diff --git a/qinling/api/app.py b/qinling/api/app.py
index f5969f99..aa1a1fa4 100644
--- a/qinling/api/app.py
+++ b/qinling/api/app.py
@@ -47,8 +47,9 @@ def setup_app(config=None):
 
     db_api.setup_db()
 
-    LOG.info('Starting periodic tasks...')
-    periodics.start_job_handler()
+    if cfg.CONF.api.enable_job_handler:
+        LOG.info('Starting periodic tasks...')
+        periodics.start_job_handler()
 
     app = pecan.make_app(
         app_conf.pop('root'),
diff --git a/qinling/api/controllers/v1/execution.py b/qinling/api/controllers/v1/execution.py
index 310ba094..7cf91184 100644
--- a/qinling/api/controllers/v1/execution.py
+++ b/qinling/api/controllers/v1/execution.py
@@ -75,7 +75,7 @@ class ExecutionsController(rest.RestController):
     @rest_utils.wrap_wsme_controller_exception
     @wsme_pecan.wsexpose(resources.Execution, types.uuid)
     def get(self, id):
-        LOG.info("Fetch resource.", resource={'type': self.type, 'id': id})
+        LOG.info("Get resource.", resource={'type': self.type, 'id': id})
 
         execution_db = db_api.get_execution(id)
 
diff --git a/qinling/api/controllers/v1/function.py b/qinling/api/controllers/v1/function.py
index 9b5302b1..0170c024 100644
--- a/qinling/api/controllers/v1/function.py
+++ b/qinling/api/controllers/v1/function.py
@@ -69,7 +69,7 @@ class FunctionsController(rest.RestController):
     @rest_utils.wrap_pecan_controller_exception
     @pecan.expose()
     def get(self, id):
-        LOG.info("Fetch resource.", resource={'type': self.type, 'id': id})
+        LOG.info("Get resource.", resource={'type': self.type, 'id': id})
 
         download = strutils.bool_from_string(
             pecan.request.GET.get('download', False)
diff --git a/qinling/api/controllers/v1/job.py b/qinling/api/controllers/v1/job.py
index 3cdec0a5..1d1695b3 100644
--- a/qinling/api/controllers/v1/job.py
+++ b/qinling/api/controllers/v1/job.py
@@ -84,7 +84,7 @@ class JobsController(rest.RestController):
     @rest_utils.wrap_wsme_controller_exception
     @wsme_pecan.wsexpose(resources.Job, types.uuid)
     def get(self, id):
-        LOG.info("Fetch resource.", resource={'type': self.type, 'id': id})
+        LOG.info("Get resource.", resource={'type': self.type, 'id': id})
         job_db = db_api.get_job(id)
 
         return resources.Job.from_dict(job_db.to_dict())
diff --git a/qinling/api/controllers/v1/runtime.py b/qinling/api/controllers/v1/runtime.py
index fc963104..e4c47e55 100644
--- a/qinling/api/controllers/v1/runtime.py
+++ b/qinling/api/controllers/v1/runtime.py
@@ -42,7 +42,7 @@ class RuntimesController(rest.RestController):
     @rest_utils.wrap_wsme_controller_exception
     @wsme_pecan.wsexpose(resources.Runtime, types.uuid)
     def get(self, id):
-        LOG.info("Fetch resource.", resource={'type': self.type, 'id': id})
+        LOG.info("Get resource.", resource={'type': self.type, 'id': id})
 
         runtime_db = db_api.get_runtime(id)
 
diff --git a/qinling/config.py b/qinling/config.py
index 3731a710..816bb4e6 100644
--- a/qinling/config.py
+++ b/qinling/config.py
@@ -41,7 +41,12 @@ api_opts = [
         help='Number of workers for Qinling API service '
              'default is equal to the number of CPUs available if that can '
              'be determined, else a default worker count of 1 is returned.'
-    )
+    ),
+    cfg.BoolOpt(
+        'enable_job_handler',
+        default=True,
+        help='Enable job handler.'
+    ),
 ]
 
