feat: implement a templated endpoint for visibility into chat requests (#2333)

* feat: implement a templated endpoint for visibility into chat requests

* feat: improve to tokenize too

* fix: adjust return type

* feat: simplify prepare_chat_input logic and adjust start stop chars

router/src/lib.rs

@@ -1157,6 +1157,12 @@ pub(crate) struct GenerateResponse {
     pub details: Option<Details>,
 }
 
+#[derive(Serialize, ToSchema)]
+pub(crate) struct ChatTokenizeResponse {
+    pub(crate) tokenize_response: TokenizeResponse,
+    pub(crate) templated_text: String,
+}
+
 #[derive(Serialize, ToSchema)]
 #[serde(transparent)]
 pub(crate) struct TokenizeResponse(Vec<SimpleToken>);

router/src/server.rs

@@ -8,6 +8,7 @@ use crate::kserve::{
     kserve_model_metadata, kserve_model_metadata_ready,
 };
 use crate::validation::ValidationError;
+use crate::ChatTokenizeResponse;
 use crate::{
     usage_stats, BestOfSequence, Details, ErrorResponse, FinishReason, FunctionName,
     GenerateParameters, GenerateRequest, GenerateResponse, GrammarType, HubModelInfo,
@@ -22,7 +23,7 @@ use crate::{
     CompletionRequest, CompletionType, DeltaToolCall, Function, Prompt, Tool, VertexRequest,
     VertexResponse,
 };
-use crate::{FunctionDefinition, HubPreprocessorConfig, ToolCall, ToolChoice, ToolType};
+use crate::{FunctionDefinition, HubPreprocessorConfig, ToolCall, ToolChoice, ToolType, Tools};
 use async_stream::__private::AsyncStream;
 use axum::extract::Extension;
 use axum::http::{HeaderMap, HeaderValue, Method, StatusCode};
@@ -115,6 +116,107 @@ async fn get_model_info(info: Extension<Info>) -> Json<Info> {
     Json(info.0)
 }
 
+#[utoipa::path(
+    post,
+    tag = "Text Generation Inference",
+    path = "/chat_tokenize",
+    request_body = ChatRequest,
+    responses((status = 200, description = "Templated and tokenized ChatRequest", body = ChatTokenizeResponse))
+)]
+async fn get_chat_tokenize(
+    Extension(infer): Extension<Infer>,
+    Json(req): Json<ChatRequest>,
+) -> Result<(HeaderMap, Json<ChatTokenizeResponse>), (StatusCode, Json<ErrorResponse>)> {
+    metrics::counter!("tgi_request_count").increment(1);
+
+    let ChatRequest {
+        model,
+        max_tokens,
+        messages,
+        seed,
+        stop,
+        stream,
+        tools,
+        tool_choice,
+        tool_prompt,
+        temperature,
+        response_format,
+        ..
+    } = req;
+
+    let tool_prompt = tool_prompt.unwrap_or_default();
+    let (inputs, _grammar, _tool_grammar) = prepare_chat_input(
+        &infer,
+        response_format,
+        tools,
+        tool_choice,
+        &tool_prompt,
+        messages,
+    )?;
+
+    let generate_request = GenerateRequest {
+        inputs,
+        parameters: GenerateParameters {
+            best_of: None,
+            temperature,
+            repetition_penalty: None,
+            frequency_penalty: None,
+            top_k: None,
+            top_p: None,
+            typical_p: None,
+            do_sample: true,
+            max_new_tokens: max_tokens,
+            return_full_text: None,
+            stop: stop.unwrap_or_default(),
+            truncate: None,
+            watermark: false,
+            details: false,
+            decoder_input_details: !stream,
+            seed,
+            top_n_tokens: None,
+            grammar: _grammar,
+            adapter_id: model.as_ref().filter(|m| *m != "tgi").map(String::from),
+        },
+    };
+
+    let input = generate_request.inputs.clone();
+    let encoding = infer.tokenize(generate_request).await?;
+    if let Some(encoding) = encoding {
+        let tokens: Vec<SimpleToken> = encoding
+            .get_ids()
+            .iter()
+            .zip(encoding.get_offsets())
+            .map(|(&id, &(start, stop))| {
+                let text = input
+                    .chars()
+                    .skip(start)
+                    .take(stop - start)
+                    .collect::<String>();
+                SimpleToken {
+                    id,
+                    text,
+                    start,
+                    stop,
+                }
+            })
+            .collect();
+
+        let resp = ChatTokenizeResponse {
+            tokenize_response: TokenizeResponse(tokens),
+            templated_text: input,
+        };
+        Ok((HeaderMap::new(), Json(resp)))
+    } else {
+        Err((
+            StatusCode::NOT_FOUND,
+            Json(ErrorResponse {
+                error: "No fast tokenizer or tokenizer.json for this model".to_string(),
+                error_type: "no fast tokenizer".to_string(),
+            }),
+        ))
+    }
+}
+
 #[utoipa::path(
 get,
 tag = "Text Generation Inference",
@@ -1034,63 +1136,14 @@ async fn chat_completions(
         Some(temperature) if temperature == 0.0 => (false, None),
         other => (true, other),
     };
-
-    // response_format and tools are mutually exclusive
-    if response_format.is_some() && tools.as_ref().is_some() {
-        metrics::counter!("tgi_request_failure", "err" => "validation").increment(1);
-        return Err((
-            StatusCode::UNPROCESSABLE_ENTITY,
-            Json(ErrorResponse {
-                error: "Grammar and tools are mutually exclusive".to_string(),
-                error_type: "grammar and tools".to_string(),
-            }),
-        ));
-    }
-
-    // extract tool grammar if present
-    let tool_grammar = match ToolGrammar::apply(tools, tool_choice) {
-        Ok(grammar) => grammar,
-        Err(err) => {
-            metrics::counter!("tgi_request_failure", "err" => "validation").increment(1);
-            tracing::error!("{err}");
-            return Err((
-                StatusCode::UNPROCESSABLE_ENTITY,
-                Json(ErrorResponse {
-                    error: err.to_string(),
-                    error_type: err.error_type().to_string(),
-                }),
-            ));
-        }
-    };
-
-    // determine the appropriate arguments for apply_chat_template
-    let tools_grammar_prompt = tool_grammar
-        .as_ref()
-        .map(|t| (GrammarType::Json(serde_json::json!(t)), tool_prompt));
-
-    let (tools_grammar_prompt, grammar) = match response_format {
-        Some(response_format) => (None, Some(response_format)),
-        None => (
-            tools_grammar_prompt.clone(),
-            tools_grammar_prompt.map(|(grammar, _)| grammar.clone()),
-        ),
-    };
-
-    // apply chat template to flatten the request into a single input
-    let inputs = match infer.apply_chat_template(messages, tools_grammar_prompt) {
-        Ok(inputs) => inputs,
-        Err(err) => {
-            metrics::counter!("tgi_request_failure", "err" => "validation").increment(1);
-            tracing::error!("{err}");
-            return Err((
-                StatusCode::UNPROCESSABLE_ENTITY,
-                Json(ErrorResponse {
-                    error: err.to_string(),
-                    error_type: err.error_type().to_string(),
-                }),
-            ));
-        }
-    };
+    let (inputs, grammar, tool_grammar) = prepare_chat_input(
+        &infer,
+        response_format,
+        tools,
+        tool_choice,
+        &tool_prompt,
+        messages,
+    )?;
 
