--- title: Plugin Develop --- This documentation is about developing plugin in Lua. For other languages, see [external plugin](./external-plugin.md). ## 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`: ```yaml 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: ```yaml 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](https://github.com/apache/apisix/blob/master/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`](https://github.com/apache/apisix/blob/master/apisix/plugins/example-plugin.lua) 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. ```lua 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](./control-api.md#get-v1schema) 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](#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](https://json-schema.org) descriptions and check functions. Similarly, take the example-plugin plugin as an example to see its configuration data: ```json { "example-plugin": { "i": 1, "s": "s", "t": [1] } } ``` Let's look at its schema description : ```lua 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. ```lua 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](./terminology/plugin-metadata.md), so they define the plugin's `metadata_schema`. ```lua title="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](https://github.com/apache/apisix/blob/master/apisix/plugins/key-auth.lua) 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](./admin-api.md#consumer) resource. ```lua title="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](./terminology/plugin.md#plugins-execution-lifecycle) to run, generally access or rewrite. If you don't know the [OpenResty lifecycle](https://github.com/openresty/lua-nginx-module/blob/master/README.markdown#directives), 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. ```lua 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](https://github.com/apache/apisix/blob/35269581e21473e1a27b11cceca6f773cad0192a/apisix/plugins/limit-count.lua#L177)** ### extra phase Besides OpenResty's phases, we also provide extra phases to satisfy specific purpose: * `delayed_body_filter` ```lua 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: ```lua function _M.access(conf, ctx) core.log.warn(core.json.encode(conf)) ...... end ``` conf: ```json { "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 : ```lua 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. ```lua 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: ```yaml 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](https://github.com/apache/apisix/blob/master/example/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](./customize-nginx-configuration.md), for example : ```yaml # 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. ```lua 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 `.`: ```lua encrypt_fields = {"clickhouse.password"} ``` Currently not supported yet: 1. more than two levels of nesting 2. 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](https://github.com/apache/apisix/blob/85563f016c35834763376894e45908b2fb582d87/apisix/cli/config.lua#L75), you can modify them in `config.yaml`. ```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: ```lua 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](plugins/public-api.md) 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](./control-api.md). Take a look at example-plugin plugin: ```lua 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: ```shell curl -i -X GET "http://127.0.0.1:9090/v1/plugin/example-plugin/hello" ``` [Read more about control API introduction](./control-api.md) ## 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****](https://github.com/openresty/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: ```perl === 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](https://github.com/apache/apisix/blob/master/t/lib/server.lua#L36). For example, see [proxy-rewrite](https://github.com/apache/apisix/blob/master/t/plugin/proxy-rewrite.t). 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](building-apisix.md) 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. ## Additional Resource(s) - Key Concepts - [Plugins](https://apisix.apache.org/docs/apisix/terminology/plugin/) - [Apache APISIX Extensions Guide](https://apisix.apache.org/blog/2021/10/29/extension-guide/) - [Create a Custom Plugin in Lua](https://docs.api7.ai/apisix/how-to-guide/custom-plugins/create-plugin-in-lua) - [example-plugin code](https://github.com/apache/apisix/blob/master/apisix/plugins/example-plugin.lua)