 PECAN_GROUP = 'pecan'
diff --git a/qinling/db/sqlalchemy/api.py b/qinling/db/sqlalchemy/api.py
index ee69dd7d..49dc0755 100644
--- a/qinling/db/sqlalchemy/api.py
+++ b/qinling/db/sqlalchemy/api.py
@@ -19,6 +19,7 @@ import threading
 from oslo_config import cfg
 from oslo_db import exception as oslo_db_exc
 from oslo_db.sqlalchemy import utils as db_utils
+from oslo_log import log as logging
 import sqlalchemy as sa
 
 from qinling import context
@@ -30,6 +31,7 @@ from qinling import exceptions as exc
 from qinling import status
 
 CONF = cfg.CONF
+LOG = logging.getLogger(__name__)
 
 _SCHEMA_LOCK = threading.RLock()
 _initialized = False
@@ -366,14 +368,11 @@ def create_function_service_mapping(values, session=None):
     mapping = models.FunctionServiceMapping()
     mapping.update(values.copy())
 
+    # Ignore duplicate error for FunctionServiceMapping
     try:
         mapping.save(session=session)
-    except oslo_db_exc.DBDuplicateEntry as e:
-        raise exc.DBError(
-            "Duplicate entry for FunctionServiceMapping: %s" % e.columns
-        )
-
-    return mapping
+    except oslo_db_exc.DBDuplicateEntry:
+        session.close()
 
 
 @db_base.session_aware()
@@ -412,14 +411,11 @@ def create_function_worker(values, session=None):
     mapping = models.FunctionWorkers()
     mapping.update(values.copy())
 
+    # Ignore duplicate error for FunctionWorkers
     try:
         mapping.save(session=session)
-    except oslo_db_exc.DBDuplicateEntry as e:
-        raise exc.DBError(
-            "Duplicate entry for FunctionWorkers: %s" % e.columns
-        )
-
-    return mapping
+    except oslo_db_exc.DBDuplicateEntry:
+        session.close()
 
 
 @db_base.session_aware()
diff --git a/qinling/db/sqlalchemy/migration/alembic_migrations/versions/001_pike.py b/qinling/db/sqlalchemy/migration/alembic_migrations/versions/001_pike.py
index 5e5d3656..4ab02d7c 100644
--- a/qinling/db/sqlalchemy/migration/alembic_migrations/versions/001_pike.py
+++ b/qinling/db/sqlalchemy/migration/alembic_migrations/versions/001_pike.py
@@ -102,6 +102,7 @@ def upgrade():
         sa.Column('function_id', sa.String(length=36), nullable=False),
         sa.Column('worker_name', sa.String(length=255), nullable=False),
         sa.PrimaryKeyConstraint('id'),
+        sa.UniqueConstraint('function_id', 'worker_name'),
         sa.ForeignKeyConstraint(
             ['function_id'], [u'functions.id'], ondelete='CASCADE'
         ),
diff --git a/qinling/db/sqlalchemy/models.py b/qinling/db/sqlalchemy/models.py
index de194071..54bb686f 100644
--- a/qinling/db/sqlalchemy/models.py
+++ b/qinling/db/sqlalchemy/models.py
@@ -38,7 +38,10 @@ class Function(model_base.QinlingSecureModelBase):
     runtime_id = sa.Column(
         sa.String(36), sa.ForeignKey(Runtime.id), nullable=True
     )
-    runtime = relationship('Runtime', back_populates="functions")
+    # We want to get runtime info when we query function
+    runtime = relationship(
+        'Runtime', back_populates="functions", innerjoin=True, lazy='joined'
+    )
     memory_size = sa.Column(sa.Integer)
     timeout = sa.Column(sa.Integer)
     code = sa.Column(st.JsonLongDictType(), nullable=False)
@@ -65,6 +68,10 @@ class FunctionServiceMapping(model_base.QinlingModelBase):
 class FunctionWorkers(model_base.QinlingModelBase):
     __tablename__ = 'function_workers'
 
