to avoid a) opening a large number of Sessions or Cursors and b) avoid
reusing a Session/Cursor pair in more than one thread. Each operation,
except folds, use the Session/Cursor pair corresponding to the scheduler
id (roughly "core") they are running on. Each vnode instance will have
(count(schedulers) + count(active folds)) Session/Cursor pairs in use so
be sure to set session_max large enough when opening the connection to
WiredTiger. This method will cause problems with scheduler threads going
to "sleep" so be sure to run schedmon to wake them up.
reasonable setting for the WiredTiger cache size at runtime. This cache
is shared across all vnodes regarless of how many are active at any
given time. The algorithm is: max(1GB, 1/3 (RAM - Beam RSS size)). We don't
enable direct_io on purpose and data will be double buffered in WiredTiger's
cache and the filesystem buffer cache. This turns out to be faster than
direct I/O despite wasting a bit of RAM.
answer is 'no'). So far there has been no effort to validate that these
settings are in fact the best for Riak/KV or CS data access patterns. These
particular settings are, at best, an educated guess based on past experience,
the docs and reading about the benchmark the WiredTiger team published here:
https://github.com/wiredtiger/wiredtiger/wiki/YCSB-Mapkeeper-benchmark
Before modifying files to add wterl, check to make sure the addition hasn't
already been made. Also change to do a stagedevrel build instead of a
devrel build.
Versions of WiredTiger prior to 1.3.3 had trouble handling riak restarts,
returning errors from wterl:session_create that would prevent riak from
restarting if it was not cleanly shut down on the previous run. We
previously avoided checking the return value of wterl:session_create to
avoid this problem. WT 1.3.3 fixes this, so reinstate the check of the
wterl:session_create return value.
Since 1.3.0 folded the session sync function into the session checkpoint
function, the wterl:sync/(2,3) functions are now renamed
wterl:checkpoint/(1,2). See
http://source.wiredtiger.com/1.3.0/upgrading.html for details.
