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feat: redlock example (#10)
* feat: redlock with go example * feat: redlock with go example x02
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‎redlock-go/Dockerfile

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FROM golang:1.20 as builder
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WORKDIR /app
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COPY go.mod go.sum ./
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RUN go mod download
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COPY app/ ./app/
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RUN CGO_ENABLED=0 GOOS=linux go build -v -o /go/bin/app ./app/main.go
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FROM alpine:latest
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COPY --from=builder /go/bin/app /go/bin/app
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CMD ["/go/bin/app"]

‎redlock-go/README.md

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# Example: Redlock with Go
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[Redlock](https://redis.io/docs/manual/patterns/distributed-locks/) is a recognized algorithm based on Redis for
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distributed locks, ensuring consistent operation and protection against failures such as network partitions and Redis crashes.
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It operates by having a client application send lock requests, using [`SET`](https://www.dragonflydb.io/docs/command-reference/strings/set.md) commands, to multiple **primary Redis instances**.
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The lock is successfully acquired when more than half of these instances agree on the lock acquisition.
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To release the lock, the client issues [`DEL`](https://www.dragonflydb.io/docs/command-reference/generic/del) commands to all the instances involved.
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Redlock also takes into account the lock validity time, retry on failure, lock extension, and many other aspects, which makes it a robust and reliable solution for distributed locking.
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Since Dragonfly is highly compatible with Redis and both `SET` and `DEL` commands are fully supported, Redlock implementations can be easily used with Dragonfly.
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## Packages Used
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- The [go-redis](https://github.com/redis/go-redis) client is used. It has strongly typed methods for various commands.
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It is also the recommended Go client to interact with Dragonfly.
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- The [redsync](https://github.com/go-redsync/redsync) is a Go implementation of the Redlock algorithm.
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It is used to acquire and release locks in a distributed environment.
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## Local Setup
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- Make sure that you have [Go v1.20+](https://go.dev/dl/) installed locally.
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- Make sure that you have [Docker](https://docs.docker.com/engine/install/) installed locally.
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- Run Dragonfly instances & the Redlock service:
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```bash
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# within the root directory of this example (dragonfly-examples/redlock-go)
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docker compose build --no-cache && docker compose up
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```
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- Use the API endpoint to acquire the lock:
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```bash
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curl -v --url http://localhost:8080/try-to-acquire-global-lock
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```
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- For the first time, the lock should be acquired successfully:
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```text
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HTTP/1.1 200 OK
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Date: Thu, 15 Feb 2024 19:29:09 GMT
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Content-Length: 13
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Content-Type: text/plain; charset=utf-8
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lock acquired
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```
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- If we try to acquire the lock again in a short period, it should fail:
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```text
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HTTP/1.1 400 Bad Request
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Content-Type: text/plain; charset=utf-8
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X-Content-Type-Options: nosniff
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Date: Thu, 15 Feb 2024 19:29:56 GMT
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Content-Length: 42
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lock already taken, locked nodes: [0 1 2]
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```

‎redlock-go/app/main.go

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package main
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import (
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"net/http"
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"time"
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"github.com/go-redsync/redsync/v4"
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redsyncredis "github.com/go-redsync/redsync/v4/redis"
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redsyncpool "github.com/go-redsync/redsync/v4/redis/goredis/v9"
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"github.com/redis/go-redis/v9"
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)
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// These hosts are reachable from within the Docker network.
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const (
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dragonflyHost0 = "dragonfly-instance-0:6379"
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dragonflyHost1 = "dragonfly-instance-1:6379"
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dragonflyHost2 = "dragonfly-instance-2:6379"
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)
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const (
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// The name of the global lock.
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globalLockKeyName = "my-global-lock"
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// The expiry of the global lock.
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globalLockExpiry = time.Minute
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// Number of retries to acquire the global lock.
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globalLockRetries = 8
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// The delay between retries to acquire the global lock.
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globalLockRetryDelay = 10 * time.Millisecond
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)
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func main() {
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// Create three clients for each instance of Dragonfly.
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var (
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hosts = []string{dragonflyHost0, dragonflyHost1, dragonflyHost2}
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clients = make([]redsyncredis.Pool, len(hosts))
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)
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for idx, addr := range hosts {
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client := redis.NewClient(&redis.Options{
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Addr: addr,
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})
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clients[idx] = redsyncpool.NewPool(client)
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}
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// Create an instance of 'Redsync' to work with locks.
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rs := redsync.New(clients...)
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// Create a global lock mutex.
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globalMutex := rs.NewMutex(
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globalLockKeyName,
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redsync.WithExpiry(globalLockExpiry),
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redsync.WithTries(globalLockRetries),
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redsync.WithRetryDelay(globalLockRetryDelay),
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)
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// Create an HTTP server that exposes an endpoint to acquire the global lock.
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// Normally, the lock should be released after the work is done.
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// For demonstration purposes, the lock is released after the configured expiry,
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// so that you can check the lock keys in Dragonfly instances.
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http.HandleFunc("/try-to-acquire-global-lock", func(w http.ResponseWriter, r *http.Request) {
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if err := globalMutex.Lock(); err != nil {
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http.Error(w, err.Error(), http.StatusBadRequest)
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return
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}
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w.WriteHeader(http.StatusOK)
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_, _ = w.Write([]byte("lock acquired"))
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})
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if err := http.ListenAndServe(":8080", nil); err != nil {
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panic(err)
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}
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}

