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[NOGIL] Fix Producer.close() races with concurrent calls and with itself #2313

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[NOGIL] Fix Producer.close() races with concurrent calls and with itself #2313

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db3c515
Fix Producer.close() races with concurrent calls and with itself
ojasvajain Jul 21, 2026
3bc5ed9
Replace pytest-forked with subprocess-based test isolation
ojasvajain Jul 21, 2026
24e926c
Fix subprocess_isolated import and flaky close() timing assertion
ojasvajain Jul 21, 2026
b9118ac
Rename tests/parallel to tests/concurrency and add integration tests …
ojasvajain Jul 22, 2026
85f31c7
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ojasvajain Jul 27, 2026
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129 changes: 96 additions & 33 deletions src/confluent_kafka/src/Producer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,12 @@

#include "confluent_kafka.h"

#ifdef _WIN32
#include <windows.h>
#else
#include <unistd.h>
#endif


/**
* @brief KNOWN ISSUES
Expand Down Expand Up @@ -296,12 +302,11 @@
if (!dr_cb || dr_cb == Py_None)
dr_cb = self->u.Producer.default_dr_cb;

if (!self->rk) {
if (!Handle_enter_rk_use(self)) {
#ifdef RD_KAFKA_V_HEADERS
if (rd_headers)
rd_kafka_headers_destroy(rd_headers);
#endif
PyErr_SetString(PyExc_RuntimeError, ERR_MSG_PRODUCER_CLOSED);
return NULL;
}

Expand All @@ -323,6 +328,8 @@
key_len, msgstate);
#endif

Handle_exit_rk_use(self);

if (err) {
if (msgstate)
Producer_msgstate_destroy(msgstate);
Expand Down Expand Up @@ -421,12 +428,13 @@
if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|d", kws, &tmout))
return NULL;

if (!self->rk) {
PyErr_SetString(PyExc_RuntimeError, ERR_MSG_PRODUCER_CLOSED);
if (!Handle_enter_rk_use(self))
return NULL;
}

r = Producer_poll0(self, cfl_timeout_ms(tmout));

Handle_exit_rk_use(self);

if (r == -1)
return NULL;

Expand Down Expand Up @@ -469,10 +477,8 @@
if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|d", kws, &tmout))
return NULL;

if (!self->rk) {
PyErr_SetString(PyExc_RuntimeError, ERR_MSG_PRODUCER_CLOSED);
if (!Handle_enter_rk_use(self))
return NULL;
}

total_timeout_ms = cfl_timeout_ms(tmout);
CallState_begin(self, &cs);
Expand Down Expand Up @@ -507,6 +513,7 @@
* interruptibility) */
chunk_count++;
if (check_signals_between_chunks(self, &cs)) {
Handle_exit_rk_use(self);
return NULL; /* Signal detected */
}

Expand All @@ -524,12 +531,16 @@
}
}

if (!CallState_end(self, &cs))
if (!CallState_end(self, &cs)) {
Handle_exit_rk_use(self);
return NULL;
}

if (err) /* Get the queue length on error (timeout) */
qlen = rd_kafka_outq_len(self->rk);

Handle_exit_rk_use(self);

return cfl_PyInt_FromInt(qlen);
}

Expand All @@ -542,6 +553,37 @@
if (!self->rk)
Py_RETURN_TRUE;

/* Only one concurrent close() can destroy rk, otherwise,
* two threads could both reach rd_kafka_destroy() on the
* same handle (a double-free). The losing thread(s) wait for the
* winner to finish and then return True, same as a normal close(),
* rather than racing it. */
if (!atomic_int_cas(&self->closing, 0, 1)) {
while (self->rk) {
CallState_begin(self, &cs);
#ifdef _WIN32
Sleep(100);
#else
usleep(100000);

Check warning on line 567 in src/confluent_kafka/src/Producer.c

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SonarQube-Confluent / SonarQube Code Analysis

Remove use of this obsolete "usleep" function. Replace it by a call to "nanosleep" or "setitimer". 

[S1911] Obsolete POSIX functions should not be used
 See more on https://sonarqube.confluent.io/project/issues?id=confluent-kafka-python&pullRequest=2313&issues=8d11b50b-d243-4507-8ff4-d90aba771682&open=8d11b50b-d243-4507-8ff4-d90aba771682
#endif
CallState_end(self, &cs);

@k-raina Kaushik Raina (k-raina) Jul 29, 2026

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CallState_end returns 0 when PyErr_CheckSignals() fired or a callback crashed — and it leaves a Python exception set.
Should we check return value of this?

