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GNU/Linux |
Debian 6.0.0(Squeeze) |
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rrdgraph_libdbi(1) |
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rrdgraph_libdbi − fetching data for graphing in rrdtool graph via libdbi
<rrdfile> = sql//<libdbi driver>/<driver−option−name>=<driver−option−value>/...[/rrdminstepsize=<stepsize>][/rrdfillmissing=<fill missing n samples>]//<table>/<unixtimestamp column>/<data value column>[/derive]/<where clause 1>/.../<where clause n>
This pseudo-rrd-filename defines a sql datasource:
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sql// |
magic cookie−prefix for a libdbi type datasource |
<libdbi driver>
which libdbi driver to use (e.g: mysql)
<driver−option−name>=<driver−option−value>
defines the parameters that are required to connect to the database with the given libdbi driver (These drivers are libdbi dependent − for details please look at the driver documentation of libdbi!)
/rrdminstepsize=<minimum step size>
defines the minimum number of the step−length used for graphing (default: 300 seconds)
/rrdfillmissing=<fill missing steps>
defines the number of steps to fill with the last value to avoid NaN boxes due to data−insertation jitter (default: 0 steps)
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<table> |
defines the table from which to fetch the resultset. |
If there is a need to fetch
data from several tables, these tables can be defined by
separating the tablenames with a "+"
hex−type−encoding via %xx are translated to the
actual value, use %% to use %
<[*]unixtimestamp column>
defines the column of E<lt>tableE<gt> which contains the unix−timestamp − if this is a DATETIME field in the database, then prefix with leading '*' hex−type−encoding via %xx are translated to the actual value, use %% to use %
<data value column>
defines the column of E<lt>tableE<gt> which contains the value column, which should be graphed hex−type−encoding via %xx are translated to the actual value, use %% to use %
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/derive |
defines that the data value used should be the delta of the 2 consecutive values (to simulate COUNTER or DERIVE type datasources) |
/<where clause(s)>
defines one (ore more) where clauses that are joined with AND to filter the entries in the <lt>table<gt> hex−type−encoding via %xx are translated to the actual value, use %% to use %
the returned
value column-names, which can be used as ds-names, are:
min, avg, max, count and
sigma
are returned to be used as ds−names in your DS definition. The reason for using this is that if the consolidation function is used for min/avg and max, then the engine is used several times. And this results in the same SQL Statements used several times
Here an example of a table in a MySQL database:
DB connect information
dbhost=127.0.0.1
user=rrd
password=secret
database=rrd
here the table:
CREATE TABLE RRDValue (
RRDKeyID bigint(20) NOT NULL,
UnixTimeStamp int(11) NOT NULL,
value double default NOT NULL,
PRIMARY KEY (RRDKeyID,UnixTimeStamp)
);
and the RRDKeyID we want to graph for is: 1141942900757789274
The pseudo rrd-filename to access this is: "sql//mysql/host=127.0.0.1/dbname=rrd/username=rrd/password=secret//RRDValue/UnixTimeStamp/value/RRDKeyID=1141464142203608274"
To illustrate this here a command to create a graph that contains the actual values.
DS_BASE="sql//mysql/host=127.0.0.1/dbname=rrd/username=rrd/password=passwd//RRDValue/UnixTimeStamp/value/RRDKeyID=1141942900757789274"
rrdtool graph test.png −−imgformat=PNG −−start=−1day −−end=+3hours −−width=1000 −−height=600 \
"DEF:min=$DS_BASE:min:AVERAGE" \
"LINE1:min#FF0000:value" \
"DEF:avg=$DS_BASE:avg:AVERAGE" \
"LINE1:avg#00FF00:average" \
"DEF:max=$DS_BASE:max:AVERAGE" \
"LINE1:max#FF0000:max" \
"DEF:sigma=$DS_BASE:sigma:AVERAGE" \
"CDEF:upper=avg,4,sigma,*,+" \
"LINE1:upper#0000FF:+4 sigma" \
"CDEF:lower=avg,4,sigma,*,−" \
"LINE1:lower#0000FF:−4 sigma"
* Naturally you can also use any other kind of driver that libdbi supports − e.g postgres, ...
* From the way
the data source is joined, it should also be possible to do
joins over different tables
(separate tables with "," in table and add in the
WHERE Clauses the table equal joins.
This has not been tested!!!)
* It should
also be relatively simple to add to the database using the
same data source string.
This has not been implemented...
* The
aggregation functions are ignored and several data columns
are used instead
to avoid querying the same SQL several times
when minimum, average and maximum are needed for
graphing...
* for
DB efficiency you should think of having 2
tables, one containing historic values and the other
containing the latest data.
This second table should be kept small to allow for the
least ammount of blocking SQL statements.
Whith mysql you can even use myisam table-type for the first
and InnoDB for the second.
This is especially interresting as with tables with +100M
rows myisam is much smaller then InnoDB.
* To debug the SQL statements set the environment variable RRDDEBUGSQL and the actual SQL statements and the timing is printed to stderr.
* at least on
Linux please make sure that the libdbi driver is explicitly
linked against libdbi.so.0
check via ldd /usr/lib/dbd/libmysql.so, that there is a line
with libdbi.so.0.
otherwise at least the perl module RRDs will fail because
the dynamic linker can not find some symbols from libdbi.so.
(this only happens when the libdbi driver is actually used
the first time!)
This is KNOWN to be the case with
RHEL4 and FC4 and
FC5 ! (But actually this is a bug with libdbi
make files!)
* at least
version 0.8.1 of libdbiexhibits a bug with
BINARY fields
(shorttext,text,mediumtext,longtext and possibly also
BINARY and BLOB fields),
that can result in coredumps of rrdtool.
The tool will tell you on stderr if this occures, so that
you know what may be the reason.
If you are not experiencing these coredumps, then set the
environment variable
RRD_NO_LIBDBI_BUG_WARNING ,
and then the message will not get shown.
Martin Sperl <rrdtool@martin.sperl.org>
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rrdgraph_libdbi(1) | |