OMERO.web upgrade

The OME team is committed to providing frequent, project-wide upgrades with security fixes, bug fixes and new functionality. We try to make the schedule for these releases as public as possible. You may want to take a look at the Trello boards for exactly what will go into a release. See also OMERO.server upgrade.

See the full details of OMERO 5.6.11 features in the CHANGELOGS.

This guide aims to be as definitive as possible so please do not be put off by the level of detail; upgrading should be a straightforward process.

Upgrade checklist

Check prerequisites

Before starting the upgrade, please ensure that you have reviewed and satisfied all the system requirements with correct versions for installation.


Make sure you have activated the correct virtual environment then upgrade OMERO.web via pip:

$ pip install --upgrade 'omero-web>=5.25.0'

If the `omero-web` upgrade requires an upgrade to `omero-py` (e.g. for new features), this will happen automatically above. However, even when an `omero-py` upgrade is not required, there may be some benefits to upgrading:

$ pip install --upgrade 'omero-py>=5.19.2'


We now recommend that omero-web is installed in a separate python virtual environment.

If you are migrating to a new virtual environment, where $OMERODIR does not refer to a server with an existing config, you will need to export and re-import the configuration from your previous installation.

OLD_INSTALLATION/bin/omero config get --show-password > properties.backup

# omero-web virtual env
omero config load properties.backup

If you generated configuration stanzas using omero web config which enables OMERO.web via NGINX, you should regenerate your config files, remembering to merge in any of your own modifications if necessary. You should carry out this step even for minor version upgrades as there may be fixes which require it.

omero web config nginx > new.confg

More examples can be found under Configuration.

Plugin updates

OMERO.web plugins are very closely integrated into the webclient. For this reason, it is possible that an update of OMERO will cause issues with an older version of a plugin. It is best when updating the server to also install any available plugin updates according to their own documentation.

All official OMERO.web plugins can be installed from PyPI. You should remove all previously installed plugins and install the latest versions using pip.

Clear the sessions store (optional)

During an upgrade, it might be necessary to clear the sessions store before restarting OMERO.web. This is the case when either OMERO.web or Django introduced backwards incompatible changes in the way sessions are stored or if the session serialization format has been modified via omero.web.session_serializer.


Clearing the sessions store will terminate all OMERO.web sessions and log out all users.

The process for clearing the session store depends on the storage backend:

  • OMERO.web sessions are stored on the filesystem if the omero.web.session_engine property is set to either omeroweb.filesessionstore or django.contrib.sessions.backends.file or if omero.web.session_engine is unset.

    Sessions are stored under a temporary folder determined by the output of tempfile.gettempdir(), usually /tmp. By default, each session is stored as a separate file prefixed with sessionid so the following command will delete all stored sessions:

    $ rm /tmp/sessionid*

    If omero.web.session_cookie_name is set, its value will be used as the prefix of the file sessions and the command above needs to be modified accordingly.

  • OMERO.web sessions are stored using the Redis store if the omero.web.session_engine property is set to django.contrib.sessions.backends.cache and Redis is configured via the omero.web.caches property by setting the BACKEND to django.core.cache.backends.redis.RedisCache and LOCATION to the URL of the Redis instance.

    Sessions are stored as key/value pairs in the Redis store with the name of the key including django.contrib.sessions.cache and can be managed using the redis-cli utility. Assuming a default local Redis store, the following command can be used to delete all the Redis keys associated with OMERO.web sessions:

    $ redis-cli keys '*django.contrib.sessions.cache*'  | xargs redis-cli del

    If Redis URL points to a different hostname, port or database number, the command above needs to be adjusted accordingly.

Restart OMERO.web

Finally, restart OMERO.web with the following command:

$ omero web restart


If you encounter errors during an OMERO.web upgrade, etc., you should retain as much log information as possible, including the output of omero web diagnostics to the OMERO team via the mailing lists available on the support page.

Maintenance & Scaling

If you have not already done so, there are a number of additional steps that can be performed on your OMERO.web installation to improve its functioning. For example, you may need to set up a regular task to clear out any stale OMERO.web session files. More information can be found in the various walkthroughs available from OMERO.web installation and maintenance.

Additionally, it is recommended to use a WSGI-capable server such as NGINX. Information can be found under OMERO.web installation and maintenance.