vault backup: 2026-03-07 09:54:02

Work/Resources/Redis Cheatsheet.md

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+# Redis Cheatsheet
+
+## Memory & Diagnostics
+
+```bash
+# Overall memory stats
+redis-cli INFO memory
+
+# Human-readable used memory
+redis-cli INFO memory | grep used_memory_human
+
+# Total number of keys
+redis-cli DBSIZE
+
+# Memory usage of a specific key (in bytes)
+redis-cli MEMORY USAGE "some:key"
+
+# Find biggest keys per type (safe, non-blocking)
+redis-cli --bigkeys
+
+# Top 30 keys by memory usage (scans first 500 keys)
+redis-cli --scan --pattern "*" | head -500 | while read key; do
+  bytes=$(redis-cli MEMORY USAGE "$key" 2>/dev/null)
+  echo "$bytes $key"
+done | sort -rn | head -30
+
+# Full scan (slow on large datasets)
+redis-cli --scan | while read key; do
+  bytes=$(redis-cli MEMORY USAGE "$key" 2>/dev/null)
+  echo "$bytes $key"
+done | sort -rn | head -50
+
+# Memory doctor -- quick health check
+redis-cli MEMORY DOCTOR
+```
+
+## Key Inspection
+
+```bash
+# Count keys matching a pattern
+redis-cli --scan --pattern "cache:*" | wc -l
+redis-cli --scan --pattern "horizon:*" | wc -l
+redis-cli --scan --pattern "queues:*" | wc -l
+
+# Check key type
+redis-cli TYPE "some:key"
+
+# Check TTL (-1 = no expiry, -2 = key doesn't exist)
+redis-cli TTL "some:key"
+
+# Find keys with no expiry (sample first 100)
+redis-cli --scan --pattern "*" | head -100 | while read key; do
+  ttl=$(redis-cli TTL "$key")
+  if [ "$ttl" = "-1" ]; then echo "NO EXPIRY: $key ($(redis-cli MEMORY USAGE "$key") bytes)"; fi
+done
+
+# List all key prefixes and their counts
+redis-cli --scan | sed 's/:[^:]*$//' | sort | uniq -c | sort -rn | head -30
+```
+
+## Streams
+
+```bash
+# Stream length
+redis-cli XLEN "stream:key"
+
+# Stream info (memory, first/last entry, etc.)
+redis-cli XINFO STREAM "stream:key"
+
+# Trim stream to max N entries
+redis-cli XTRIM "stream:key" MAXLEN 10000
+
+# Delete a stream entirely
+redis-cli DEL "stream:key"
+
+# Read last 5 entries
+redis-cli XREVRANGE "stream:key" + - COUNT 5
+```
+
+## Hashes, Lists, Sets, Sorted Sets
+
+```bash
+# Hash: field count and sample fields
+redis-cli HLEN "hash:key"
+redis-cli HSCAN "hash:key" 0 COUNT 10
+
+# List: length and sample
+redis-cli LLEN "list:key"
+redis-cli LRANGE "list:key" 0 9
+
+# Set: member count and sample
+redis-cli SCARD "set:key"
+redis-cli SSCAN "set:key" 0 COUNT 10
+
+# Sorted set: member count and top 10 by score
+redis-cli ZCARD "zset:key"
+redis-cli ZREVRANGE "zset:key" 0 9 WITHSCORES
+```
+
+## Memory Limits & Eviction
+
+```bash
+# Set memory limit (runtime, no restart)
+redis-cli CONFIG SET maxmemory 2gb
+
+# Set eviction policy
+redis-cli CONFIG SET maxmemory-policy volatile-lru
+
+# Persist config changes to redis.conf
+redis-cli CONFIG REWRITE
+
+# Check current settings
+redis-cli CONFIG GET maxmemory
+redis-cli CONFIG GET maxmemory-policy
+redis-cli CONFIG GET save
+```
+
+### Eviction policies
+
+| Policy | Behavior |
+|---|---|
+| `noeviction` | Refuse writes when full (default -- dangerous) |
+| `volatile-lru` | Evict LRU keys that have a TTL set |
+| `allkeys-lru` | Evict any LRU key |
+| `volatile-ttl` | Evict keys with shortest TTL first |
+| `volatile-random` | Evict random keys that have a TTL |
+| `allkeys-random` | Evict any random key |
+
+## Persistence
+
+```bash
+# Disable RDB snapshots (prevents fork that doubles memory)
+redis-cli CONFIG SET save ""
+
+# Trigger manual save (blocks until done)
+redis-cli SAVE
+
+# Trigger background save (forks -- dangerous if low memory)
+redis-cli BGSAVE
+
+# Check last save time
+redis-cli LASTSAVE
+
+# Check if background save is in progress
+redis-cli INFO persistence | grep rdb_bgsave_in_progress
+```
+
+## Bulk Operations
+
+```bash
+# Delete all keys matching a pattern (use with care)
+redis-cli --scan --pattern "prefix:*" | xargs -L 100 redis-cli DEL
+
+# Count + size of keys matching a pattern
+redis-cli --scan --pattern "horizon:*" | while read key; do
+  redis-cli MEMORY USAGE "$key"
+done | awk '{s+=$1} END {printf "Total: %.2f MB\n", s/1024/1024}'
+
+# Flush current database (DESTRUCTIVE)
+redis-cli FLUSHDB
+
+# Flush all databases (DESTRUCTIVE)
+redis-cli FLUSHALL
+```
+
+## Monitoring
+
+```bash
+# Watch commands in real time (Ctrl+C to stop)
+redis-cli MONITOR
+
+# Slow log -- queries that took longer than threshold
+redis-cli SLOWLOG GET 10
+
+# Connected clients
+redis-cli INFO clients | grep connected_clients
+
+# Stats since startup
+redis-cli INFO stats
+```
+
+## Config File Locations
+
+```
+/etc/redis/redis.conf          # Debian/Ubuntu default
+/etc/redis.conf                # RHEL/CentOS
+/etc/redis/6379.conf           # Multi-instance setups
+```