How does the fetch function in rrdfetch work?

rrdfetch – Fetch data from an RRD. Synopsis. Description. The fetch function is normally used internally by the graph function to get data from RRD s. fetch will analyze the RRD and try to retrieve the data in the resolution requested. The data fetched is printed to stdout.

How to fetch data from a JSON file?

Approach: We have a JSON file containing data in the form of an array of objects. In our code, we are using jQuery to complete our task. The jQuery code uses getJSON () method to fetch the data from the file’s location using an AJAX HTTP GET request. It takes two arguments.

How to get JSON data from a response?

To get the JSON data from the response, we execute the json() function. The json() function also returns a promise. This is why we just return it and chain another then function. In the second then function we get the actual JSON data as a parameter.

How does the flush command work in RRDtool?

If specified, a flush command is sent to the server before reading the RRD files. This allows rrdtool to return fresh data even if the daemon is configured to cache values for a long time. For a list of accepted formats, see the -l option in the rrdcached manual.

When to use an optional suffix in rrdfetch?

An optional suffix may be used (e.g. 5m instead of 300 seconds). rrdfetch will try to match your request, but it will return data even if no absolute match is possible. See “RESOLUTION INTERVAL”. start of the time series. A time in seconds since epoch (1970-01-01) is required. Negative numbers are relative to the current time.

How is the fetchfunction used in RRD graph?

Description The fetchfunction is normally used internally by the graph function to get data from RRDs. fetchwill analyze the RRDand try to retrieve the data in the resolution requested. The data fetched is printed to stdout. *UNKNOWN*data is often represented by the string “NaN” depending on your OS’s printf function. filename

How to get RRDtool to fetch anything other than the finest resolution?

In order to get RRDtool to fetch anything other than the finest resolution RRA both the start and end time must be specified on boundaries that are multiples of the desired resolution. Consider the following example: