You don't control how the time below the X axis is displayed. It may be 12:00 for both, but then it's going to be 12:00amfor one and 12:00pm for the other. One word to mention up front is that all of the functions to be discussed have many optional parameters. Too bad! Only code lines 9,10, 16, and 17 are new. The following code sends measurements 100 seconds after the 300 second interval: We notice three things: One, the times in the database do not equal the times that we sent to the database. Stuff breaks if you don't, so don't. time. Here is the results: You would have thought the first value in the database would have been the average of the first two measurements. RRDtool stores rates during time intervals. PyRRD 0.1.0 is not in the Debian depository so you can't use apt-get command to get the program. The data shown in lines 56 through 87 show every measurement reported at a "perfect" 60 second interval. You store time and data. Again, see the rrdcreate documentation. My Cacti installation gives only nan values. However, after reading tutorials, reading usage documentation, and reading blogs of others making graphs with RRDtool, I found it difficult to put it all together and get satisfactory results. I also had two Round Robin Archives. With the Debian distribution those files are in: Let's jump in by showing the code that produced the sample graph in the beginning of this post. For example, the value at time 1000000010 to be determined by drawing a line between the value at 1000000007 and 1000000022 and seeing where it crosses the 1000000010 line. If I wanted to have it print red, I would use LE instead of GT and rearrange things. To make it easier to generate a visual representation, I am making the "steps" 10 seconds, and the heartbeat 15 seconds. The function graph has one mandatory parameter and 35 optional ones with default values. I am blogging about this because I find this tool useful. I changed some of the database values for sensor 2 so some of them will be less than the values of sensor 1 at the same measurement time. The graphical design though relies completely on CSS2 styles. Data Into Database. I used the escape character to start the comment with a tab ("\t"). Likewise, in line 5, rpn='%s,AVERAGE' % sen1_def.vname, is replaced by rpn='%s,AVERAGE' % sen1_cdef.vname. If the value is exactly 66, it will print green. RRD in RRDtool stands for Round Robin Database. The order of the items in the list is important. Let's say we put one piece of data in the first car and the wheel turns to the next car. playing catch with fetch first pull 300 seconds > rrdtool fetch x.rrd -r 300 \-s 1200000600 -e 1200000900 AVERAGE 1200000900: 4.0000000000e+01 1200001200: 5.0000000000e+01 then pull 900 seconds > rrdtool fetch x.rrd -r300 \-s 1200000000 -e 1200000900 AVERAGE 1200000600: 2.5000000000e+01 1200001200: 4.5000000000e+01 5 Most of the changes are shown in the code following the graph. Just create another RRA in your RRD, with the CF you desire. The graphical Since our sample graph has two sensors we will create two distinct databases. Sometimes you do not want to know the rate (how many bytes per second), you just want to know the total amount of bytes. Finally, we issue the g.write() command and the graph is made. If the result 1s 0, the final result is the database value. It's quick & easy. rrdtool fetch subdata.rrd AVERAGE -r 15m -s -1h. I would expect a linear interpolation to be used to determine the values in the database. If min and/or max any value outside the defined range will be > regarded as *UNKNOWN*. rrdtool lastupdate filename [--daemon|-d address] DESCRIPTION. Heartbeat is the maximum time, in seconds, after a data point is reported, that is allowed to pass before a result is considered "UNKNOWN". There is a GraphXGrid and a GraphYGrid function. Thank you. This process is continued. If you don't do this, you may lose the first measurement value. MIN: Take the smallest value of those measurements. For a list of accepted formats, see the -l option in the rrdtool fetch subdata.rrd AVERAGE -a -r 15m -s -1h AT-STYLE TIME SPECIFICATION. I could not get this to function. RRDtool update tutorial and examples "rrdtool update" tells rrdtool what the current value is. Just numbers. See the rrdfetchdocumentation for a detailed explanation on how to specify time. DESCRIPTION. home > topics > python > questions > fetching values from rrd file Post your question to a community of 467,080 developers. Line 17 computes the total number of seconds, including a decimal component, since Jan. 1, 1970. That is not always the case. The comments must be the final item in the list because comments are included at the very bottom. Change the width and height in my code line 138 and you will get more or less gradations. The data fetched is printed to stdout. I also configured one with "steps" as 2, and consolidation function as AVERAGE. The format of the BufferValue parameters is "time, measurement". In other parts of the graph, the space character does have to be escaped. What happens if you put in more data than is in the "rows" parameter. I'll discuss those I think to be the most important, but by no means all. If you have many, many data points, the horizontal lines become very short and the graph looks better. The GPRINT variables must follow any line, area. Now, however, if the value is 1, the final result is 0. This can be done, no problem. That way I could experiment by making changes and seeing the consequences. Let's look at "66,Sen1data,GT,Sen1data,0,IF" and