public synchronized void exec() {
        try {
            final TaskContext taskContext = taskContextFactory.current();
            taskContext.info(() -> "Deleting old processor tasks");
            lockAndDelete();
        } catch (final RuntimeException e) {
            LOGGER.error(e.getMessage(), e);
        }
    }
Synchronised as we don't want to run more than once concurrently.
stroom-processor/stroom-processor-impl-db/src/main/java/stroom/processor/impl/db/ProcessorTaskDeleteExecutorImpl.java