+    __table_args__ = (
+        sa.UniqueConstraint('function_id', 'worker_name'),
+    )
+
     id = model_base.id_column()
     function_id = sa.Column(
         sa.String(36),
diff --git a/qinling/engine/default_engine.py b/qinling/engine/default_engine.py
index 4944e27b..bb22c8a5 100644
--- a/qinling/engine/default_engine.py
+++ b/qinling/engine/default_engine.py
@@ -16,6 +16,7 @@ from oslo_config import cfg
 from oslo_log import log as logging
 import requests
 
+from qinling import context
 from qinling.db import api as db_api
 from qinling.engine import utils
 from qinling import status
@@ -99,12 +100,35 @@ class DefaultEngine(object):
 
             if function.service:
                 func_url = '%s/execute' % function.service.service_url
+
                 LOG.debug(
                     'Found service url for function: %s, url: %s',
                     function_id, func_url
                 )
 
-                data = {'input': input, 'execution_id': execution_id}
+                download_url = (
+                    'http://%s:%s/v1/functions/%s?download=true' %
+                    (CONF.kubernetes.qinling_service_address,
+                     CONF.api.port, function_id)
+                )
+                data = {
+                    'execution_id': execution_id,
+                    'input': input,
+                    'function_id': function_id,
+                    'entry': function.entry,
+                    'download_url': download_url,
+                }
+                if CONF.pecan.auth_enable:
+                    data.update(
+                        {
+                            'token': context.get_ctx().auth_token,
+                            'auth_url': CONF.keystone_authtoken.auth_uri,
+                            'username': CONF.keystone_authtoken.username,
+                            'password': CONF.keystone_authtoken.password,
+                            'trust_id': function.trust_id
+                        }
+                    )
+
                 success, res = utils.url_request(
                     self.session, func_url, body=data
                 )
@@ -141,8 +165,6 @@ class DefaultEngine(object):
                 identifier=identifier,
                 labels=labels,
                 input=input,
-                entry=function.entry,
-                trust_id=function.trust_id
             )
             success, res = self.orchestrator.run_execution(
                 execution_id,
@@ -150,6 +172,8 @@ class DefaultEngine(object):
                 input=input,
                 identifier=identifier,
                 service_url=service_url,
+                entry=function.entry,
+                trust_id=function.trust_id
             )
 
             logs = ''
@@ -171,18 +195,18 @@ class DefaultEngine(object):
             execution.logs = logs
             execution.status = status.SUCCESS if success else status.FAILED
 
-            # No service is created in orchestrator for single container.
-            if not image:
-                mapping = {
-                    'function_id': function_id,
-                    'service_url': service_url,
-                }
-                db_api.create_function_service_mapping(mapping)
-                worker = {
-                    'function_id': function_id,
-                    'worker_name': worker_name
-                }
-                db_api.create_function_worker(worker)
+        # No service is created in orchestrator for single container.
+        if not image:
+            mapping = {
+                'function_id': function_id,
+                'service_url': service_url,
+            }
+            db_api.create_function_service_mapping(mapping)
+            worker = {
+                'function_id': function_id,
+                'worker_name': worker_name
+            }
+            db_api.create_function_worker(worker)
 
     def delete_function(self, ctx, function_id):
         """Deletes underlying resources allocated for function."""
@@ -195,12 +219,9 @@ class DefaultEngine(object):
         LOG.info('Deleted.', resource=resource)
 
     def scaleup_function(self, ctx, function_id, runtime_id, count=1):
-        function = db_api.get_function(function_id)
-
         worker_names = self.orchestrator.scaleup_function(
             function_id,
             identifier=runtime_id,
-            entry=function.entry,
             count=count
         )
 
diff --git a/qinling/engine/utils.py b/qinling/engine/utils.py
index 138cb893..169b6450 100644
--- a/qinling/engine/utils.py
+++ b/qinling/engine/utils.py
@@ -11,18 +11,33 @@
 #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 #    License for the specific language governing permissions and limitations
 #    under the License.
+import time
 
 from oslo_log import log as logging
+import requests
+import six
 
 LOG = logging.getLogger(__name__)
 
