server : add arg for disabling prompt caching (#18776)

* server : add arg for disabling prompt caching

Disabling prompt caching is useful for clients who are restricted to
sending only OpenAI-compat requests and want deterministic
responses.

* address review comments

* address review comments

common/arg.cpp

@@ -2877,10 +2877,18 @@ common_params_context common_params_parser_init(common_params & params, llama_ex
             params.n_threads_http = value;
         }
     ).set_examples({LLAMA_EXAMPLE_SERVER}).set_env("LLAMA_ARG_THREADS_HTTP"));
+    add_opt(common_arg(
+        {"--cache-prompt"},
+        {"--no-cache-prompt"},
+        string_format("whether to enable prompt caching (default: %s)", params.cache_prompt ? "enabled" : "disabled"),
+        [](common_params & params, bool value) {
+            params.cache_prompt = value;
+        }
+    ).set_examples({LLAMA_EXAMPLE_SERVER}).set_env("LLAMA_ARG_CACHE_PROMPT"));
     add_opt(common_arg(
         {"--cache-reuse"}, "N",
         string_format(
-            "min chunk size to attempt reusing from the cache via KV shifting (default: %d)\n"
+            "min chunk size to attempt reusing from the cache via KV shifting, requires prompt caching to be enabled (default: %d)\n"
             "[(card)](https://ggml.ai/f0.png)", params.n_cache_reuse
         ),
         [](common_params & params, int value) {

common/common.h

@@ -476,6 +476,7 @@ struct common_params {
     int32_t timeout_write     = timeout_read; // http write timeout in seconds
     int32_t n_threads_http    = -1;           // number of threads to process HTTP requests (TODO: support threadpool)
     int32_t n_cache_reuse     = 0;            // min chunk size to reuse from the cache via KV shifting
+    bool    cache_prompt      = true;         // whether to enable prompt caching
     int32_t n_ctx_checkpoints = 8;            // max number of context checkpoints per slot
     int32_t cache_ram_mib     = 8192;         // -1 = no limit, 0 - disable, 1 = 1 MiB, etc.
 

tools/server/server-task.cpp

@@ -160,6 +160,7 @@ task_params server_task::params_from_json_cmpl(
     defaults.n_keep        = params_base.n_keep;
     defaults.n_predict     = params_base.n_predict;
     defaults.n_cache_reuse = params_base.n_cache_reuse;
+    defaults.cache_prompt  = params_base.cache_prompt;
     defaults.antiprompt    = params_base.antiprompt;
 
     // enabling this will output extra debug information in the HTTP responses from the server
@@ -169,7 +170,7 @@ task_params server_task::params_from_json_cmpl(
     params.stream           = json_value(data,       "stream",             false);
     auto stream_opt         = json_value(data,       "stream_options",     json::object());
     params.include_usage    = json_value(stream_opt, "include_usage",      false);
-    params.cache_prompt     = json_value(data,       "cache_prompt",       true);
+    params.cache_prompt     = json_value(data,       "cache_prompt",       defaults.cache_prompt);
     params.return_tokens    = json_value(data,       "return_tokens",      false);
     params.return_progress  = json_value(data,       "return_progress",    false);
     params.n_predict        = json_value(data,       "n_predict",          json_value(data, "max_tokens", defaults.n_predict));