fix: do not consume a lot of time to collect debug data if no one is listening

cubicweb/cwvreg.py

@@ -38,7 +38,7 @@ from rql import RQLHelper
 from yams.constraints import BASE_CONVERTERS
 
 from cubicweb import _
-from cubicweb.debug import emit_to_debug_channel
+from cubicweb.debug import debug_channel_has_subscribers, emit_to_debug_channel
 from cubicweb import (
     CW_SOFTWARE_ROOT,
     ETYPE_NAME_MAP,
@@ -84,7 +84,8 @@ class CWRegistry(Registry):
         """
         super().__init__(True)
         self.vreg = vreg
-        self.add_select_best_listener(self._emit_registry_debug_information)
+        if debug_channel_has_subscribers("registry_decisions"):
+            self.add_select_best_listener(self._emit_registry_debug_information)
 
     def _emit_registry_debug_information(self, debug_registry_select_best):
         emit_to_debug_channel("registry_decisions", debug_registry_select_best)

cubicweb/debug.py

@@ -30,6 +30,10 @@ SUBSCRIBERS = {
 }
 
 
+def debug_channel_has_subscribers(channel):
+    return len(SUBSCRIBERS.get(channel, [])) > 0
+
+
 def subscribe_to_debug_channel(channel, subscriber):
     """
     Allow to subscribe a callable to one of the debug channels.

cubicweb/server/querier.py

@@ -43,7 +43,7 @@ from cubicweb import ValidationError, Unauthorized, UnknownEid, QueryError
 from cubicweb.rqlrewrite import RQLRelationRewriter
 from cubicweb import Binary, server
 from cubicweb.rset import ResultSet
-from cubicweb.debug import emit_to_debug_channel
+from cubicweb.debug import debug_channel_has_subscribers, emit_to_debug_channel
 
 from cubicweb.utils import RepeatList
 from cubicweb.misc.source_highlight import highlight_terminal
@@ -544,6 +544,8 @@ class QuerierHelper:
         always use substitute arguments in queries (i.e. avoid query such as
         'Any X WHERE X eid 123'!)
         """
+        use_debug_channel = debug_channel_has_subscribers("rql")
+
         if server.DEBUG & (server.DBG_RQL | server.DBG_SQL):
             if server.DEBUG & (server.DBG_MORE | server.DBG_SQL):
                 print("*" * 80)
@@ -583,14 +585,15 @@ class QuerierHelper:
         plan.rql_query_tracing_token = str(uuid.uuid4())
         prepare_plan(plan, self.schema, self._repo.vreg.rqlhelper)
 
-        query_debug_informations = {
-            "rql": rql,
-            "rql_query_tracing_token": plan.rql_query_tracing_token,
-            "args": args,
-            # remove the last part of the stack which is: this line
-            "callstack": "".join(traceback.format_stack()[:-1]),
-            "description": "",
-        }
+        if use_debug_channel:
+            query_debug_informations = {
+                "rql": rql,
+                "rql_query_tracing_token": plan.rql_query_tracing_token,
+                "args": args,
+                # remove the last part of the stack which is: this line
+                "callstack": "".join(traceback.format_stack()[:-1]),
+                "description": "",
+            }
 
         start = time.time()
         # execute the plan
@@ -609,8 +612,9 @@ class QuerierHelper:
                 cnx.commit_state = "uncommitable"
             raise
 
-        query_debug_informations["time"] = (time.time() - start) * 1000
-        query_debug_informations["result"] = results
+        if use_debug_channel:
+            query_debug_informations["time"] = (time.time() - start) * 1000
+            query_debug_informations["result"] = results
 
         # build a description for the results if necessary
         descr = ()
@@ -640,9 +644,11 @@ class QuerierHelper:
                 descr = _build_descr(cnx, results, basedescr, todetermine)
             # FIXME: get number of affected entities / relations on non
             # selection queries ?
-            query_debug_informations["description"] = descr
+            if use_debug_channel:
+                query_debug_informations["description"] = descr
 
-        emit_to_debug_channel("rql", query_debug_informations)
+        if use_debug_channel:
+            emit_to_debug_channel("rql", query_debug_informations)
 
         # return a result set object
         return ResultSet(results, rql, args, descr, variables)

cubicweb/server/sources/native.py

@@ -49,7 +49,7 @@ from cubicweb import (
     ViolatedConstraint,
 )
 from cubicweb import transaction as tx, server, neg_role, _
-from cubicweb.debug import emit_to_debug_channel
+from cubicweb.debug import debug_channel_has_subscribers, emit_to_debug_channel
 from cubicweb.schema import VIRTUAL_RTYPES
 from cubicweb.cwconfig import CubicWebNoAppConfiguration
 from cubicweb.server import hook
@@ -792,14 +792,15 @@ class NativeSQLSource(SQLAdapterMixIn, AbstractSource):
         """Execute a query.
         it's a function just so that it shows up in profiling
         """
-
-        query_debug_informations = {
-            "sql": query,
-            "args": args,
-            "rollback": False,
-            "callstack": "".join(traceback.format_stack()[:-1]),
-            "rql_query_tracing_token": rql_query_tracing_token,
-        }
+        use_debug_channel = debug_channel_has_subscribers("sql")
+        if use_debug_channel:
+            query_debug_informations = {
+                "sql": query,
+                "args": args,
+                "rollback": False,
+                "callstack": "".join(traceback.format_stack()[:-1]),
+                "rql_query_tracing_token": rql_query_tracing_token,
+            }
 
         start = time.time()
 
@@ -819,7 +820,8 @@ class NativeSQLSource(SQLAdapterMixIn, AbstractSource):
             if rollback:
                 try:
                     cnx.cnxset.rollback()
-                    query_debug_informations["rollback"] = True
+                    if use_debug_channel:
+                        query_debug_informations["rollback"] = True
                     if self.repo.config.mode != "test":
                         self.debug("transaction has been rolled back")
                 except Exception as rollback_exc:
@@ -872,8 +874,9 @@ class NativeSQLSource(SQLAdapterMixIn, AbstractSource):
             )
             raise
         finally:
-            query_debug_informations["time"] = (time.time() - start) * 1000
-            emit_to_debug_channel("sql", query_debug_informations)
+            if use_debug_channel:
+                query_debug_informations["time"] = (time.time() - start) * 1000
+                emit_to_debug_channel("sql", query_debug_informations)
         return cursor
 
     def doexecmany(self, cnx, query, args):