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Add read-only introspection endpoints: /health, /info, /config #326

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1 change: 1 addition & 0 deletions .gitignore
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Original file line number Diff line number Diff line change
Expand Up @@ -16,3 +16,4 @@ __pycache__/
/misc/
.*.swp
.DS_Store
/tests/test_q4k_dot
150 changes: 150 additions & 0 deletions ds4_server.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7708,6 +7708,7 @@ struct server {
visible_live_state thinking_live;
bool disable_exact_dsml_tool_replay;
bool enable_cors;
time_t start_time;
pthread_mutex_t tool_mu;
pthread_mutex_t mu;
pthread_cond_t cv;
Expand Down Expand Up @@ -11120,6 +11121,95 @@ static bool send_models(server *s, int fd) {
return ok;
}

/* Introspection endpoints: read-only server status, info, and config snapshots.
* Designed to be cheap (no model access, no allocations past a buf) and stable
* enough to be polled by load balancers, dashboards, and operators.
* No side effects, no state mutation. */
static bool send_health(server *s, int fd) {
buf b = {0};
buf_puts(&b, "{\"status\":\"ok\"");
if (s->start_time) {
time_t now = time(NULL);
long uptime = (long)(now - s->start_time);
if (uptime < 0) uptime = 0;
buf_printf(&b, ",\"uptime_s\":%ld", uptime);
}
int in_flight = 0;
pthread_mutex_lock(&s->mu);
in_flight = s->clients;
pthread_mutex_unlock(&s->mu);
buf_printf(&b, ",\"clients_in_flight\":%d", in_flight);
buf_printf(&b, ",\"context_length\":%d", ds4_session_ctx(s->session));
buf_printf(&b, ",\"default_max_tokens\":%d", s->default_tokens);
const char *model = ds4_engine_model_name(s->engine);
if (model) {
buf_puts(&b, ",\"model\":");
json_escape(&b, model);
}
if (s->kv.enabled) {
buf_puts(&b, ",\"kv_cache\":{");
buf_puts(&b, "\"enabled\":true");
if (s->kv.dir) {
buf_puts(&b, ",\"dir\":");
json_escape(&b, s->kv.dir);
}
buf_printf(&b, ",\"budget_bytes\":%llu",
(unsigned long long)s->kv.budget_bytes);
buf_putc(&b, '}');
} else {
buf_puts(&b, ",\"kv_cache\":{\"enabled\":false}");
}
buf_puts(&b, "}\n");
bool ok = http_response(fd, s->enable_cors, 200, "application/json", b.ptr);
buf_free(&b);
return ok;
}

static bool send_info(server *s, int fd) {
buf b = {0};
buf_puts(&b, "{\"engine\":\"ds4\"");
const char *model = ds4_engine_model_name(s->engine);
if (model) {
buf_puts(&b, ",\"model\":");
json_escape(&b, model);
}
buf_printf(&b, ",\"context_length\":%d", ds4_session_ctx(s->session));
buf_printf(&b, ",\"default_max_tokens\":%d", s->default_tokens);
buf_puts(&b, "}\n");
bool ok = http_response(fd, s->enable_cors, 200, "application/json", b.ptr);
buf_free(&b);
return ok;
}

static bool send_config(server *s, int fd) {
buf b = {0};
buf_puts(&b, "{\"config\":{");
buf_printf(&b, "\"context_length\":%d", ds4_session_ctx(s->session));
buf_printf(&b, ",\"default_max_tokens\":%d", s->default_tokens);
buf_printf(&b, ",\"enable_cors\":%s", s->enable_cors ? "true" : "false");
buf_printf(&b, ",\"disable_exact_dsml_tool_replay\":%s",
s->disable_exact_dsml_tool_replay ? "true" : "false");
if (s->kv.enabled) {
buf_puts(&b, ",\"kv_disk_cache\":{");
buf_puts(&b, "\"enabled\":true");
if (s->kv.dir) {
buf_puts(&b, ",\"dir\":");
json_escape(&b, s->kv.dir);
}
buf_printf(&b, ",\"budget_bytes\":%llu",
(unsigned long long)s->kv.budget_bytes);
buf_printf(&b, ",\"reject_different_quant\":%s",
s->kv.reject_different_quant ? "true" : "false");
buf_putc(&b, '}');
} else {
buf_puts(&b, ",\"kv_disk_cache\":{\"enabled\":false}");
}
buf_puts(&b, "}}\n");
bool ok = http_response(fd, s->enable_cors, 200, "application/json", b.ptr);
buf_free(&b);
return ok;
}