     // build the request passing some parameters
     let generate_request = GenerateRequest {
@@ -1360,8 +1413,11 @@ async fn tokenize(
             .iter()
             .zip(encoding.get_offsets())
             .map(|(&id, &(start, stop))| {
-                let text: String =
-                    String::from_utf8_lossy(&input.as_bytes()[start..stop]).to_string();
+                let text = input
+                    .chars()
+                    .skip(start)
+                    .take(stop - start)
+                    .collect::<String>();
                 SimpleToken {
                     id,
                     text,
@@ -2036,6 +2092,7 @@ async fn start(
     }
     let info_routes = Router::new()
         .route("/", get(health))
+        .route("/chat_tokenize", post(get_chat_tokenize))
         .route("/info", get(get_model_info))
         .route("/health", get(health))
         .route("/ping", get(health))
@@ -2332,3 +2389,36 @@ fn create_post_processor(
 
     Ok(post_processor)
 }
+
+type PreparedInput = (String, Option<GrammarType>, Option<Tools>);
+
+fn prepare_chat_input(
+    infer: &Infer,
+    response_format: Option<GrammarType>,
+    tools: Option<Vec<Tool>>,
+    tool_choice: ToolChoice,
+    tool_prompt: &str,
+    messages: Vec<Message>,
+) -> Result<PreparedInput, InferError> {
+    if response_format.is_some() && tools.is_some() {
+        return Err(InferError::ToolError(
+            "Grammar and tools are mutually exclusive".into(),
+        ));
+    }
+
+    if let Some(format) = response_format {
+        let inputs = infer.apply_chat_template(messages, None)?;
+        return Ok((inputs, Some(format), None));
+    }
+
+    // if tools are set, apply the tool grammar and then the chat template
+    let tool_grammar: Option<Tools> = ToolGrammar::apply(tools, tool_choice)?;
+    let grammar = tool_grammar
+        .as_ref()
+        .map(|t| GrammarType::Json(serde_json::json!(t)));
+    let tools_grammar_prompt = tool_grammar
+        .as_ref()
+        .map(|t| (GrammarType::Json(serde_json::json!(t)), tool_prompt.into()));
+    let inputs = infer.apply_chat_template(messages, tools_grammar_prompt)?;
+    Ok((inputs, grammar, tool_grammar))
+}