feat(backend): avoid dropping the boxed stream at the end of the callback

backends/llamacpp/csrc/ffi.hpp

@@ -21,6 +21,7 @@ namespace huggingface::tgi::backends::llamacpp {
 
 
 #include "backends/llamacpp/src/lib.rs.h"
+#include "rust/cxx.h"
 
 
 namespace huggingface::tgi::backends::llamacpp {
@@ -61,17 +62,22 @@ namespace huggingface::tgi::backends::llamacpp {
 
         explicit llama_cpp_backend_impl_t(multi_worker_backend_t &&backend) : mInner_(std::move(backend)) {}
 
-        size_t generate(
+        size_t stream(
                 rust::Slice<const uint32_t> input_tokens,
                 rust::Slice <uint32_t> generated_tokens,
-                const generation_params_t &generation_params,
+                const generation_params_t generation_params,
                 const sampling_params_t &sampling_params,
-                rust::Fn<void(uint32_t, float_t, bool)> callback
+                OpaqueStream *stream,
+                rust::Fn<void(OpaqueStream *, uint32_t, float_t, bool)> callback
         ) {
             // Define the visitor lambda function which requires the has_emplace_generate constraint on T
-            static auto inner_fw = [=, &generation_params, &sampling_params]<has_emplace_generate T>(T &&backend)
+            static auto inner_fw = [=, &sampling_params, &stream, &callback]<has_emplace_generate T>(T &&backend)
                     -> std::expected<size_t, backend_error_t> {
 
+                auto context_forwarding_callback = [=, &stream](uint32_t new_token_id, float_t logits, bool is_eos){
+                    callback(stream, new_token_id, logits, is_eos);
+                };
+
                 // Ask the compiler to create view over Rust slice transmuting from uint32_t* to int32_t*
                 auto input_tokens_v =
                         std::span(reinterpret_cast<const llama_token *>(input_tokens.data()), input_tokens.size());
@@ -79,7 +85,12 @@ namespace huggingface::tgi::backends::llamacpp {
                         std::span(reinterpret_cast<llama_token *>(generated_tokens.data()), generated_tokens.size());
 
                 return backend.generate(
-                        input_tokens_v, generated_tokens_v, generation_params, sampling_params, callback);
+                        input_tokens_v,
+                        generated_tokens_v,
+                        generation_params,
+                        sampling_params,
+                        context_forwarding_callback
+                );
             };
 
             if (const auto result = std::visit(inner_fw, mInner_); result.has_value()) {

backends/llamacpp/src/backend.rs

@@ -1,23 +1,27 @@
 use crate::ffi::{
     create_single_worker_backend, GenerationParams, LlamaCppBackendImpl, SamplingParams,
 };
+use crate::OpaqueStream;
 use async_trait::async_trait;
 use cxx::UniquePtr;
 use std::path::{Path, PathBuf};
 use std::sync::mpsc::{channel, Receiver, SendError, Sender};
 use std::sync::Arc;
 use std::thread::{spawn, JoinHandle};
-use text_generation_router::infer::{Backend, InferError, InferStreamResponse};
+use text_generation_router::infer::{Backend, GeneratedText, InferError, InferStreamResponse};
 use text_generation_router::validation::{
     ValidGenerateRequest, ValidParameters, ValidStoppingParameters,
 };
-use text_generation_router::Token;
+use text_generation_router::{FinishReason, Token};
 use thiserror::Error;
 use tokio::sync::mpsc::{unbounded_channel, UnboundedSender};
 use tokio::sync::TryAcquireError;
+use tokio::time::Instant;
 use tokio_stream::wrappers::UnboundedReceiverStream;
 use tracing::{error, info};
 
+type BoxedOpaqueStream = Box<OpaqueStream>;
+
 unsafe impl Send for LlamaCppBackendImpl {}
 
 impl From<&ValidParameters> for SamplingParams {
@@ -86,7 +90,7 @@ impl LlamaCppBackend {
         );
 
         let (submitter, receiver) = channel();
-        let handle = spawn(|| scheduler_loop(backend, receiver));
+        let handle = unsafe { spawn(|| scheduler_loop(backend, receiver)) };
         Ok(Self {
             backlog: submitter,
             scheduler_handle: handle,
@@ -94,47 +98,59 @@ impl LlamaCppBackend {
     }
 }
 
