Holding open even a read-only connection while reading an RPM database can corrupt it. Even with Redhat's own tools.

The issue may exhibit itself like so:
 

rpmdb: Thread/process  failed: Thread died in Berkeley DB library
error: db3 error(-30974) from dbenv->failchk: DB_RUNRECOVERY: Fatal error, run database recovery

See the Resolution section below for steps to follow to resolve this corruption issue.

If RPMDB claims it's corrupted, it could be just stale locks from a killed Chef Client or other process. Make sure you figure out which PID was killed while it was trying to rpm -qa and then compare to the output of

 

cd /var/lib/rpm
/usr/lib/rpm/rpmdb_stat -CA

Here is the lock portion of the output when there are no locks present. A lock identifier will look like this 12926/140090959366048 and appear in these two sections.

Locks grouped by lockers:
Locker Mode Count Status ----------------- Object ---------------
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Locks grouped by object:
Locker Mode Count Status ----------------- Object ---------------

If all processes that should be accessing the RPMDB are gone, but you still see locks in the rpmdb_stat output, then you probably have your "corruption" candidate.

Delete those locks with rm -rf /var/lib/rpm/__db.0*, then try your rpm -qa again. This time, reading should be successful unless there actually is a problem with the database's data.

You can reproduce this situation on CentOS 6.x with the following shell script:

for i in {1..30}; do 
if [[ "$i" -eq 3 ]]; then 
   ( /bin/rpm -qa > /dev/null ; kill -9 $! ) & 
else 
  /bin/rpm -qa > /dev/null &  
fi  
done

That kill on the third rpm -qa doesn't allow the process to cleanly close the database resulting in instant corruption.

Any other attempts at a similar "read-only" command afterward result in output like:

[root@chef-432 rpm]# rpm -qa
rpmdb: Thread/process 12926/140090959366048 failed: Thread died in Berkeley DB library
error: db3 error(-30974) from dbenv->failchk: DB_RUNRECOVERY: Fatal error, run database recovery
error: cannot open Packages index using db3 -  (-30974)
error: cannot open Packages database in /var/lib/rpm
rpmdb: Thread/process 12926/140090959366048 failed: Thread died in Berkeley DB library
error: db3 error(-30974) from dbenv->failchk: DB_RUNRECOVERY: Fatal error, run database recovery
error: cannot open Packages database in /var/lib/rpm

We have noticed the most issue with this when the yum_package resource is used in the old omnibus_updater cookbook. The modern https://github.com/chef-cookbooks/chef_client_updater cookbook is not supposed to have the issue.