From 1a66f5f232d6c2869ef4e439eafe5a820f61a976 Mon Sep 17 00:00:00 2001

From: Thierry Bordaz <tbordaz@redhat.com>

Date: Wed, 15 Feb 2017 11:31:27 +0100

Subject: [PATCH] Ticket 49076 - To debug DB_DEADLOCK condition, allow to reset

 DB_TXN_NOWAIT flag on txn_begin

Bug Description:

    For debug reason it is interesting to have a new configuration ldbm backend config

    option (nsslapd-db-transaction-wait) that allows to hang on deadlock

    rather to let the server handling retries.

Fix Description:

    The fix introduce a new attribute nsslapd-db-transaction-wait under

    "cn=config,cn=ldbm database,cn=plugins,cn=config".

    By default it is "off" (ldbm returns DB_DEADLOCK) and can be changed

    online.

    It is taken into account when a new transcation begin.

https://pagure.io/389-ds-base/issue/49076

Reviewed by: William Brown, Ludwig Krispenz

Platforms tested: F23

Flag Day: no

Doc impact: no

---

 dirsrvtests/tests/tickets/ticket49076_test.py | 103 ++++++++++++++++++++++++++

 ldap/servers/slapd/back-ldbm/dblayer.c        |   9 ++-

 ldap/servers/slapd/back-ldbm/dblayer.h        |   3 +

 ldap/servers/slapd/back-ldbm/ldbm_config.c    |  22 ++++++

 ldap/servers/slapd/back-ldbm/ldbm_config.h    |   1 +

 5 files changed, 137 insertions(+), 1 deletion(-)

 create mode 100644 dirsrvtests/tests/tickets/ticket49076_test.py

diff --git a/dirsrvtests/tests/tickets/ticket49076_test.py b/dirsrvtests/tests/tickets/ticket49076_test.py

new file mode 100644

index 0000000..c4a2c1b

--- /dev/null

+++ b/dirsrvtests/tests/tickets/ticket49076_test.py

@@ -0,0 +1,103 @@

+import time

+import ldap

+import logging

+import pytest

+from lib389 import DirSrv, Entry, tools, tasks

+from lib389.tools import DirSrvTools

+from lib389._constants import *

+from lib389.properties import *

+from lib389.tasks import *

+from lib389.utils import *

+from lib389.topologies import topology_st as topo

+

+DEBUGGING = os.getenv("DEBUGGING", default=False)

+if DEBUGGING:

+    logging.getLogger(__name__).setLevel(logging.DEBUG)

+else:

+    logging.getLogger(__name__).setLevel(logging.INFO)

+log = logging.getLogger(__name__)

+

+ldbm_config = "cn=config,%s" % (DN_LDBM)

+txn_begin_flag = "nsslapd-db-transaction-wait"

+TEST_USER_DN = 'cn=test,%s' % SUFFIX

+TEST_USER = "test"

+

+def _check_configured_value(topology_st, attr=txn_begin_flag, expected_value=None, required=False):

+    entries = topology_st.standalone.search_s(ldbm_config, ldap.SCOPE_BASE, 'cn=config')

+    if required:

+        assert (entries[0].hasValue(attr))

+    if entries[0].hasValue(attr):

+        topology_st.standalone.log.info('Current value is %s' % entries[0].getValue(attr))

+        assert (entries[0].getValue(attr) == expected_value)

+        

+def _update_db(topology_st):

+    topology_st.standalone.add_s(

+        Entry((TEST_USER_DN, {'objectclass': "top person organizationalPerson inetOrgPerson".split(),

+                              'cn': TEST_USER,

+                              'sn': TEST_USER,

+                              'givenname': TEST_USER})))

+    topology_st.standalone.delete_s(TEST_USER_DN)

+

+def test_ticket49076(topo):

+    """Write your testcase here...

+

+    Also, if you need any testcase initialization,

+    please, write additional fixture for that(include finalizer).

