[pbs-devel] [PATCH proxmox-backup v2 1/3] proxmox-rest-server: OutputFormatter: add new format_data_streaming method

Tue Apr 12 16:15:08 CEST 2022

that takes the data in form of a `Box<dyn SerializableReturn + Send>`
instead of a Value.

Implement it in json and extjs formatter, by starting a thread and
stream the serialized data via a `BufWriter<SenderWriter>` and use
the Receiver side as a stream for the response body.

Signed-off-by: Dominik Csapak <d.csapak at proxmox.com>
---
 proxmox-rest-server/Cargo.toml       |  1 +
 proxmox-rest-server/src/formatter.rs | 67 +++++++++++++++++++++++++++-
 2 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/proxmox-rest-server/Cargo.toml b/proxmox-rest-server/Cargo.toml
index 56aa91e8..a957f8df 100644
--- a/proxmox-rest-server/Cargo.toml
+++ b/proxmox-rest-server/Cargo.toml
@@ -27,6 +27,7 @@ serde = { version = "1.0", features = [ "derive" ] }
 serde_json = "1.0"
 tokio = { version = "1.6", features = ["signal", "process"] }
 tokio-openssl = "0.6.1"
+tokio-stream = "0.1.0"
 tower-service = "0.3.0"
 url = "2.1"
 
diff --git a/proxmox-rest-server/src/formatter.rs b/proxmox-rest-server/src/formatter.rs
index 709a6b1e..2e9a01fa 100644
--- a/proxmox-rest-server/src/formatter.rs
+++ b/proxmox-rest-server/src/formatter.rs
@@ -7,7 +7,7 @@ use serde_json::{json, Value};
 use hyper::header;
 use hyper::{Body, Response, StatusCode};
 
-use proxmox_router::{HttpError, RpcEnvironment};
+use proxmox_router::{HttpError, RpcEnvironment, SerializableReturn};
 use proxmox_schema::ParameterError;
 
 /// Extension to set error message for server side logging
@@ -18,6 +18,13 @@ pub trait OutputFormatter: Send + Sync {
     /// Transform json data into a http response
     fn format_data(&self, data: Value, rpcenv: &dyn RpcEnvironment) -> Response<Body>;
 
+    /// Transform serializable data into a streaming http response
+    fn format_data_streaming(
+        &self,
+        data: Box<dyn SerializableReturn + Send>,
+        rpcenv: &dyn RpcEnvironment,
+    ) -> Result<Response<Body>, Error>;
+
     /// Transform errors into a http response
     fn format_error(&self, err: Error) -> Response<Body>;
 
@@ -50,6 +57,16 @@ fn json_data_response(data: Value) -> Response<Body> {
     response
 }
 
+fn json_data_response_streaming(body: Body) -> Result<Response<Body>, Error> {
+    let response = Response::builder()
+        .header(
+            header::CONTENT_TYPE,
+            header::HeaderValue::from_static(JSON_CONTENT_TYPE),
+        )
+        .body(body)?;
+    Ok(response)
+}
+
 fn add_result_attributes(result: &mut Value, rpcenv: &dyn RpcEnvironment) {
     let attributes = match rpcenv.result_attrib().as_object() {
         Some(attr) => attr,
@@ -61,6 +78,22 @@ fn add_result_attributes(result: &mut Value, rpcenv: &dyn RpcEnvironment) {
     }
 }
 
+fn start_data_streaming(
+    value: Value,
+    data: Box<dyn SerializableReturn + Send>,
+) -> tokio::sync::mpsc::Receiver<Result<Vec<u8>, Error>> {
+    let (writer, reader) = tokio::sync::mpsc::channel(1);
+
+    tokio::task::spawn_blocking(move || {
+        let output = proxmox_async::blocking::SenderWriter::from_sender(writer);
+        let mut output = std::io::BufWriter::new(output);
+        let mut serializer = serde_json::Serializer::new(&mut output);
+        let _ = data.sender_serialize(&mut serializer, value);
+    });
+
+    reader
+}
+
 struct JsonFormatter();
 
 /// Format data as ``application/json``
@@ -84,6 +117,21 @@ impl OutputFormatter for JsonFormatter {
         json_data_response(result)
     }
 
+    fn format_data_streaming(
+        &self,
+        data: Box<dyn SerializableReturn + Send>,
+        rpcenv: &dyn RpcEnvironment,
+    ) -> Result<Response<Body>, Error> {
+        let mut value = json!({});
+
+        add_result_attributes(&mut value, rpcenv);
+
+        let reader = start_data_streaming(value, data);
+        let stream = tokio_stream::wrappers::ReceiverStream::new(reader);
+
+        json_data_response_streaming(Body::wrap_stream(stream))
+    }
+
     fn format_error(&self, err: Error) -> Response<Body> {
         let mut response = if let Some(apierr) = err.downcast_ref::<HttpError>() {
             let mut resp = Response::new(Body::from(apierr.message.clone()));
@@ -140,6 +188,23 @@ impl OutputFormatter for ExtJsFormatter {
         json_data_response(result)
     }
 
+    fn format_data_streaming(
+        &self,
+        data: Box<dyn SerializableReturn + Send>,
+        rpcenv: &dyn RpcEnvironment,
+    ) -> Result<Response<Body>, Error> {
+        let mut value = json!({
+            "success": true,
+        });
+
+        add_result_attributes(&mut value, rpcenv);
+
+        let reader = start_data_streaming(value, data);
+        let stream = tokio_stream::wrappers::ReceiverStream::new(reader);
+
+        json_data_response_streaming(Body::wrap_stream(stream))
+    }
+
     fn format_error(&self, err: Error) -> Response<Body> {
         let mut errors = HashMap::new();
 
-- 
2.30.2




