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This is a Riak storage backend that uses WiredTiger, an Erlang interface to the WiredTiger k/v pair storage engine, and an abstract async thread-pool layer for Erlang's NIF API called c_src/async_nif.h.
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Gregory Burd 77e0dacdb5 Use a set of {Session, Cursor} pairs ("passes") for calls into WiredTiger 
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.
2013-03-26 14:17:21 -04:00
c_src Cursor delete operation only requires cursor handle and key (no need for a value) 2013-03-21 18:44:13 -04:00
src Use a set of {Session, Cursor} pairs ("passes") for calls into WiredTiger 2013-03-26 14:17:21 -04:00
.gitignore Build from source pulled from a specific branch on GitHub for "basho" 2013-03-12 17:16:15 -04:00
enable-wterl modify enable-wterl to avoid adding wterl repeatedly 2012-10-26 10:22:59 -04:00
Makefile Add some more depth to the targets. 2013-03-07 16:03:30 -05:00
README.md add README 2012-03-27 22:27:50 -04:00
rebar update rebar and rebar.config 2012-10-26 09:25:35 -04:00
rebar.config Mistakenly allowed a file rename from another branch here. Use "wterl" 2013-03-14 17:36:45 -04:00

README.md

wterl is an Erlang interface to the WiredTiger database, and is written to support a Riak storage backend that uses WiredTiger.

This backend currently supports only key-value storage and retrieval.

Remaining work includes:

  • The wterl:session_create function currently returns an error under certain circumstances, so we currently ignore its return value.
  • The riak_kv_wterl_backend module is currently designed to rely on the fact that it runs in just a single Erlang scheduler thread, which is necessary because WiredTiger doesn't allow a session to be used concurrently by different threads. If the KV node design ever changes to involve concurrency across scheduler threads, this current design will no longer work correctly.
  • Currently the riak_kv_wterl_backend module is stored in this repository, but it really belongs in the riak_kv repository.
  • There are currently some stability issues with WiredTiger that can sometimes cause errors when restarting KV nodes with non-empty WiredTiger storage.

Future support for secondary indexes requires WiredTiger features that are under development but are not yet available.

Deploying

You can deploy wterl into a Riak devrel cluster using the enable-wterl script. Clone the riak repo, change your working directory to it, and then execute the enable-wterl script. It adds wterl as a dependency, runs make all devrel, and then modifies the configuration settings of the resulting dev nodes to use the WiredTiger storage backend.