+    """

+    

+    # check default value is DB_TXN_NOWAIT

+    _check_configured_value(topo, expected_value="off")

+    

+    # tests we are able to update DB

+    _update_db(topo)

+    

+    # switch to wait mode

+    topo.standalone.modify_s(ldbm_config,

+                                    [(ldap.MOD_REPLACE, txn_begin_flag, "on")])

+                                    # check default value is DB_TXN_NOWAIT

+    _check_configured_value(topo, expected_value="on")

+    _update_db(topo)

+    

+    

+    # switch back to "normal mode"

+    topo.standalone.modify_s(ldbm_config,

+                                    [(ldap.MOD_REPLACE, txn_begin_flag, "off")])

+    # check default value is DB_TXN_NOWAIT

+    _check_configured_value(topo, expected_value="off")

+    # tests we are able to update DB

+    _update_db(topo)

+    

+    # check that settings are not reset by restart

+    topo.standalone.modify_s(ldbm_config,

+                                    [(ldap.MOD_REPLACE, txn_begin_flag, "on")])

+                                    # check default value is DB_TXN_NOWAIT

+    _check_configured_value(topo, expected_value="on")

+    _update_db(topo)

+    topo.standalone.restart(timeout=10)

+    _check_configured_value(topo, expected_value="on")

+    _update_db(topo)

+    

+    # switch default value

+    topo.standalone.modify_s(ldbm_config,

+                                    [(ldap.MOD_DELETE, txn_begin_flag, None)])

+    # check default value is DB_TXN_NOWAIT

+    _check_configured_value(topo, expected_value="off")

+    # tests we are able to update DB

+    _update_db(topo)

+    topo.standalone.restart(timeout=10)

+    _check_configured_value(topo, expected_value="off")

+    # tests we are able to update DB

+    _update_db(topo)    

+                              

+

+    if DEBUGGING:

+        # Add debugging steps(if any)...

+        pass

+

+

+if __name__ == '__main__':

+    # Run isolated

+    # -s for DEBUG mode

+    CURRENT_FILE = os.path.realpath(__file__)

+    pytest.main("-s %s" % CURRENT_FILE)

+

diff --git a/ldap/servers/slapd/back-ldbm/dblayer.c b/ldap/servers/slapd/back-ldbm/dblayer.c

index 683994f..507a3cc 100644

--- a/ldap/servers/slapd/back-ldbm/dblayer.c

+++ b/ldap/servers/slapd/back-ldbm/dblayer.c

@@ -3374,6 +3374,8 @@ dblayer_txn_begin_ext(struct ldbminfo *li, back_txnid parent_txn, back_txn *txn,

     if (priv->dblayer_enable_transactions)

     {

+        int txn_begin_flags;

+

         dblayer_private_env *pEnv = priv->dblayer_env;

         if(use_lock) slapi_rwlock_rdlock(pEnv->dblayer_env_lock);

         if (!parent_txn)

@@ -3383,11 +3385,16 @@ dblayer_txn_begin_ext(struct ldbminfo *li, back_txnid parent_txn, back_txn *txn,

             if (par_txn_txn) {

                 parent_txn = par_txn_txn->back_txn_txn;

             }

+                }

+        if (priv->dblayer_txn_wait) {

+                txn_begin_flags = 0;

+        } else {

+                txn_begin_flags = DB_TXN_NOWAIT;

         }

         return_value = TXN_BEGIN(pEnv->dblayer_DB_ENV,

                                  (DB_TXN*)parent_txn,

                                  &new_txn.back_txn_txn,

-                                 DB_TXN_NOWAIT);

+                                 txn_begin_flags);

         if (0 != return_value) 

         {

             if(use_lock) slapi_rwlock_unlock(priv->dblayer_env->dblayer_env_lock);

diff --git a/ldap/servers/slapd/back-ldbm/dblayer.h b/ldap/servers/slapd/back-ldbm/dblayer.h

index e02e6e0..e4307fc 100644

--- a/ldap/servers/slapd/back-ldbm/dblayer.h

+++ b/ldap/servers/slapd/back-ldbm/dblayer.h

@@ -104,6 +104,9 @@ struct dblayer_private

                                         * the mpool */

     int dblayer_recovery_required;

     int dblayer_enable_transactions;

+    int dblayer_txn_wait;           /* Default is "off" (DB_TXN_NOWAIT) but for

+                                     * support purpose it could be helpful to set

+                                     * "on" so that backend hang on deadlock */

     int dblayer_durable_transactions;

     int dblayer_checkpoint_interval;

     int dblayer_circular_logging;

diff --git a/ldap/servers/slapd/back-ldbm/ldbm_config.c b/ldap/servers/slapd/back-ldbm/ldbm_config.c

index 8541224..dfe7a13 100644

--- a/ldap/servers/slapd/back-ldbm/ldbm_config.c

+++ b/ldap/servers/slapd/back-ldbm/ldbm_config.c

@@ -636,6 +636,27 @@ static int ldbm_config_db_transaction_logging_set(void *arg, void *value, char *

     return retval;

