Time Syntax
The Time syntax defines how you can convert or translate timestamps and other time related values to alternative formats. A relative time syntax is available for specifying and calculating times in relation to other times. See Relative Time Syntax.
Rate Unit Conversion
When displaying a rate (value per unit of time) in a Time
Chart
, the display is sensitive to the size of the
chart's span
or
bucket
parameter, if the thing being
graphed is a sum()
or count()
of log data.
You can use timechart(function=sum(bytes),span=1h)
to show an hourly rate. But sometimes you want a rate (say
Kibytes/sec
) for which it does not make
sense to create a bucket for each. Previously we have suggested to use a
successive eval()
to reduce the chart inputs, but
that's rather cumbersome and also sensitive to the size of the buckets
(the span of each bar in the chart). Unit conversions can resolve this.
Source-Unit is a Sum or Count
You can convert using a syntax like
timechart(function=sum(bytes),
unit="bytes/span to Mi bytes/day")
. This will make it so that
the conversion takes the timespan into account. If you use the above
with span=1d
there will be no
conversion, but if you it with
span=1h
, then the plotted values will
be multiplied by 24 (because there are 24hours in a day). You can use
/span
or /bucket
interchangeably.
Source-Unit is Already a Rate
You can convert using a syntax like
timechart(..., unit="bytes/sec to
Mibytes/day")
. In this case, the source is already a rate
(measured in units per time). With this the conversion is applied
independently of the length of the span (bucket size) for the graph.
Expressing Rates & Units
Units in this system is either a base unit (like events or bytes) or a rate, like a base unit per time unit. The syntax for a base unit is this
base_unit ::= Number_opt SIunit_opt unitname_opt
Number_opt ::= ([0-9]+)?
SIunit_opt ::= ([KMGP]i?
| )
unitname_opt ::= (' '? <string>)?
Tip
Units can be expressed as SI units or binary units. An example of a
base unit is 2Gi bytes
. We use the
standard SI-units K, M, G, and P to denote 1000-based kilo, mega,
giga and peta; whereas Ki, Mi, Gi, and Pi designate the binary
multiple 1024n style. See the National
Institute of Standards & Technology's
Reference
on Prefixes for Binary Multiples for a detailed explanation.
The unitname_opt
can optionally be
separated from the SI unit with a single space to be able to
differentiate names unit names starting with an
i
.
Time units follow the same pattern, as you see here:
time_unit ::= Number_opt Time
Number_opt ::= ([0-9]+)?
Time ::= prefix-of( "seconds, "milliseconds", "minutes", "hours" "days" )
| "ms"
| "bucket"
| "span"
The non-uniq prefixes m
and
mi
are interpreted as minutes.
Whereas, ms
designates milliseconds. A
rate is like so:
Rate ::= base_unit "/" time_unit
Since the entirety of base-unit is optional — a missing base unit is implied to be one — you can convert from events/second to events/hour with a minimal expression such as this:
unit="/s to /h"
The to
side of such a conversion must
be a rate, whereas the left side can be a basic unit, which is
interpreted as unit/bucket
.