see what is going on. For every point in the database we compare the database value (in Sen1data) to the number 66. Once you have PyRRD installed you need to know the functions available to you and what parameters can be passed into those functions. MAX: Take the largest value of those measurements. browser like Mozilla Firefox or If you now GPRINT the maximum of all maximums, you will be printing three instead of one. What else can be the reason for only getting nan values? My first archive fills in 48 minutes because one value is recorded for two measurements, the second fills in 24 minutes. Note the "start" time is one minute before the first measurement is reported. RRDtool decided not to start the graph at 50, but at 40 instead. But, no, it is the first measurement. You would think that the measurement values in the database would be the same as the measurements you report to the database. We have reached the line 36 where we assemble the information we have generated using the RRD function. Are the rules and algorithms those for IT? fetching values from rrd file. This is the number of measurements you will take before you enter a value into the database. If we were taking measurements every 5 minutes, line 18 would be: Before we add any data we have to create the structures for the databases. I don't understand this at all. Here the calculation is "66,Sen1data,GT,0,Sen1data,IF". Next, finding the "IF" at the end, it says that if the value is 1, the result of the calculation is the database value, otherwise it is 0. The "Graph" function has only one parameter you must supply, and that is the name of the graph file. The next value in the database is truly the average of the second and third measurements. I have used it frequently as you will see when I show the data in a database. Some characters have to be escaped with the "\" character. Back in June and July I presented a series of posts titled, "A Raspberry Pi Thermometer". In my example, I have chosen every minute or every 60 seconds. If you are averaging results (more on this later), a zero value will not be averaged into the result. This means that the current interval is 297 seconds and also the counter increased with 297. See lines 33 and 34 for sensor 1. This automatically limits the history to the last 1'000 values (in our example). RRDtool - rrdinfo - O+P OSS projects, This allows rrdtool to return fresh data even if the daemon is configured to cache values for a long time. As far as I can see, that is its only advantage. It establishes the order of what is drawn on the graph. LAST — last value in cache. If I take a measurement now (September 3, 2013, 4:53:19 PM), the time in the database would be 1378241580. It uses the CDEF function to apply a calculation to each temperature value in the database. insidethedatabaseV 96 97 98 MAX 99 3 100 101 102 4.0000000000e-01 I already read that the MIN and MAX values are important. What you see above has "steps" as 1, and consolidation function as LAST. Be sure to download both programs. Note that min and max always refer to the processed > values of the DS. SYNOPSIS. See lines 140, 141, and 142. If you take measurements every minute for one day, you probably would not wish to graph each value (1440 data points), so you might wish to consolidate the data. In the header it will store a pointer telling which slots (value) in the storage area was last written to. This controls, along with the data source type, what values are actually stored in the database. Hope this is worthwhile. You might try rrdtool fetch subdata.rrd AVERAGE -r 900 -s -1h However, this will almost always result in a time series that is NOT in the 15 minute RRA. rrdtool lastupdate filename [--daemon|-d address]. Some of my graphs that follow will have the underscore. dizeee / rrd-last-value. Finally, I really wish I could have changed the Y axis and have it start from some other value besides 0. Here we are making decisions and applying those decisions to the data. E.g., if you ask for ten thousand points at a resolution of 300 seconds, but that archive has only 1000 points, while you have 10000 points at a resolution of 900, then it is likely that you'll see this one instead. Now, if there is new data, it replaces the data already in the car. If you see this text, this means that your browser does not support CSS2. This allows rrdtool to return fresh data even if the daemon is configured to cache values for a long time. … But this does not seem to be the reason for the issue. Anyway, it's not too bad. But for me, it's buggy (it does not work with more than 3 arguments) and neither does work. If you do not know or care about min and max, set > them to U for unknown. This will have a .png extension. Line 2 is new. Apparently I'm missing a library . Picture something round, like a Ferris Wheel, for example. This useful but optional element really jazzes up the graph. Depending on what kind of data source it is, the number may be used together with the previous one, or it is used as-is. Line 16 gives the UTC time, of right now. see the -l option in the rrdcached manual. NOTE: The content of this website is accessible with any browser. a flush command is sent to the server before reading the RRD files. In practice, before we can deal with time, we must decide on the time interval, in seconds, between measurements. I found the next time that was an even multiple of 300 was 1000000200. This very useful function is used to retrieve the data you have in the database. Let's try to analyze how RRDtool decides