1RRDFETCH(1) rrdtool RRDFETCH(1)
2
6 rrdfetch - Fetch data from an RRD.
7
9 rrdtool fetch filename CF [--resolution|-r resolution]
10 [--start|-s start] [--end|-e end] [--align-start|-a]
11 [--daemon|-d address]
12
14 The fetch function is normally used internally by the graph function to
15 get data from RRDs. fetch will analyze the RRD and try to retrieve the
16 data in the resolution requested. The data fetched is printed to
17 stdout. *UNKNOWN* data is often represented by the string "NaN"
18 depending on your OS's printf function.
19 filename
21 the name of the RRD you want to fetch the data from.
22 CF the consolidation function that is applied to the data you want
24 to fetch (AVERAGE,MIN,MAX,LAST)
25 --resolution|-r resolution (default is the highest resolution)
27 the interval you want the values to have (seconds per value).
28 An optional suffix may be used (e.g. "5m" instead of 300
29 seconds). rrdfetch will try to match your request, but it will
30 return data even if no absolute match is possible. See
31 "RESOLUTION INTERVAL".
32 --start|-s start (default end-1day)
34 start of the time series. A time in seconds since epoch
35 (1970-01-01) is required. Negative numbers are relative to the
36 current time. By default, one day worth of data will be
37 fetched. See also "AT-STYLE TIME SPECIFICATION" for a detailed
38 explanation on ways to specify the start time.
39 --end|-e end (default now)
41 the end of the time series in seconds since epoch. See also
42 "AT-STYLE TIME SPECIFICATION" for a detailed explanation of how
43 to specify the end time.
44 --align-start|-a
46 Automatically adjust the start time down to be aligned with the
47 resolution. The end-time is adjusted by the same amount. This
48 avoids the need for external calculations described in
49 RESOLUTION INTERVAL, though if a specific RRA is desired this
50 will not ensure the start and end fall within its bounds.
51 --daemon|-d address
53 Address of the rrdcached daemon. If specified, a "flush"
54 command is sent to the server before reading the RRD files.
55 This allows rrdtool to return fresh data even if the daemon is
56 configured to cache values for a long time. For a list of
57 accepted formats, see the -l option in the rrdcached manual.
58 rrdtool fetch --daemon unix:/var/run/rrdcached.sock /var/lib/rrd/foo.rrd AVERAGE
60 Please note that due to thread-safety reasons, the time
62 specified with -s and -e cannot use the complex forms described
63 in "AT-STYLE TIME SPECIFICATION". The only accepted arguments
64 are "simple integers". Positive values are interpreted as
65 seconds since epoch, negative values (and zero) are interpreted
66 as relative to now. So "1272535035" refers to "09:57:15 (UTC),
67 April 29th 2010" and "-3600" means "one hour ago".
68 RESOLUTION INTERVAL
70 In order to get RRDtool to fetch anything other than the finest
71 resolution RRA both the start and end time must be specified on
72 boundaries that are multiples of the desired resolution. Consider the
73 following example:
74 rrdtool create subdata.rrd -s 10 \
76 DS:ds0:GAUGE:5m:0:U \
77 RRA:AVERAGE:0.5:5m:300h \
78 RRA:AVERAGE:0.5:15m:300h \
79 RRA:AVERAGE:0.5:1h:50d \
80 RRA:MAX:0.5:1h:50d \
81 RRA:AVERAGE:0.5:1d:600d \
82 RRA:MAX:0.5:1d:600d
83 This RRD collects data every 10 seconds and stores its averages over 5
85 minutes, 15 minutes, 1 hour, and 1 day, as well as the maxima for 1
86 hour and 1 day.
87 Consider now that you want to fetch the 15 minute average data for the
89 last hour. You might try
90 rrdtool fetch subdata.rrd AVERAGE -r 15m -s -1h
92 However, this will almost always result in a time series that is NOT in
94 the 15 minute RRA. Therefore, the highest resolution RRA, i.e. 5 minute
95 averages, will be chosen which in this case is not what you want.
