server: health: fix race condition on slots data using tasks queue (ggml-org#5634)

* server: health: fix race condition on slots data using tasks queue

* server: health:
    * include_slots only if slots_endpoint
    * fix compile warning task.target_id not initialized.

Author: phymbert

examples/server/README.md

@@ -140,6 +140,8 @@ node index.js
   - 200 -> `{"status": "no slot available", "slots_idle": 0, "slots_processing": 32}` if no slot are currently available.
   - 503 -> `{"status": "no slot available", "slots_idle": 0, "slots_processing": 32}` if the query parameter `fail_on_no_slot` is provided and no slot are currently available.
 
+  If the query parameter `include_slots` is passed, `slots` field will contain internal slots data except if `--slots-endpoint-disable` is set.
+
 - **POST** `/completion`: Given a `prompt`, it returns the predicted completion.
 
     *Options:*

examples/server/server.cpp

@@ -1394,6 +1394,46 @@ struct llama_server_context
             case TASK_TYPE_NEXT_RESPONSE: {
                 // do nothing
             } break;
+            case TASK_TYPE_SLOTS_DATA: {
+                json slots_data        = json::array();
+                int n_idle_slots       = 0;
+                int n_processing_slots = 0;
+
+                for (llama_client_slot &slot: slots) {
+                    if (slot.available()) {
+                        n_idle_slots++;
+                    } else {
+                        n_processing_slots++;
+                    }
+                    json slot_data = get_formated_generation(slot);
+                    slot_data["id"] = slot.id;
+                    slot_data["task_id"] = slot.task_id;
+                    slot_data["state"] = slot.state;
+                    slot_data["prompt"] = slot.prompt;
+                    slot_data["next_token"] = {
+                            {"has_next_token", slot.has_next_token},
+                            {"n_remain", slot.n_remaining},
+                            {"num_tokens_predicted", slot.n_decoded},
+                            {"stopped_eos", slot.stopped_eos},
+                            {"stopped_word", slot.stopped_word},
+                            {"stopped_limit", slot.stopped_limit},
+                            {"stopping_word", slot.stopping_word},
+                    };
+                    slots_data.push_back(slot_data);
+                }
+                LOG_TEE("task %i - slots data: idle=%i processing=%i\n", task.id, n_idle_slots, n_processing_slots);
+                task_result res;
+                res.id = task.id;
+                res.multitask_id = task.multitask_id;
+                res.stop = true;
+                res.error = false;
+                res.result_json = {
+                        { "idle",       n_idle_slots       },
+                        { "processing", n_processing_slots },
+                        { "slots",      slots_data         }
+                };
+                queue_results.send(res);
+            } break;
         }
     }
 
@@ -2557,34 +2597,38 @@ int main(int argc, char **argv)
         server_state current_state = state.load();
         switch(current_state) {
             case SERVER_STATE_READY: {
-                int available_slots  = 0;
-                int processing_slots = 0;
-                for (llama_client_slot &slot: llama.slots) {
-                    if (slot.available()) {
-                        available_slots++;
-                    } else {
-                        processing_slots++;
-                    }
+                // request slots data using task queue
+                task_server task;
+                task.id   = llama.queue_tasks.get_new_id();
+                task.type = TASK_TYPE_SLOTS_DATA;
+                task.target_id = -1;
+
+                llama.queue_results.add_waiting_task_id(task.id);
+                llama.queue_tasks.post(task);
+
+                // get the result
+                task_result result = llama.queue_results.recv(task.id);
+                llama.queue_results.remove_waiting_task_id(task.id);
+
+                int n_idle_slots       = result.result_json["idle"];
+                int n_processing_slots = result.result_json["processing"];
+
+                json health = {
+                        {"status",           "ok"},
+                        {"slots_idle",       n_idle_slots},
+                        {"slots_processing", n_processing_slots}};
+                res.status = 200; // HTTP OK
+                if (sparams.slots_endpoint && req.has_param("include_slots")) {
+                    health["slots"] = result.result_json["slots"];
                 }
-                if (available_slots > 0) {
-                    json health = {
-                            {"status",           "ok"},
-                            {"slots_idle",       available_slots},
-                            {"slots_processing", processing_slots}};
-                    res.set_content(health.dump(), "application/json");
-                    res.status = 200; // HTTP OK
-                } else {
-                    json health = {
-                            {"status",           "no slot available"},
-                            {"slots_idle",       available_slots},
-                            {"slots_processing", processing_slots}};
-                    res.set_content(health.dump(), "application/json");
+
+                if (n_idle_slots == 0) {
+                    health["status"] = "no slot available";
                     if (req.has_param("fail_on_no_slot")) {
                         res.status = 503; // HTTP Service Unavailable
-                    } else {
-                        res.status = 200; // HTTP OK
                     }
                 }
+                res.set_content(health.dump(), "application/json");
                 break;
             }
             case SERVER_STATE_LOADING_MODEL:
@@ -2600,26 +2644,20 @@ int main(int argc, char **argv)
 
     if (sparams.slots_endpoint) {
         svr.Get("/slots", [&](const httplib::Request&, httplib::Response& res) {
-            json slots;
-            for (llama_client_slot & slot : llama.slots) {
-                json slot_data = llama.get_formated_generation(slot);
-                slot_data["id"] = slot.id;
-                slot_data["task_id"] = slot.task_id;
-                slot_data["state"] = slot.state;
-                slot_data["prompt"] = slot.prompt;
-                slot_data["next_token"] = {
-                        {"has_next_token", slot.has_next_token},
-                        {"n_remain", slot.n_remaining},
-                        {"num_tokens_predicted", slot.n_decoded},
-                        {"stopped_eos", slot.stopped_eos},
-                        {"stopped_word", slot.stopped_word},
-                        {"stopped_limit", slot.stopped_limit},
-                        {"stopping_word", slot.stopping_word},
-                };
+            // request slots data using task queue
+            task_server task;
+            task.id = llama.queue_tasks.get_new_id();
+            task.type = TASK_TYPE_SLOTS_DATA;
+            task.target_id = -1;
 
-                slots.push_back(slot_data);
-            }
-            res.set_content(slots.dump(), "application/json");
+            llama.queue_results.add_waiting_task_id(task.id);
+            llama.queue_tasks.post(task);
+
+            // get the result
+            task_result result = llama.queue_results.recv(task.id);
+            llama.queue_results.remove_waiting_task_id(task.id);
+
+            res.set_content(result.result_json["slots"].dump(), "application/json");
             res.status = 200; // HTTP OK
         });
     }

examples/server/utils.hpp

@@ -49,7 +49,8 @@ enum server_state {
 enum task_type {
     TASK_TYPE_COMPLETION,
     TASK_TYPE_CANCEL,
-    TASK_TYPE_NEXT_RESPONSE
+    TASK_TYPE_NEXT_RESPONSE,
+    TASK_TYPE_SLOTS_DATA
 };
 
 struct task_server {