Hello,
I'm writing an envoy plugin that replaces certain HTTP responses and I'm confused about using set_http_response_body(start, size, value); (in the plugin implementation) and expect_set_buffer_bytes (in the integration test)
A simple example code that replaces HTTP responses:
fn on_http_response_body(&mut self, body_size: usize, end_of_stream: bool) -> Action {
...
if some_condition {
let bytes = vec![....];
let size = body_size; // <---------------- THIS
self.set_http_response_body(0, size, bytes.as_slice());
// ^^^^--------- AND THIS
}
...
}From my testing and debugging with an actual running Envoy instance, it looks like the size parameter has to be set EXACTLY to body_size argument, otherwise, there would be leftovers from the previous response (if the original response is larger than the replacement).
If I'm not mistaken, the data flow goes like this:
- https://github.com/proxy-wasm/proxy-wasm-cpp-host/blob/main/src/exports.cc#L508
- https://github.com/envoyproxy/envoy/blob/b508cb4d78bea275a9cebc43c9000b2b41cc9e56/source/extensions/common/wasm/context.cc#L141-L146
- https://github.com/envoyproxy/envoy/blob/b508cb4d78bea275a9cebc43c9000b2b41cc9e56/envoy/buffer/buffer.h#L225-L229
so the buffer is drained up to size argument.
However, passing the original body size doesn't work with this tool. .expect_set_buffer_bytes(Some(BufferType::HttpResponseBody), Some(expected_body)) computes the size internally from expected_body and cannot be changed.
I did a dummy workaround in my fork (vojty@a0af2e9) that makes it work.
Is this a bug or am I missing something?
Hello,
I'm writing an envoy plugin that replaces certain HTTP responses and I'm confused about using
set_http_response_body(start, size, value);(in the plugin implementation) andexpect_set_buffer_bytes(in the integration test)A simple example code that replaces HTTP responses:
From my testing and debugging with an actual running Envoy instance, it looks like the
sizeparameter has to be set EXACTLY tobody_sizeargument, otherwise, there would be leftovers from the previous response (if the original response is larger than the replacement).If I'm not mistaken, the data flow goes like this:
so the buffer is drained up to
sizeargument.However, passing the original body size doesn't work with this tool.
.expect_set_buffer_bytes(Some(BufferType::HttpResponseBody), Some(expected_body))computes the size internally fromexpected_bodyand cannot be changed.I did a dummy workaround in my fork (vojty@a0af2e9) that makes it work.
Is this a bug or am I missing something?