Hi, I have some questions about this proposal. 1. If using similar C/S mode, whether the encoding and decoding process will affect the performance.
2.Can we use protobuf, a more popular encoding and decoding toolkit? Thanks! *发件人: *Zexuan Luo <spacewan...@apache.org> *发送时间: *2021年4月16日 14:52 *收件人: *dev@apisix.apache.org *主题: *[Proposal] support using other languages to write plugin for APISIX 1. Background APISIX currently only supports writing plugins in Lua. If other languages are supported, it will greatly broaden the APISIX ecosystem and user base. 2. Solution Since WASM is not yet mature, we consider implementing it through local IPC. For the sake of discussion, the following will assume that the plugin is written in Java. However, in practice, our solution can be interfaced with other languages. 2.1 Terminology Several terms are defined here. Plugin Runner: The service that runs the plugin, written in the same language as the plugin. In the first version, we assume that there will be only one Plugin Runner. 2.2 Plugin Runner lifecycle To simplify user operation and reduce the difficulty of upgrading, Plugin Runner is managed by APISIX. APISIX starts the Plugin Runner when it starts and ends it when it ends. if the Plugin Runner quits in the middle, APISIX will restart it automatically. 2.3 Timing of APISIX communication with Plugin Runner ``` Router ----> Global Plugin (written in Lua) ---> Ext Plugin (ext-plugin-pre-req) ----> Lua Plugin (Router) ---> Ext plugin (ext-plugin-post-req) ---> Upstream ``` Running the Ext Plugin in the Global Plugin is not supported at this time, as the global logic can be executed uniformly in the Plugin Runner. Running Ext Plugin after getting an upstream response is not supported at this time. We can support it later with a buffering response. ext-plugin-pre runs before all non-global Lua plugins, and ext-plugin-post runs after all non-global Lua plugins. 2.4 How APISIX communicates with Plugin Runner APISIX communicates with Plugin Runner through a unix socket. The communication protocol is as follows. 2.4.1 Communication format ``` 1 byte of type + 3 bytes of length + data ``` The type can be 0 ~ 7, and the length can be [0, 8M). data length is determined by length. Since Ext Plugin usually does not exchange too much data, 8M should be enough. The reason for taking 4 bytes is to keep the header small enough to be read efficiently. The current type takes the following values. 0 means error 1 means prepare_conf 2 means http_req_call The data is serialized in capnproto, a binary serialization format. capnproto is supported by many programming languages: https://capnproto.org/otherlang.html The advantages of choosing capnproto are. 1. focus on serialization performance 2. partial deserialization support, so that decode can be done only when it is needed 2.4.2 Communication steps Each ext plugin will have the following configuration. ``` { "conf": [ { "name": "configuration name", "value": "configuration value" } ], "extra_info": [ ... ] } ``` conf can be used to set the execution configuration of the plugin-related requests inside Plugin Runner. The default data sent to Plugin Runner is only the most common information. If you want additional information, you need to declare it in extra_info beforehand. To save communication costs, conf is sent separately. 1. APISIX will check if conf has a corresponding token in the local cache. 2. If not, APISIX sends a prepare_conf request to ask Plugin Runner to cache the conf and return a token. (Note that Plugin Runner's cache time needs to be longer than APISIX's cache time.) 3. APISIX sends an http_req_call request to Plugin Runner. 4. Plugin Runner executes the request and returns a response to APISIX. 5. APISIX processes the request based on the response 2.4.3 proto Refer to https://capnproto.org/language.html The following is the proto for error response ``` enum ErrorCode { BAD_REQUEST @0; # Plugin Runner can't understand APISIX SERVICE_UNAVAILABLE @1; # Plugin Runner can't handle the request CONF_TOKEN_NOT_FOUND @2; } struct ErrorResp { Code @0 :ErrorCode; } ``` The following is the proto of prepare_conf request ``` struct PrepareConfReq { conf @0 :List(Pair); } ``` Response ``` struct PrepareConfResp { conf_token @0 :UInt32; } ``` Here is the proto for http_req_call request ``` struct Pair { name @0 :Text; value @1 :Text; } struct PairData { name @0 :Text; value @1 :Data; } enum Method { GET @0; ... } struct HTTPReqCallReq { id @0 :UInt32; src_ip @1 :Data; method @2 :Method; path @3 :Text; args @4 :List(Pair); headers @5 :List(Pair); conf_token @6 :UInt32; extra_info @7 :List(PairData); } ``` Response ``` struct HTTPReqCallResp { id @0 :UInt32; struct Stop { status @0 :UInt16; headers @1 :List(Pair); body @2 :Data; } struct Rewrite { path @0 :Text; headers @1 :List(Pair); # Note that args are modified in full. # Either empty, meaning no args need to be moved # or the entire modified args, not the incrementally changed parts args @2 :List(Pair); } # What needs to be done when the response is received action action :union { # Do nothing continue @1 :Void; # Equivalent to core.response.exit(status, body), allowing additional headers to be set stop @2 :Stop; # Rewrite the request rewrite @3 :Rewrite; } } ``` 2.4.4 Error handling Logging and returning 503 error codes 2.4.5 Environment variables APISIX configures the Plugin Runner with a number of environment variables when it is started. APISIX_LISTEN_ADDRESS: the address that the Plugin Runner needs to listen to APISIX_CONF_EXPIRE_TIME: Plugin Runner needs to cache conf for longer than this