-fn scheduler_loop(
+fn llama_generate_callback(
+    channel: *mut OpaqueStream,
+    new_token_id: u32,
+    new_token_logit: f32,
+    is_eos: bool,
+) {
+    let response = InferStreamResponse::Intermediate {
+        token: Token {
+            id: new_token_id,
+            text: "".to_string(),
+            logprob: new_token_logit,
+            special: false,
+        },
+        top_tokens: vec![],
+    };
+    println!("Generated token: {new_token_id} -> logits={new_token_logit}, is_eos={is_eos}");
+
+    unsafe {
+        if let Err(ref err) = (*channel).0.send(Ok(response)) {
+            error!(
+                "Failed to send back token to the client: {}",
+                err.to_string()
+            );
+        }
+    }
+}
+
+unsafe fn scheduler_loop(
     mut backend: UniquePtr<LlamaCppBackendImpl>,
     mut backlog: Receiver<InferContext>,
 ) {
     loop {
-        println!("Looping");
         if let Ok(mut ctx) = backlog.recv() {
-            println!("{ctx:?}, {}", &ctx.generated_tokens.capacity());
-            match backend.pin_mut().generate(
+            let stream = BoxedOpaqueStream::new(OpaqueStream(ctx.stream));
+            let stream_ptr = Box::into_raw(stream);
+            let result = backend.pin_mut().stream(
                 &ctx.input_tokens,
                 &mut ctx.generated_tokens,
-                &ctx.generation_params,
+                ctx.generation_params,
                 &ctx.sampling_params,
-                |new_token_id: u32, new_token_logit: f32, is_eos: bool| {
-                    let response = InferStreamResponse::Intermediate {
-                        token: Token {
-                            id: new_token_id,
-                            text: "".to_string(),
-                            logprob: new_token_logit,
-                            special: false,
-                        },
-                        top_tokens: vec![],
-                    };
-                    println!("Generated token: {response:?}");
-                    // let _ = tokio::spawn(async {
-                    //     match ctx.stream.send(Ok(response)) {
-                    //         Ok(_) => {}
-                    //         Err(ref err) => {
-                    //             error!(
-                    //                 "Failed to send back token to the client: {}",
-                    //                 err.to_string()
-                    //             );
-                    //         }
-                    //     }
-                    // });
-                },
-            ) {
+                stream_ptr,
+                llama_generate_callback,
+            );
+
+            // Make sure we re-keep track of the OpaqueStream box
+            let _ = Box::from_raw(stream_ptr);
+
+            match result {
                 Ok(n_tokens) => {
                     unsafe {
                         ctx.generated_tokens.set_len(n_tokens);
                     }
+
                     println!(
                         "Generated {} tokens -> {:?}",
                         n_tokens, &ctx.generated_tokens

backends/llamacpp/src/lib.rs

@@ -1,4 +1,6 @@
 use crate::ffi::SamplingParams;
+use text_generation_router::infer::{InferError, InferStreamResponse};
+use tokio::sync::mpsc::UnboundedSender;
 
 pub mod backend;
 
@@ -14,6 +16,8 @@ impl Default for SamplingParams {
     }
 }
 
+struct OpaqueStream(UnboundedSender<Result<InferStreamResponse, InferError>>);
+
 #[cxx::bridge(namespace = "huggingface::tgi::backends::llamacpp")]
 mod ffi {
     #[derive(Debug, Copy, Clone)]
@@ -31,6 +35,10 @@ mod ffi {
         seed: u64,
     }
 
+    extern "Rust" {
+        type OpaqueStream;
+    }
+
     unsafe extern "C++" {
         include!("backends/llamacpp/csrc/ffi.hpp");
 
@@ -47,13 +55,22 @@ mod ffi {
         #[rust_name = "create_single_worker_backend"]
         fn create_single_worker_backend(modelPath: &str) -> Result<UniquePtr<LlamaCppBackendImpl>>;
 
-        fn generate(
+        // fn generate(
+        //     self: Pin<&mut LlamaCppBackendImpl>,
+        //     tokens: &[u32],
+        //     generated: &mut [u32],
+        //     generation_params: GenerationParams,
+        //     sampling_params: &SamplingParams,
+        // ) -> Result<usize>;
+
+        unsafe fn stream(
             self: Pin<&mut LlamaCppBackendImpl>,
             tokens: &[u32],
             generated: &mut [u32],
-            generation_params: &GenerationParams,
+            generation_params: GenerationParams,
             sampling_params: &SamplingParams,
-            callback: fn(u32, f32, bool),
+            stream: *mut OpaqueStream,
+            callback: unsafe fn(*mut OpaqueStream, u32, f32, bool),
         ) -> Result<usize>;
     }
 }