What possible reasons can [Sidekiq](https://github.com/mperham/sidekiq) prevent from processing jobs in the queue? The queue is full. The log file `sidekiq.log` indicates no activity at all. Thus the queue is full but the log is empty, and Sidekiq does not seem to process items. There seem to no worker processing jobs. Restarting Redis or flush it with [FLUSHALL](http://redis.io/commands/flushall) or [FLUSHDB](http://redis.io/commands/flushdb) has no effect. Sidekiq has been started with

```
bundle exec sidekiq -L log/sidekiq.log

```

and produces the following log file:

```
2013-05-30..Booting Sidekiq 2.12.0 using redis://localhost:6379/0 with options {}
2013-05-30..Running in ruby 1.9.3p374 (2013-01-15 revision 38858) [i686-linux]
2013-05-30..See LICENSE and the LGPL-3.0 for licensing details.
2013-05-30..Starting processing, hit Ctrl-C to stop

```

How can you find out what went wrong? Are there any hidden log files?