Overview
Redis configuration can be managed through the redis.conf file or dynamically at runtime using the CONFIG command. This guide covers configuration directives, runtime management, and best practices.
Configuration File
Starting Redis with a Configuration File
Redis must be started with the configuration file path as the first argument:
./redis-server /path/to/redis.conf
Unit Specifications
Redis supports convenient memory size units (case insensitive):
1k => 1000 bytes1kb => 1024 bytes1m => 1000000 bytes1mb => 1024*1024 bytes1g => 1000000000 bytes1gb => 102410241024 bytes
CONFIG Commands
CONFIG GET
Retrieve the value of configuration parameters.
# Get a specific configuration
CONFIG GET maxmemory
# Get multiple configurations
CONFIG GET maxmemory maxmemory-policy
# Use glob patterns
CONFIG GET max*
CONFIG GET *memory*
CONFIG SET
Change configuration parameters at runtime without restarting Redis.
# Set a single parameter
CONFIG SET maxmemory 2gb
# Set multiple parameters
CONFIG SET maxmemory 2gb maxmemory-policy allkeys-lru
Some configuration directives are immutable and cannot be changed at runtime. Others are protected and require special permissions. Changing configuration at runtime does not persist across restarts unless you use CONFIG REWRITE.
CONFIG REWRITE
Persist runtime configuration changes back to the redis.conf file:
This command rewrites the configuration file, preserving comments and structure while updating changed values.
Core Configuration Directives
Network Configuration
bind
Specify which network interfaces Redis should listen on:
# Listen on localhost only (default, secure)
bind 127.0.0.1 -::1
# Listen on specific IP addresses
bind 192.168.1.100 10.0.0.1
# Listen on all interfaces (NOT recommended for production)
bind * -::*
port
Set the TCP port (default: 6379):
port 6379
# Disable TCP socket
port 0
tcp-backlog
Set the TCP listen() backlog for high-traffic environments:
On Linux, ensure /proc/sys/net/core/somaxconn and tcp_max_syn_backlog are set appropriately.
tcp-keepalive
Send TCP keepalive messages to detect dead peers:
# Send ACKs every 300 seconds
tcp-keepalive 300
timeout
Close idle client connections after N seconds (0 to disable):
# Close connections idle for 300 seconds
timeout 300
# Never close idle connections
timeout 0
General Configuration
daemonize
Run Redis as a daemon:
pidfile
Specify the PID file location:
pidfile /var/run/redis_6379.pid
loglevel
Set the server verbosity level:
# Options: debug, verbose, notice, warning, nothing
loglevel notice
logfile
Specify the log file path:
# Log to file
logfile /var/log/redis/redis-server.log
# Log to stdout
logfile ""
databases
Set the number of databases:
# Default is 16 databases (0-15)
databases 16
Snapshotting Configuration
save
Configure automatic RDB snapshots:
# Save after 3600 seconds if at least 1 key changed
# Save after 300 seconds if at least 100 keys changed
# Save after 60 seconds if at least 10000 keys changed
save 3600 1 300 100 60 10000
# Disable snapshotting
save ""
stop-writes-on-bgsave-error
Stop accepting writes if background save fails:
stop-writes-on-bgsave-error yes
rdbcompression
Compress RDB files using LZF:
rdbchecksum
Add CRC64 checksum to RDB files:
dbfilename
Set the RDB filename:
dir
Set the working directory for RDB and AOF files:
Memory Management
maxmemory
Set a memory usage limit:
# Set 2GB limit
maxmemory 2gb
# No limit (default)
# maxmemory 0
When using replicas, set maxmemory lower than available RAM to account for replica output buffers.
maxmemory-policy
Define eviction policy when maxmemory is reached:
# Available policies:
# volatile-lru - Evict using LRU, only keys with expire set
# allkeys-lru - Evict any key using LRU
# volatile-lfu - Evict using LFU, only keys with expire set
# allkeys-lfu - Evict any key using LFU
# volatile-lrm - Evict using LRM, only keys with expire set
# allkeys-lrm - Evict any key using LRM
# volatile-random - Remove random key with expire set
# allkeys-random - Remove random key
# volatile-ttl - Remove key with nearest expire time
# noeviction - Return errors on write operations (default)
maxmemory-policy noeviction
- LRU (Least Recently Used): Updates timestamp on both read and write operations
- LRM (Least Recently Modified): Updates timestamp only on write operations
- LFU (Least Frequently Used): Tracks access frequency
maxmemory-samples
Number of keys to sample for eviction algorithms:
# Default is 5, higher is more accurate but slower
maxmemory-samples 5
Client Configuration
maxclients
Maximum number of simultaneous client connections:
In Redis Cluster, each node uses two connections (incoming and outgoing), so size accordingly.
Module Loading
Load Redis modules at startup:
loadmodule /path/to/my_module.so
loadmodule /path/to/other_module.so
loadmodule /path/to/module.so arg1 arg2 arg3
Including Configuration Files
Include additional configuration files:
# Include single file
include /path/to/local.conf
# Include with wildcards
include /path/to/fragments/*.conf
Include directives at the beginning of the file for base configuration, or at the end to override settings.
Configuration Management Best Practices
Store your redis.conf in version control to track changes and enable rollback.
Test Configuration Changes
Before applying to production:
# Test configuration file syntax
redis-server /path/to/redis.conf --test-memory 1
# Use CONFIG SET to test changes before persisting
CONFIG SET maxmemory 2gb
# Verify behavior, then:
CONFIG REWRITE
Regularly audit your configuration:
# Get all configuration
CONFIG GET *
# Check specific security settings
CONFIG GET bind
CONFIG GET protected-mode
CONFIG GET requirepass
Add comments explaining why specific values were chosen:
# Increased maxclients for high-traffic application
# Based on load testing results from 2024-01-15
maxclients 50000
Runtime Configuration Examples
Example: Adjust Memory Settings
# Check current memory usage
INFO memory
# Set memory limit and eviction policy
CONFIG SET maxmemory 4gb
CONFIG SET maxmemory-policy allkeys-lru
# Persist changes
CONFIG REWRITE
Example: Enable Logging
# Change log level for debugging
CONFIG SET loglevel debug
# Change log file location
CONFIG SET logfile /var/log/redis/debug.log
# Revert after debugging
CONFIG SET loglevel notice
Example: Adjust Snapshot Frequency
# More frequent snapshots for critical data
CONFIG SET save "900 1 300 10 60 10000"
# Persist configuration
CONFIG REWRITE
Configuration Reset
Reset specific configuration parameters to their default values by using CONFIG SET with appropriate values, or edit redis.conf and restart Redis.
See Also