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fix(zfs): use a live iostat sample instead of a since-boot average #640

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Merged
VVelox merged 1 commit into from
Oct 12, 2026
Merged

fix(zfs): use a live iostat sample instead of a since-boot average #640

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80 changes: 62 additions & 18 deletions snmp/zfs
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@VVelox VVelox Oct 11, 2026

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This totally kills the ability to use it as a extend as it will result in a timeout. Docs need updated to reflect the output of this needs update to dump the results to a file and read via /bin/cat /var/cache/zfs.extend.

Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ zfs - LibreNMS JSON SNMP extend for gathering backups for ZFS

=head1 VERSION

0.3.0
0.4.0

=head1 DESCRIPTION

Expand All @@ -27,9 +27,32 @@ Gzip the output and convert to Base64.
Include the full information for `zpool status $pool` for each pool
in the return.

=head2 -o <file>

The file to write the output to when -w is used.

Defaults: /var/cache/zfs.extend

=head2 -w

Write the output out to the file specified by -o.

=head2 -q

If -w is specified, don't print anything.

=head1 SNMPD SETUP EXAMPLES

extend zfs /etc/snmp/zfs
Each pool is sampled over a live two second `zpool iostat` interval, so a run
takes roughly two seconds per pool. On a host with more than a pool or two
that is long enough for the extend to time out, so the output is written to a
file via cron and SNMPD reads that instead of running this directly.

extend zfs /bin/cat /var/cache/zfs.extend

Then the extend is set to be ran via cron.

*/5 * * * * /etc/snmp/zfs -w -q

=head1 REQUIREMENTS

Expand Down Expand Up @@ -97,13 +120,19 @@ my %opts;
my $opts_p;
my $opts_b;
my $opts_s;
my $opts_w;
my $opts_q;
my $opts_o;
my $version;
my $help;
#getopts( 'pbs', \%opts );
GetOptions(
p => \$opts_p,
b => \$opts_b,
s => \$opts_s,
w => \$opts_w,
q => \$opts_q,
'o=s' => \$opts_o,
v => \$version,
version => \$version,
h => \$help,
Expand All @@ -112,6 +141,13 @@ GetOptions(
$opts{p} = $opts_p;
$opts{b} = $opts_b;
$opts{s} = $opts_s;
$opts{w} = $opts_w;
$opts{q} = $opts_q;
$opts{o} = $opts_o;

if ( !defined( $opts{o} ) ) {
$opts{o} = '/var/cache/zfs.extend';
}

if ($version) {
pod2usage( -exitval => 255, -verbose => 99, -sections => qw(VERSION), -output => \*STDOUT, );
Expand Down Expand Up @@ -191,7 +227,7 @@ while ( defined( $pools[$pools_int] ) ) {
$newPool{expandsz} = 0;
}

my $iostat = `zpool iostat -l -q -p -H $newPool{name}`;
my $iostat = `zpool iostat -y -l -q -p -H $newPool{name} 2 1`;
chomp($iostat);
$iostat =~ s/\t+/,/g;
$iostat =~ s/\,\-\,\-\,/\,0\,0\,/g;
Expand Down Expand Up @@ -490,23 +526,31 @@ if ( $opts{p} && !$opts{b} ) {

my $return_string = $j->encode( \%head_hash );

if ( !$opts{p} && !$opts{b} ) {
print $return_string. "\n";
exit 0;
} elsif ( !$opts{b} ) {
print $return_string;
exit 0;
my $output = $return_string . "\n";
if ( $opts{p} && !$opts{b} ) {
$output = $return_string;
}

my $compressed_string;
gzip \$return_string => \$compressed_string;
my $compressed = encode_base64($compressed_string);
$compressed =~ s/\n//g;
$compressed = $compressed . "\n";
if ( length($compressed) > length($return_string) ) {
print $return_string. "\n";
} else {
print $compressed;
if ( $opts{b} ) {
my $compressed_string;
gzip \$return_string => \$compressed_string;
my $compressed = encode_base64($compressed_string);
$compressed =~ s/\n//g;
$compressed = $compressed . "\n";
if ( length($compressed) <= length($return_string) ) {
$output = $compressed;
}
} ## end if ( $opts{b} )

if ( $opts{w} ) {
my $tmp_file = $opts{o} . '.tmp.' . $$;
write_file( $tmp_file, $output );
rename( $tmp_file, $opts{o} )
|| die( 'Failed to rename "' . $tmp_file . '" to "' . $opts{o} . '"' );
}

if ( !$opts{w} || !$opts{q} ) {
print $output;
}

exit 0;
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