Locks to prevent duplicate installations running at the same time

Easybuild creates a lock before starting the installation of an easyconfig file, to avoid a collision between multiple installations running at the same time.

If an EasyBuild session tries to install an easyconfig file when a lock for that installation already exists, it will be automatically aborted with an error like “Lock ... already exists, aborting!”.

Note

Locking of installations was implemented in EasyBuild version 4.2.0 .

Contents

• Locks to prevent duplicate installations running at the same time
  • Locking implementation details
  • Removing locks
  • Configuration options related to installation locks
    • Ignoring locks (--ignore-locks)
    • Waiting for locks to be removed (--wait-on-lock)
  • Locks directory

Locking implementation details

Easybuild will create a lock when starting an installation if no corresponding lock exists yet, regardless of whether the installation was requested explicitly or is performed to resolve a dependency.

The name of the lock corresponds to the full path of the installation directory, with slashes (/) and dashes (-) replaced by underscores (_), and with an additional .lock added at the end.

Locks are created in the Locks directory.

The lock created by EasyBuild is an empty directory (rather than a file), because that can be created more atomically on modern filesystems.

For example, if OpenFOAM-7-foss-2019b.eb is being installed to /apps/easybuild/software, an empty directory that serves as a lock for this installation will be created at /apps/easybuild/software/.locks/_apps_easybuild_software_OpenFOAM_7_foss_2019b.lock (assuming the default Locks directory is used).

A lock is automatically removed by Easybuild when the installation ends, regardless of whether the installation was successful or not. Therefore, new installations of the same easyconfig will be aborted in case of:

• another installation for the same easyconfig is in progress;
• a previous installation of the same easyconfig was abruptly interrupted;

Removing locks

If a previous installation was abruptly interrupted and a lock was left in place, it can be easily removed using the rmdir command (since the lock is actually an empty directory).

Configuration options related to installation locks

The behaviour of the locking mechanism in Easybuild can be tuned with the following configuration options:

Ignoring locks (--ignore-locks)

Using the --ignore-locks configuration option, you can instruct EasyBuild to ignore any existing locks. Locks that exist are left untouched, even if the installation completes successfully.

Use this with caution, since installations may be (partially) overwritten if another EasyBuild session is also performing those installations!

Waiting for locks to be removed (--wait-on-lock)

Using the --wait-on-lock configuration option, you can change how EasyBuild deals with existing locks, by specifying how frequently EasyBuild should check whether an existing lock was removed. By specifying a non-zero value S, you can indicate how many seconds EasyBuild should wait before checking again whether the lock is still in place.

Note

EasyBuild will wait indefinitely for an existing lock to be removed if --wait-on-lock is set to a non-zero value…

If the lock is never removed, the EasyBuild session will never terminate; it will keep checking every S seconds whether the lock is still in place.

By default, EasyBuild will abort the installation with an error like “Lock ... already exists, aborting!” if a corresponding lock already exists, which is equivalent to setting --wait-on-lock to zero (0), implying that no waiting should be done at all.

Locks directory

If desired, an alternate location where locks should be created and checked for can be specified via the --locks-dir configuration option.

Note

Keep in mind that a path on a shared filesystem should be used, to ensure that active EasyBuild sessions running on different systems use the same locks directory.

By default, locks are created in a hidden subdirectory .locks in the top-level software installation directory; that is, the software subdirectory of the installpath configuration setting of the active EasyBuild session.