telegraf/plugins/inputs/bcache/README.md

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# Telegraf plugin: bcache
Get bcache stat from stats_total directory and dirty_data file.
# Measurements
Meta:
- tags: `backing_dev=dev bcache_dev=dev`
Measurement names:
- dirty_data
- bypassed
- cache_bypass_hits
- cache_bypass_misses
- cache_hit_ratio
- cache_hits
- cache_miss_collisions
- cache_misses
- cache_readaheads
### Description
```
dirty_data
Amount of dirty data for this backing device in the cache. Continuously
updated unlike the cache set's version, but may be slightly off.
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bypassed
Amount of IO (both reads and writes) that has bypassed the cache
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cache_bypass_hits
cache_bypass_misses
Hits and misses for IO that is intended to skip the cache are still counted,
but broken out here.
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cache_hits
cache_misses
cache_hit_ratio
Hits and misses are counted per individual IO as bcache sees them; a
partial hit is counted as a miss.
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cache_miss_collisions
Counts instances where data was going to be inserted into the cache from a
cache miss, but raced with a write and data was already present (usually 0
since the synchronization for cache misses was rewritten)
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cache_readaheads
Count of times readahead occurred.
```
# Example output
Using this configuration:
```
[bcache]
# Bcache sets path
# If not specified, then default is:
# bcachePath = "/sys/fs/bcache"
#
# By default, telegraf gather stats for all bcache devices
# Setting devices will restrict the stats to the specified
# bcache devices.
# bcacheDevs = ["bcache0", ...]
```
When run with:
```
./telegraf --config telegraf.conf --input-filter bcache --test
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```
It produces:
```
* Plugin: bcache, Collection 1
> [backing_dev="md10" bcache_dev="bcache0"] bcache_dirty_data value=11639194
> [backing_dev="md10" bcache_dev="bcache0"] bcache_bypassed value=5167704440832
> [backing_dev="md10" bcache_dev="bcache0"] bcache_cache_bypass_hits value=146270986
> [backing_dev="md10" bcache_dev="bcache0"] bcache_cache_bypass_misses value=0
> [backing_dev="md10" bcache_dev="bcache0"] bcache_cache_hit_ratio value=90
> [backing_dev="md10" bcache_dev="bcache0"] bcache_cache_hits value=511941651
> [backing_dev="md10" bcache_dev="bcache0"] bcache_cache_miss_collisions value=157678
> [backing_dev="md10" bcache_dev="bcache0"] bcache_cache_misses value=50647396
> [backing_dev="md10" bcache_dev="bcache0"] bcache_cache_readaheads value=0
```