== link:index.html[Index] -> link:other.html[Other information]

Other: Usage graphs
-------------------

When link:http://oss.oetiker.ch/rrdtool/[RRDtool] is available in your
system, the information collector option of the
link:config_general.html[General] section can be activated to generate
several usage graphs.

These graphs will represent several metrics (shown as current,
average, max, and total measures) against various time intervals (1
hour, 6 hours, 1 day, 1 week, 1 month).

The graphs can be accessed through the link:config_status.html[status
section] and the link:config_virtual_servers.html#logging[logging tab]
of each virtual server.

link:config_status.html[Status section]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Three types of graphs are available. You can switch between them at
any time.

[[traffic]]
Server-traffic
^^^^^^^^^^^^^^

This is a straight forward representation showing the amount of bytes
per second that were downloaded from and uploaded to the server.

image::media/images/other_graphs_traffic.png[Server-traffic]

[[connections]]
Connections / Requests
^^^^^^^^^^^^^^^^^^^^^^

This one displays HTTP requests and TCP connections. Since you can
have Keep-alive enabled connections, several HTTP requests can be
issued through the same one thus considerably improving the web
server's performance. Worst case scenario, both graphs will the
same. In normal conditions HTTP requests can be much higher than TCP
connections.

image::media/images/other_graphs_conns.png[Connections / Requests]

[[timeouts]]
Connections Timeout
^^^^^^^^^^^^^^^^^^^

This graph will show the maximum, minimum and average number of
connections that are timed out per second. These timeouts can happen
for several reasons. If Keep-alive is enabled, a client will be able
to keep the connection lingering to improve performance. If this
happened indefinitely, sooner or later the server would be unable to
serve new requests. These connections must naturally expire according
to a configurable value to leave space for new users. Connections can
also timeout if a backend ceases to respond, which is something you
will need to monitor.

Since each pixel of the graph can correspond to several seconds,
minutes, or hours, it makes sense that the upper borders of the red zone
will correspond to the maximum number of timeouts. The lower borders
will be the minimum, and the darker line in the middle will represent
the calculated average.

image::media/images/other_graphs_timeouts.png[Connections Timeout]

[[vserver]]
link:config_virtual_servers.html#logging[Virtual server's logging tab]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Just like the Server-traffic graph, it displays the amount of bytes
per second moving back and forth, in this case limited to a specific
virtual server. The `global` representation would show the total
amount of data transmitted by the whole server, which corresponds to
the sum of every virtual server's outbound traffic.

image::media/images/other_graphs_logging.png[Virtual server logging]
