We've just released memcached beta 1.3.2. It's available for
download immediately at the google code site:
http://code.google.com/p/memcached/downloads
There is one known bug (UDP support is somewhat lacking), but it was
recently discovered by client authors attempting to implement the
protocol, so I think we're good.
We have quite a bit of confidence in this release as we've probably
spent more effort testing it than implementing new features, but I
wouldn't recommend you immediately switch all of your production sites
over. I would, however, hope that you'd ignore my recommendations and
do it anyway (or at least, test it really, really hard).
Release notes are below. They're also in beta, so if something's
wrong (you're not credited properly, or an important new feature was
overlooked), be sure to let us know so we can get it right before the
next release.
Memcached 1.3 Beta 2 Release Notes
==============================
====
Date: 2009-03-11 Wed
Table of Contents
=================
1 New Features
1.1 Binary Protocol
1.1.1 Client Availability
1.2 Performance
1.3 Stats
1.3.1 New Stats
1.3.2 More Granular Stats
1.3.3 Removed stats
2 Bug Fixes
3 Development Info
4 Feedback
5 Contributors
1 New Features
~~~~~~~~~~~~~~~
1.1 Binary Protocol
====================
A new feature that brings new features. We now have goodness like
CAS-everywhere (e.g. delete), silent, but verifiable mutation
commands, and many other wonders.
Note that the original protocol is *not* deprecated. It will be
supported indefinitely, although some new features may only be
available in the binary protocol.
1.1.1 Client Availability
--------------------------
Many clients for the binary protocol are available.
* C
libmemcached supports just about anything you can do with a
memcached
protocol and is the foundation for many clients in many different
languages (which you can find linked from the project page).
Project page: [ http://tangent.org/552/libmemcached.html ]
* Java
spymemcached has very good text and binary protocol support over
IPv4
and IPv6 with a quite comprehensive test suite.
Project page: [ http://code.google.com/p/spymemcached/ ]
* Protocol Spec
NIH problem? Go write your own client. :)
[ http://cloud.github.com/downloads/dustin/memcached/protocol-
binary.txt ]
1.2 Performance
================
Lots of effort has gone into increasing performance.
Facebook-inspired contention reduction with per-thread stat collection
and the Facebook connection dispatch and thread starvation prevention
contributions helped our scalability.
Lock analysis also showed us that we had quite a bit of contention on
hash table expansion which has been moved into its own thread, greatly
improving the scalability on multicore hardware.
A variety of smaller things also shook out of performance testing and
analysis.
1.3 Stats
==========
There are several new stats and some new ways to look at older stats.
1.3.1 New Stats
----------------
* Delete
The global stats now contain statistics on deletion.
delete_hits refers to the number of times a deletion command was
issued which resulted in a modification of the cache while
delete_misses refers to the number of times a deletion command was
issued which had no effect due to a key mismatch.
* Incr/Decr
Incr and decr each have a pair of stats showing when a
successful/unsuccessful incr occurred. incr_hits, incr_misses,
decr_hits, and decr_misses show where such mutations worked and
where
they failed to find an existing object to mutate.
* CAS
CAS stats are tracked in three different ways:
+ cas_hits
Number of attempts to CAS in a new value that worked.
+ cas_misses
Number of attempts to CAS in a value where the key was not found.
+ cas_badval
Number of attempts to CAS in a value where the CAS failed due to
the
object changing between the gets and the update.
* slab class evicted time
Per slab class, you can now see how recently accessed the most
recent
evicted data was. This is a useful gauge to determine eviction
velocity on a slab so you can know whether evictions are healthy or
if
you've got a problem.
1.3.2 More Granular Stats
--------------------------
Where possible, stats are now tracked individually by slab class. The
following stats are available on a per-slab-class basis (via "stats
slabs"):
* get_hits
* cmd_set
* delete_hits
* incr_hits
* decr_hits
* cas_hits
* cas_badval
(misses are obviously not available as they refer to a non-existent
item)
1.3.3 Removed stats
--------------------
"stats malloc" and "stats maps" have been removed.
