Because redis.Redis(...) ctor creates connection pool on initialization
and we can rely on it.

Another reason: Redis ctor (in form of StrictRedis.__init__()) has logic
how to process arguments and does selecting - either it is TCP (`host` and
`port` args), or UNIX socket (`unix_socket_path` arg):

    https://lab.nexedi.com/nexedi/slapos/blob/95dbb5b2/slapos/recipe/redis/MyRedis2410.py#L560

Since we are going to introduce unix socket support to redis recipe in
the next patch, and don't want to duplicate StrictRedis.__init__() logic
in promise code, let's refactor promise to delegate argument processing
logic to Redis.

/reviewed-by @kazuhiko  (on !27)
/cc @alain.takoudjou

- update Redis software to latest upstream in 2.8.* series (which now
  supports IPv6 out of the box);

- update Redis instance template to the one from 2.8.23 and re-merge our
  templating changes to it (file/dir locations, port and binding, master
  password).

  The whole diff to pristine 2.8.23 redis conf is now this:

  diff --git a/.../redis-2.8.23/redis.conf b/slapos/recipe/redis/template/redis.conf.in
  index 870959f..2895539 100644
  --- a/.../redis-2.8.23/redis.conf
  +++ b/slapos/recipe/redis/template/redis.conf.in
  @@ -46 +46 @@ daemonize no
  -pidfile /var/run/redis.pid
  +pidfile %(pid_file)s
  @@ -50 +50 @@ pidfile /var/run/redis.pid
  -port 6379
  +port %(port)s
  @@ -69,0 +70 @@ tcp-backlog 511
  +bind %(ipv6)s
  @@ -108 +109 @@ loglevel notice
  -logfile ""
  +logfile %(log_file)s
  @@ -174 +175 @@ rdbcompression yes
  -# hit to pay (around 10%) when saving and loading RDB files, so you can disable it
  +# hit to pay (around 10%%) when saving and loading RDB files, so you can disable it
  @@ -192 +193 @@ dbfilename dump.rdb
  -dir ./
  +dir %(server_dir)s
  @@ -217 +218 @@ dir ./
  -# masterauth <master-password>
  +%(master_passwd)s

NOTE There are test failures for almost all Redis versions when machine
have not small amount of CPUs:

    https://github.com/antirez/redis/issues/2715#issuecomment-151608948

Because the failure is in replication test, and so far we do not use
replication, and there is no feedback from upstream author to handle
this (for 7 days for my detailed report, and for ~ 3 months for this
issue in general), we can just disable replication test as a temporary
solution.  ( to handle remote patches with md5 hash easily the building
recipe is changed to slapos.recipe.cmmi )

NOTE Redis updated to 2.8 version because GitLab uses this series.
If/when we need more recent one we can add [redis30] in addition to
[redis28].

/reviewed-by @kazuhiko  (on !27 and on !26)
/cc @alain.takoudjou, @jerome

Ruby 2.1.7 contain security and other bugfixes:

    https://www.ruby-lang.org/en/news/2015/08/18/ruby-2-1-7-released/

/reviewed-by @kazuhiko  (on nexedi/slapos!28)

Compared to our currently-packaged 9.2.8 postgresql 9.2.14 contains a lot of
fixes including security ones. On the path of updating, we cleanup postgresql
component a bit. Details are in commit logs.

/reviewed-by @kazuhiko  (on !25)

Compared to 9.2.8 postgresql 9.2.14 contains a lot of fixes including
security ones:

    http://www.postgresql.org/docs/current/static/release-9-2-9.html
    http://www.postgresql.org/docs/current/static/release-9-2-10.html
    http://www.postgresql.org/docs/current/static/release-9-2-11.html
    http://www.postgresql.org/docs/current/static/release-9-2-12.html
    http://www.postgresql.org/docs/current/static/release-9-2-13.html
    http://www.postgresql.org/docs/current/static/release-9-2-14.html

Currently we have recipes to build both postgresql 9.1 and 9.2 (see
9f1f0759 "provide both postgres 9.1 and 9.2") which mostly duplicate
each other with minor difference that 9.1 is built with perl and 9.2
without (perl added to 9.1 in dbbd9a96 "Include Perl in Postgres").

To reduce the duplication let's move common compilation bits to common
section.