 
 def url_request(request_session, url, body=None):
     """Send request to a service url."""
-    try:
-        # Default execution duration is 3min, could be configurable
-        r = request_session.post(url, json=body, timeout=(3, 180))
-        return True, r.json()
-    except Exception:
-        LOG.exception("Failed to request url %s", url)
-        return False, {'error': 'Function execution timeout.'}
+    exception = None
+
+    for a in six.moves.xrange(10):
+        try:
+            # Default execution duration is 3min, could be configurable
+            r = request_session.post(url, json=body, timeout=(3, 180))
+            return True, r.json()
+        except requests.ConnectionError as e:
+            exception = e
+            LOG.warning("Could not connect to service. Retrying.")
+            time.sleep(1)
+        except Exception:
+            LOG.exception("Failed to request url %s", url)
+            return False, {'error': 'Function execution timeout.'}
+
+    LOG.exception("Could not connect to function service. Reason: %s",
+                  exception)
+
+    return False, {'error': 'Internal service error.'}
diff --git a/qinling/orchestrator/kubernetes/manager.py b/qinling/orchestrator/kubernetes/manager.py
index 4a0b010b..ded947f9 100644
--- a/qinling/orchestrator/kubernetes/manager.py
+++ b/qinling/orchestrator/kubernetes/manager.py
@@ -20,7 +20,6 @@ import jinja2
 from kubernetes import client
 from oslo_log import log as logging
 import requests
-import six
 import tenacity
 import yaml
 
@@ -234,19 +233,18 @@ class KubernetesManager(base.OrchestratorBase):
 
         return ret.items[-count:]
 
-    def _prepare_pod(self, pod, deployment_name, function_id, labels=None,
-                     entry=None, trust_id=None, actual_function=None):
+    def _prepare_pod(self, pod, deployment_name, function_id, labels=None):
         """Pod preparation.
 
         1. Update pod labels.
-        2. Expose service and trigger package download.
+        2. Expose service.
         """
-        name = pod.metadata.name
-        actual_function = actual_function or function_id
+        pod_name = pod.metadata.name
+        labels = labels or {}
 
         LOG.info(
             'Prepare pod %s in deployment %s for function %s',
-            name, deployment_name, function_id
+            pod_name, deployment_name, function_id
         )
 
         # Update pod label.
@@ -255,6 +253,8 @@ class KubernetesManager(base.OrchestratorBase):
         # Create service for the chosen pod.
         service_name = "service-%s" % function_id
         labels.update({'function_id': function_id})
+
+        # TODO(kong): Make the service type configurable.
         service_body = self.service_template.render(
             {
                 "service_name": service_name,
@@ -262,19 +262,32 @@ class KubernetesManager(base.OrchestratorBase):
                 "selector": pod_labels
             }
         )
-        ret = self.v1.create_namespaced_service(
-            self.conf.kubernetes.namespace, yaml.safe_load(service_body)
-        )
-        node_port = ret.spec.ports[0].node_port
-
-        LOG.debug(
-            'Service created for pod %s, service name: %s, node port: %s',
-            name, service_name, node_port
-        )
+        try:
+            ret = self.v1.create_namespaced_service(
+                self.conf.kubernetes.namespace, yaml.safe_load(service_body)
+            )
+            LOG.debug(
+                'Service created for pod %s, service name: %s',
+                pod_name, service_name
+            )
+        except Exception as e:
+            # Service already exists
+            if e.status == 409:
+                LOG.debug(
+                    'Service already exists for pod %s, service name: %s',
+                    pod_name, service_name
+                )
+                time.sleep(1)
+                ret = self.v1.read_namespaced_service(
+                    service_name, self.conf.kubernetes.namespace
+                )
+            else:
+                raise
 
         # Get external ip address for an arbitrary node.
-        ret = self.v1.list_node()
-        addresses = ret.items[0].status.addresses
+        node_port = ret.spec.ports[0].node_port
+        nodes = self.v1.list_node()
+        addresses = nodes.items[0].status.addresses
         node_ip = None
         for addr in addresses:
             if addr.type == 'ExternalIP':
@@ -286,53 +299,9 @@ class KubernetesManager(base.OrchestratorBase):
                 if addr.type == 'InternalIP':
                     node_ip = addr.address
 
