Code

use log::warn;
use proxy_wasm::traits::{Context, HttpContext};
use proxy_wasm::types::{Action, LogLevel};

proxy_wasm::main! {{
    proxy_wasm::set_log_level(LogLevel::Trace);
    proxy_wasm::set_http_context(|_, _| -> Box<dyn HttpContext> { Box::new(HttpCall) });
}}

struct HttpCall;

impl Context for HttpCall {}

impl HttpContext for HttpCall {
    fn on_http_request_headers(&mut self, _: usize, _: bool) -> Action {
        warn!("on_http_request_headers");

        // set wasm_process_req_body = true
        self.set_property(vec!["wasm_process_req_body"], Some("true".as_bytes()));

        let test_header = self.get_http_request_header("test");

        match test_header {
            Some(s) => warn!("header test: {}", s),
            None => warn!("no test header"),
        }

        Action::Continue
    }

    fn on_http_request_body(&mut self, _body_size: usize, _end_of_stream: bool) -> Action {
        warn!("on_http_request_body");

        let body = self.get_http_request_body(0, _body_size);

        match body {
            Some(b) => warn!("body: {:?}", String::from_utf8(b).unwrap()),
            None => warn!("no body"),
        }

        Action::Continue
    }
}

Test

Prepare

## build plugin
cargo build --target wasm32-wasi --release

## setup plugin
wasm:
  plugins:
    - name: wasm_test
      priority: 30000
      file: wasm-plugin/target/wasm32-wasi/release/wasm_plugin.wasm

## setup route
curl -i http://127.0.0.1:9080/apisix/admin/routes/1  -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -d '
{
    "uri": "/*",
    "plugins": {
         "wasm_test": {
             "conf": "blahblah"
         }
    },
    "upstream": {
        "type": "roundrobin",
        "nodes": {
            "httpbin.org": 1
        }
    }
}'

Case 1

curl -XPOST 127.0.0.1:9080/anything --data '{"test":"test"}' -H "Content-Type: application/json" -H "test: aHeader"

{
  "args": {}, 
  "data": "{\"test\":\"test\"}", 
  "files": {}, 
  "form": {}, 
  "headers": {
    "Accept": "*/*", 
    "Content-Length": "15", 
    "Content-Type": "application/json", 
    "Host": "127.0.0.1", 
    "Test": "aHeader", 
    "User-Agent": "curl/7.81.0", 
    "X-Amzn-Trace-Id": "Root=1-632c9c74-19a6ebbf6b30bf1a6af9e647", 
    "X-Forwarded-Host": "127.0.0.1"
  }, 
  "json": {
    "test": "test"
  }, 
  "method": "GET", 
  "origin": "127.0.0.1, 47.240.173.85", 
  "url": "http://127.0.0.1/anything"
}

2022/09/23 01:33:40 [warn] 19381#19381: *4006 on_http_request_headers, client: 127.0.0.1, server: _, request: "GET /anything HTTP/1.1", host: "127.0.0.1:9080"
2022/09/23 01:33:40 [warn] 19381#19381: *4006 header test: aHeader, client: 127.0.0.1, server: _, request: "GET /anything HTTP/1.1", host: "127.0.0.1:9080"
2022/09/23 01:33:40 [warn] 19381#19381: *4006 on_http_request_body, client: 127.0.0.1, server: _, request: "GET /anything HTTP/1.1", host: "127.0.0.1:9080"
2022/09/23 01:33:40 [warn] 19381#19381: *4006 body: "{\"test\":\"test\"}", client: 127.0.0.1, server: _, request: "GET /anything HTTP/1.1", host: "127.0.0.1:9080"

Case 2

curl -XPOST 127.0.0.1:9080/anything -H "Content-Type: application/json" -H "test: aHeader"

{
  "args": {}, 
  "data": "", 
  "files": {}, 
  "form": {}, 
  "headers": {
    "Accept": "*/*", 
    "Content-Type": "application/json", 
    "Host": "127.0.0.1", 
    "Test": "aHeader", 
    "User-Agent": "curl/7.81.0", 
    "X-Amzn-Trace-Id": "Root=1-632c9d62-408889882d28075c3a94f29c", 
    "X-Forwarded-Host": "127.0.0.1"
  }, 
  "json": null, 
  "method": "POST", 
  "origin": "127.0.0.1, 47.240.173.85", 
  "url": "http://127.0.0.1/anything"
}

2022/09/23 01:37:38 [warn] 19381#19381: *10098 on_http_request_headers, client: 127.0.0.1, server: _, request: "POST /anything HTTP/1.1", host: "127.0.0.1:9080"
2022/09/23 01:37:38 [warn] 19381#19381: *10098 header test: aHeader, client: 127.0.0.1, server: _, request: "POST /anything HTTP/1.1", host: "127.0.0.1:9080"
2022/09/23 01:37:38 [warn] 19381#19381: *10098 on_http_request_body, client: 127.0.0.1, server: _, request: "POST /anything HTTP/1.1", host: "127.0.0.1:9080"
2022/09/23 01:37:38 [warn] 19381#19381: *10098 no body, client: 127.0.0.1, server: _, request: "POST /anything HTTP/1.1", host: "127.0.0.1:9080"

Case 3

curl -XPOST 127.0.0.1:9080/anything

{
  "args": {}, 
  "data": "", 
  "files": {}, 
  "form": {}, 
  "headers": {
    "Accept": "*/*", 
    "Host": "127.0.0.1", 
    "User-Agent": "curl/7.81.0", 
    "X-Amzn-Trace-Id": "Root=1-632c9d93-567179c15a03b33b387cc306", 
    "X-Forwarded-Host": "127.0.0.1"
  }, 
  "json": null, 
  "method": "POST", 
  "origin": "127.0.0.1, 47.240.173.85", 
  "url": "http://127.0.0.1/anything"
}

2022/09/23 01:38:27 [warn] 19381#19381: *11347 on_http_request_headers, client: 127.0.0.1, server: _, request: "POST /anything HTTP/1.1", host: "127.0.0.1:9080"
2022/09/23 01:38:27 [warn] 19381#19381: *11347 no test header, client: 127.0.0.1, server: _, request: "POST /anything HTTP/1.1", host: "127.0.0.1:9080"
2022/09/23 01:38:27 [warn] 19381#19381: *11347 on_http_request_body, client: 127.0.0.1, server: _, request: "POST /anything HTTP/1.1", host: "127.0.0.1:9080"
2022/09/23 01:38:27 [warn] 19381#19381: *11347 no body, client: 127.0.0.1, server: _, request: "POST /anything HTTP/1.1", host: "127.0.0.1:9080"