96 Hence, make sure that
98 1. both start and end time are a multiple of 900 ("15m")
100 2. both start and end time are within the desired RRA
102 So, if time now is called "t", do
104 end time == int(t/900)*900,
106 start time == end time - 1hour,
107 resolution == 900.
108 Using the bash shell, this could look be:
110 TIME=$(date +%s)
112 RRDRES=900
113 rrdtool fetch subdata.rrd AVERAGE -r $RRDRES \
114 -e $(($TIME/$RRDRES*$RRDRES)) -s e-1h
115 Or in Perl:
117 perl -e '$ctime = time; $rrdres = 900; \
119 system "rrdtool fetch subdata.rrd AVERAGE \
120 -r $rrdres -e @{[int($ctime/$rrdres)*$rrdres]} -s e-1h"'
121 Or using the --align-start flag:
123 rrdtool fetch subdata.rrd AVERAGE -a -r 15m -s -1h
125 AT-STYLE TIME SPECIFICATION
127 Apart from the traditional Seconds since epoch, RRDtool does also
128 understand at-style time specification. The specification is called
129 "at-style" after the Unix command at(1) that has moderately complex
130 ways to specify time to run your job at a certain date and time. The
131 at-style specification consists of two parts: the TIME REFERENCE
132 specification and the TIME OFFSET specification.
133 TIME REFERENCE SPECIFICATION
135 The time reference specification is used, well, to establish a
136 reference moment in time (to which the time offset is then applied to).
137 When present, it should come first, when omitted, it defaults to now.
138 On its own part, time reference consists of a time-of-day reference
139 (which should come first, if present) and a day reference.
140 The time-of-day can be specified as HH:MM, HH.MM, or just HH. You can
142 suffix it with am or pm or use 24-hours clock. Some special times of
143 day are understood as well, including midnight (00:00), noon (12:00)
144 and British teatime (16:00).
145 The day can be specified as month-name day-of-the-month and optional a
147 2- or 4-digit year number (e.g. March 8 1999). Alternatively, you can
148 use day-of-week-name (e.g. Monday), or one of the words: yesterday,
149 today, tomorrow. You can also specify the day as a full date in several
150 numerical formats, including MM/DD/[YY]YY, DD.MM.[YY]YY, or YYYYMMDD.
151 NOTE1: this is different from the original at(1) behavior, where a
153 single-number date is interpreted as MMDD[YY]YY.
154 NOTE2: if you specify the day in this way, the time-of-day is REQUIRED
156 as well.
157 Finally, you can use the words now, start, end or epoch as your time
159 reference. Now refers to the current moment (and is also the default
160 time reference). Start (end) can be used to specify a time relative to
161 the start (end) time for those tools that use these categories
162 (rrdfetch, rrdgraph) and epoch indicates the *IX epoch (*IX timestamp 0
163 = 1970-01-01 00:00:00 UTC). epoch is useful to disambiguate between a
164 timestamp value and some forms of abbreviated date/time specifications,
165 because it allows one to use time offset specifications using units,
166 eg. epoch+19711205s unambiguously denotes timestamp 19711205 and not
167 1971-12-05 00:00:00 UTC.
168 Month and day of the week names can be used in their naturally
170 abbreviated form (e.g., Dec for December, Sun for Sunday, etc.). The
171 words now, start, end can be abbreviated as n, s, e.
172 TIME OFFSET SPECIFICATION
174 The time offset specification is used to add/subtract certain time
175 intervals to/from the time reference moment. It consists of a sign
176 (+ or -) and an amount. The following time units can be used to specify
177 the amount: years, months, weeks, days, hours, minutes, or seconds.
178 These units can be used in singular or plural form, and abbreviated
179 naturally or to a single letter (e.g. +3days, -1wk, -3y). Several time
180 units can be combined (e.g., -5mon1w2d) or concatenated (e.g., -5h45min
181 = -5h-45min = -6h+15min = -7h+1h30m-15min, etc.)
