otel: fix segfaults when otel not configured

src/nxt_otel.c

@@ -67,7 +67,7 @@ nxt_otel_propagate_header(nxt_task_t *task, nxt_http_request_t *r)
      * if we didn't inherit a trace id then we need to add the
      * traceparent header to the request
      */
-    } else if (r->otel->trace_id == NULL) {
+    } else {
 
         nxt_otel_rs_copy_traceparent(traceval, r->otel->trace);
 
@@ -92,15 +92,6 @@ nxt_otel_propagate_header(nxt_task_t *task, nxt_http_request_t *r)
 
         nxt_otel_rs_add_event_to_trace(r->otel->trace,
                                        &traceparent_name, &traceparent);
-
-    /*
-     * potentially nxt_http_request_error called before headers
-     * finished parsing
-     */
-    } else {
-        nxt_log(task, NXT_LOG_DEBUG,
-                "not propagating tracing headers for missing trace");
-        return;
     }
 
     f = nxt_list_add(r->resp.fields);
@@ -311,17 +302,13 @@ nxt_otel_test_and_call_state(nxt_task_t *task, nxt_http_request_t *r)
 void
 nxt_otel_request_error_path(nxt_task_t *task, nxt_http_request_t *r)
 {
-    if (r->otel->trace == NULL) {
+    if (r->otel == NULL || r->otel->trace == NULL) {
         return;
     }
 
     // response headers have been cleared
     nxt_otel_propagate_header(task, r);
-
-    // collect span immediately
-    if (r->otel) {
-        nxt_otel_state_transition(r->otel, NXT_OTEL_COLLECT_STATE);
-    }
+    nxt_otel_state_transition(r->otel, NXT_OTEL_COLLECT_STATE);
     nxt_otel_test_and_call_state(task, r);
 }
 
@@ -344,6 +331,9 @@ nxt_otel_parse_traceparent(void *ctx, nxt_http_field_t *field, uintptr_t data)
      */
 
     r = ctx;
+    if (r->otel == NULL) {
+        return NXT_OK;
+    }
 
     if (field->value_length != NXT_OTEL_TRACEPARENT_LEN) {
         goto error_state;
@@ -391,6 +381,10 @@ nxt_otel_parse_tracestate(void *ctx, nxt_http_field_t *field, uintptr_t data)
     s.start = field->value;
 
     r = ctx;
+    if (r->otel == NULL) {
+        return NXT_OK;
+    }
+
     r->otel->trace_state = s;
 
     /*