If you depended on these commands for anything, please let us know so
we can bring them back in a more maintainable way.
2 Bug Fixes
~~~~~~~~~~~~
* Build fixes on ubuntu (gcc and icc) and FreeBSD
* bad interaction with cas + incr (bug 15)
* setuid failures are reported properly at daemonization time
* decr overflow causing unnecessary truncation to 0 (bug 21)
* failure to bind on Linux with no network (i.e. laptop dev)
* some memcached-tool cleanup
3 Development Info
~~~~~~~~~~~~~~~~~~~
We've added a bunch of tests and new code coverage reports.
All included code in this release has been tested against the
following platforms (using the in-tree test suite):
* ubuntu 8.10 (64-bit, both gcc and icc)
* ubuntu 8.04 (32-bit)
* OS X 10.5 (ppc and intel)
* OpenSolaris 5.11 x86 (with and without dtrace)
* FreeBSD 7 x86
4 Feedback
~~~~~~~~~~~
Please try this version. Make it suffer. Report feedback to the list
or file bugs as you find them.
* Mailing List: [ http://groups.google.com/group/memcached ]
* Issue Tracker: [ http://code.google.com/p/memcached/issues/list ]
* IRC: #memcached on freenode
5 Contributors
~~~~~~~~~~~~~~~
The following people contributed to this release since 1.2.6.
Note that this is based on who contributed changes, not how they were
done. In many cases, a code snippet on the mailing list or a bug
report ended up as a commit with your name on it.
Note that this is just a summary of how many changes each person made
which doesn't necessarily reflect how significant each change was.
For details on what led up into a branch, either grab the git repo and
look at the output of `git log 1.2.6..1.3.2` or use a web view.
* Repo list: [ http://code.google.com/p/memcached/wiki/
DevelopmentRepos]
* Web View: [ http://github.com/dustin/memcached/commits/1.3.2 ]
104 Dustin Sallings
49 Trond Norbye
32 Toru Maesaka
31 dormando
8 Steve Yen
7 hachi
6 Aaron Stone
6 Brian Aker
4 Victor Kirkebo
2 Ricky Zhou
1 Jonathan Bastien-Filiatrault
1 Evan Klitzke
1 Eric Lambert
Date: 2009-03-11 Wed
Table of Contents
=================
1 New Features
1.1 Binary Protocol
1.1.1 Client Availability
1.2 Performance
1.3 Stats
1.3.1 New Stats
1.3.2 More Granular Stats
1.3.3 Removed stats
2 Bug Fixes
3 Development Info
4 Feedback
5 Contributors
1 New Features
~~~~~~~~~~~~~~~
1.1 Binary Protocol
====================
A new feature that brings new features. We now have goodness like
CAS-everywhere (e.g. delete), silent, but verifiable mutation
commands, and many other wonders.
Note that the original protocol is *not* deprecated. It will be
supported indefinitely, although some new features may only be
available in the binary protocol.
1.1.1 Client Availability
--------------------------
Many clients for the binary protocol are available.
* C
libmemcached supports just about anything you can do with a
memcached
protocol and is the foundation for many clients in many different
languages (which you can find linked from the project page).
Project page: [ http://tangent.org/552/libmemcached.html ]
* Java
spymemcached has very good text and binary protocol support over
IPv4
and IPv6 with a quite comprehensive test suite.
Project page: [ http://code.google.com/p/spymemcached/ ]
* Protocol Spec
NIH problem? Go write your own client. :)
[ http://cloud.github.com/downloads/dustin/memcached/protocol-
binary.txt ]
1.2 Performance
================
Lots of effort has gone into increasing performance.
Facebook-inspired contention reduction with per-thread stat collection
and the Facebook connection dispatch and thread starvation prevention
contributions helped our scalability.