 }

+

+static void *ldbm_config_db_transaction_wait_get(void *arg)

+{

+    struct ldbminfo *li = (struct ldbminfo *) arg;

+

+    return (void *) ((uintptr_t)li->li_dblayer_private->dblayer_txn_wait);

+}

+

+static int ldbm_config_db_transaction_wait_set(void *arg, void *value, char *errorbuf, int phase, int apply)

+{

+    struct ldbminfo *li = (struct ldbminfo *) arg;

+    int retval = LDAP_SUCCESS;

+    int val = (int) ((uintptr_t)value);

+

+    if (apply) {

+        li->li_dblayer_private->dblayer_txn_wait = val;

+    }

+

+    return retval;

+}

+

 static void *ldbm_config_db_logbuf_size_get(void *arg) 

 {

     struct ldbminfo *li = (struct ldbminfo *) arg;

@@ -1517,6 +1538,7 @@ static config_info ldbm_config[] = {

     {CONFIG_DB_DURABLE_TRANSACTIONS, CONFIG_TYPE_ONOFF, "on", &ldbm_config_db_durable_transactions_get, &ldbm_config_db_durable_transactions_set, CONFIG_FLAG_ALWAYS_SHOW},

     {CONFIG_DB_CIRCULAR_LOGGING, CONFIG_TYPE_ONOFF, "on", &ldbm_config_db_circular_logging_get, &ldbm_config_db_circular_logging_set, 0},

     {CONFIG_DB_TRANSACTION_LOGGING, CONFIG_TYPE_ONOFF, "on", &ldbm_config_db_transaction_logging_get, &ldbm_config_db_transaction_logging_set, 0},

+    {CONFIG_DB_TRANSACTION_WAIT, CONFIG_TYPE_ONOFF, "off", &ldbm_config_db_transaction_wait_get, &ldbm_config_db_transaction_wait_set, CONFIG_FLAG_ALWAYS_SHOW|CONFIG_FLAG_ALLOW_RUNNING_CHANGE},

     {CONFIG_DB_CHECKPOINT_INTERVAL, CONFIG_TYPE_INT, "60", &ldbm_config_db_checkpoint_interval_get, &ldbm_config_db_checkpoint_interval_set, CONFIG_FLAG_ALWAYS_SHOW|CONFIG_FLAG_ALLOW_RUNNING_CHANGE},

     {CONFIG_DB_COMPACTDB_INTERVAL, CONFIG_TYPE_INT, "2592000"/*30days*/, &ldbm_config_db_compactdb_interval_get, &ldbm_config_db_compactdb_interval_set, CONFIG_FLAG_ALWAYS_SHOW|CONFIG_FLAG_ALLOW_RUNNING_CHANGE},

     {CONFIG_DB_TRANSACTION_BATCH, CONFIG_TYPE_INT, "0", &dblayer_get_batch_transactions, &dblayer_set_batch_transactions, CONFIG_FLAG_ALWAYS_SHOW|CONFIG_FLAG_ALLOW_RUNNING_CHANGE},

diff --git a/ldap/servers/slapd/back-ldbm/ldbm_config.h b/ldap/servers/slapd/back-ldbm/ldbm_config.h

index f481937..ddec3a8 100644

--- a/ldap/servers/slapd/back-ldbm/ldbm_config.h

+++ b/ldap/servers/slapd/back-ldbm/ldbm_config.h

@@ -80,6 +80,7 @@ struct config_info {

 #define CONFIG_DB_DURABLE_TRANSACTIONS "nsslapd-db-durable-transaction"

 #define CONFIG_DB_CIRCULAR_LOGGING "nsslapd-db-circular-logging"

 #define CONFIG_DB_TRANSACTION_LOGGING "nsslapd-db-transaction-logging"

+#define CONFIG_DB_TRANSACTION_WAIT "nsslapd-db-transaction-wait"

 #define CONFIG_DB_CHECKPOINT_INTERVAL "nsslapd-db-checkpoint-interval"

 #define CONFIG_DB_COMPACTDB_INTERVAL "nsslapd-db-compactdb-interval"

 #define CONFIG_DB_TRANSACTION_BATCH  "nsslapd-db-transaction-batch-val"

-- 

2.9.3