nodetool invalidatecountercache

Invalidates the counter cache on the node.

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Synopsis

nodetool [connection_options] invalidatecountercache

Description

nodetool invalidatecountercache clears all entries from the counter cache on the node. The counter cache stores counter cell values, allowing faster access to frequently read counters by avoiding disk reads for their current values.

After invalidation, the cache is empty and will be repopulated as subsequent counter read operations occur.

Counter-Specific Cache

This cache only affects counter columns. If the workload does not use counters, this cache will be empty and invalidation has no effect.

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Examples

Basic Usage

nodetool invalidatecountercache

Invalidate and Monitor Refill

nodetool invalidatecountercache
watch -n 5 'nodetool info | grep "Counter Cache"'

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Counter Cache Overview

What the Counter Cache Stores

Cached Data	Description
Counter cell location	Reference to counter column
Current counter value	Most recent counter value
Merge information	Data for counter merges

How It Improves Performance

Without Counter Cache:
  Counter Read → Read all counter shards from disk → Merge → Return value

With Counter Cache Hit:
  Counter Read → Return cached merged value
  (Avoids disk reads and merge computation)

Counter Operations

Counters in Cassandra are distributed and require merging values from multiple sources:

1. Local shard value
2. Remote shard values
3. Historical values for consistency

The counter cache stores the merged result, avoiding repeated computation.

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When to Use

After Counter Repair

Clear potentially inconsistent cached values:

# After running repair on counter tables
nodetool invalidatecountercache

Troubleshooting Counter Discrepancies

If counter values appear incorrect:

# Clear counter cache
nodetool invalidatecountercache

# Re-read counters to get fresh values

After Counter Table Restore

Following restore from backup:

# After restoring counter data
nodetool invalidatecountercache

Memory Optimization

Release memory if counter cache is large:

# Check current size
nodetool info | grep "Counter Cache"

# Clear if necessary
nodetool invalidatecountercache

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Impact Assessment

Immediate Effects

Aspect	Impact
Counter cache entries	All cleared
Memory usage	Temporarily reduced
Counter read latency	Temporarily increases
Disk I/O for counters	Increases

Recovery Timeline

Phase	Duration	Cache State
Immediately after	0	Empty
Warming up	Minutes	Partially filled
Fully warm	Hours	Optimally filled

Impact Scope

Impact is limited to counter column workloads. Non-counter reads are unaffected.

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Monitoring Cache Status

Before and After

# Check cache status before
echo "Before invalidation:"
nodetool info | grep -A 5 "Counter Cache"

# Invalidate
nodetool invalidatecountercache

# Check immediately after
echo "After invalidation:"
nodetool info | grep -A 5 "Counter Cache"

Monitor Refill Progress

#!/bin/bash
# monitor_countercache_refill.sh

echo "=== Counter Cache Refill Monitor ==="
echo "Press Ctrl+C to stop"
echo ""

while true; do
    info=$(nodetool info 2>/dev/null | grep -A 2 "Counter Cache")
    entries=$(echo "$info" | grep "entries" | awk '{print $4}')
    hit_rate=$(echo "$info" | grep "hit rate" | awk '{print $4}')
    size=$(echo "$info" | grep "size" | awk '{print $4}')

    echo "$(date '+%H:%M:%S') - Entries: $entries, Hit Rate: $hit_rate, Size: $size"
    sleep 10
done

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Workflow: Counter Cache Management

#!/bin/bash
# counter_cache_management.sh

echo "=== Counter Cache Management ==="

# 1. Check current state
echo "1. Current counter cache status:"
nodetool info | grep -A 3 "Counter Cache"

# 2. Check if counters are in use
entries=$(nodetool info 2>/dev/null | grep -A 1 "Counter Cache" | grep "entries" | awk '{print $4}')
if [ "$entries" = "0" ]; then
    echo ""
    echo "Counter cache is empty - no counters in use or caching disabled."
    echo "Invalidation would have no effect."
    exit 0
fi

