hash

Provides information about the vBucket hash tables.

Syntax

Request syntax:

cbstats [hostname]:11210 hash
cbstats [hostname]:11210 hash detail

Description

Requesting these stats does affect performance, so don’t do it too regularly, but it’s useful for debugging certain types of performance issues. For example, if your hash table is tuned to have too few buckets for the data load within it, the max_depth will be too large, and performance will suffer.

It is also possible to get more detailed hash tables stats by using ‘hash detail’. This prints per-vbucket stats. Each stat is prefixed with vb_ followed by a number, a colon, then the individual stat name. For example, the stat representing the size of the hash table for vbucket 0 is vb_0:size=.

Options

None

Examples

Hash request

cbstats 10.5.2.54:11210 hash

Hash response

 avg_count:    0
 avg_max:      0
 avg_min:      0
 largest_max:  0
 largest_min:  0
 max_count:    0
 min_count:    0
 total_counts: 0

Table 1. Hash response stats
Stat	Description
`avg_count`	The average number of items per vbucket.
`avg_max`	The average max depth of a vbucket hash table.
`avg_min`	The average min depth of a vbucket hash table.
`largest_max`	The largest hash table depth of in all vbuckets.
`largest_min`	The largest minimum hash table depth of all vbuckets.
`max_count`	The largest number of items in a vbucket.
`min_count`	The smallest number of items in a vbucket.
`total_counts`	The total number of items in all vbuckets.

Hash detail

cbstats 10.5.2.54:11210 hash detail

Hash detail response

 avg_count:                0
 avg_max:                  0
 avg_min:                  0
 largest_max:              0
 largest_min:              0
 max_count:                0
 min_count:                0
 total_counts:             0
 vb_0:counted:             0
 vb_0:locks:               5
 vb_0:max_depth:           0
 vb_0:mem_size:            0
 vb_0:mem_size_counted:    0
 vb_0:min_depth:           0
 vb_0:reported:            0
 vb_0:resized:             0
 vb_0:size:                3079
 vb_0:state:               replica
 ...

Table 2. Hash detail response stats
Stat	Description
state	The current state of this vbucket.
size	Number of hash buckets.
locks	Number of locks covering hash table operations.
min_depth	Minimum number of items found in a bucket.
max_depth	Maximum number of items found in a bucket.
reported	Number of items this hash table reports having.
counted	Number of items found while walking the table.
resized	Number of times the hash table resized.
mem_size	Running sum of memory used by each item.
mem_size_counted	Counted sum of current memory used by each item.