feat: Implement traffic splitting plugin

[Firstsawyou]

close #2303 close #2603

What this PR does / why we need it:

Implement a traffic splitting plugin, the plugin is named traffic-split. The main function of the plug-in is to divide the request traffic according to the specified ratio and divert it to the corresponding "upstream". The functions of Gray release, Blue-green release and Custom release can be realized through this plugin.

Related issue：
https://github.com/apache/apisix/issues/2303

https://github.com/apache/apisix/issues/2603

Mailing list discussion address:
https://lists.apache.org/thread.html/rf02dc53a4af5d98d2513d89256b47466934d129af06d0bdcdb49cc8e%40%3Cdev.apisix.apache.org%3E

Pre-submission checklist:

• Did you explain what problem does this PR solve? Or what new features have been added?
• Have you added corresponding test cases?
• Have you modified the corresponding document?
• Is this PR backward compatible? If it is not backward compatible, please discuss on the mailing list first

[moonming]

Please write a better title and desc

[tokers]

@Firstsawyou CI failed, please fix it.

[Firstsawyou]

@spacewander @membphis @tokers
Help me take a look at this test case: https://github.com/apache/apisix/pull/2935/files#diff-1badbb10ecfbb255409af122651c06a0b308ba0d51e672180d4e78719dce7e88R128. When executing this test case, the following error message is prompted:

nginx: [emerg] Lua code block missing the closing long bracket "]=]" in /home/runner/work/apisix/apisix/t/servroot/conf/nginx.conf:148
nginx: [emerg] Lua code block missing the closing long bracket "]=]" in /home/runner/work/apisix/apisix/t/servroot/conf/nginx.conf:148
nginx: [emerg] Lua code block missing the closing long bracket "]=]" in /home/runner/work/apisix/apisix/t/servroot/conf/nginx.conf:148

I don't know what caused this.

[moonming]

@Firstsawyou What is the name of this plugin? the PR title and code file are not the same.

[Firstsawyou]

@Firstsawyou What is the name of this plugin? the PR title and code file are not the same.

updated.

[moonming]

@Firstsawyou What is the name of this plugin? the PR title and code file are not the same.

updated.

Not yet , please read your desc again

[membphis]

Reduce the total code length in content_by_lua_block

[Firstsawyou]

Thank you very much, I will try.

[tokers]

We should use traffic split instead dynamic-upstream, in the future, the traffic split plugin will provide the labels based selector to choose nodes inside a upstream, this function is not covered by the name dynamic-upstream, which gives us an illusion this plugin is used for choosing one upstream from multiple upstreams.

[Firstsawyou]

We should use traffic split instead dynamic-upstream, in the future, the traffic split plugin will provide the labels based selector to choose nodes inside a upstream, this function is not covered by the name dynamic-upstream, which gives us an illusion this plugin is used for choosing one upstream from multiple upstreams.

Ok i will update later.

[Firstsawyou]

There was a problem when this pr handled the conflict. A related pr has been newly submitted.

[moonming]

No, please fix it in this PR

[tokers]

@Firstsawyou Could you paste some sample traffic split configurations here to help us understand the schema better.

[tokers]

@Firstsawyou Please resolve the conflicts.

[Firstsawyou]

@Firstsawyou Could you paste some sample traffic split configurations here to help us understand the schema better.

@tokers These are two cases, which will help you understand：

Grayscale Release

Traffic is split according to the weight value configured by upstreams in the plugin (the rule of match is not configured, and match is passed by default). The request traffic is divided into 4:2, 2/3 of the traffic reaches the upstream of the 1981 port in the plugin, and 1/3 of the traffic reaches the upstream of the default 1980 port on the route.

{
    "weight": 2
}

There is only a weight value in the plugin upstreams, which represents the weight value of the upstream traffic arriving on the route.

curl http://127.0.0.1:9080/apisix/admin/routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -d '
{
    "uri": "/index.html",
    "plugins": {
        "traffic-split": {
            "rules": [
                {
                    "upstreams": [
                        {
                            "upstream": {
                                "name": "upstream_A",
                                "type": "roundrobin",
                                "nodes": {
                                    "127.0.0.1:1981":10
                                },
                                "timeout": {
                                    "connect": 15,
                                    "send": 15,
                                    "read": 15
                                }
                            },
                            "weight": 4
                        },
                        {
                            "weight": 2
                        }
                    ]
                }
            ]
        }
    },
    "upstream": {
            "type": "roundrobin",
            "nodes": {
                "127.0.0.1:1980": 1
            }
    }
}'

Custom Release

Multiple matching rules can be set in match (multiple conditions in vars are the relationship of add, and the relationship between multiple vars rules is the relationship of or; as long as one of the vars rules passes, it means match passed), only one is configured here, and the traffic is divided into 4:2 according to the value of weight. Among them, only the weight part represents the proportion of upstream on the route. When match fails to match, all traffic will only hit upstream on the route.

curl http://127.0.0.1:9080/apisix/admin/routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -d '
{
    "uri": "/index.html",
    "plugins": {
        "traffic-split": {
            "rules": [
                {
                    "match": [
                        {
                            "vars": [
                                ["arg_name","==","jack"],
                                ["http_user-id",">","23"],
                                ["http_apisix-key","~~","[a-z]+"]
                            ]
                        }
                    ],
                    "upstreams": [
                        {
                            "upstream": {
                                "name": "upstream_A",
                                "type": "roundrobin",
                                "nodes": {
                                    "127.0.0.1:1981":10
                                }
                            },
                            "weight": 4
                        },
                        {
                            "weight": 2
                        }
                    ]
                }
            ]
        }
    },
    "upstream": {
            "type": "roundrobin",
            "nodes": {
                "127.0.0.1:1980": 1
            }
    }
}'

[juzhiyuan]

This should not work :(