How does one get the time of the received message in Erlang?
I want to calculate something according to the frequency of the received messages to the gen_server.
e.g. message 1, some time, message 2 some time.
get the time between messages.
Thanks
You can use statistics(wall_clock) each time you receive a message.
The second member of the tuple it returns will be the time between the two receives (in milliseconds).
Edit:
As rvirding mentions in his comment, you can also use now() and then calculate the time difference accordingly. Take a look at supervisor.erl found in the $ERL_TOP/lib/stdlib/src/ directory of your Erlang/OTP distribution. The last lines of that module (functions addRestart, inPeriod and difference) calculate the frequency of restarts using now().
Related
I have one endpoint for which I would like to see number of requests at a given time (not period). For instance, how many requests were received at 9.30 a.m.
The function I believe I can make use of might be: echo_requests_total, but it just accumulates the count and if I try increase() or rate() functions even those do not produce the expected output, which is obvious.
I am not even sure about what I want is even possible or not.
Any help would be appreciated.
I have a situation where I'm trying to count the number of files loaded into the system I am monitoring. I'm sending a "load time" metric to Datadog each time a file is loaded, and I need to send an alert whenever an expected file does not appear. To do this, I was going to count up the number of "load time" metrics sent to Datadog in a 24 hour period, then use anomaly detection to see whether it was less than the normal number expected. However, I'm having some trouble finding a way to consistently pull out this count for use in the alert.
I can't use the count_nonzero function, as some of my files are empty and have a load time of 0. I do know about .as_count() and count:metric{tags}, but I haven't found a way to include an evaluation interval with either of these. I've tried using .rollup(count, time) to count up the metrics sent, but this call seems to return variable results based on the rollup interval. For instance, if I compare intervals of 2000 and 4000 seconds, I would expect each 4000 second interval to count up about the sum of two 2000 second intervals over the same time period. This does not seem to be what happens at all - the counts for the smaller intervals seem to add up to much more than the count for the larger one. Additionally some rollup intervals display decimal numbers as counts, which does not make any sense to me if this function is doing what I thought it was.
Does anyone have any thoughts on how to accomplish this? I'd really appreciate any new ideas.
Been rolling around the web and forums, cannot find a resource on this.
What I am to achieve is create an alert for when there is no change in data for a period of time.
We are monitoring openfiles for our webserver/s so this number fluctuates rather often. Noticed that when the number is stagnant it points to an issue on the server. So what we want is if openfile remains X for 2minutes alert us.
I made such an alert through a small succession of things:
I have an exclusive 'alerting dummy board', for all the alerts, since I can only have one alert per graph (grafana version 6.6.0)
I use the following query: avg_over_time(delta(Sensor_Data[1m])[20s:]) - this calculates the 20s average of 'first_value-last_value of 1min interval'
My data gathering program feeds into prometheus and this in turn into grafana -- if this program freezes, it might continue sending the last value to prometheus, and the above query will drop to strictly zero.
so I have an alert which goes off if the above query is within a range (-0.01, 0.01) for a minute (a typical value of the above query with system running is abs(query) > 0.18)
Thus, Grafana sends an alert if the Sensor_Data value does not change within about 2-3 minutes.
If you do use Prometheus and Alert manager, There is a nice function that worked for me.
changes
So using something like this in Alert manager will trigger if no changes for the time interval
changes(metric_name[5m]) = 0
This has worked for me. Make sure you're using a rate or increase function (no change means it will drop to zero) and filter the query like the following:
increase(metric_name) > 0
Then, in Alert Config, set "If no data or all values are null" to "Alerting". That way, when there's no data, the alert will be triggered.
After a mailing at t0, I will have several "delivered" (and open and click) events (schema and example)
mailing_name, timestamp, email_id, event_type
niceattack, 2016-07-14 12:11:00, 42, open
niceattack, 2016-07-14 12:11:08, 842, open
niceattack, 2016-07-14 12:11:34, 847, open
I would like to see for a mailing how long it takes to be delivered to half of the recipients. So say that I'm sending an email to 1000 addresses now, the first open event is in 2 min, the last one is going to be in a week (and min/max first last seems to be easy to find) but what I'd like to see is that half of the recipients opened it in the first 2 hours after it was sent.
The goal is to send being able to compare is sending now vs on sat morning makes a difference on how fast it's open on average, or if one specific mailing get quicker exposure, and correlate that with other events (how many click on a link, take a specific action on our site...)
I tried to use a cumulate function (how many open event for mailing for each point), but it seems that the cumulative function isn't yet implemented https://github.com/influxdata/influxdb/issues/813
How do you solve that problem with influxdb?
Solving this problem with InfluxDB alone is not currently possible, however if you're willing to add Kapacitor into the mix, then it should be possible. In particular you'll need to write a User Defined Function (UDF) for that cumulative function in Kapacitor.
The general process will look like the following:
Install and Configure Kapacitor
Create a UDF for the cumulative function you're looking for
Enable that UDF inside of Kapacitor
Write a TICKscript that uses the UDF and writes the results back to InfluxDB
Enable a task defined by the TICKscript you've written
Query the InfluxDB instance to get the results of the cumulative function.
My appoligies for being so high level on this. This is a fairly involved process, but should give you the result you're looking for.
How do you check the uptime of a Phoenix/Elixir/Erlang application? If you do :observer.start() and look at the System tab, you can see the uptime in the Statistics area. But I want to be able to pull that information programmatically and include it in a report. I've figured out where to get most of that data from, but I don't see where it pulls uptime from.
You can use either statistics(runtime):
Returns information about runtime, in milliseconds.
This is the sum of the runtime for all threads in the Erlang runtime
system and can therefore be greater than the wall clock time.
Or statistics(wall_clock):
Returns information about wall clock. wall_clock can be used in the
same manner as runtime, except that real time is measured as opposed
to runtime or CPU time.
In both cases, you need to call them at the beginning of your program in order to reset their timers. When you want to print the time passed just do:
{_, Time1} = statistics(runtime).
Or
{_, Time2} = statistics(wall_clock).
Accordingly, and then you will have the time in Time1 or Time2. For more information take a look at erlang:statistics/1
Note: If you want the total time elapsed since the Erlang VM started you can take the first element from the tuple: {Total_Time, Time_Since_Last_Call} = statistics(wall_clock).