Re: Handling notices, warnings, etc.

"Joel Nothman" <[email protected]> Tue, 02 Jun 2009 01:57:41 +1000

Newsgroups	gmane.comp.python.db.psycopg.devel
Message-ID	<[email protected]>


On Tue, 02 Jun 2009 01:35:31 +1000, <psycopg-request-IAPFreCvJWPBWskQ1e/[email protected]>  
wrote:

> Il giorno lun, 01/06/2009 alle 17.32 +0200, Federico Di Gregorio ha  
> scritto:
>> Il giorno mar, 02/06/2009 alle 01.10 +1000, Joel Nothman ha scritto:
>> > At first I had troubles with Python threads (none was available to
>> > make
>> > the call to connection.notice_handler). If I have understood the
>> > nature of
>> > the threading problem correctly, I solved these by replacing
>> > Py_BEGIN_ALLOW_THREADS with gstate = PyGILState_Ensure(), etc.
>>
>> Your patch makes psycopg lock other Python threads during the execution
>> of possibly slow libpq calls. PyGILState_XXX functions are supposed to
>> be used from C threads to acquire the GIL and allow the execution of
>> Python API calls (locking out other threads) but we don't need that
>> because the code is already executing as a Python thread.
> You probably just want to put PyGILState_XXX around the Python API call
> in the notice processor.

Thanks Frederico. Much appreciated. I found the API documentation quite  
unclear as to the role of PyGILState_XXX (but I haven't dealt much with  
concurrency handling in a few years). And so I wasn't sure whether it did  
one thing or its reverse!

Using Ensure only for the API call, the updated diff is attached.

- Joel

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notice_handler.diff (application/octet-stream, 2.5 KB)

diff --git a/psycopg/connection.h b/psycopg/connection.h
index 701f46e..a0886ba 100644
--- a/psycopg/connection.h
+++ b/psycopg/connection.h
@@ -72,6 +72,7 @@ typedef struct {
     /* notice processing */
     PyObject *notice_list;
     PyObject *notice_filter;
+    PyObject *notice_handler; /* Optional callback */
     struct connectionObject_notice *notice_pending;
 
     /* notifies */
diff --git a/psycopg/connection_int.c b/psycopg/connection_int.c
index 8b54bad..5aa4b35 100644
--- a/psycopg/connection_int.c
+++ b/psycopg/connection_int.c
@@ -58,6 +58,13 @@ conn_notice_callback(void *args, const char *message)
         notice->message = strdup(message);
         notice->next = self->notice_pending;
         self->notice_pending = notice;
+
+        if (self->notice_handler != Py_None) {
+			PyGILState_STATE gstate;
+			gstate = PyGILState_Ensure();
+            PyObject_CallFunction(self->notice_handler, "s", message);
+            PyGILState_Release(gstate);
+        }
     }
 }
 
diff --git a/psycopg/connection_type.c b/psycopg/connection_type.c
index 4bba61c..cc31594 100644
--- a/psycopg/connection_type.c
+++ b/psycopg/connection_type.c
@@ -406,6 +406,7 @@ static struct PyMemberDef connectionObject_members[] = {
         "The current client encoding."},
     {"notices", T_OBJECT, offsetof(connectionObject, notice_list), RO},
     {"notifies", T_OBJECT, offsetof(connectionObject, notifies), RO},
+    {"notice_handler", T_OBJECT, offsetof(connectionObject, notice_handler), 0},
     {"dsn", T_STRING, offsetof(connectionObject, dsn), RO,
         "The current connection string."},
     {"status", T_INT,
@@ -469,6 +470,7 @@ connection_setup(connectionObject *self, const char *dsn)
     self->string_types = PyDict_New();
     self->binary_types = PyDict_New();
     self->notice_pending = NULL;
+    self->notice_handler = Py_None;
 
     pthread_mutex_init(&(self->lock), NULL);
 
@@ -512,6 +514,7 @@ connection_dealloc(PyObject* obj)
     Py_CLEAR(self->async_cursor);
     Py_CLEAR(self->notice_list);
     Py_CLEAR(self->notice_filter);
+    Py_CLEAR(self->notice_handler);
     Py_CLEAR(self->notifies);
     Py_CLEAR(self->string_types);
     Py_CLEAR(self->binary_types);
@@ -563,6 +566,7 @@ connection_traverse(connectionObject *self, visitproc visit, void *arg)
     Py_VISIT(self->async_cursor);
     Py_VISIT(self->notice_list);
     Py_VISIT(self->notice_filter);
+    Py_VISIT(self->notice_handler);
     Py_VISIT(self->notifies);
     Py_VISIT(self->string_types);
     Py_VISIT(self->binary_types);