<s>
collectd	B-Language
is	O
a	O
Unix	O
daemon	O
that	O
collects	O
,	O
transfers	O
and	O
stores	O
performance	O
data	O
of	O
computers	O
and	O
network	O
equipment	O
.	O
</s>
<s>
The	O
acquired	O
data	O
is	O
meant	O
to	O
help	O
system	B-Application
administrators	I-Application
maintain	O
an	O
overview	O
over	O
available	O
resources	O
to	O
detect	O
existing	O
or	O
looming	O
bottlenecks	O
.	O
</s>
<s>
The	O
first	O
version	O
of	O
the	O
daemon	O
was	O
written	O
in	O
2005	O
by	O
Florian	O
Forster	O
and	O
has	O
been	O
further	O
developed	O
as	O
free	B-Application
open-source	I-Application
project	I-Application
.	O
</s>
<s>
Most	O
files	O
of	O
the	O
source	O
code	O
are	O
licensed	O
under	O
the	O
terms	O
of	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
,	O
version2	O
(	O
GPLv2	O
)	O
,	O
the	O
remaining	O
files	O
are	O
licensed	O
under	O
other	O
open	O
source	O
licenses	O
.	O
</s>
<s>
collectd	B-Language
uses	O
a	O
modular	O
design	O
:	O
The	O
daemon	O
itself	O
only	O
implements	O
infrastructure	O
for	O
filtering	O
and	O
relaying	O
data	O
as	O
well	O
as	O
auxiliary	O
functions	O
and	O
requires	O
very	O
few	O
resources	O
,	O
it	O
even	O
runs	O
on	O
OpenWrt-powered	O
embedded	B-Architecture
devices	I-Architecture
.	O
</s>
<s>
Data	O
acquisition	O
and	O
storage	O
is	O
handled	O
by	O
plug-ins	B-Application
in	O
the	O
form	O
of	O
shared	O
objects	O
.	O
</s>
<s>
This	O
way	O
code	O
specific	O
to	O
one	O
operating	B-General_Concept
system	I-General_Concept
is	O
mostly	O
kept	O
out	O
of	O
the	O
actual	O
daemon	O
.	O
</s>
<s>
Plug-ins	B-Application
may	O
have	O
their	O
own	O
dependencies	O
,	O
for	O
example	O
a	O
specific	O
operating	B-General_Concept
system	I-General_Concept
or	O
software	B-Library
libraries	I-Library
.	O
</s>
<s>
Other	O
tasks	O
performed	O
by	O
the	O
plug-ins	B-Application
include	O
processing	O
of	O
“	O
notifications	O
”	O
and	O
log	O
messages	O
.	O
</s>
<s>
Data	O
acquisition	O
plug-ins	B-Application
,	O
called	O
"	O
read	O
plug-ins	B-Application
"	O
in	O
collectd	B-Language
's	O
documentation	O
,	O
can	O
be	O
roughly	O
put	O
into	O
three	O
categories	O
:	O
</s>
<s>
Operating	B-General_Concept
system	I-General_Concept
plug-ins	B-Application
collect	O
information	O
such	O
as	O
CPU	O
utilization	O
,	O
memory	O
usage	O
,	O
or	O
number	O
of	O
users	O
logged	O
into	O
a	O
system	O
.	O
</s>
<s>
These	O
plug-ins	B-Application
usually	O
need	O
to	O
be	O
ported	O
to	O
each	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Not	O
all	O
such	O
plug-ins	B-Application
are	O
available	O
for	O
all	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
Application	O
plug-ins	B-Application
collect	O
performance	O
data	O
from	O
or	O
about	O
an	O
application	O
running	O
on	O
the	O
same	O
or	O
a	O
remote	O
computer	O
,	O
for	O
example	O
the	O
Apache	B-Application
HTTP	I-Application
Server	I-Application
.	O
</s>
<s>
These	O
plug-ins	B-Application
often	O
use	O
software	B-Library
libraries	I-Library
but	O
are	O
usually	O
otherwise	O
operating	B-General_Concept
system	I-General_Concept
independent	O
.	O
</s>
<s>
Generic	O
plug-ins	B-Application
offer	O
basic	O
functions	O
that	O
the	O
user	O
can	O
employ	O
to	O
perform	O
specific	O
tasks	O
.	O
</s>
<s>
Examples	O
are	O
querying	O
of	O
network	O
equipment	O
using	O
SNMP	B-Protocol
or	O
execution	O
of	O
custom	O
programs	O
or	O
scripts	O
.	O
</s>
<s>
So	O
called	O
"	O
write	O
plug-ins	B-Application
"	O
offer	O
the	O
possibility	O
to	O
store	O
the	O
collected	O
data	O
on	O
disk	O
using	O
RRD	B-Language
-	O
or	O
CSV-files	O
,	O
or	O
to	O
send	O
data	O
over	O
the	O
network	O
to	O
a	O
remote	O
instance	O
of	O
the	O
daemon	O
.	O
</s>
<s>
Included	O
in	O
the	O
source	O
code	O
distribution	O
of	O
collectd	B-Language
is	O
the	O
so-called	O
"	O
network	O
"	O
plug-in	B-Application
,	O
which	O
can	O
be	O
used	O
to	O
send	O
and	O
receive	O
data	O
to/from	O
other	O
instances	O
of	O
the	O
daemon	O
.	O
</s>
<s>
In	O
a	O
typical	O
networked	O
setup	O
the	O
daemon	O
would	O
run	O
on	O
each	O
monitored	O
host	O
(	O
called	O
"	O
clients	O
"	O
)	O
with	O
the	O
network	O
plug-in	B-Application
configured	O
to	O
send	O
collected	O
data	O
to	O
one	O
or	O
more	O
network	O
addresses	O
.	O
</s>
<s>
On	O
one	O
or	O
more	O
so	O
called	O
"	O
servers	O
"	O
the	O
same	O
daemon	O
would	O
run	O
but	O
with	O
a	O
different	O
configuration	O
,	O
so	O
that	O
the	O
network	O
plug-in	B-Application
receives	O
data	O
instead	O
of	O
sending	O
it	O
.	O
</s>
<s>
Often	O
the	O
RRDtool-plug-in	O
is	O
used	O
on	O
servers	O
to	O
store	O
the	O
performance	O
data	O
.	O
</s>
<s>
The	O
plug-in	B-Application
uses	O
a	O
binary	O
network	O
protocol	O
over	O
UDP	B-Protocol
.	O
</s>
<s>
Both	O
,	O
IPv4	B-Protocol
and	O
IPv6	B-Protocol
are	O
supported	O
as	O
network	B-Application
layer	I-Application
.	O
</s>
<s>
It	O
is	O
possible	O
to	O
use	O
unicast	B-Protocol
(	O
point-to-point	O
)	O
and	O
multicast	O
(	O
point-to-group	O
)	O
addressing	O
.	O
</s>