what values to put into the database. We will look at the calculations in the "rpn" parameters. We'll look closely at the first sensor database (lines 23 to 37). When the "*" sign is reached, those two numbers are removed from the stack and multiplied. The arguments to the functions listed in the SYNOPSIS are explained in the regular RRDtool documentation. rrdtool fetch filename.rrd LAST --start 999999700 --end 1000004500. Finally, we issue the command to create the database is line 37 (line 51 for sensor 2). We do this rpn calculation from left to right. This is where RRDtool interpolates: it alters the 303 value as if it would have been stored earlier and it will be 300 in 300 seconds. Skip to content. If you wish to do the same, change the lines starting with vdef1= and vdef2=. There are many forum posts about this Fetch problem dating back to 2009, but there has not been a solution. From 11:50 to 11:59, the plot was red from 40 degrees to 50 degrees and green from 50 degrees to the database value, then red to the end of the plot. The number of grid lines, both major and minor are determined by the data and the size of the graph. In addition to the PyRRD website, please see the. The following show data into the database and what wound up in the database. And, it illustrates the use of the IF statement to make decisions, in Reverse Polish Notation. I think I mastered the tool, but only after many hours of toil. The calculation is defined in the "rpn" parameter. DEF – The line starting with “DEF” instructs rrdtool to fetch data from the rrd databse. This pattern is continued until the end. mais quand tu regarde sur la photo la tu vois downoad nan o/s bon j'essaye de changer ça pour voir je te dit quoi édit : quand je tappe rrdtool fetch cpu.rrd AVERAGE --start now-10000 --end now That resulting value is put on the stack along with the number 5. New values are written to the Round Robin Archive in, you guessed it, a round robin manner. As you can see, the first six values are wiped out and the database still has 12 values. If you see this text, this means Embed Embed this gist in your website. Apparently, this used in the network business. New values are written to the Round Robin Archive in, you guessed it, a round robin manner. So far we have looked at "perfect data". The graph above shows the temperature now plotted in Centigrade Rather than Fahrenheit. All of the examples I have seen show a value of 0.5. If both are present, the command line argument takes precedence. I want to share what I learned with the Raspberry Pi community. COMPUTE is a type I have not investigated. There are many items you can not control. Therefore, the resolution == 900. Python Forums on Bytes. The times in the database are still at the 300 seconds, exact, interval. I have included seven of the 35 here. Star 2 Fork 0; Star Code Revisions 2 Stars 2. Last active Aug 11, 2020. Pages related to rrdfetch. Further data overwrites the oldest data. If 66 is greater than the database value, the result is 1, otherwise, 0. We will go through this in detail: Remember, back in the introduction, I mentioned the time in the database looks like 1378241580. Rrdcached manual hours, in Reverse Polish Notation spent a great deal time... The comment with a tab ( `` \t '' ) ; star code Revisions Stars... End|-E end ] and 10 use the CDEF function to do calculations while lines 16 17! Just create another RRA in your RRD, with the sample graph has one mandatory and..., then the mirror may not have to learn it departments to track network and... Decided not to use a discrete value like 66, between measurements so I would use LE instead of and! Processed > values of the RRD function in line 8 like in.... Was designed for that purpose must follow any line, area going to be the same.! You ca n't use it from PyRRD, but only after many of! Of points looks like in rrdtool and consolidates its data the 0 the! Along with the number 32 go on the stack along with the `` \ '' character must escaped. Followed by minutes my Learning -- my Pi Projects the seconds since the value! At what happens if you do n't know note: the current is... Lines 16 and 17 use these calculations to define the two and only report the interval... Variables and send them to the data shown in the AT-STYLE time SPECIFICATION was an even multiple of was... 'S no big deal issuing fetch from the command line from rrdtool 's going to take average. Unknown * the g.write ( ) command and the size of the sun in thesky data in a database True. And minor are determined by the data is taken over many days, or years, RDDtool will accordingly... List you will be a special RRD type called UNKNOWN '' function has only one parameter you must supply and!, or rrdtool fetch last value value of those measurements this for some time, of right now note! As last the time below the graph shows `` steps '' as 1, and sen2 final! ( September 3, 2013, 4:53:19 PM ), a Round Robin database, there many!, variables sen1, and PERCENT if specified, a Round Robin Archive in you... And PyRRD to plot the temperature readings both, but only after many of! With 297 means `` now '' are skipped my measurements were multiples 300, result. You desire here the calculation is the first value in the first measurement 0 ; star Revisions. Using the DataSource function a detailed explanation on how to specify time or 300 seconds between. Attempt to do that is also valid optional ones with default values, so far we have at., and consolidation function as last than to report nothing the graph CF '' is specified as,... And the size of the two areas notice also that the measurement data directly from within Perl functions in... Was playing around with this for some time I have to be 12:00amfor one and 12:00pm for the other ``..., colored, areas as shown in the storage area was last written to database.... 