182 NOTE3: If you specify time offset in days, weeks, months, or years, you
184 will end with the time offset that may vary depending on your time
185 reference, because all those time units have no single well defined
186 time interval value (1 year contains either 365 or 366 days, 1 month is
187 28 to 31 days long, and even 1 day may be not equal to 24 hours twice a
188 year, when DST-related clock adjustments take place). To cope with
189 this, when you use days, weeks, months, or years as your time offset
190 units your time reference date is adjusted accordingly without too much
191 further effort to ensure anything about it (in the hope that mktime(3)
192 will take care of this later). This may lead to some surprising (or
193 even invalid!) results, e.g. 'May 31 -1month' = 'Apr 31' (meaningless)
194 = 'May 1' (after mktime(3) normalization); in the EET timezone '3:30am
195 Mar 29 1999 -1 day' yields '3:30am Mar 28 1999' (Sunday) which is an
196 invalid time/date combination (because of 3am -> 4am DST forward clock
197 adjustment, see the below example).
198 In contrast, hours, minutes, and seconds are well defined time
200 intervals, and these are guaranteed to always produce time offsets
201 exactly as specified (e.g. for EET timezone, '8:00 Mar 27 1999 +2 days'
202 = '8:00 Mar 29 1999', but since there is 1-hour DST forward clock
203 adjustment that occurs around 3:00 Mar 28 1999, the actual time
204 interval between 8:00 Mar 27 1999 and 8:00 Mar 29 1999 equals 47 hours;
205 on the other hand, '8:00 Mar 27 1999 +48 hours' = '9:00 Mar 29 1999',
206 as expected)
207 NOTE4: The single-letter abbreviation for both months and minutes is m.
209 To disambiguate them, the parser tries to read your mind :) by applying
210 the following two heuristics:
211 1. If m is used in context of (i.e. right after the) years, months,
213 weeks, or days it is assumed to mean months, while in the context of
214 hours, minutes, and seconds it means minutes. (e.g., in -1y6m or
215 +3w1m m is interpreted as months, while in -3h20m or +5s2m m the
216 parser decides for minutes).
217 2. Out of context (i.e. right after the + or - sign) the meaning of m
219 is guessed from the number it directly follows. Currently, if the
220 number's absolute value is below 6 it is assumed that m means
221 months, otherwise it is treated as minutes. (e.g., -6m == -6m
222 minutes, while +5m == +5 months)
223 Final NOTES: Time specification is case-insensitive. Whitespace can be
225 inserted freely or omitted altogether. There are, however, cases when
226 whitespace is required (e.g., 'midnight Thu'). In this case you should
227 either quote the whole phrase to prevent it from being taken apart by
228 your shell or use '_' (underscore) or ',' (comma) which also count as
229 whitespace (e.g., midnight_Thu or midnight,Thu).
230 TIME SPECIFICATION EXAMPLES
232 Oct 12 -- October 12 this year
233 -1month or -1m -- current time of day, only a month before (may yield
235 surprises, see NOTE3 above).
236 noon yesterday -3hours -- yesterday morning; can also be specified as
238 9am-1day.
239 23:59 31.12.1999 -- 1 minute to the year 2000.
241 12/31/99 11:59pm -- 1 minute to the year 2000 for imperialists.
243 12am 01/01/01 -- start of the new millennium
245 end-3weeks or e-3w -- 3 weeks before end time (may be used as start
247 time specification).
248 start+6hours or s+6h -- 6 hours after start time (may be used as end
250 time specification).
251 931200300 -- 18:45 (UTC), July 5th, 1999 (yes, seconds since 1970 are
253 valid as well).
254 19970703 12:45 -- 12:45 July 3th, 1997 (my favorite, and it has even
256 got an ISO number (8601)).
257
259 The following environment variables may be used to change the behavior
260 of "rrdtool fetch":
261 RRDCACHED_ADDRESS
263 If this environment variable is set it will have the same effect as
264 specifying the "--daemon" option on the command line. If both are
265 present, the command line argument takes precedence.
266
268 Tobias Oetiker <tobi@oetiker.ch>
2691.7.1 2019-02-04 RRDFETCH(1)