# 3. Proceed with invalidation
echo ""
echo "2. Invalidating counter cache..."
nodetool invalidatecountercache

# 4. Verify
echo ""
echo "3. Cache status after invalidation:"
nodetool info | grep -A 3 "Counter Cache"

# 5. Monitor refill
echo ""
echo "4. Monitoring refill (30 seconds)..."
for i in {1..6}; do
    sleep 5
    entries=$(nodetool info 2>/dev/null | grep -A 1 "Counter Cache" | grep "entries" | awk '{print $4}')
    echo "  Entries: $entries"
done

echo ""
echo "=== Complete ==="

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Cluster-Wide Operations

Invalidate on All Nodes

#!/bin/bash
# invalidate_countercache_cluster.sh

echo "Invalidating counter cache cluster-wide..."# Get list of node IPs from local nodetool status


nodes=$(nodetool status | grep "^UN" | awk '{print $2}')

for node in $nodes; do
    echo -n "$node: "
    ssh "$node" "nodetool invalidatecountercache 2>/dev/null && echo "invalidated" || echo "FAILED""
done

echo ""
echo "Monitor recovery with: nodetool info | grep 'Counter Cache'"

Rolling Invalidation

#!/bin/bash
# rolling_countercache_invalidate.sh# Get list of node IPs from local nodetool status


nodes=$(nodetool status | grep "^UN" | awk '{print $2}')
WAIT_TIME=120  # 2 minutes between nodes

for node in $nodes; do
    echo "$(date): Invalidating counter cache on $node..."
    ssh "$node" "nodetool invalidatecountercache"

    echo "Waiting ${WAIT_TIME}s for cache warmup..."
    sleep $WAIT_TIME

    hit_rate=$(ssh "$node" "nodetool info 2>/dev/null | grep -A 2 "Counter Cache" | grep "hit rate" | awk '{print $4}')"
    echo "  Hit rate: $hit_rate"
done

echo "Rolling invalidation complete."

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Configuration

Counter Cache Settings

# cassandra.yaml
counter_cache_size_in_mb:   # Default: min(2.5% of heap, 50MB)
counter_cache_save_period: 7200  # Save interval in seconds
counter_cache_keys_to_save:  # Keys to save on shutdown

Check Configuration

# View current counter cache configuration
nodetool info | grep "Counter Cache"

# Check cassandra.yaml
grep counter_cache /etc/cassandra/cassandra.yaml

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Troubleshooting

Counter Cache Always Empty

# Check if any tables use counters
cqlsh -e "SELECT keyspace_name, table_name FROM system_schema.columns WHERE type = 'counter' ALLOW FILTERING;"

# If no counter tables, cache will be empty

Low Hit Rate

# Check cache size vs counter working set
nodetool info | grep "Counter Cache"

# Consider increasing cache size if entries are at capacity
# but hit rate is low

Counter Values Incorrect After Invalidation

# Run repair on counter tables
nodetool repair -pr my_keyspace counter_table

# Then allow cache to rebuild with correct values

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Counter Best Practices

Counter Cache Guidelines

1. Understand counter workload - Only useful if using counter columns
2. Invalidate after repair - Ensure cached values are consistent
3. Monitor hit rates - Low hit rate may indicate sizing issue
4. Consider alternatives - For simple counting, regular columns may be better
5. Test impact - Measure latency impact before production invalidation

Counter Limitations

Remember that Cassandra counters have specific limitations:

• Cannot be part of primary key
• Can only increment/decrement (no set)
• Subject to consistency challenges
• Counter cache helps mitigate read overhead

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Related Commands

Command	Relationship
invalidatekeycache	Invalidate key cache
invalidaterowcache	Invalidate row cache
info	View cache statistics
setcachecapacity	Adjust cache sizes
repair	Repair data including counters