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A zpool_influxdb command is introduced to ease the collection of zpool statistics into the InfluxDB time-series database. Examples are given on how to integrate with the telegraf statistics aggregator, a companion to influxdb. Finally, a grafana dashboard template is included to show how pool latency distributions can be visualized in a ZFS + telegraf + influxdb + grafana environment. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Signed-off-by: Richard Elling <Richard.Elling@RichardElling.com> Closes #10786
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include $(top_srcdir)/config/Rules.am | ||
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bin_PROGRAMS = zpool_influxdb | ||
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zpool_influxdb_SOURCES = \ | ||
zpool_influxdb.c | ||
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zpool_influxdb_LDADD = \ | ||
$(top_builddir)/lib/libspl/libspl.la \ | ||
$(top_builddir)/lib/libnvpair/libnvpair.la \ | ||
$(top_builddir)/lib/libzfs/libzfs.la |
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# Influxdb Metrics for ZFS Pools | ||
The _zpool_influxdb_ program produces | ||
[influxdb](https://github.com/influxdata/influxdb) line protocol | ||
compatible metrics from zpools. In the UNIX tradition, _zpool_influxdb_ | ||
does one thing: read statistics from a pool and print them to | ||
stdout. In many ways, this is a metrics-friendly output of | ||
statistics normally observed via the `zpool` command. | ||
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## Usage | ||
When run without arguments, _zpool_influxdb_ runs once, reading data | ||
from all imported pools, and prints to stdout. | ||
```shell | ||
zpool_influxdb [options] [poolname] | ||
``` | ||
If no poolname is specified, then all pools are sampled. | ||
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| option | short option | description | | ||
|---|---|---| | ||
| --execd | -e | For use with telegraf's `execd` plugin. When [enter] is pressed, the pools are sampled. To exit, use [ctrl+D] | | ||
| --no-histogram | -n | Do not print histogram information | | ||
| --signed-int | -i | Use signed integer data type (default=unsigned) | | ||
| --sum-histogram-buckets | -s | Sum histogram bucket values | | ||
| --tags key=value[,key=value...] | -t | Add tags to data points. No tag sanity checking is performed. | | ||
| --help | -h | Print a short usage message | | ||
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#### Histogram Bucket Values | ||
The histogram data collected by ZFS is stored as independent bucket values. | ||
This works well out-of-the-box with an influxdb data source and grafana's | ||
heatmap visualization. The influxdb query for a grafana heatmap | ||
visualization looks like: | ||
``` | ||
field(disk_read) last() non_negative_derivative(1s) | ||
``` | ||
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Another method for storing histogram data sums the values for lower-value | ||
buckets. For example, a latency bucket tagged "le=10" includes the values | ||
in the bucket "le=1". | ||
This method is often used for prometheus histograms. | ||
The `zpool_influxdb --sum-histogram-buckets` option presents the data from ZFS | ||
as summed values. | ||
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## Measurements | ||
The following measurements are collected: | ||
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| measurement | description | zpool equivalent | | ||
|---|---|---| | ||
| zpool_stats | general size and data | zpool list | | ||
| zpool_scan_stats | scrub, rebuild, and resilver statistics (omitted if no scan has been requested) | zpool status | | ||
| zpool_vdev_stats | per-vdev statistics | zpool iostat -q | | ||
| zpool_io_size | per-vdev I/O size histogram | zpool iostat -r | | ||
| zpool_latency | per-vdev I/O latency histogram | zpool iostat -w | | ||
| zpool_vdev_queue | per-vdev instantaneous queue depth | zpool iostat -q | | ||
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### zpool_stats Description | ||
zpool_stats contains top-level summary statistics for the pool. | ||
Performance counters measure the I/Os to the pool's devices. | ||
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#### zpool_stats Tags | ||
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| label | description | | ||
|---|---| | ||
| name | pool name | | ||
| path | for leaf vdevs, the pathname | | ||
| state | pool state, as shown by _zpool status_ | | ||
| vdev | vdev name (root = entire pool) | | ||
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#### zpool_stats Fields | ||
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| field | units | description | | ||
|---|---|---| | ||
| alloc | bytes | allocated space | | ||
| free | bytes | unallocated space | | ||
| size | bytes | total pool size | | ||
| read_bytes | bytes | bytes read since pool import | | ||
| read_errors | count | number of read errors | | ||
| read_ops | count | number of read operations | | ||
| write_bytes | bytes | bytes written since pool import | | ||
| write_errors | count | number of write errors | | ||
| write_ops | count | number of write operations | | ||
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### zpool_scan_stats Description | ||
Once a pool has been scrubbed, resilvered, or rebuilt, the zpool_scan_stats | ||
contain information about the status and performance of the operation. | ||
Otherwise, the zpool_scan_stats do not exist in the kernel, and therefore | ||
cannot be reported by this collector. | ||
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#### zpool_scan_stats Tags | ||