}
Py_RETURN_TRUE;
}

/* Signal in-flight calls to stop, and wait for them to finish
* using self->rk before destroying it -- see Handle_enter_rk_use().
* New calls will see `closing` and fail with ERR_MSG_PRODUCER_CLOSED. */
while (atomic_int_get(&self->active_calls) > 0) {
CallState_begin(self, &cs);
#ifdef _WIN32
Sleep(100);
#else
usleep(100000);

Check warning on line 582 in src/confluent_kafka/src/Producer.c

View check run for this annotation

SonarQube-Confluent / SonarQube Code Analysis

Remove use of this obsolete "usleep" function. Replace it by a call to "nanosleep" or "setitimer". 

[S1911] Obsolete POSIX functions should not be used
 See more on https://sonarqube.confluent.io/project/issues?id=confluent-kafka-python&pullRequest=2313&issues=50f38792-4a85-49bc-bde2-26a440c113fa&open=50f38792-4a85-49bc-bde2-26a440c113fa
#endif
CallState_end(self, &cs);
}

CallState_begin(self, &cs);

/* Flush any pending messages (wait indefinitely to ensure delivery) */
Expand Down Expand Up @@ -817,10 +859,8 @@
return cfl_PyInt_FromInt(0);
}

if (!self->rk) {
PyErr_SetString(PyExc_RuntimeError, ERR_MSG_PRODUCER_CLOSED);
if (!Handle_enter_rk_use(self))
return NULL;
}

/* Allocate arrays for librdkafka messages and msgstates */
rkmessages = calloc(message_cnt, sizeof(*rkmessages));
Expand Down Expand Up @@ -849,6 +889,8 @@
messages_list, rkt, partition, rkmessages, msgstates, message_cnt);

cleanup:
Handle_exit_rk_use(self);

/* Cleanup resources */
if (rkt)

@k-raina Kaushik Raina (k-raina) Jul 29, 2026

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A concurrent close() frees rk, and rd_kafka_topic_destroy will use rkt->rkt_rk. Can this cause concurrency bug?

rd_kafka_topic_destroy(rkt);
Expand All @@ -871,21 +913,22 @@
if (!PyArg_ParseTuple(args, "|d", &tmout))
return NULL;

if (!self->rk) {
PyErr_SetString(PyExc_RuntimeError, ERR_MSG_PRODUCER_CLOSED);
if (!Handle_enter_rk_use(self))
return NULL;
}

CallState_begin(self, &cs);

error = rd_kafka_init_transactions(self->rk, cfl_timeout_ms(tmout));

if (!CallState_end(self, &cs)) {
Handle_exit_rk_use(self);
if (error) /* Ignore error in favour of callstate exception */
rd_kafka_error_destroy(error);
return NULL;
}

Handle_exit_rk_use(self);

if (error) {
cfl_PyErr_from_error_destroy(error);
return NULL;
Expand All @@ -897,13 +940,13 @@
static PyObject *Producer_begin_transaction(Handle *self) {
rd_kafka_error_t *error;

if (!self->rk) {
PyErr_SetString(PyExc_RuntimeError, ERR_MSG_PRODUCER_CLOSED);
if (!Handle_enter_rk_use(self))
return NULL;
}

error = rd_kafka_begin_transaction(self->rk);

Handle_exit_rk_use(self);

if (error) {
cfl_PyErr_from_error_destroy(error);
return NULL;
Expand All @@ -924,16 +967,17 @@
if (!PyArg_ParseTuple(args, "OO|d", &offsets, &metadata, &tmout))
return NULL;

if (!self->rk) {
PyErr_SetString(PyExc_RuntimeError, ERR_MSG_PRODUCER_CLOSED);
if (!Handle_enter_rk_use(self))
return NULL;
}

if (!(c_offsets = py_to_c_parts(offsets)))
if (!(c_offsets = py_to_c_parts(offsets))) {
Handle_exit_rk_use(self);

@k-raina Kaushik Raina (k-raina) Jul 29, 2026

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Earch exist branch calls Handle_exit_rk_use. Wondering if we could use "goto exit:" semantics to future proof codebase from "new branch missing Handle_exit_rk_use calls" bugs?

