On Mon, 5 Dec 2016, Bob Gregory wrote:
Yo yo, David.
I think you're convincing me, at least on the service/programname. That
means we can default all of the required host, service, timestamp
fields. I
also like the simpler approach of using the fractional part to decide
which
kind of metric we're sending. That's a better user-experience.
I still feel reasonably strongly that we oughtn't to default the other
fields, since the usual case of riemann is for them to be absent.
Are you satisfied with the host, service, timestamp fields having
defaults?
That means that the following
action(type="omriemann" metric="1") will send {host:$hostname, time:
$timereported, service: $programname}
While it's not going to be very useful, it's at least something you can
dump to console on the Riemann host and see that data are flowing.
what about status? is it normally/commonly left blank?
as long as the syntax checker for the module can report a config error if
you
don't have at least one of description, metric, status defined in an
action()
call (with an error message that will make it obvious to the admin why
they are
getting the error)
David Lang
On Mon, 5 Dec 2016 at 11:39 David Lang <[email protected]> wrote:
On Mon, 5 Dec 2016, Bob Gregory wrote:
@ David Lang, moving omriemann discussion back over here.
we need to try and come up with a reasonable default value for
parameters.
I think I disagree with that. Most of the fields aren't required, and we
shouldn't send them unless configured otherwise. The intention isn't
that
all logs will go to riemann, but only a small subset of logs, after
being
substantially transformed.
the biggest thing we need to do is make sure that whatever the user
attempts to
send should not stall the feed, so it will either need to be discarded
(IMHO a
bad idea) or 'fixed up' if it's not valid.
* Description is an unusual field to include - I definitely wouldn't
include the entire log message as a default.
* The programname makes little sense as a service. IF I see that "nginx"
or
"rsyslog" is oscillating between 20 and 57 on a graph, what does that
tell
me?
the number of lines of rsyslog data you are getting if nothing else
(which
may be something you want to monitor :-)
again, I'm trying to make the defaults do something sane if nothing is
configured. It's better to have someone do a trivial configuration and
get
flooded with data than to have them have to get a lot of things right
before
anything shows up.
* TTL can be defaulted by Riemann. We shouldn't set it to 0. I'm not
actually sure what happens with a TTL of 0, I'd guess the event
immediately
expires, which would be problematic for many cases.
Ok, as long as Riemann is designed to survive when no TTL is provided.
* The tags as used by rsyslog are unlikely to map meaningfully to the
tags
used by riemann because they have very different use cases. I mostly
use
tags in rsyslog to tell me whether my logs are json, or HTTP access
logs,
or PHP exceptions etc so that I know how to handle the output of
mmnormalize
- that's not useful data in my monitoring stack.
again, I'm looking to set a default that has a chance of working, if you
are
always setting the tag, the default doesn't matter.
I set the tags to contain a lot more info, is this a connection or
disconnection, is this a login or failed login, etc.
It turns out, on a re-reading, that the metric isn't required either -
it's
absolutely valid to send the event {host: localhost, service: "openvpn",
status: "up | down" } for example.
ok, makes sense.
Given that we can't make reasonable guesses about what the user
intends, I
think the sensible approach is to _not send_ any field for which we
don't
have
a value specified, with the exception of the source host and the
timestamp
which have obviously sane defaults.
Here I disagree, not sending anything is likely to generate support
requests of
"I configured omriemann and got a bunch of blank events, what's wrong".
I'd
rather send extra data by default so that the people experimenting can at
least
see stuff show up. It's much easier to then tinker with what's showing up
than
to have to figure out what things you have to put in to get anything to
show up.
Other than that, I think we're in agreement. I particularly like the
idea
of allowing metric to be a json object, that definitely simplifies the
impstats case.
how do you signal metric types?
I don't - that's down to upstream collectors. Riemann doesn't care what
the
metric represents, it's just a number. It has no concept of the type of
a
metric, it just cares about the service name and host and allows you to
do
interesting things with the data stream. We use Collectd at Made, and
that
sends metrics with gauge/counter/derive in the service name.
ok, that's interesting. Every other montioring tool I've used wants it
specified
as it's passed in. In many cases, this can be configured to different
things on
different servers for the same metric.
There is an expectation that you would only use a single field from
metric,
metric_f, metric_s64 etc. I've never actually tried sending more than
one
metric to riemann in a message, because clients tend to explicitly
forbid
it. Internally, all those protobuf fields map down to the same metric
field, so I'm unsure whether riemann will reject the message or select
one
of the fields in an unspecified precedence. Deciding which of those
protobuf
fields to send is a open problem. Any thoughts on that?
we don't want the user to have to specify the specific type, that's too
likely
to lead to someone picking the wrong type. Everything is a string in
rsyslog to
start with, so I'd say that the metric should use the s64 if there is no
fractinal portion and double if there is.
I have no idea what we would do if some anarchist sent us the json
object
{
"metrics": { "service": "trololol", "metric_f": 0.2, "metric_int": 27
}}.
We can either reject the message and log an error, or specify some
precedence order. I don't have a strong feeling either way; it's
probably
ok if we reformat your integer as a double, but I generally like
software
to fail fast instead of limping along doing something unexpected.
That's one reason for not specifying them individually :-)
But rather than the JSON looking like:
{ "metrics": { "service": "trololol", "metric_f": 0.2, "metric_int": 27
}}
I would have it be something more like:
{ "service": "trololol", "metrics": {"foo":"0.2", "bar":"27"}}
then you would do something like
action(type="omriemann" host="$hostname" service="$!service_"
description=""
metrics="$!metrics" target="ip to riemann server" port="port of server")
host could be left out and let it default to $hostname
David Lang
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