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| label | description | | ||
|---|---| | ||
| name | pool name | | ||
| function | name of the scan function running or recently completed | | ||
| state | scan state, as shown by _zpool status_ | | ||
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#### zpool_scan_stats Fields | ||
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| field | units | description | | ||
|---|---|---| | ||
| errors | count | number of errors encountered by scan | | ||
| examined | bytes | total data examined during scan | | ||
| to_examine | bytes | prediction of total bytes to be scanned | | ||
| pass_examined | bytes | data examined during current scan pass | | ||
| issued | bytes | size of I/Os issued to disks | | ||
| pass_issued | bytes | size of I/Os issued to disks for current pass | | ||
| processed | bytes | data reconstructed during scan | | ||
| to_process | bytes | total bytes to be repaired | | ||
| rate | bytes/sec | examination rate | | ||
| start_ts | epoch timestamp | start timestamp for scan | | ||
| pause_ts | epoch timestamp | timestamp for a scan pause request | | ||
| end_ts | epoch timestamp | completion timestamp for scan | | ||
| paused_t | seconds | elapsed time while paused | | ||
| remaining_t | seconds | estimate of time remaining for scan | | ||
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### zpool_vdev_stats Description | ||
The ZFS I/O (ZIO) scheduler uses five queues to schedule I/Os to each vdev. | ||
These queues are further divided into active and pending states. | ||
An I/O is pending prior to being issued to the vdev. An active | ||
I/O has been issued to the vdev. The scheduler and its tunable | ||
parameters are described at the | ||
[ZFS documentation for ZIO Scheduler] | ||
(https://openzfs.github.io/openzfs-docs/Performance%20and%20Tuning/ZIO%20Scheduler.html) | ||
The ZIO scheduler reports the queue depths as gauges where the value | ||
represents an instantaneous snapshot of the queue depth at | ||
the sample time. Therefore, it is not unusual to see all zeroes | ||
for an idle pool. | ||
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#### zpool_vdev_stats Tags | ||
| label | description | | ||
|---|---| | ||
| name | pool name | | ||
| vdev | vdev name (root = entire pool) | | ||
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#### zpool_vdev_stats Fields | ||
| field | units | description | | ||
|---|---|---| | ||
| sync_r_active_queue | entries | synchronous read active queue depth | | ||
| sync_w_active_queue | entries | synchronous write active queue depth | | ||
| async_r_active_queue | entries | asynchronous read active queue depth | | ||
| async_w_active_queue | entries | asynchronous write active queue depth | | ||
| async_scrub_active_queue | entries | asynchronous scrub active queue depth | | ||
| sync_r_pend_queue | entries | synchronous read pending queue depth | | ||
| sync_w_pend_queue | entries | synchronous write pending queue depth | | ||
| async_r_pend_queue | entries | asynchronous read pending queue depth | | ||
| async_w_pend_queue | entries | asynchronous write pending queue depth | | ||
| async_scrub_pend_queue | entries | asynchronous scrub pending queue depth | | ||
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### zpool_latency Histogram | ||
ZFS tracks the latency of each I/O in the ZIO pipeline. This latency can | ||
be useful for observing latency-related issues that are not easily observed | ||
using the averaged latency statistics. | ||
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The histogram fields show cumulative values from lowest to highest. | ||
The largest bucket is tagged "le=+Inf", representing the total count | ||
of I/Os by type and vdev. | ||
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#### zpool_latency Histogram Tags | ||
| label | description | | ||
|---|---| | ||
| le | bucket for histogram, latency is less than or equal to bucket value in seconds | | ||
| name | pool name | | ||
| path | for leaf vdevs, the device path name, otherwise omitted | | ||
| vdev | vdev name (root = entire pool) | | ||
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#### zpool_latency Histogram Fields | ||
| field | units | description | | ||
|---|---|---| | ||
| total_read | operations | read operations of all types | | ||
| total_write | operations | write operations of all types | | ||
| disk_read | operations | disk read operations | | ||
| disk_write | operations | disk write operations | | ||
| sync_read | operations | ZIO sync reads | | ||
| sync_write | operations | ZIO sync writes | | ||
| async_read | operations | ZIO async reads| | ||
| async_write | operations | ZIO async writes | | ||
| scrub | operations | ZIO scrub/scan reads | | ||
| trim | operations | ZIO trim (aka unmap) writes | | ||
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### zpool_io_size Histogram | ||
ZFS tracks I/O throughout the ZIO pipeline. The size of each I/O is used | ||
to create a histogram of the size by I/O type and vdev. For example, a | ||
4KiB write to mirrored pool will show a 4KiB write to the top-level vdev | ||
(root) and a 4KiB write to each of the mirror leaf vdevs. | ||
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The ZIO pipeline can aggregate I/O operations. For example, a contiguous | ||
series of writes can be aggregated into a single, larger I/O to the leaf | ||
vdev. The independent I/O operations reflect the logical operations and | ||
the aggregated I/O operations reflect the physical operations. | ||
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The histogram fields show cumulative values from lowest to highest. | ||
The largest bucket is tagged "le=+Inf", representing the total count | ||
