How to Add Redis Cache Expire and Memory‑Limit Experiments to ChaosBlade

Background

Operators need to simulate Redis failure scenarios such as forcing all keys to expire or triggering memory eviction. ChaosBlade adds two experiments: Redis cache expiration and Redis cache memory‑limit.

Redis Cache Expiration Experiment

Purpose

Simulate expiration of a single key or all keys to test application behavior on cache loss.

Implementation

Uses the go-redis client to call the EXPIRE command and modify the TTL of a specified key.

Usage

# Expire a key after 1 minute
blade create redis cache-expire --addr 192.168.56.101:6379 --password 123456 --key test1 --expiry 1m

# Set new expiry only when it is greater than the current TTL (option GT)
blade create redis cache-expire --addr 192.168.56.101:6379 --password 123456 --key test1 --option GT --expiry 1m

Documentation

https://chaosblade.io/docs/experiment-types/host/redis/blade_create_redis_cache_expire

Redis Cache Memory‑Limit Experiment

Purpose

Modify Redis maxmemory configuration to exceed the limit and trigger the eviction policy.

Implementation

Uses go-redis to change the maxmemory setting.

Usage

# Set maxmemory to 256M
blade create redis cache-limit --addr 192.168.56.101:6379 --password 123456 --size 256M

# Reduce maxmemory to 50% of the original value
blade create redis cache-limit --addr 192.168.56.101:6379 --password 123456 --percent 50

Documentation

https://chaosblade.io/docs/experiment-types/host/redis/blade_create_redis_cache_limit

Contribution Guide for Adding the Experiments

Repository

Fork and clone the middleware repository, then create a development branch:

git clone https://github.com/chaosblade-io/chaosblade-exec-middleware
cd chaosblade-exec-middleware
git checkout -b dev

Directory Structure

Create the Redis experiment package: mkdir -p exec/redis File redis.go defines the command specification:

package redis

import (
    "github.com/chaosblade-io/chaosblade-spec-go/spec"
)

type RedisCommandSpec struct{ spec.BaseExpModelCommandSpec }

func (*RedisCommandSpec) Name() string        { return "redis" }
func (*RedisCommandSpec) ShortDesc() string   { return "Redis experiment" }
func (*RedisCommandSpec) LongDesc() string    { return "Redis experiment" }

func NewRedisCommandSpec() spec.ExpModelCommandSpec {
    return &RedisCommandSpec{
        spec.BaseExpModelCommandSpec{
            ExpActions: []spec.ExpActionCommandSpec{
                NewCacheExpireActionSpec(),
                NewCacheLimitActionSpec(),
            },
            ExpFlags: []spec.ExpFlagSpec{},
        },
    }
}

Register the spec in model_darwin.go, model_linux.go, model_windows.go and in build/spec.go (see https://github.com/chaosblade-io/chaosblade-exec-middleware/blob/main/build/spec.go).

Implementation files for the two experiments:

https://github.com/chaosblade-io/chaosblade-exec-middleware/blob/main/exec/redis/redis_cache_expire.go

https://github.com/chaosblade-io/chaosblade-exec-middleware/blob/main/exec/redis/redis_cache_limit.go

Build

Compile the middleware for the target platform:

# macOS
make build_darwin

# Linux x86
make build_linux

# Linux ARM
make build_linux_arm

The resulting binaries are placed in the target directory. Replace the existing chaos_middleware binary and chaosblade-middleware-spec-1.7.2.yaml on the test server with the new versions.

Testing

Run the experiments and verify Redis state before and after:

# Expire a key
blade create redis cache-expire --addr 192.168.56.101:6379 --password 123456 --key test1 --expiry 1m

# Limit memory
blade create redis cache-limit --addr 192.168.56.101:6379 --password 123456 --size 256M

Use the Redis CLI to check TTL or maxmemory values to confirm the changes.

Pull Request Workflow

Commit changes with a signed commit message.

Push the dev branch to GitHub.

Create a Pull Request targeting main.

Address review comments and merge after approval.