/usr/share/doc/slony1-2-doc/adminguide/usingslonik.html

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><H1
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><A
NAME="USINGSLONIK"
>7.3. Using Slonik</A
></H1
><A
NAME="AEN10079"
></A
><P
> It's a bit of a pain writing <SPAN
CLASS="APPLICATION"
>Slonik</SPAN
>
scripts by hand, particularly as you start working with <SPAN
CLASS="PRODUCTNAME"
>Slony-I</SPAN
>
clusters that may be comprised of increasing numbers of nodes and
sets.  Some problems that have been noticed include the following:

<P
></P
></P><UL
><LI
><P
> If you are using <SPAN
CLASS="PRODUCTNAME"
>Slony-I</SPAN
> as a
<SPAN
CLASS="QUOTE"
>"master/slave"</SPAN
> replication system with one
<SPAN
CLASS="QUOTE"
>"master"</SPAN
> node and one <SPAN
CLASS="QUOTE"
>"slave"</SPAN
> node, it may
be sufficiently mnemonic to call the <SPAN
CLASS="QUOTE"
>"master"</SPAN
> node 1 and
the <SPAN
CLASS="QUOTE"
>"slave"</SPAN
> node 2.</P
><P
> Unfortunately, as the number of nodes increases, the mapping of
IDs to nodes becomes way less obvious, particularly if you have a
cluster where the origin might shift from node to node over
time.</P
></LI
><LI
><P
> Similarly, if there is only one replication set, it's
fine for that to be <SPAN
CLASS="QUOTE"
>"set 1,"</SPAN
> but if there are a
multiplicity of sets, the numbering involved in using set numbers may
grow decreasingly intuitive.</P
></LI
><LI
><P
> People have observed that
<SPAN
CLASS="APPLICATION"
>Slonik</SPAN
> does not provide any notion of
iteration.  It is common to want to create a set of similar <A
HREF="stmtstorepath.html"
>SLONIK STORE
     PATH</A
> entries, since, in most cases, hosts will
likely access a particular server via the same host name or IP
address.</P
></LI
><LI
><P
> Users seem interested in wrapping everything possible
in <TT
CLASS="COMMAND"
>TRY</TT
> blocks, which is regrettably somewhat
<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>less</I
></SPAN
> useful than might be
hoped...</P
></LI
></UL
><P></P
><P
> These have assortedly pointed to requests for such enhancements
as:

<P
></P
></P><UL
><LI
><P
> Named nodes, named sets</P
><P
> This is supported in <SPAN
CLASS="PRODUCTNAME"
>Slony-I</SPAN
> 1.1 by the <A
HREF="stmtdefine.html"
>SLONIK DEFINE</A
> and <A
HREF="stmtinclude.html"
>SLONIK INCLUDE</A
> statements.</P
><P
> The use of <A
HREF="stmtinclude.html"
>SLONIK INCLUDE</A
> to allow creating
<SPAN
CLASS="QUOTE"
>"preamble files"</SPAN
> has proven an invaluable tool to reduce
errors.  The preamble file is set up <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>once</I
></SPAN
>,
verified <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>once</I
></SPAN
>, and then that verified script may
be used with confidence for each slonik script.</P
></LI
><LI
><P
> Looping and control constructs</P
><P
> It seems to make little sense to create a fullscale parser as
Yet Another Little Language grows into a rather larger one.  There are
plenty of scripting languages out there that can be used to construct
Slonik scripts; it is unattractive to force yet another one on people.</P
></LI
></UL
><P></P
><P
> There are several ways to work around these issues that have
been seen <SPAN
CLASS="QUOTE"
>"in the wild"</SPAN
>:</P
><P
></P
><UL
><LI
><P
> Embedding generation of slonik inside shell
scripts</P
><P
> The test bed found in the <TT
CLASS="FILENAME"
>src/ducttape</TT
>
directory takes this approach.</P
></LI
><LI
><P
> The <A
HREF="additionalutils.html#ALTPERL"
> altperl tools </A
>
use Perl code to generate Slonik scripts.</P
><P
> You define the cluster's configuration as a set of Perl
objects; each script walks through the Perl objects as needed to
generate a slonik script for that script's purpose.</P
></LI
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slony1-2-doc 2.2.4-3 / usr / share / doc / slony1-2-doc / adminguide / usingslonik.html
