Merge pull request #2 from ysugimoto/support-grpcwebtext-content-type

Provide grpc-web-text mode polyfill

Author: ysugimoto

README.md

@@ -232,6 +232,25 @@ local cors = require("grpc-gateway.cors")
 cors("http://localhost:8080") -- or cors() to set "*"
 ```
 
+## Polyfill grpc-web-text mode
+
+In default, nginx can proxy only `application/grpc-web+proto` which means request body will come as binary,
+So nginx cannot support `application/grpc-web-text` mode because rquest body will come as base64-encoded string.
+
+So this package also provide a tiny polyfill:
+
+```lua
+location / {
+  access_by_lua_block {
+    local polyfill = require("grpc-gateway.polyfill")
+    polyfill()
+  }
+
+  grpc_pass localhost:9000;
+}
+```
+
+
 ## License
 
 MIT

grpc-gateway/polyfill.lua

@@ -0,0 +1,16 @@
+return function()
+  -- nginx's gRPC proxy supports only grpcweb protocol whose request body accepts only binary proto format.
+  -- So if user requests with 'Content-Type: application/grpc-web-text', we need to decode request body as binary.
+  if ngx.req.get_headers()["Content-Type"] == "application/grpc-web-text" then
+    ngx.req.read_body()
+    local body = ngx.req.get_body_data()
+    local decoded, err = ngx.decode_base64(body)
+    if err then
+      ngx.status = ngx.HTTP_INTERNAL_SERVER_ERROR
+      ngx.say("Failed to decode base64 body for grpc-web-text protocol")
+      ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR)
+      return
+    end
+    nex.req.set_body_data(decoded)
+  end
+end

lua-resty-grpc-gateway.rockspec

@@ -21,6 +21,7 @@ build = {
       ["grpc-gateway.request"] = "grpc-gateway/request.lua",
       ["grpc-gateway.response"] = "grpc-gateway/response.lua",
       ["grpc-gateway.util"] = "grpc-gateway/util.lua",
-      ["grpc-gateway.cors"] = "grpc-gateway/cors.lua"
+      ["grpc-gateway.cors"] = "grpc-gateway/cors.lua",
+      ["grpc-gateway.polyfill"] = "grpc-gateway/polyfill.lua"
    }
 }