[Title VII] Prometheus PromQL simple usage

Explanation

Based on an article basis, where do some some basic queries about the CPU, memory, disk.

CPU

By querying the metric is node_cpu_seconds_totalto get all the information of the current CPU

Parameters directly through this, will be found in the data is the data currently collected all related to the CPU.

In this case it is necessary to use iratethe function for homeopathic growth distance vector calculations per second in the actual sequence.

According to the label and then screened to query as follows:

irate(node_cpu_seconds_total{job="node"}[5m])

Avg after the polymerization using the data query, and then used to distinguish by example, you can do so respective data sub-query instance.

avg(irate(node_cpu_seconds_total{job="node_srv"}[5m])) by (instance)

The above statement to query data to CPU, CPU contains all the data, and we want to query the CPU load is 5 minutes

Ideas can be like this: check out the CPU idle value mode='idle', multiplied by one hundred come after idle percentage, with 100 minus the percentage of CPU idle percentage used to draw

as follows:

100 - ((avg(irate(node_cpu_seconds_total{job="node_srv",mode="idle"}[5m])) by (instance)) * 100)

RAM

About metric value memory are the following:

• node_memory_MemTotal_bytes Total amount of memory on the host
• node_memory_MemFree_bytes Free memory on the host
• node_memory_Buffers_bytes Memory Buffer Size
• node_memory_Cached_bytes Memory cache size

So based on the above metrics, you can make a lot of inquiries.

Calculate the percentage of memory usage:

The idea is to subtract the amount of free memory, and cache buffer zone with a total memory, and then divided by the total memory

(node_memory_MemTotal_bytes - (node_memory_MemFree_bytes + node_memory_Buffers_bytes + node_memory_Cached_bytes)) / node_memory_MemTotal_bytes * 100

Finally, multiplied by one hundred to obtain the percentage of
results are as follows:

Disk Monitoring

For disk monitoring, divided into three types:

1. Space surveillance
2. Disk read and write IO monitor
3. Expected saturation monitoring, meaning that the current state of the disk write speed, how long it is expected to disk will be filled

Disk space utilization percentage

According to the label filtering, query a partition space utilization

The principle is: the same partition, with the remaining space obtained by subtracting the total space used space, divided by the total space utilization percentage obtained

(node_filesystem_size_bytes{mountpoint="/"} - node_filesystem_free_bytes{mountpoint="/"}) / node_filesystem_size_bytes{mountpoint="/"} * 100

Expected saturation

Here it involves some algorithms, formulas listed directly.

This formula derived value, when the disk will be filled in the conditions of a certain time period in the future, the value will be a negative number.

predict_linear(node_filesystem_free_bytes{mountpoint="/"}[1h], 4*3600) < 0