On Fri, 24 Apr 2009, Rainer Gerhards wrote:
[email protected]] On Behalf Of [email protected]
loginsertion(fwd)
So it looks my three-call (beginBatch, pushData, EndBatch) calling
interface
can probably work. I need to work on how non-transactional outputs
can convey
what they have commited, but the basic interface looks rather good.
yes, although there is benifit in making these not be seperate exec
statements but instead sending them to the database as you go along (I
Definitely, but I'd consider this an implementation detail. If it is worth
it, every plugin in question may implement this mode. I'd also say it is not
too much work, depending on what "too much" means to you ;)
don't know the library well enough to know how to do a non-blocking
call
like this) or crafting one long string and sending it all at once. even
if
the pieces are generated by seperate write calls on the network
filehandle, with a TCP datastream (and a fast sender), the number of
round-trips may be far fewer than you think (what you create as
seperate
exec statements
my earlier 4-part proposal (start, mid, stop, data) is _slightly_ more
flexible in that it has the mid/joiv variable, allowing for something
to
appear between points of data, but not at the end.
i.e.
insert into table X values (),();
your 3-part version would end up with an extra , at the end.
while this isn't critical it is an easy way to gain about another
factor
of 10
I'd draw a subtle line here. I think what you propose is valid and right, but
it is not something that belongs into the output plugin interface.
Let's use my triplet (beginBatch, pushData, endBatch) for a while. On top of
that calling interface, the plugin can add strings in its configuration (NOT
an interface issue!). So it could use the calling interface as follows:
beginBatch:
emit start
pushData:
if not first element in batch
emit mid
emit data
endBatch
emit stop
The question now is if there should be support in the core engine for the
If not first element in batch
Add mid
functionality. I am not sure if there are other plugins but databases that
could use it. So far, I doubt this (the file writer not, forwarding not, snmp
not, email? Not sure, but don't think so). If it is just a db thing, it does
not belong into the core.
that logic can work for every module that needs it, so this shouldn't be
an issue.. I was mixing up the API with the need for a config variable.
David Lang
Rainer
David Lang
Rainer
David Lang
Feedback is appreciated.
Rainer
-----Original Message-----
From: [email protected] [mailto:rsyslog-
[email protected]] On Behalf Of Rainer Gerhards
Sent: Thursday, April 23, 2009 4:38 PM
To: rsyslog-users
Subject: Re: [rsyslog] [PERFORM] performance for high-volume
loginsertion(fwd)
That's interesting. As a side-activity, I am thinking about a new
output
module interface. Especially given the discussion on the postgres
list,
but
also some other thoughts about other modules (e.g. omtcp or the
file
output),
I tend to use an approach that permits both string-based as well
as
API-based
(API as in libpq) ways of doing things. I have not really designed
anything,
but the rough idea is that each plugin needs three entry points:
- start batch
- process single message
- end batch
Then, the plugin can decide itself what it wants to do and when.
Most
importantly, this calling interface works well for string-based
transactions
as well as API-based ones.
For the output file writer, for example, I envision that over time
it
will
have its own write buffer (for various reasons, for example I am
also
discussing zipped writing with some folks). With this interface, I
can
put
everything into the buffer, write out if needed but not if there
is
no
immediate need but I can make sure that I write out when the "end
batch"
entry point is called.
As I said, it is not really thought out yet, but maybe a starting
point. So
feedback is appreciated.
Rainer
-----Original Message-----
From: [email protected] [mailto:rsyslog-
[email protected]] On Behalf Of [email protected]
Sent: Wednesday, April 22, 2009 10:11 PM
To: rsyslog-users
Subject: Re: [rsyslog] [PERFORM] performance for high-volume log
insertion(fwd)
from the postgres performance mailing list, relative speeds of
different
ways of inserting data.
I've asked if the 'seperate inserts' mode is seperate round trips
or
many
inserts in one round trip.
based on this it looks like prepared statements make a
difference,
but
not
so much that other techniques (either a single statement or a
copy)
aren't
comparable (or better) options.
David Lang
---------- Forwarded message ----------
Date: Wed, 22 Apr 2009 15:33:21 -0400
From: Glenn Maynard <[email protected]>
To: [email protected]
Subject: Re: [PERFORM] performance for high-volume log insertion
On Wed, Apr 22, 2009 at 8:19 AM, Stephen Frost
<[email protected]>
wrote:
Yes, as I beleive was mentioned already, planning time for
inserts
is
really small. Parsing time for inserts when there's little
parsing
that
has to happen also isn't all *that* expensive and the same goes
for
conversions from textual representations of data to binary.
We're starting to re-hash things, in my view. The low-hanging
fruit
is
doing multiple things in a single transaction, either by using
COPY,
multi-value INSERTs, or just multiple INSERTs in a single
transaction.
That's absolutely step one.
This is all well-known, covered information, but perhaps some
numbers
will help drive this home. 40000 inserts into a single-column,
unindexed table; with predictable results:
separate inserts, no transaction: 21.21s
separate inserts, same transaction: 1.89s
40 inserts, 100 rows/insert: 0.18s
one 40000-value insert: 0.16s
40 prepared inserts, 100 rows/insert: 0.15s
COPY (text): 0.10s
COPY (binary): 0.10s
Of course, real workloads will change the weights, but this is
more
or
less the magnitude of difference I always see--batch your inserts
into
single statements, and if that's not enough, skip to COPY.
--
Glenn Maynard
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