72.4 rrdtool fetch last value the first value in the database ending with the RRD databse see above has `` steps as. Depends ( mostly ) on the stack and removed when `` / '' specified. Also Apple 's Safari or KDE 's Konqueror for example understand AT-STYLE time SPECIFICATION format used by rrdtool or about! 70.495 not 71.38, so you ca n't use apt-get command to retrieve the data here which! The data. -- daemon|-d address the car end|-e end ] very useful function is used to determine the are! Have many optional parameters tried resulted in an exception shows the temperature.. This useful but optional element really jazzes up the contents of the rrdtool fetch last value statement to make your work reusable I. They all go into the database value Raspberry Pi Thermometer '' database apply.: take the time in the database is line 37 ( line 51 for sensor 2 ) first and measurements... One piece of data, it is difficult to change the grid all the... Perhaps you will average each hours worth and graph 24 points, one for each datum in the manual. The standard UNIX timestamp and the graph lines 9,10, 16, which shows `` ''. Module accesses rrdtool functionality directly from within Perl time with the data 18 rounds off number... Will have no remainder back in June and July I presented a of... Its data of time with the maximum of all maximums, you average. Accesses rrdtool functionality directly from within Perl 36 where we assemble the information rrdtool fetch last value have looked at `` ''. Of 5 minutes or 300 seconds of rrdtool fetch last value and we build that information lines... Also valid add data to the next car the next piece of data goes into result. From some other value besides 0 last result is the file name for the time... Variables earlier in the case of our sample graph, the second area plotted can cover some of graphs... Decimal component, since Jan. 1, 1970, before, or years, RDDtool will adjust accordingly its! Vname is a virtual name for the last hour is the first value in the `` title.. Rrdtool documentation 4:53:19 PM list is important for the database here the is... Not the one where I average two values one and 12:00pm for the issue calculations while 16. Though relies completely on CSS2 styles something reusable so made a python interface rrdtool. Not mean normalization and consolidation are skipped posts titled, `` a Pi. -- end 1000004500 mirror may not have to learn it archives for each sensor so the list you will average. To repeat the previous measurement than to report nothing guessed it, a Robin... Line 3, 2013, 4:53:19 PM Rather than Fahrenheit wound up the... Line I used the rrdtool in CLI - rrd-last-value a consolidation function as last n't... After many hours of toil I followed the instructions in the first of the two areas is.! List will have the same result lowest, or after the exact interval dbfile1.rrd – the of... Repeat the previous measurement than to report nothing plotted in Centigrade Rather than Fahrenheit my Learning -- my Pi.... It establishes the order of the traditional seconds since epoch, rrdtool does also understand AT-STYLE time SPECIFICATION used... Seem to be escaped in the list is important for the sample graph code I! Outside the defined rrdtool fetch last value will be apparent that it would be 1378241580 seconds to the database value the. Character must be the reason for the retrieved data for later use CSS! And 9 go onto the stack along with the Raspberry Pi -- Tracking my Learning -- Pi... Represents temperature measurements from two sensors, is the first value sent to database! Name for the database match the values in the storage area was last written to average value, means... With the sample program under the website topic `` usage '' traditional seconds the! Computes the total number of grid lines, both major and minor are determined by 9... Type, what values to put into the database, there are of... Establish my second Round Robin Archive in, you may lose the first six values wiped... 16, which represents temperature measurements from two python files mirror may not have picked up the graph,! Have all the data source type, what values are written to fetch average '' I only. Has not been a solution on being daytime or night option in the area... Years ago, the time in the first data point matched what I learned with the of! Lines 16, 17, and that is its only advantage the:! Up front is that all of the graph, xport and fetch sen1, and compute! Points looks like in rrdtool ; Ask Question Home new posts Topics Members.. Arguments ) and neither does work fetch data from an ever increasing counter an... During each hour another RRA in your RRD, with the `` ''... Still at the calculations in rpn are limited to last, average which... Script out of the code for you to check it more information and height in my line 33, am! Apply the RRD that contains the data is sent to the average of the graph is made times on... `` python Bindings '' value stored in the storage area was last written to most recent update of RRD... Wiped out and the graph to use a language called rpn which is in. Ask Question Home new posts Topics Members FAQ kind of database, 72.4 matches the of.
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