diff --git a/swh/lister/bitbucket/tasks.py b/swh/lister/bitbucket/tasks.py
index 4d18213..841d6cc 100644
--- a/swh/lister/bitbucket/tasks.py
+++ b/swh/lister/bitbucket/tasks.py
@@ -1,52 +1,57 @@
 # Copyright (C) 2017-2018 the Software Heritage developers
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import random
 from celery import group
 
 from swh.scheduler.celery_backend.config import app
 from swh.scheduler.task import SWHTask
 
 from .lister import BitBucketLister
 
 GROUP_SPLIT = 10000
 
 
 def new_lister(api_baseurl='https://api.bitbucket.org/2.0'):
     return BitBucketLister(api_baseurl=api_baseurl)
 
 
 @app.task(name='swh.lister.bitbucket.tasks.IncrementalBitBucketLister',
           base=SWHTask, bind=True)
 def incremental_bitbucket_lister(self, **lister_args):
     self.log.debug('%s, lister_args=%s' % (
         self.name, lister_args))
     lister = new_lister(**lister_args)
     lister.run(min_bound=lister.db_last_index(), max_bound=None)
     self.log.debug('%s OK' % (self.name))
 
 
 @app.task(name='swh.lister.bitbucket.tasks.RangeBitBucketLister',
           base=SWHTask, bind=True)
 def range_bitbucket_lister(self, start, end, **lister_args):
     self.log.debug('%s(start=%s, end=%d), lister_args=%s' % (
         self.name, start, end, lister_args))
     lister = new_lister(**lister_args)
     lister.run(min_bound=start, max_bound=end)
     self.log.debug('%s OK' % (self.name))
 
 
 @app.task(name='swh.lister.bitbucket.tasks.FullBitBucketRelister',
           base=SWHTask, bind=True)
 def full_bitbucket_relister(self, split=None, **lister_args):
     self.log.debug('%s, lister_args=%s' % (
         self.name, lister_args))
     lister = new_lister(**lister_args)
     ranges = lister.db_partition_indices(split or GROUP_SPLIT)
     random.shuffle(ranges)
     group(range_bitbucket_lister.s(minv, maxv, **lister_args)
           for minv, maxv in ranges)()
     self.log.debug('%s OK (spawned %s subtasks)' % (self.name, len(ranges)))
 
 
+@app.task(name='swh.lister.bitbucket.tasks.ping',
+          base=SWHTask, bind=True)
+def ping(self):
+    self.log.debug(self.name)
+    return 'OK'
diff --git a/swh/lister/debian/tasks.py b/swh/lister/debian/tasks.py
index a922195..875551f 100644
--- a/swh/lister/debian/tasks.py
+++ b/swh/lister/debian/tasks.py
@@ -1,17 +1,24 @@
 # Copyright (C) 2017-2018 the Software Heritage developers
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 from swh.scheduler.celery_backend.config import app
 from swh.scheduler.task import SWHTask
 
 from .lister import DebianLister
 
 
 @app.task(name='swh.lister.debian.tasks.DebianListerTask',
           base=SWHTask, bind=True)
 def debian_lister(self, distribution, **lister_args):
     self.log.debug('%s, lister_args=%s' % (
         self.name, lister_args))
     DebianLister(**lister_args).run(distribution)
     self.log.debug('%s OK' % (self.name))
+
+
+@app.task(name='swh.lister.debian.tasks.ping',
+          base=SWHTask, bind=True)
+def ping(self):
+    self.log.debug(self.name)
+    return 'OK'
diff --git a/swh/lister/github/tasks.py b/swh/lister/github/tasks.py
index fdc7c39..eda4f51 100644
--- a/swh/lister/github/tasks.py
+++ b/swh/lister/github/tasks.py
@@ -1,53 +1,58 @@
 # Copyright (C) 2017-2018 the Software Heritage developers
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import random
 
 from celery import group
 
 from swh.scheduler.celery_backend.config import app
 from swh.scheduler.task import SWHTask
 
 from swh.lister.github.lister import GitHubLister
 
 GROUP_SPLIT = 10000
 
 
 def new_lister(api_baseurl='https://api.github.com', **kw):
     return GitHubLister(api_baseurl=api_baseurl, **kw)
 
