },
    "upstream": {
            "type": "roundrobin",
            "nodes": {
                "127.0.0.1:1980": 1
            }
    }
}'

However, it may not take effect in APISIX 2.5. You can try it in versions before 2.5.

[Ben0625]

You can try the traffic-split plug-in. Here is an example of configuration:

curl http://127.0.0.1:9080/apisix/admin/routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -d '
{
    "uri": "/hello",
    "plugins": {
        "traffic-split": {
            "rules": [
                {
                    "match": [
                        {
                            "vars": [
                                ["http_id","==","1"]
                            ]
                        }
                    ],
                    "weighted_upstreams": [
                        {
                            "upstream": {
                                "name": "upstream_A",
                                "type": "roundrobin",
                                "nodes": {
                                    "127.0.0.1:1981":1
                                }
                            },
                            "weight": 3
                        }
                    ]
                },
                {
                    "match": [
                        {
                            "vars": [
                                ["http_id","==","2"]
                            ]
                        }
                    ],
                    "weighted_upstreams": [
                        {
                            "upstream": {
                                "name": "upstream_B",
                                "type": "roundrobin",
                                "nodes": {
                                    "127.0.0.1:1982":1
                                }
                            },
                            "weight": 3
                        }
                    ]
                }
            ]
        }
    },
    "upstream": {
            "type": "roundrobin",
            "nodes": {
                "127.0.0.1:1980": 1
            }
    }
}'

However, it may not take effect in APISIX 2.5. You can try it in versions before 2.5.

I modify some input args at Line 281 of traffic-spllit.lua and try it in version 2.0 and there exist a bug. When I first send a request with "id = 1", it correctly chooses upstream_A. But after that, no matter what I send with "id = 1" or "id = 2", it always chooses upstream_A and never chooses upstream_B.

Then I reload APISIX, this time I first send a request with "id = 2", it correctly chooses upstream_B. Then if I request with "id = 1" or "id = 2", it always chooses upstream_B.

It seems that the problem is at Line 281 and Line 288 of traffic-split.lua

local rr_up, err = core.lrucache.plugin_ctx(plugin_name, ctx, new_rr_obj, weighted_upstreams)
local upstream = rr_up:find()

I print the log to see weighted_upstreams before Line 281 and it is correct. But Line 288 does not give the right output.

[Firstsawyou]

I modify some input args at Line 281 of traffic-spllit.lua and try it in version 2.0 and there exist a bug. When I first send a request with "id = 1", it correctly chooses upstream_A. But after that, no matter what I send with "id = 1" or "id = 2", it always chooses upstream_A and never chooses upstream_B.

Then I reload APISIX, this time I first send a request with "id = 2", it correctly chooses upstream_B. Then if I request with "id = 1" or "id = 2", it always chooses upstream_B.

It seems that the problem is at Line 281 and Line 288 of traffic-split.lua

local rr_up, err = core.lrucache.plugin_ctx(plugin_name, ctx, new_rr_obj, weighted_upstreams)
local upstream = rr_up:find()

I print the log to see weighted_upstreams before Line 281 and it is correct. But Line 288 does not give the right output.

Yes, this is a known bug. If you want to implement this function in APISIX 2.5, you can refer to the following PR to modify the traffic-split.lua code.
https://github.com/apache/apisix/pull/4092/files#diff-95a2018f002f15f5fb0714075b5ef27a1db113c186bfe20ae705f6023080b38fL280-L283

[Ben0625]

Since I use APISIX 2.0 before, I try your change at APISIX 2.0 and it works!
local rr_up, err = lrucache(weighted_upstreams, nil, new_rr_obj, weighted_upstreams)
Good job! @Firstsawyou

[Ben0625]

I find a new bug here:
When I set 2 nodes in "upstream.nodes" attribute for 2 rules, something unexpected happens.

curl http://127.0.0.1:9080/apisix/admin/routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -d '
{
    "uri": "/hello",
    "plugins": {
        "traffic-split": {
            "rules": [
                {
                    "match": [
                        {
                            "vars": [
                                ["http_id","==","1"]
                            ]
                        }
                    ],
                    "weighted_upstreams": [
                        {
                            "upstream": {
                                "name": "upstream_A",
                                "type": "roundrobin",
                                "nodes": {
                                    "127.0.0.1:1980":1,
                                    "127.0.0.1:1981":1
                                }
                            },
                            "weight": 3
                        }
                    ]
                },
                {
                    "match": [
                        {
                            "vars": [
                                ["http_id","==","2"]
                            ]
                        }
                    ],
                    "weighted_upstreams": [
                        {
                            "upstream": {
                                "name": "upstream_B",
                                "type": "roundrobin",
                                "nodes": {
                                    "127.0.0.1:1982":1,
                                    "127.0.0.1:1983":1
                                }
                            },
                            "weight": 3
                        }
                    ]
                }
            ]
        }
    },
    "upstream": {
            "type": "roundrobin",
            "nodes": {
                "127.0.0.1:1980": 1
            }
    }
}'

Reproduce steps:

1. Request with id=1 for several times
2. Request with id=2 for several times

Then you will see nodes of upstream_A be picked when requesting with id = 2 for some time. It looks messed up.

[Firstsawyou]

Reproduce steps:

1. Request with id=1 for several times
2. Request with id=2 for several times

Then you will see nodes of upstream_A be picked when requesting with id = 2 for some time. It looks messed up.

This scenario has been covered by test cases, please see here: https://github.com/apache/apisix/blob/master/t/plugin/traffic-split2.t#L513-L613
By the way, what is your APISIX version?

[Ben0625]

This scenario has been covered by test cases, please see here: https://github.com/apache/apisix/blob/master/t/plugin/traffic-split2.t#L513-L613
By the way, what is your APISIX version?

My APISIX version is 2.0. I modify a little bit (At Line 194) to let this plugin run successfully.
upstream.set(ctx, upstream_key, ctx.conf_version, up_conf, matched_route)
This test case you mention works good for me too, but what I want to point out is the number of "upstream.nodes" attribute

"nodes": {
"127.0.0.1:1980":1,
"127.0.0.1:1981":1
}
"nodes": {
"127.0.0.1:1982":1,
"127.0.0.1:1983":1
}

I set 2 nodes instead of 1 and run the Reproduce steps. Then it messed up.

[Firstsawyou]

My APISIX version is 2.0. I modify a little bit (At Line 194) to let this plugin run successfully.
upstream.set(ctx, upstream_key, ctx.conf_version, up_conf, matched_route)
This test case you mention works good for me too, but what I want to point out is the number of "upstream.nodes" attribute

The number of upstream nodes is not affected. There are many bug fixes between APISIX 2.0 and APISIX 2.5. You should upgrade to version 2.5 and try again.