-        # Download code package into container.
         pod_service_url = 'http://%s:%s' % (node_ip, node_port)
-        request_url = '%s/download' % pod_service_url
-        download_url = (
-            'http://%s:%s/v1/functions/%s?download=true' %
-            (self.conf.kubernetes.qinling_service_address,
-             self.conf.api.port, actual_function)
-        )
 
-        data = {
-            'download_url': download_url,
-            'function_id': actual_function,
-            'entry': entry,
-            'trust_id': trust_id
-        }
-        if self.conf.pecan.auth_enable:
-            data.update(
-                {
-                    'token': context.get_ctx().auth_token,
-                    'auth_url': self.conf.keystone_authtoken.auth_uri,
-                    'username': self.conf.keystone_authtoken.username,
-                    'password': self.conf.keystone_authtoken.password,
-                }
-            )
-
-        LOG.info(
-            'Send request to pod %s, request_url: %s', name, request_url
-        )
-
-        exception = None
-        for a in six.moves.xrange(10):
-            try:
-                r = self.session.post(request_url, json=data)
-                if r.status_code != requests.codes.ok:
-                    raise exc.OrchestratorException(
-                        'Failed to download function code package.'
-                    )
-
-                return name, pod_service_url
-            except (requests.ConnectionError, requests.Timeout) as e:
-                exception = e
-                LOG.warning("Could not connect to service. Retrying.")
-                time.sleep(1)
-
-        raise exc.OrchestratorException(
-            'Could not connect to function service. Reason: %s', exception
-        )
+        return pod_name, pod_service_url
 
     def _create_pod(self, image, pod_name, labels, input):
         pod_body = self.pod_template.render(
@@ -372,8 +341,7 @@ class KubernetesManager(base.OrchestratorBase):
         return pod_labels
 
     def prepare_execution(self, function_id, image=None, identifier=None,
-                          labels=None, input=None, entry='main.main',
-                          trust_id=None):
+                          labels=None, input=None):
         """Prepare service URL for function.
 
         For image function, create a single pod with input, so the function
@@ -395,7 +363,7 @@ class KubernetesManager(base.OrchestratorBase):
 
         try:
             pod_name, url = self._prepare_pod(
-                pod[0], identifier, function_id, labels, entry, trust_id
+                pod[0], identifier, function_id, labels
             )
             return pod_name, url
         except Exception:
@@ -404,14 +372,38 @@ class KubernetesManager(base.OrchestratorBase):
             raise exc.OrchestratorException('Execution preparation failed.')
 
     def run_execution(self, execution_id, function_id, input=None,
-                      identifier=None, service_url=None):
+                      identifier=None, service_url=None, entry='main.main',
+                      trust_id=None):
         if service_url:
             func_url = '%s/execute' % service_url
+            download_url = (
+                'http://%s:%s/v1/functions/%s?download=true' %
+                (self.conf.kubernetes.qinling_service_address,
+                 self.conf.api.port, function_id)
+            )
+
             data = {
-                'input': input,
                 'execution_id': execution_id,
+                'input': input,
+                'function_id': function_id,
+                'entry': entry,
+                'download_url': download_url,
+                'trust_id': trust_id
             }
-            LOG.debug('Invoke function %s, url: %s', function_id, func_url)
+            if self.conf.pecan.auth_enable:
+                data.update(
+                    {
+                        'token': context.get_ctx().auth_token,
+                        'auth_url': self.conf.keystone_authtoken.auth_uri,
+                        'username': self.conf.keystone_authtoken.username,
+                        'password': self.conf.keystone_authtoken.password,
+                    }
+                )
+
+            LOG.debug(
+                'Invoke function %s, url: %s, data: %s',
+                function_id, func_url, data
+            )
 
             return utils.url_request(self.session, func_url, body=data)
         else:
@@ -425,7 +417,6 @@ class KubernetesManager(base.OrchestratorBase):
                     self.conf.kubernetes.namespace
                 )
                 status = pod.status.phase
-
                 time.sleep(0.5)
 
             output = self.v1.read_namespaced_pod_log(
@@ -453,47 +444,26 @@ class KubernetesManager(base.OrchestratorBase):
             label_selector=selector
         )
 