 
 @app.task(name='swh.lister.github.tasks.IncrementalGitHubLister',
           base=SWHTask, bind=True)
 def incremental_github_lister(self, **lister_args):
     self.log.debug('%s, lister_args=%s' % (
         self.name, lister_args))
     lister = new_lister(**lister_args)
     lister.run(min_bound=lister.db_last_index(), max_bound=None)
     self.log.debug('%s OK' % (self.name))
 
 
 @app.task(name='swh.lister.github.tasks.RangeGitHubLister',
           base=SWHTask, bind=True)
 def range_github_lister(self, start, end, **lister_args):
     self.log.debug('%s(start=%s, end=%d), lister_args=%s' % (
         self.name, start, end, lister_args))
     lister = new_lister(**lister_args)
     lister.run(min_bound=start, max_bound=end)
     self.log.debug('%s OK' % (self.name))
 
 
 @app.task(name='swh.lister.github.tasks.FullGitHubRelister',
           base=SWHTask, bind=True)
 def full_github_relister(self, split=None, **lister_args):
     self.log.debug('%s, lister_args=%s' % (
         self.name, lister_args))
     lister = new_lister(**lister_args)
     ranges = lister.db_partition_indices(split or GROUP_SPLIT)
     random.shuffle(ranges)
     group(range_github_lister.s(minv, maxv, **lister_args)
           for minv, maxv in ranges)()
     self.log.debug('%s OK (spawned %s subtasks)' % (self.name, len(ranges)))
 
 
+@app.task(name='swh.lister.github.tasks.ping',
+          base=SWHTask, bind=True)
+def ping(self):
+    self.log.debug(self.name)
+    return 'OK'
diff --git a/swh/lister/gitlab/tasks.py b/swh/lister/gitlab/tasks.py
index eacb82f..eb8a4cb 100644
--- a/swh/lister/gitlab/tasks.py
+++ b/swh/lister/gitlab/tasks.py
@@ -1,59 +1,66 @@
 # Copyright (C) 2018 the Software Heritage developers
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import random
 
 from celery import group
 
 from swh.scheduler.celery_backend.config import app
 from swh.scheduler.task import SWHTask
 
 from .. import utils
 from .lister import GitLabLister
 
 
 NBPAGES = 10
 
 
 def new_lister(api_baseurl='https://gitlab.com/api/v4',
                instance='gitlab', sort='asc', per_page=20):
     return GitLabLister(
         api_baseurl=api_baseurl, instance=instance, sort=sort)
 
 
 @app.task(name='swh.lister.gitlab.tasks.IncrementalGitLabLister',
           base=SWHTask, bind=True)
 def incremental_gitlab_lister(self, **lister_args):
     self.log.debug('%s, lister_args=%s' % (
         self.name, lister_args))
     lister_args['sort'] = 'desc'
     lister = new_lister(**lister_args)
     total_pages = lister.get_pages_information()[1]
     # stopping as soon as existing origins for that instance are detected
     lister.run(min_bound=1, max_bound=total_pages, check_existence=True)
     self.log.debug('%s OK' % (self.name))
 
 
 @app.task(name='swh.lister.gitlab.tasks.RangeGitLabLister',
           base=SWHTask, bind=True)
 def range_gitlab_lister(self, start, end, **lister_args):
     self.log.debug('%s(start=%s, end=%d), lister_args=%s' % (
         self.name, start, end, lister_args))
     lister = new_lister(**lister_args)
     lister.run(min_bound=start, max_bound=end)
     self.log.debug('%s OK' % (self.name))
 
