Version: Next

Plugin Develop

This documentation is about developing plugin in Lua. For other languages, see external plugin.

Where to put your plugins#

Use the extra_lua_path parameter in conf/config.yaml file to load your custom plugin code (or use extra_lua_cpath for compiled .so or .dll file).

For example, you can create a directory /path/to/example:

apisix:
    ...
    extra_lua_path: "/path/to/example/?.lua"

The structure of the example directory should look like this:

├── example
│   └── apisix
│       ├── plugins
│       │   └── 3rd-party.lua
│       └── stream
│           └── plugins
│               └── 3rd-party.lua

note

The directory (/path/to/example) must contain the /apisix/plugins subdirectory.

Enable the plugin#

To enable your custom plugin, add the plugin list to conf/config.yaml and append your plugin name. For instance:

plugins: # See `conf/config.yaml.example` for an example
  - ... # Add existing plugins
  - your-plugin # Add your custom plugin name (name is the plugin name defined in the code)

warning

In particular, most APISIX plugins are enabled by default when the plugins field configuration is not defined (The default enabled plugins can be found in apisix/cli/config.lua).

Once the plugins configuration is defined in conf/config.yaml, the new plugins list will replace the default configuration instead of merging. Therefore, when defining the plugins field, make sure to include the built-in plugins that are being used. To maintain consistency with the default behavior, you can include all the default enabled plugins defined in apisix/cli/config.lua.

Writing plugins#

The example-plugin plugin in this repo provides an example.

Naming and priority#

Specify the plugin name (the name is the unique identifier of the plugin and cannot be duplicate) and priority in the code.

local plugin_name = "example-plugin"

local _M = {
    version = 0.1,
    priority = 0,
    name = plugin_name,
    schema = schema,
    metadata_schema = metadata_schema,
}

Note: The priority of the new plugin cannot be same to any existing ones, you can use the /v1/schema method of control API to view the priority of all plugins. In addition, plugins with higher priority value will be executed first in a given phase (see the definition of phase in choose-phase-to-run). For example, the priority of example-plugin is 0 and the priority of ip-restriction is 3000. Therefore, the ip-restriction plugin will be executed first, then the example-plugin plugin. It's recommended to use priority 1 ~ 99 for your plugin unless you want it to run before some builtin plugins.

Note: the order of the plugins is not related to the order of execution.

Schema and check#

Write JSON Schema descriptions and check functions. Similarly, take the example-plugin plugin as an example to see its configuration data:

{
  "example-plugin": {
    "i": 1,
    "s": "s",
    "t": [1]
  }
}

Let's look at its schema description :

local schema = {
    type = "object",
    properties = {
        i = {type = "number", minimum = 0},
        s = {type = "string"},
        t = {type = "array", minItems = 1},
        ip = {type = "string"},
        port = {type = "integer"},
    },
    required = {"i"},
}

The schema defines a non-negative number i, a string s, a non-empty array of t, and ip / port. Only i is required.

At the same time, we need to implement the check_schema(conf, schema_type) method to complete the specification verification.

function _M.check_schema(conf)
    return core.schema.check(schema, conf)
end

note

Note: the project has provided the public method "core.schema.check", which can be used directly to complete JSON verification.

The input parameter schema_type is used to distinguish between different schemas types. For example, many plugins need to use some metadata, so they define the plugin's metadata_schema.

example-plugin.lua

-- schema definition for metadata
local metadata_schema = {
    type = "object",
    properties = {
        ikey = {type = "number", minimum = 0},
        skey = {type = "string"},
    },
    required = {"ikey", "skey"},
}

function _M.check_schema(conf, schema_type)
    --- check schema for metadata
    if schema_type == core.schema.TYPE_METADATA then
        return core.schema.check(metadata_schema, conf)
    end
    return core.schema.check(schema, conf)
end

Another example, the key-auth plugin needs to provide a consumer_schema to check the configuration of the plugins attribute of the consumer resource in order to be used with the Consumer resource.

key-auth.lua


local consumer_schema = {
    type = "object",
    properties = {
        key = {type = "string"},
    },
    required = {"key"},
}

function _M.check_schema(conf, schema_type)
    if schema_type == core.schema.TYPE_CONSUMER then
        return core.schema.check(consumer_schema, conf)
    else
        return core.schema.check(schema, conf)
    end
end

Choose phase to run#

Determine which phase to run, generally access or rewrite. If you don't know the OpenResty lifecycle, it's recommended to learn about it in advance. For example key-auth is an authentication plugin, thus the authentication should be completed before forwarding the request to any upstream service. Therefore, the plugin must be executed in the rewrite phases. Similarly, if you want to modify or process the response body or headers you can do that in the body_filter or in the header_filter phases respectively.