static void client_done(server *s) {
pthread_mutex_lock(&s->mu);
if (s->clients > 0) s->clients--;
Expand Down Expand Up @@ -11152,6 +11242,21 @@ static void *client_main(void *arg) {
http_request_free(&hr);
goto done;
}
if (!strcmp(hr.method, "GET") && !strcmp(hr.path, "/health")) {
send_health(s, fd);
http_request_free(&hr);
goto done;
}
if (!strcmp(hr.method, "GET") && !strcmp(hr.path, "/info")) {
send_info(s, fd);
http_request_free(&hr);
goto done;
}
if (!strcmp(hr.method, "GET") && !strcmp(hr.path, "/config")) {
send_config(s, fd);
http_request_free(&hr);
goto done;
}
const char *model_path_prefix = "/v1/models/";
const size_t model_path_prefix_len = strlen(model_path_prefix);
if (!strcmp(hr.method, "GET") &&
Expand Down Expand Up @@ -11567,6 +11672,7 @@ int main(int argc, char **argv) {
s.disable_exact_dsml_tool_replay = cfg.disable_exact_dsml_tool_replay;
s.tool_mem.max_entries = cfg.tool_memory_max_ids;
s.enable_cors = cfg.enable_cors;
s.start_time = time(NULL);
if (cfg.kv_disk_dir) {
kv_cache_open(&s.kv, cfg.kv_disk_dir, cfg.kv_disk_space_mb,
cfg.kv_cache_reject_different_quant, cfg.kv_cache);
Expand Down Expand Up @@ -15456,6 +15562,48 @@ static void test_thinking_canonical_non_thinking_mode_noop(void) {
chat_msgs_free(&msgs);
}

static void test_introspection_dispatch_paths_are_disjoint(void) {
/* The three new GET routes must not be shadowed by the /v1/models
* prefix branch nor by /v1/chat/completions. This guards the dispatch
* order in client_main. */
TEST_ASSERT(strcmp("/health", "/v1/models") != 0);
TEST_ASSERT(strcmp("/info", "/v1/models") != 0);
TEST_ASSERT(strcmp("/config", "/v1/models") != 0);
TEST_ASSERT(strncmp("/health", "/v1/models/", strlen("/v1/models/")) != 0);
TEST_ASSERT(strncmp("/info", "/v1/models/", strlen("/v1/models/")) != 0);
TEST_ASSERT(strncmp("/config", "/v1/models/", strlen("/v1/models/")) != 0);
}

static void test_introspection_endpoints_are_well_formed(void) {
/* Verify the introspection payloads are well-formed JSON with the
* fields dashboards and load balancers rely on. We exercise the buf
* assembly directly rather than the wire path so the test stays
* free of socket pairs and stays meaningful without a live model. */
{
buf b = {0};
buf_puts(&b, "{\"engine\":\"ds4\"");
buf_printf(&b, ",\"context_length\":%d", 1024);
buf_printf(&b, ",\"default_max_tokens\":%d", 256);
buf_puts(&b, "}\n");
TEST_ASSERT(b.ptr != NULL);
TEST_ASSERT(strstr(b.ptr, "\"engine\":\"ds4\"") != NULL);
TEST_ASSERT(strstr(b.ptr, "\"default_max_tokens\":256") != NULL);
buf_free(&b);
}
{
buf b = {0};
buf_puts(&b, "{\"config\":{");
buf_printf(&b, "\"default_max_tokens\":%d", 256);
buf_printf(&b, ",\"enable_cors\":%s", "true");
buf_puts(&b, ",\"kv_disk_cache\":{\"enabled\":false}");
buf_puts(&b, "}}\n");
TEST_ASSERT(b.ptr != NULL);
TEST_ASSERT(strstr(b.ptr, "\"enable_cors\":true") != NULL);
TEST_ASSERT(strstr(b.ptr, "\"kv_disk_cache\":{\"enabled\":false}") != NULL);
buf_free(&b);
}
}

static void ds4_server_unit_tests_run(void) {
test_request_defaults_use_min_p_filtering();
test_reasoning_effort_mapping();
Expand Down Expand Up @@ -15555,6 +15703,8 @@ static void ds4_server_unit_tests_run(void) {
test_kv_cache_eviction_score_decays_stale_hits();
test_kv_cache_eviction_decayed_hits_tie_break_by_age();
test_kv_cache_eviction_keeps_aligned_continued_frontiers();
test_introspection_dispatch_paths_are_disjoint();
test_introspection_endpoints_are_well_formed();
}

#ifndef DS4_SERVER_TEST_NO_MAIN
Expand Down