-    def scaleup_function(self, function_id, identifier=None,
-                         entry='main.main', count=1):
+    def scaleup_function(self, function_id, identifier=None, count=1):
         pod_names = []
         labels = {'runtime_id': identifier}
-        pods = self._choose_available_pod(
-            labels, count=count
-        )
+        pods = self._choose_available_pod(labels, count=count)
 
         if not pods:
             raise exc.OrchestratorException('Not enough workers available.')
 
-        temp_function = '%s-temp' % function_id
         for pod in pods:
-            self._prepare_pod(pod, identifier, temp_function, labels, entry,
-                              actual_function=function_id)
-
-            # Delete temporary service
-            selector = common.convert_dict_to_string(
-                {'function_id': temp_function}
+            pod_name, _ = self._prepare_pod(
+                pod, identifier, function_id, labels
             )
-            ret = self.v1.list_namespaced_service(
-                self.conf.kubernetes.namespace, label_selector=selector
-            )
-            svc_names = [i.metadata.name for i in ret.items]
-            for svc_name in svc_names:
-                self.v1.delete_namespaced_service(
-                    svc_name,
-                    self.conf.kubernetes.namespace,
-                )
-
-            # Modify pod labels to fit into correct service
-            self._update_pod_label(pod, {'function_id': function_id})
-
-            pod_names.append(pod.metadata.name)
+            pod_names.append(pod_name)
 
         LOG.info('Pods scaled up for function %s: %s', function_id, pod_names)
         return pod_names
 
-    def delete_worker(self, worker_name, **kwargs):
+    def delete_worker(self, pod_name, **kwargs):
         self.v1.delete_namespaced_pod(
-            worker_name,
+            pod_name,
             self.conf.kubernetes.namespace,
             {}
         )
diff --git a/qinling/orchestrator/kubernetes/templates/deployment.j2 b/qinling/orchestrator/kubernetes/templates/deployment.j2
index e40f2064..2b92c8dc 100644
--- a/qinling/orchestrator/kubernetes/templates/deployment.j2
+++ b/qinling/orchestrator/kubernetes/templates/deployment.j2
@@ -28,8 +28,8 @@ spec:
         - containerPort: 9090
         resources:
           limits:
-            cpu: "0.5"
-            memory: 512Mi
+            cpu: "0.3"
+            memory: 256Mi
           requests:
             cpu: "0.1"
-            memory: 128Mi
+            memory: 64Mi
diff --git a/qinling/orchestrator/kubernetes/templates/pod.j2 b/qinling/orchestrator/kubernetes/templates/pod.j2
index 4391c56c..182501b7 100644
--- a/qinling/orchestrator/kubernetes/templates/pod.j2
+++ b/qinling/orchestrator/kubernetes/templates/pod.j2
@@ -19,9 +19,9 @@ spec:
       {% endif %}
   restartPolicy: Never
   resources:
-    limits:
-      cpu: "0.5"
-      memory: 512Mi
-    requests:
-      cpu: "0.1"
-      memory: 128Mi
+      limits:
+        cpu: "0.3"
+        memory: 256Mi
+      requests:
+        cpu: "0.1"
+        memory: 64Mi
diff --git a/qinling/utils/executions.py b/qinling/utils/executions.py
index 2693c230..21989f83 100644
--- a/qinling/utils/executions.py
+++ b/qinling/utils/executions.py
@@ -12,32 +12,61 @@
 #    See the License for the specific language governing permissions and
 #    limitations under the License.
 