of I/Os by type and vdev. | ||
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Note: trim I/Os can be larger than 16MiB, but the larger sizes are | ||
accounted in the 16MiB bucket. | ||
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#### zpool_io_size Histogram Tags | ||
| label | description | | ||
|---|---| | ||
| le | bucket for histogram, I/O size is less than or equal to bucket value in bytes | | ||
| name | pool name | | ||
| path | for leaf vdevs, the device path name, otherwise omitted | | ||
| vdev | vdev name (root = entire pool) | | ||
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#### zpool_io_size Histogram Fields | ||
| field | units | description | | ||
|---|---|---| | ||
| sync_read_ind | blocks | independent sync reads | | ||
| sync_write_ind | blocks | independent sync writes | | ||
| async_read_ind | blocks | independent async reads | | ||
| async_write_ind | blocks | independent async writes | | ||
| scrub_read_ind | blocks | independent scrub/scan reads | | ||
| trim_write_ind | blocks | independent trim (aka unmap) writes | | ||
| sync_read_agg | blocks | aggregated sync reads | | ||
| sync_write_agg | blocks | aggregated sync writes | | ||
| async_read_agg | blocks | aggregated async reads | | ||
| async_write_agg | blocks | aggregated async writes | | ||
| scrub_read_agg | blocks | aggregated scrub/scan reads | | ||
| trim_write_agg | blocks | aggregated trim (aka unmap) writes | | ||
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#### About unsigned integers | ||
Telegraf v1.6.2 and later support unsigned 64-bit integers which more | ||
closely matches the uint64_t values used by ZFS. By default, zpool_influxdb | ||
uses ZFS' uint64_t values and influxdb line protocol unsigned integer type. | ||
If you are using old telegraf or influxdb where unsigned integers are not | ||
available, use the `--signed-int` option. | ||
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## Using _zpool_influxdb_ | ||
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The simplest method is to use the execd input agent in telegraf. For older | ||
versions of telegraf which lack execd, the exec input agent can be used. | ||
For convenience, one of the sample config files below can be placed in the | ||
telegraf config-directory (often /etc/telegraf/telegraf.d). Telegraf can | ||
be restarted to read the config-directory files. | ||
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### Example telegraf execd configuration | ||
```toml | ||
# # Read metrics from zpool_influxdb | ||
[[inputs.execd]] | ||
# ## default installation location for zpool_influxdb command | ||
command = ["/usr/bin/zpool_influxdb", "--execd"] | ||
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## Define how the process is signaled on each collection interval. | ||
## Valid values are: | ||
## "none" : Do not signal anything. (Recommended for service inputs) | ||
## The process must output metrics by itself. | ||
## "STDIN" : Send a newline on STDIN. (Recommended for gather inputs) | ||
## "SIGHUP" : Send a HUP signal. Not available on Windows. (not recommended) | ||
## "SIGUSR1" : Send a USR1 signal. Not available on Windows. | ||
## "SIGUSR2" : Send a USR2 signal. Not available on Windows. | ||
signal = "STDIN" | ||
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## Delay before the process is restarted after an unexpected termination | ||
restart_delay = "10s" | ||
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## Data format to consume. | ||
## Each data format has its own unique set of configuration options, read | ||
## more about them here: | ||
## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_INPUT.md | ||
data_format = "influx" | ||
``` | ||
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### Example telegraf exec configuration | ||
```toml | ||
# # Read metrics from zpool_influxdb | ||
[[inputs.exec]] | ||
# ## default installation location for zpool_influxdb command | ||
commands = ["/usr/bin/zpool_influxdb"] | ||
data_format = "influx" | ||
``` | ||
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## Caveat Emptor | ||
* Like the _zpool_ command, _zpool_influxdb_ takes a reader | ||
lock on spa_config for each imported pool. If this lock blocks, | ||
then the command will also block indefinitely and might be | ||
unkillable. This is not a normal condition, but can occur if | ||
there are bugs in the kernel modules. | ||
For this reason, care should be taken: | ||
* avoid spawning many of these commands hoping that one might | ||
finish | ||
* avoid frequent updates or short sample time | ||
intervals, because the locks can interfere with the performance | ||
of other instances of _zpool_ or _zpool_influxdb_ | ||
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## Other collectors | ||
There are a few other collectors for zpool statistics roaming around | ||
the Internet. Many attempt to screen-scrape `zpool` output in various | ||
ways. The screen-scrape method works poorly for `zpool` output because | ||
of its human-friendly nature. Also, they suffer from the same caveats | ||
as this implementation. This implementation is optimized for directly | ||
collecting the metrics and is much more efficient than the screen-scrapers. | ||
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## Feedback Encouraged | ||
Pull requests and issues are greatly appreciated at | ||
https://github.com/openzfs/zfs |
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### Dashboards for zpool_influxdb | ||
This directory contains a collection of dashboards related to ZFS with data | ||
collected from the zpool_influxdb collector. |
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