Eg. go to pattern is used in other parts of codebase

confluent-kafka-python/src/confluent_kafka/src/Producer.c

Lines 891 to 905 in 85f31c7

cleanup:
Handle_exit_rk_use(self);
/* Cleanup resources */
if (rkt)
rd_kafka_topic_destroy(rkt);
if (rkmessages)
free(rkmessages);
if (msgstates)
free(msgstates);
if (PyErr_Occurred())
return NULL;
return cfl_PyInt_FromInt(good);

return NULL;
}

if (!(cgmd = py_to_c_cgmd(metadata))) {
rd_kafka_topic_partition_list_destroy(c_offsets);
Handle_exit_rk_use(self);
return NULL;
}

Expand All @@ -946,11 +990,14 @@
rd_kafka_topic_partition_list_destroy(c_offsets);

if (!CallState_end(self, &cs)) {
Handle_exit_rk_use(self);
if (error) /* Ignore error in favour of callstate exception */
rd_kafka_error_destroy(error);
return NULL;
}

Handle_exit_rk_use(self);

if (error) {
cfl_PyErr_from_error_destroy(error);
return NULL;
Expand All @@ -967,21 +1014,22 @@
if (!PyArg_ParseTuple(args, "|d", &tmout))
return NULL;

if (!self->rk) {
PyErr_SetString(PyExc_RuntimeError, ERR_MSG_PRODUCER_CLOSED);
if (!Handle_enter_rk_use(self))
return NULL;
}

CallState_begin(self, &cs);

error = rd_kafka_commit_transaction(self->rk, cfl_timeout_ms(tmout));

if (!CallState_end(self, &cs)) {
Handle_exit_rk_use(self);
if (error) /* Ignore error in favour of callstate exception */
rd_kafka_error_destroy(error);
return NULL;
}

Handle_exit_rk_use(self);

if (error) {
cfl_PyErr_from_error_destroy(error);
return NULL;
Expand All @@ -998,21 +1046,22 @@
if (!PyArg_ParseTuple(args, "|d", &tmout))
return NULL;

if (!self->rk) {
PyErr_SetString(PyExc_RuntimeError, ERR_MSG_PRODUCER_CLOSED);
if (!Handle_enter_rk_use(self))
return NULL;
}

CallState_begin(self, &cs);

error = rd_kafka_abort_transaction(self->rk, cfl_timeout_ms(tmout));

if (!CallState_end(self, &cs)) {
Handle_exit_rk_use(self);
if (error) /* Ignore error in favour of callstate exception */
rd_kafka_error_destroy(error);
return NULL;
}

Handle_exit_rk_use(self);

if (error) {
cfl_PyErr_from_error_destroy(error);
return NULL;
Expand All @@ -1034,10 +1083,8 @@
&in_flight, &blocking))
return NULL;

if (!self->rk) {
PyErr_SetString(PyExc_RuntimeError, ERR_MSG_PRODUCER_CLOSED);
if (!Handle_enter_rk_use(self))
return NULL;
}

if (in_queue)
purge_strategy = RD_KAFKA_PURGE_F_QUEUE;
Expand All @@ -1048,6 +1095,8 @@

err = rd_kafka_purge(self->rk, purge_strategy);

Handle_exit_rk_use(self);

if (err) {
cfl_PyErr_Format(err, "Purge failed: %s",
rd_kafka_err2str(err));
Expand Down Expand Up @@ -1403,9 +1452,23 @@


static Py_ssize_t Producer__len__(Handle *self) {
if (!self->rk)
Py_ssize_t len;

/* __len__ must never raise, so we can't use Handle_enter_rk_use()
* (which sets an exception on failure) -- fall back to returning 0,
* , if the Handle is closed/closing. */
if (atomic_int_get(&self->closing) || !self->rk)
return 0;
atomic_int_inc(&self->active_calls);
if (atomic_int_get(&self->closing) || !self->rk) {
atomic_int_dec(&self->active_calls);
return 0;
return rd_kafka_outq_len(self->rk);
}

len = rd_kafka_outq_len(self->rk);

atomic_int_dec(&self->active_calls);
return len;
}


Expand Down
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