+from oslo_log import log as logging
+
 from qinling.db import api as db_api
+from qinling.db.sqlalchemy import models
 from qinling import exceptions as exc
 from qinling import status
 
+LOG = logging.getLogger(__name__)
+
+
+def _update_function_db(function_id):
+    # NOTE(kong): Store function info in cache?
+    func_db = db_api.get_function(function_id)
+    runtime_db = func_db.runtime
+    if runtime_db and runtime_db.status != status.AVAILABLE:
+        raise exc.RuntimeNotAvailableException(
+            'Runtime %s is not available.' % func_db.runtime_id
+        )
+
+    # Function update is done using UPDATE ... FROM ... WHERE
+    # non-locking clause.
+    while func_db:
+        count = func_db.count
+        modified = db_api.conditional_update(
+            models.Function,
+            {
+                'count': count + 1,
+            },
+            {
+                'id': function_id,
+                'count': count
+            },
+            insecure=True,
+        )
+        if not modified:
+            LOG.warning("Retrying to update function count.")
+            func_db = db_api.get_function(function_id)
+            continue
+        else:
+            break
+
+    return func_db.runtime_id
+
 
 def create_execution(engine_client, params):
     function_id = params['function_id']
     is_sync = params.get('sync', True)
 
-    with db_api.transaction():
-        func_db = db_api.get_function(function_id)
-        runtime_db = func_db.runtime
-        if runtime_db and runtime_db.status != status.AVAILABLE:
-            raise exc.RuntimeNotAvailableException(
-                'Runtime %s is not available.' % func_db.runtime_id
-            )
+    runtime_id = _update_function_db(function_id)
 
-        # Increase function invoke count, the updated_at field will be also
-        # updated.
-        func_db.count = func_db.count + 1
-
-        params.update({'status': status.RUNNING})
-        db_model = db_api.create_execution(params)
+    params.update({'status': status.RUNNING})
+    db_model = db_api.create_execution(params)
 
     engine_client.create_execution(
-        db_model.id, function_id, func_db.runtime_id,
+        db_model.id, function_id, runtime_id,
         input=params.get('input'), is_sync=is_sync
     )
 
diff --git a/requirements.txt b/requirements.txt
index 5d97470a..ce724245 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -29,3 +29,4 @@ python-swiftclient>=3.2.0 # Apache-2.0
 croniter>=0.3.4 # MIT License
 python-dateutil>=2.4.2  # BSD
 tenacity>=3.2.1  # Apache-2.0
+PyMySQL>=0.7.6  # MIT License
diff --git a/runtimes/python2/server.py b/runtimes/python2/server.py
index 9ebbaae5..b8d0ad81 100644
--- a/runtimes/python2/server.py
+++ b/runtimes/python2/server.py
@@ -23,7 +23,6 @@ import time
 import traceback
 import zipfile
 
-from flask import abort
 from flask import Flask
 from flask import request
 from flask import Response
@@ -32,60 +31,20 @@ from keystoneauth1 import session
 import requests
 
 app = Flask(__name__)
-zip_file = ''
-function_module = 'main'
-function_method = 'main'
-auth_url = None
-username = None
-password = None
-trust_id = None
+downloaded = False
+downloading = False
 
 
-@app.route('/download', methods=['POST'])
-def download():
-    params = request.get_json() or {}
-
-    download_url = params.get('download_url')
-    function_id = params.get('function_id')
-    entry = params.get('entry')
-
-    global auth_url
-    global username
-    global password
-    global trust_id
-    token = params.get('token')
-    auth_url = params.get('auth_url')
-    username = params.get('username')
-    password = params.get('password')
-    trust_id = params.get('trust_id')
-
-    headers = {}
-    if token:
-        headers = {'X-Auth-Token': token}
-
-    global zip_file
-    zip_file = '%s.zip' % function_id
-
-    app.logger.info(
-        'Request received, download_url:%s, headers: %s, entry: %s' %
-        (download_url, headers, entry)
+def setup_logger(loglevel):
+    global app
+    root = logging.getLogger()
+    root.setLevel(loglevel)
+    ch = logging.StreamHandler(sys.stdout)
+    ch.setLevel(loglevel)
+    ch.setFormatter(
+        logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
     )
-
-    # Get function code package from Qinling service.
-    r = requests.get(download_url, headers=headers, stream=True)
-    with open(zip_file, 'wb') as fd:
-        for chunk in r.iter_content(chunk_size=65535):
-            fd.write(chunk)
-
-    if not zipfile.is_zipfile(zip_file):
-        abort(500)
-    app.logger.info('Code package downloaded to %s' % zip_file)
-
-    global function_module
-    global function_method
-    function_module, function_method = tuple(entry.rsplit('.', 1))
-
-    return 'success'
+    app.logger.addHandler(ch)
 
