render_list errors

Running cat foo | render_list -s /var/run/renderd/renderd.sock -n 8 -m default -f I get errors

Starting 8 rendering threads

Meta tiles rendered: Rendered 10 tiles in 0.00 seconds (11074.20 tiles/s)
Total tiles rendered: Rendered 640 tiles in 0.00 seconds (708748.62 tiles/s)
Total tiles handled from input: Rendered 10 tiles in 0.00 seconds (11074.20 tiles/s)
rendering failed, pausing

Meta tiles rendered: Rendered 20 tiles in 0.00 seconds (14836.79 tiles/s)
Total tiles rendered: Rendered 1280 tiles in 0.00 seconds (949554.88 tiles/s)
Total tiles handled from input: Rendered 20 tiles in 0.00 seconds (14836.79 tiles/s)

Meta tiles rendered: Rendered 30 tiles in 0.00 seconds (20876.83 tiles/s)
Total tiles rendered: Rendered 1920 tiles in 0.00 seconds (1336116.88 tiles/s)
Total tiles handled from input: Rendered 30 tiles in 0.00 seconds (20876.83 tiles/s)

Meta tiles rendered: Rendered 40 tiles in 0.00 seconds (26472.54 tiles/s)
Total tiles rendered: Rendered 2560 tiles in 0.00 seconds (1694242.25 tiles/s)
Total tiles handled from input: Rendered 40 tiles in 0.00 seconds (26472.54 tiles/s)
rendering failed, pausing
rendering failed, pausing
rendering failed, pausing
rendering failed, pausing
rendering failed, pausing
rendering failed, pausing
rendering failed, pausing

I ran renderd in foreground mode and got this

renderd[1845]: DEBUG: Got incoming connection, fd 8, number 1
renderd[1845]: DEBUG: Got incoming connection, fd 10, number 2
renderd[1845]: DEBUG: Got incoming connection, fd 11, number 3
renderd[1845]: DEBUG: Got incoming connection, fd 12, number 4
renderd[1845]: DEBUG: Got incoming connection, fd 13, number 5
renderd[1845]: DEBUG: Got incoming connection, fd 14, number 6
renderd[1845]: DEBUG: Got incoming request with protocol version 2
renderd[1845]: Recv Error on fd 10 (Success). Read 65 bytes
renderd[1845]: DEBUG: Got incoming connection, fd 15, number 7
renderd[1845]: DEBUG: Got incoming request with protocol version 0
renderd[1845]: DEBUG: Got command Ignore fd(10) xml(), z(0), x(0), y(0)
renderd[1845]: WARNING: Ignoring unknown command Ignore fd(10) xml(), z(0), x(0), y(0)
renderd[1845]: DEBUG: Sending NotDone response(4)
renderd[1845]: DEBUG: Got incoming request with protocol version 2
renderd[1845]: Recv Error on fd 11 (Success). Read 65 bytes
renderd[1845]: DEBUG: Got incoming connection, fd 16, number 8
renderd[1845]: DEBUG: Got incoming request with protocol version 2
renderd[1845]: Recv Error on fd 8 (Success). Read 65 bytes
renderd[1845]: DEBUG: Got incoming request with protocol version 0
renderd[1845]: DEBUG: Got command Ignore fd(8) xml(), z(0), x(0), y(0)
renderd[1845]: WARNING: Ignoring unknown command Ignore fd(8) xml(), z(0), x(0), y(0)
renderd[1845]: DEBUG: Sending NotDone response(4)
renderd[1845]: DEBUG: Got incoming request with protocol version 0

I did a git bisect and this is the commit where it was introduced

pnorman@osm2pgsqlbench:~/osm/mod_tile$ git bisect bad
fdc317a8f36f001d3eb2a864eb7cff55f11fdeb7 is the first bad commit
commit fdc317a8f36f001d3eb2a864eb7cff55f11fdeb7
Author: Kai Krueger <kakrueger@gmail.com>
Date:   Sun Oct 13 23:22:08 2013 -0600

    Update mod_tile to renderd protocol to version 3.

    Include an "options" string and a "mimetype" string.

:040000 040000 a0551beb9f9874fc84e2ae21078f98bf19130265 3e75c961b2ebcfceb9f8a9307ec964d83b46ad6a M      includes
:040000 040000 a1934c59e0d8e1885e4a16b8e318a8a6cb35cedc 67035c4dbbab00909fccbaa8ccd921988f20c60d M      src

Start by comparing commit fdc317a8f36f001d3eb2a864eb7cff55f11fdeb7 with its parent, focusing on the changes under includes and src. Reproduce the render_list command with renderd in foreground mode and trace the protocol-version and command handling shown in the logs. Done means the client and daemon communicate without the repeated rendering failures or unknown Ignore commands.