‎redlock-go/docker-compose.yml

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version: '3'
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services:
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dragonfly-instance-0:
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container_name: "dragonfly-instance-0"
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image: 'ghcr.io/dragonflydb/dragonfly:v1.14.3-ubuntu'
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ulimits:
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memlock: -1
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ports:
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- "6379:6379"
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dragonfly-instance-1:
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container_name: "dragonfly-instance-1"
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image: 'ghcr.io/dragonflydb/dragonfly:v1.14.3-ubuntu'
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ulimits:
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memlock: -1
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ports:
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- "6380:6379"
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dragonfly-instance-2:
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container_name: "dragonfly-instance-2"
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image: 'ghcr.io/dragonflydb/dragonfly:v1.14.3-ubuntu'
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ulimits:
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memlock: -1
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ports:
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- "6381:6379"
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redlock-service:
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container_name: "redlock-service"
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build:
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context: .
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dockerfile: Dockerfile
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depends_on:
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- dragonfly-instance-0
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- dragonfly-instance-1
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- dragonfly-instance-2
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ports:
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- "8080:8080"

‎redlock-go/go.mod

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module example.com/m/v2
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go 1.20
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require github.com/redis/go-redis/v9 v9.4.0
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require (
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github.com/cespare/xxhash/v2 v2.2.0 // indirect
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github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
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github.com/go-redsync/redsync/v4 v4.11.0 // indirect
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github.com/hashicorp/errwrap v1.1.0 // indirect
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github.com/hashicorp/go-multierror v1.1.1 // indirect
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)

‎redlock-go/go.sum

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github.com/bsm/ginkgo/v2 v2.12.0 h1:Ny8MWAHyOepLGlLKYmXG4IEkioBysk6GpaRTLC8zwWs=
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github.com/bsm/gomega v1.27.10 h1:yeMWxP2pV2fG3FgAODIY8EiRE3dy0aeFYt4l7wh6yKA=
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github.com/cespare/xxhash/v2 v2.2.0 h1:DC2CZ1Ep5Y4k3ZQ899DldepgrayRUGE6BBZ/cd9Cj44=
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github.com/cespare/xxhash/v2 v2.2.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
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github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f h1:lO4WD4F/rVNCu3HqELle0jiPLLBs70cWOduZpkS1E78=
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github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f/go.mod h1:cuUVRXasLTGF7a8hSLbxyZXjz+1KgoB3wDUb6vlszIc=
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github.com/go-redsync/redsync/v4 v4.11.0 h1:OPEcAxHBb95EzfwCKWM93ksOwHd5bTce2BD4+R14N6k=
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github.com/go-redsync/redsync/v4 v4.11.0/go.mod h1:ZfayzutkgeBmEmBlUR3j+rF6kN44UUGtEdfzhBFZTPc=
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github.com/hashicorp/errwrap v1.0.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brvKWEqk/Jc4=
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github.com/hashicorp/errwrap v1.1.0 h1:OxrOeh75EUXMY8TBjag2fzXGZ40LB6IKw45YeGUDY2I=
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github.com/hashicorp/errwrap v1.1.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brvKWEqk/Jc4=
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github.com/hashicorp/go-multierror v1.1.1 h1:H5DkEtf6CXdFp0N0Em5UCwQpXMWke8IA0+lD48awMYo=
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github.com/hashicorp/go-multierror v1.1.1/go.mod h1:iw975J/qwKPdAO1clOe2L8331t/9/fmwbPZ6JB6eMoM=
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github.com/redis/go-redis/v9 v9.4.0 h1:Yzoz33UZw9I/mFhx4MNrB6Fk+XHO1VukNcCa1+lwyKk=
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github.com/redis/go-redis/v9 v9.4.0/go.mod h1:hdY0cQFCN4fnSYT6TkisLufl/4W5UIXyv0b/CLO2V2M=

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