NOTE I've tried to add perl to postgresql 9.2 as well and got the
following compilation error:

    ld: .../perl/libs-c/libperl.a(op.o): relocation R_X86_64_32 against `.rodata.str1.8' can not be used when making a shared object; recompile with -fPIC
    .../parts/perl/libs-c/libperl.a: could not read symbols: Bad value

which happens because libperl.a is not compiled with fPIC.

For now we don't need perl in postgresql92 and this is not handled, and
we just deduplicate building recipes without any actual change for
resulting commands how the software is built.

component/postgresql/buildout.cfg defines both postgresql92 and
postgresql sections, with postgresql being just

    [postgresql]
    <= postgresql92

On the other hand, software/postgresql uses postgresql92 in parts, but
bin = ${postgresql:location}/bin in instance, which leads to _both_
postgresql and postgresql92 being built, and postgresql92 not used at all.

Let's fix it and use postgresql everywhere.

/cc @kazuhiko

This is an important update for us because we use http-send-name-header.
A bug caused HAProxy to segfault.

Slaprunner tries to leverage multicore, and spawns multiple jobs when compiling software, based on `cpu-usage-ratio` parameter. But this currently have effect only on Make-based projects (via setting `MAKEFLAGS=-j<n>`) and does not affect software with different build systems.

Let's also provide support for parallel building for NumPy-based software and Ruby gems out of the box.

/cc @cedric.leninivin, @kazuhiko, @alain.takoudjou
/reviewed-by @jerome, @rafael  (on !22)

Most Ruby projects are built via Bundler[1], e.g. the upcoming GitLab,
and Bundler supports building/fetching dependency gems in parallel:

    http://bundler.io/v1.10/bundle_install.html#jobs

via using `--jobs <n>` command line option.

All bundler options can be also passed in via environment variable, and
this way we can use BUNDLE_JOBS=<n> for default `--jobs <n>`.

Let's use it, and this way speedup Ruby-related builds (like we already
do for Make- and NumPy- based software).

[1] http://bundler.io/

/cc @jerome, @cedric.leninivin, @kazuhiko

Starting from NumPy 1.10 numpy's distutils support parallel building

    http://docs.scipy.org/doc/numpy/user/install.html#basic-installation
    https://github.com/numpy/numpy/commit/23d54617

and this way software which uses numpy's distutils (scipy,
scikit-learn, etc) should support it too.

Let's use it, like we currently already use MAKEFLAGS for speeding up
make-based projects.

/cc @jerome, @cedric.leninivin, @kazuhiko

Currently we use '%d' and string formatting on max(1, ncpu / cpu-usage-ratio),
because `ncpu / cpu-usage-ratio` is float:

    In [1]: from __future__ import division

    In [2]: 8 / 4
    Out[2]: 2.0

and jinja2 uses future division by default:

    {{ 8 / 4 }}   ->   2.0

We can however make things more explicit, by explicitly using integer
division (// operator) and this way avoid the need for '%d' and string
formatting.

/cc @jerome, @cedric.leninivin

The calculation is full line long, and we are going to reuse this number
in a couple of new places, so this way it makes sense to first compute
jobs number separately, and then reuse the variable.

/cc @jerome, @cedric.leninivin

/reviewed-by @kazuhiko  (on !21)

Commit 6f009a9f broke generation of zope-*.conf

Partition root should be used to control overall permissions, which is
typically a safe-enough 0750 (depending on slapformat and sysadmin).
umask is applied at libc mkdir level, so this typically results in 0755
actual permission.
More restrictive permissions should only be used when really needed.

/reviewed-by @kazuhiko

This is a follow-up of commit 6f009a9f

Conflicts:
	stack/slapos.cfg

NEO is still in heavy development and it must be easy to update code on
existing deployment.

Zope integrated Products.signalstack back in 2010:

    https://github.com/zopefoundation/Zope/commit/16796274
    ( Integrated the Products.signalstack / z3c.deadlockdebugger
      packages. You can now send a SIGUSR1 signal to a Zope process and get a
      stack trace of all threads printed out on the console. This works even
      if all threads are stuck. )

In 404150b7 (wendelin: Teach -dev build to dump all threads traceback on
SIGUSR1) it was my mistake to add Products.signalstack.

/reviewed-by TrustMe
/cc @Tyagov