The following code snippet shows how to implement any logic relevant to the plugin in the OpenResty log phase.

function _M.log(conf, ctx)
-- Implement logic here
end

Note : we can't invoke ngx.exit, ngx.redirect or core.respond.exit in rewrite phase and access phase. if need to exit, just return the status and body, the plugin engine will make the exit happen with the returned status and body. example

extra phase#

Besides OpenResty's phases, we also provide extra phases to satisfy specific purpose:

delayed_body_filter

function _M.delayed_body_filter(conf, ctx)
    -- delayed_body_filter is called after body_filter
    -- it is used by the tracing plugins to end the span right after body_filter
end

Implement the logic#

Write the logic of the plugin in the corresponding phase. There are two parameters conf and ctx in the phase method, take the limit-conn plugin configuration as an example.

conf parameter#

The conf parameter is the relevant configuration information of the plugin, you can use core.log.warn(core.json.encode(conf)) to output it to error.log for viewing, as shown below:

function _M.access(conf, ctx)
    core.log.warn(core.json.encode(conf))
    ......
end

conf:

{
  "rejected_code": 503,
  "burst": 0,
  "default_conn_delay": 0.1,
  "conn": 1,
  "key": "remote_addr"
}

ctx parameter#

The ctx parameter caches data information related to the request. You can use core.log.warn(core.json.encode(ctx, true)) to output it to error.log for viewing, as shown below :

function _M.access(conf, ctx)
    core.log.warn(core.json.encode(ctx, true))
    ......
end

Others#

If your plugin has a new code directory of its own, and you need to redistribute it with the APISIX source code, you will need to modify the Makefile to create directory, such as:

$(INSTALL) -d $(INST_LUADIR)/apisix/plugins/skywalking
$(INSTALL) apisix/plugins/skywalking/*.lua $(INST_LUADIR)/apisix/plugins/skywalking/

There are other fields in the _M which affect the plugin's behavior.

local _M = {
    ...
    type = 'auth',
    run_policy = 'prefer_route',
}

run_policy field can be used to control the behavior of the plugin execution. When this field set to prefer_route, and the plugin has been configured both in the global and at the route level, only the route level one will take effect.

type field is required to be set to auth if your plugin needs to work with consumer.

Load plugin and replace plugin#

Using require "apisix.plugins.3rd-party" will load your plugin, just like require "apisix.plugins.jwt-auth" will load the jwt-auth plugin.

Sometimes you may want to override a method instead of a whole file. In this case, you can configure lua_module_hook in conf/config.yaml to introduce your hook.

Assume that your configuration is as follows:

apisix:
    ...
    extra_lua_path: "/path/to/example/?.lua"
    lua_module_hook: "my_hook"

The example/my_hook.lua will be loaded when APISIX starts, and you can use this hook to replace a method in APISIX. The example of my_hook.lua can be found under the example directory of this project.

Check external dependencies#

If you have dependencies on external libraries, check the dependent items. If your plugin needs to use shared memory, it needs to declare via customizing Nginx configuration, for example :

# put this in config.yaml:
nginx_config:
    http_configuration_snippet: |
        # for openid-connect plugin
        lua_shared_dict discovery             1m; # cache for discovery metadata documents
        lua_shared_dict jwks                  1m; # cache for JWKs
        lua_shared_dict introspection        10m; # cache for JWT verification results

The plugin itself provides the init method. It is convenient for plugins to perform some initialization after the plugin is loaded. If you need to clean up the initialization, you can put it in the corresponding destroy method.

Note : if the dependency of some plugin needs to be initialized when Nginx start, you may need to add logic to the initialization method "http_init" in the file apisix/init.lua, and you may need to add some processing on generated part of Nginx configuration file in apisix/cli/ngx_tpl.lua file. But it is easy to have an impact on the overall situation according to the existing plugin mechanism, we do not recommend this unless you have a complete grasp of the code.

Encrypted storage fields#

Some plugins require parameters to be stored encrypted, such as the password parameter of the basic-auth plugin. This plugin needs to specify in the schema which parameters need to be stored encrypted.

encrypt_fields = {"password"}

If it is a nested parameter, such as the clickhouse.password parameter of the error-log-logger plugin, it needs to be separated by .:

encrypt_fields = {"clickhouse.password"}

Currently not supported yet:

more than two levels of nesting
fields in arrays

Parameters can be stored encrypted by specifying encrypt_fields = {"password"} in the schema. APISIX will provide the following functionality.

When adding and updating resources, APISIX automatically encrypts the parameters declared in encrypt_fields and stores them in etcd
When fetching resources and when running the plugin, APISIX automatically decrypts the parameters declared in encrypt_fields

By default, APISIX has data_encryption enabled with two default keys, you can modify them in config.yaml.

apisix:
    data_encryption:
        enable: true
        keyring:
            - ...

