AxonOps Cache Dashboard Metrics Mapping
This document maps the metrics used in the AxonOps Cache dashboard.
Dashboard Overview
Section titled “Dashboard Overview”The Cache dashboard monitors Cassandra’s caching layers including KeyCache, RowCache, and CounterCache. These caches improve read performance by storing frequently accessed data in memory. The dashboard helps optimize cache configuration and monitor cache effectiveness.
Metrics Mapping
Section titled “Metrics Mapping”Cache Metrics (Applied to all cache types)
Section titled “Cache Metrics (Applied to all cache types)”| Dashboard Metric | Description | Attributes |
|---|---|---|
cas_Cache_HitRate | Cache hit ratio (0.0-1.0) | scope (KeyCache/RowCache/CounterCache), dc, rack, host_id |
cas_Cache_Size | Current cache size in bytes | scope, dc, rack, host_id |
cas_Cache_Capacity | Maximum cache capacity in bytes | scope, dc, rack, host_id |
cas_Cache_Entries | Number of entries in cache | scope, dc, rack, host_id |
cas_Cache_Requests | Total cache requests | scope, dc, rack, host_id |
Cache Types
Section titled “Cache Types”KeyCache
Section titled “KeyCache”- Caches partition index entries
- Enabled by default in Cassandra
- Reduces disk seeks for finding partition locations
RowCache
Section titled “RowCache”- Caches entire rows of data
- Disabled by default due to memory overhead
- Useful for small, hot datasets
CounterCache
Section titled “CounterCache”- Caches counter column values
- Improves counter read performance
- Only applies to counter columns
Query Examples
Section titled “Query Examples”KeyCache Hit Rate
Section titled “KeyCache Hit Rate”cas_Cache_HitRate{scope='KeyCache',dc=~'$dc',rack=~'$rack',host_id=~'$host_id'}KeyCache Size by Group
Section titled “KeyCache Size by Group”sum(cas_Cache_Size{scope='KeyCache',dc=~'$dc',rack=~'$rack',host_id=~'$host_id'}) by ($groupBy)KeyCache Requests per Second
Section titled “KeyCache Requests per Second”sum(cas_Cache_Requests{axonfunction='rate',scope='KeyCache',dc=~'$dc',rack=~'$rack',host_id=~'$host_id'}) by ($groupBy)RowCache Entries Count
Section titled “RowCache Entries Count”sum(cas_Cache_Entries{scope='RowCache',dc=~'$dc',rack=~'$rack',host_id=~'$host_id'}) by ($groupBy)CounterCache Capacity
Section titled “CounterCache Capacity”sum(cas_Cache_Capacity{scope='CounterCache',dc=~'$dc',rack=~'$rack',host_id=~'$host_id'}) by ($groupBy)Panel Organization
Section titled “Panel Organization”Key Cache Section
Section titled “Key Cache Section”-
KeyCache HitRate Per Node - Line chart showing cache hit effectiveness (0-1 scale)
-
KeyCache Size - Line chart showing memory used by cache
-
KeyCache Capacity - Line chart showing maximum cache size
-
KeyCache Number of Entries - Line chart showing entry count
-
KeyCache Requests Count Per Second - Line chart showing request rate
Row Cache Section
Section titled “Row Cache Section”-
RowCache Size - Line chart showing memory used
-
RowCache Capacity - Line chart showing maximum size
-
RowCache Number of Entries - Line chart showing entry count
-
RowCache Requests Count Per Second - Line chart showing request rate
Counter Cache Section
Section titled “Counter Cache Section”-
CounterCache HitRate - Line chart showing hit ratio
-
CounterCache Size - Line chart showing memory used
-
CounterCache Capacity - Line chart showing maximum size
-
CounterCache Number of Entries - Line chart showing entry count
-
CounterCache Requests Count Per Second - Line chart showing request rate
Filters
Section titled “Filters”-
data center (
dc) - Filter by data center -
rack - Filter by rack
-
node (
host_id) - Filter by specific node -
groupBy - Dynamic grouping by dc, rack, or host_id
Metric Aggregation
Section titled “Metric Aggregation”The dashboard uses the groupBy variable for flexible aggregation:
- Group by data center to see cache usage per DC
- Group by rack for rack-level analysis
- Group by host_id for node-level details
Legend format:
- Size metrics:
size_$groupBy - Capacity metrics:
capacity_$groupBy - Other metrics:
$groupBy
Important Notes
Section titled “Important Notes”Hit Rate Interpretation:
- Value between 0.0 and 1.0 (shown as
percentunit) - Higher values indicate better cache effectiveness
- Low hit rates may indicate cache size needs adjustment
Cache Sizing:
- Size should not exceed Capacity
- Monitor the Size/Capacity ratio
- Adjust capacity in cassandra.yaml if needed
Version Compatibility:
- Note states “Only Cassandra and DSE prior to version 6.0” for some metrics
- Cache metrics may vary in newer versions
Performance Impact:
- KeyCache has minimal overhead and high benefit
- RowCache can consume significant memory
- Monitor request rates to understand cache load
Units:
- Size and Capacity: bytes (with SI units disabled)
- Hit Rate: percentunit (0.0-1.0 scale)
- Requests: operations per second (ops)