From 12cfc7930bc7795f99828e9c0f19a31b4fccf2c7 Mon Sep 17 00:00:00 2001
From: Nicolas Patry <patry.nicolas@protonmail.com>
Date: Thu, 11 Jan 2024 19:01:43 +0100
Subject: [PATCH] Return prompt vs generated tokens. (#1436)

# What does this PR do?

Fixes #637

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Fixes # (issue)


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---
 router/src/infer.rs  | 15 +++++++++++++--
 router/src/server.rs |  8 +++++++-
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/router/src/infer.rs b/router/src/infer.rs
index 8078cee7..fdf0ae77 100644
--- a/router/src/infer.rs
+++ b/router/src/infer.rs
@@ -101,6 +101,7 @@ impl Infer {
     ) -> Result<
         (
             OwnedSemaphorePermit,
+            u32,
             UnboundedReceiverStream<Result<InferStreamResponse, InferError>>,
         ),
         InferError,
@@ -125,6 +126,7 @@ impl Infer {
 
         // MPSC channel to communicate with the background batching task
         let (response_tx, response_rx) = mpsc::unbounded_channel();
+        let input_length = valid_request.input_length;
 
         // Append the request to the queue
         self.queue.append(Entry {
@@ -141,7 +143,11 @@ impl Infer {
         self.shared.batching_task.notify_one();
 
         // Return stream
-        Ok((permit, UnboundedReceiverStream::new(response_rx)))
+        Ok((
+            permit,
+            input_length,
+            UnboundedReceiverStream::new(response_rx),
+        ))
     }
 
     /// Add a new request to the queue and return a InferResponse
@@ -153,7 +159,7 @@ impl Infer {
         let use_top_tokens = request.parameters.top_n_tokens.is_some_and(|x| x > 0);
 
         // Create stream and keep semaphore permit as long as generate lives
-        let (_permit, mut stream) = self.generate_stream(request).await?;
+        let (_permit, _input_length, mut stream) = self.generate_stream(request).await?;
 
         // Return values
         let mut result_prefill = Vec::new();
@@ -207,6 +213,7 @@ impl Infer {
         {
             Ok(InferResponse {
                 prefill: result_prefill,
+                _input_length,
                 tokens: result_tokens,
                 generated_text,
                 queued,
@@ -647,6 +654,10 @@ pub(crate) enum InferStreamResponse {
 
 #[derive(Debug)]
 pub(crate) struct InferResponse {
+    /// input_length is the input as perceived by the rust tokenizer in the
+    /// validation pathway. It is redundant with prefill.len() but prefill
+    /// has data only if the user asked for it. This will always be filled.
+    pub(crate) _input_length: u32,
     pub(crate) prefill: Vec<PrefillToken>,
     pub(crate) tokens: Vec<Token>,
     pub(crate) generated_text: GeneratedText,
diff --git a/router/src/server.rs b/router/src/server.rs
index 78e2af3b..1ec45563 100644
--- a/router/src/server.rs
+++ b/router/src/server.rs
@@ -172,6 +172,7 @@ async fn generate(
     };
 
     // Token details
+    let input_length = response._input_length;
     let details = match details {
         true => {
             // convert best_of_responses
@@ -259,6 +260,11 @@ async fn generate(
         "x-time-per-token",
         time_per_token.as_millis().to_string().parse().unwrap(),
     );
+    headers.insert("x-prompt-tokens", input_length.into());
+    headers.insert(
+        "x-generated-tokens",
+        response.generated_text.generated_tokens.into(),
+    );
 
     // Metrics
     metrics::increment_counter!("tgi_request_success");
@@ -380,7 +386,7 @@ async fn generate_stream(
         } else {
             match infer.generate_stream(req).instrument(info_span!(parent: &span, "async_stream")).await {
                 // Keep permit as long as generate_stream lives
-                Ok((_permit, mut response_stream)) => {
+                Ok((_permit, _input_length, mut response_stream)) => {
                     // Server-Sent Event stream
                     while let Some(response) = response_stream.next().await {
                         match response {