APISIX will try to decrypt the data with keys in the order of the keys in the keyring (only for parameters declared in encrypt_fields). If the decryption fails, the next key will be tried until the decryption succeeds.

If none of the keys in keyring can decrypt the data, the original data is used.

Register public API#

A plugin can register API which exposes to the public. Take batch-requests plugin as an example, this plugin registers POST /apisix/batch-requests to allow developers to group multiple API requests into a single HTTP request/response cycle:

function batch_requests()
    -- ...
end

function _M.api()
    -- ...
    return {
        {
            methods = {"POST"},
            uri = "/apisix/batch-requests",
            handler = batch_requests,
        }
    }
end

Note that the public API will not be exposed by default, you will need to use the public-api plugin to expose it.

Register control API#

If you only want to expose the API to the localhost or intranet, you can expose it via Control API.

Take a look at example-plugin plugin:

local function hello()
    local args = ngx.req.get_uri_args()
    if args["json"] then
        return 200, {msg = "world"}
    else
        return 200, "world\n"
    end
end


function _M.control_api()
    return {
        {
            methods = {"GET"},
            uris = {"/v1/plugin/example-plugin/hello"},
            handler = hello,
        }
    }
end

If you don't change the default control API configuration, the plugin will be expose GET /v1/plugin/example-plugin/hello which can only be accessed via 127.0.0.1. Test with the following command:

curl -i -X GET "http://127.0.0.1:9090/v1/plugin/example-plugin/hello"

Register custom variables#

We can use variables in many places of APISIX. For example, customizing log format in http-logger, using it as the key of limit-* plugins. In some situations, the builtin variables are not enough. Therefore, APISIX allows developers to register their variables globally, and use them as normal builtin variables.

For instance, let's register a variable called a6_labels_zone to fetch the value of the zone label in a route:

local core = require "apisix.core"

core.ctx.register_var("a6_labels_zone", function(ctx)
    local route = ctx.matched_route and ctx.matched_route.value
    if route and route.labels then
        return route.labels.zone
    end
    return nil
end)

After that, any get operation to $a6_labels_zone will call the registered getter to fetch the value.

Note that the custom variables can't be used in features that depend on the Nginx directive, like access_log_format.

Write test cases#

For functions, write and improve the test cases of various dimensions, do a comprehensive test for your plugin! The test cases of plugins are all in the "t/plugin" directory. You can go ahead to find out. APISIX uses **test-nginx** as the test framework. A test case (.t file) is usually divided into prologue and data parts by __data__. Here we will briefly introduce the data part, that is, the part of the real test case. For example, the key-auth plugin:

=== TEST 1: sanity
--- config
    location /t {
        content_by_lua_block {
            local plugin = require("apisix.plugins.key-auth")
            local ok, err = plugin.check_schema({key = 'test-key'}, core.schema.TYPE_CONSUMER)
            if not ok then
                ngx.say(err)
            end

            ngx.say("done")
        }
    }
--- request
GET /t
--- response_body
done
--- no_error_log
[error]

A test case consists of three parts :

Program code : configuration content of Nginx location
Input : http request information
Output check : status, header, body, error log check

When we request /t, which config in the configuration file, the Nginx will call "content_by_lua_block" instruction to complete the Lua script, and finally return. The assertion of the use case is response_body return "done", "no_error_log" means to check the "error.log" of Nginx. There must be no ERROR level record. The log files for the unit test are located in the following folder: 't/servroot/logs'.

The above test case represents a simple scenario. Most scenarios will require multiple steps to validate. To do this, create multiple tests === TEST 1, === TEST 2, and so on. These tests will be executed sequentially, allowing you to break down scenarios into a sequence of atomic steps.

Additionally, there are some convenience testing endpoints which can be found here. For example, see proxy-rewrite. In test 42, the upstream uri is made to redirect /test?new_uri=hello to /hello (which always returns hello world). In test 43, the response body is confirmed to equal hello world, meaning the proxy-rewrite configuration added with test 42 worked correctly.

Refer the following document to setup the testing framework.

Attach the test-nginx execution process:#

According to the path we configured in the makefile and some configuration items at the front of each .t file, the framework will assemble into a complete nginx.conf file. "t/servroot" is the working directory of Nginx and start the Nginx instance. according to the information provided by the test case, initiate the http request and check that the return items of HTTP include HTTP status, HTTP response header, HTTP response body and so on.

Where to put your plugins#

note

Enable the plugin#

warning

Writing plugins#

Naming and priority#

Schema and check#

note

Choose phase to run#

extra phase#

Implement the logic#

conf parameter#

ctx parameter#

Others#

Load plugin and replace plugin#

Check external dependencies#

Encrypted storage fields#

Register public API#

Register control API#

Register custom variables#

Write test cases#

Attach the test-nginx execution process:#

Additional Resource(s)#