 
 def _print_trace():
@@ -108,13 +67,13 @@ def _invoke_function(execution_id, zip_file, module_name, method, input,
         return_dict['result'] = func(**input)
         return_dict['success'] = True
     except Exception as e:
+        _print_trace()
+
         if isinstance(e, OSError) and 'Resource' in str(e):
             sys.exit(1)
 
         return_dict['result'] = str(e)
         return_dict['success'] = False
-
-        _print_trace()
     finally:
         print('Finished execution: %s' % execution_id)
 
@@ -130,25 +89,73 @@ def execute():
       reason, e.g. unlimited memory allocation)
     - Deal with os error for process (e.g. Resource temporarily unavailable)
     """
-
-    global zip_file
-    global function_module
-    global function_method
-    global auth_url
-    global username
-    global password
-    global trust_id
+    global downloading
+    global downloaded
 
     params = request.get_json() or {}
     input = params.get('input') or {}
     execution_id = params['execution_id']
+    download_url = params.get('download_url')
+    function_id = params.get('function_id')
+    entry = params.get('entry')
+    trust_id = params.get('trust_id')
+    auth_url = params.get('auth_url')
+    username = params.get('username')
+    password = params.get('password')
+    zip_file = '%s.zip' % function_id
+
+    function_module, function_method = 'main', 'main'
+    if entry:
+        function_module, function_method = tuple(entry.rsplit('.', 1))
 
     app.logger.info(
-        'Request received, execution_id:%s, input: %s, auth_url: %s, '
-        'username: %s, trust_id: %s' %
-        (execution_id, input, auth_url, username, trust_id)
+        'Request received, execution_id:%s, input: %s, auth_url: %s' %
+        (execution_id, input, auth_url)
     )
 
+    while downloading:
+        # wait
+        time.sleep(3)
+
+    # download function package
+    if not downloading and not downloaded:
+        downloading = True
+        token = params.get('token')
+
+        headers = {}
+        if token:
+            headers = {'X-Auth-Token': token}
+
+        app.logger.info(
+            'Downloading function, download_url:%s, entry: %s' %
+            (download_url, entry)
+        )
+
+        # Get function code package from Qinling service.
+        r = requests.get(download_url, headers=headers, stream=True)
+        with open(zip_file, 'wb') as fd:
+            for chunk in r.iter_content(chunk_size=65535):
+                fd.write(chunk)
+
+        app.logger.info('Downloaded function package to %s' % zip_file)
+        downloading = False
+        downloaded = True
+
+    if downloaded:
+        if not zipfile.is_zipfile(zip_file):
+            return Response(
+                response=json.dumps(
+                    {
+                        'output': 'The function package is incorrect.',
+                        'duration': 0,
+                        'logs': '',
+                        'success': False
+                    }
+                ),
+                status=500,
+                mimetype='application/json'
+            )
+
     # Provide an openstack session to user's function
     os_session = None
     if auth_url:
@@ -160,7 +167,6 @@ def execute():
             user_domain_name='Default'
         )
         os_session = session.Session(auth=auth, verify=False)
-
     input.update({'context': {'os_session': os_session}})
 
     manager = Manager()
@@ -207,18 +213,6 @@ def execute():
     )
 
 
-def setup_logger(loglevel):
-    global app
-    root = logging.getLogger()
-    root.setLevel(loglevel)
-    ch = logging.StreamHandler(sys.stdout)
-    ch.setLevel(loglevel)
-    ch.setFormatter(
-        logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
-    )
-    app.logger.addHandler(ch)
-
-
 setup_logger(logging.DEBUG)
 app.logger.info("Starting server")