Add mulitipathd_info text collector example

[ssinha-ionos]

multipathd_info is a script that exposes device mapper multipathing
metrics from multipathd daemon.

Signed-off-by: Saket Sinha [email protected]

[dswarbrick]

It might be prudent to specify the exact format that we want multipathd to output, in case the order of the columns changes in future (thus breaking the awk script).

Based on the columns selected by the awk script, we want dev, dm_st and chk_st, which are %d, %t and %T respectively (check multipathd show wildcards).

This produces a cleaner output which is safer (and probably easier) to parse:

# multipathd show paths format '%d %t %T'
dev dm_st  chk_st
sdd active ready 
sdb active ready 
sdh active ready 
sdf active ready

[SuperQ]

@dswarbrick Nice suggestion. It's too bad that the format string is picky, I get errors when I try and format the whole metric line with it. ☹️

[ssinha-ionos]

@dswarbrick Nice suggestion. It's too bad that the format string is picky, I get errors when I try and format the whole metric line with it.

Modified the commit based on @dswarbrick review comments.

Also corrected the metric name -

1. dm_st refers to the DM module(kernel)'s view of the path's state. It can be in one of the two states:

• active: Last I/O sent to this path successfully completed. Analogous to ready path state.
• failed: Last I/O to this path failed. Analogous to faulty path state.

2. chk_st refers to the physical state of a path. A path can be in one of the following states:

• ready: Path is up and can handle I/O requests.
• faulty: Path is down and cannot handle I/O requests.
• ghost: Path is a passive path. This state is shown in the passive path in Active/Passive mode.
• shaky: Path is up, but temporarily not available for I/O requests.

[dswarbrick]

Shebang is still incorrect (see @SuperQ's earlier comment):

$ shellcheck multipathd_info 

In multipathd_info line 1:
#/bin/bash
 ^-- SC1113: Use #!, not just #, for the shebang.

[bdrung]

And please use /bin/sh instead of /bin/bash since you do not use bash specific feautures.

[discordianfish]

LGTM