Lock analysis also showed us that we had quite a bit of contention on
hash table expansion which has been moved into its own thread, greatly
improving the scalability on multicore hardware.
A variety of smaller things also shook out of performance testing and
analysis.
1.3 Stats
==========
There are several new stats and some new ways to look at older stats.
1.3.1 New Stats
----------------
* Delete
The global stats now contain statistics on deletion.
delete_hits refers to the number of times a deletion command was
issued which resulted in a modification of the cache while
delete_misses refers to the number of times a deletion command was
issued which had no effect due to a key mismatch.
* Incr/Decr
Incr and decr each have a pair of stats showing when a
successful/unsuccessful incr occurred. incr_hits, incr_misses,
decr_hits, and decr_misses show where such mutations worked and
where
they failed to find an existing object to mutate.
* CAS
CAS stats are tracked in three different ways:
+ cas_hits
Number of attempts to CAS in a new value that worked.
+ cas_misses
Number of attempts to CAS in a value where the key was not found.
+ cas_badval
Number of attempts to CAS in a value where the CAS failed due to
the
object changing between the gets and the update.
* slab class evicted time
Per slab class, you can now see how recently accessed the most
recent
evicted data was. This is a useful gauge to determine eviction
velocity on a slab so you can know whether evictions are healthy or
if
you've got a problem.
1.3.2 More Granular Stats
--------------------------
Where possible, stats are now tracked individually by slab class. The
following stats are available on a per-slab-class basis (via "stats
slabs"):
* get_hits
* cmd_set
* delete_hits
* incr_hits
* decr_hits
* cas_hits
* cas_badval
(misses are obviously not available as they refer to a non-existent
item)
1.3.3 Removed stats
--------------------
"stats malloc" and "stats maps" have been removed.
If you depended on these commands for anything, please let us know so
we can bring them back in a more maintainable way.
2 Bug Fixes
~~~~~~~~~~~~
* Build fixes on ubuntu (gcc and icc) and FreeBSD
* bad interaction with cas + incr (bug 15)
* setuid failures are reported properly at daemonization time
* decr overflow causing unnecessary truncation to 0 (bug 21)
* failure to bind on Linux with no network (i.e. laptop dev)
* some memcached-tool cleanup
3 Development Info
~~~~~~~~~~~~~~~~~~~
We've added a bunch of tests and new code coverage reports.
All included code in this release has been tested against the
following platforms (using the in-tree test suite):
* ubuntu 8.10 (64-bit, both gcc and icc)
* ubuntu 8.04 (32-bit)
* OS X 10.5 (ppc and intel)
* OpenSolaris 5.11 x86 (with and without dtrace)
* FreeBSD 7 x86
4 Feedback
~~~~~~~~~~~
Please try this version. Make it suffer. Report feedback to the list
or file bugs as you find them.
* Mailing List: [ http://groups.google.com/group/memcached ]
* Issue Tracker: [ http://code.google.com/p/memcached/issues/list ]
* IRC: #memcached on freenode
5 Contributors
~~~~~~~~~~~~~~~
The following people contributed to this release since 1.2.6.
Note that this is based on who contributed changes, not how they were
done. In many cases, a code snippet on the mailing list or a bug
report ended up as a commit with your name on it.
Note that this is just a summary of how many changes each person made
which doesn't necessarily reflect how significant each change was.
For details on what led up into a branch, either grab the git repo and
look at the output of `git log 1.2.6..1.3.2` or use a web view.
* Repo list: [ http://code.google.com/p/memcached/wiki/
DevelopmentRepos]
* Web View: [ http://github.com/dustin/memcached/commits/1.3.2 ]
104 Dustin Sallings
49 Trond Norbye
32 Toru Maesaka
31 dormando
8 Steve Yen
7 hachi
6 Aaron Stone
6 Brian Aker
4 Victor Kirkebo
2 Ricky Zhou
1 Jonathan Bastien-Filiatrault
1 Evan Klitzke
1 Eric Lambert