 
 @app.task(name='swh.lister.gitlab.tasks.FullGitLabRelister',
           base=SWHTask, bind=True)
 def full_gitlab_relister(self, **lister_args):
     self.log.debug('%s, lister_args=%s' % (
         self.name, lister_args))
     lister = new_lister(**lister_args)
     _, total_pages, _ = lister.get_pages_information()
     ranges = list(utils.split_range(total_pages, NBPAGES))
     random.shuffle(ranges)
     group(range_gitlab_lister.s(minv, maxv, **lister_args)
           for minv, maxv in ranges)()
     self.log.debug('%s OK (spawned %s subtasks)' % (self.name, len(ranges)))
+
+
+@app.task(name='swh.lister.gitlab.tasks.ping',
+          base=SWHTask, bind=True)
+def ping(self):
+    self.log.debug(self.name)
+    return 'OK'
diff --git a/swh/lister/npm/tasks.py b/swh/lister/npm/tasks.py
index d032061..a34290c 100644
--- a/swh/lister/npm/tasks.py
+++ b/swh/lister/npm/tasks.py
@@ -1,64 +1,71 @@
 # Copyright (C) 2018 the Software Heritage developers
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 from datetime import datetime
 from contextlib import contextmanager
 
 from swh.scheduler.celery_backend.config import app
 from swh.scheduler.task import SWHTask
 
 from swh.lister.npm.lister import NpmLister, NpmIncrementalLister
 from swh.lister.npm.models import NpmVisitModel
 
 
 @contextmanager
 def save_registry_state(lister):
     params = {'headers': lister.request_headers()}
     registry_state = lister.session.get(lister.api_baseurl, **params)
     registry_state = registry_state.json()
     keys = ('doc_count', 'doc_del_count', 'update_seq', 'purge_seq',
             'disk_size', 'data_size', 'committed_update_seq',
             'compacted_seq')
 
     state = {key: registry_state[key] for key in keys}
     state['visit_date'] = datetime.now()
     yield
     npm_visit = NpmVisitModel(state)
     lister.db_session.add(npm_visit)
     lister.db_session.commit()
 
 
 def get_last_update_seq(lister):
     """Get latest ``update_seq`` value for listing only updated packages.
     """
     query = lister.db_session.query(NpmVisitModel.update_seq)
     row = query.order_by(NpmVisitModel.uid.desc()).first()
     if not row:
         raise ValueError('No npm registry listing previously performed ! '
                          'This is required prior to the execution of an '
                          'incremental listing.')
     return row[0]
 
 
 @app.task(name='swh.lister.npm.tasks.NpmListerTask',
           base=SWHTask, bind=True)
 def npm_lister(self, **lister_args):
     self.log.debug('%s, lister_args=%s' % (
         self.name, lister_args))
     lister = NpmLister(**lister_args)
     with save_registry_state(lister):
         lister.run()
     self.log.debug('%s OK' % (self.name))
 
 
 @app.task(name='swh.lister.npm.tasks.NpmIncrementalListerTask',
           base=SWHTask, bind=True)
 def npm_incremental_lister(self, **lister_args):
     self.log.debug('%s, lister_args=%s' % (
         self.name, lister_args))
     lister = NpmIncrementalLister(**lister_args)
     update_seq_start = get_last_update_seq(lister)
     with save_registry_state(lister):
         lister.run(min_bound=update_seq_start)
     self.log.debug('%s OK' % (self.name))
+
+
+@app.task(name='swh.lister.npm.tasks.ping',
+          base=SWHTask, bind=True)
+def ping(self):
+    self.log.debug(self.name)
+    return 'OK'
diff --git a/swh/lister/pypi/tasks.py b/swh/lister/pypi/tasks.py
index 65e9348..5a1fc5f 100644
--- a/swh/lister/pypi/tasks.py
+++ b/swh/lister/pypi/tasks.py
@@ -1,19 +1,24 @@
 # Copyright (C) 2018 the Software Heritage developers
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 from swh.scheduler.task import SWHTask
 from swh.scheduler.celery_backend.config import app
 
 from .lister import PyPILister
 
 
 @app.task(name='swh.lister.pypi.tasks.PyPIListerTask',
           base=SWHTask, bind=True)
 def pypi_lister(self, **lister_args):
     self.log.debug('%s(), lister_args=%s' % (
         self.name, lister_args))
     PyPILister(**lister_args).run()
     self.log.debug('%s OK' % (self.name))
 
 
+@app.task(name='swh.lister.pypi.tasks.ping',
+          base=SWHTask, bind=True)
+def ping(self):
+    self.log.debug(self.name)
+    return 'OK'