konserve-s3

A backend for konserve that supports Amazon S3 and any S3-compatible storage API.

Usage

Add to your dependencies:

Configuration

(require '[konserve-s3.core]  ;; Registers the :s3 backend
         '[konserve.core :as k])

(def config
  {:backend :s3
   :region "us-west-1"
   :bucket "my-bucket"
   :id #uuid "550e8400-e29b-41d4-a716-446655440000"
   ;; Optional:
   :access-key "your-access-key"
   :secret "your-secret"
   :endpoint-override {:protocol :https
                       :hostname "fly.storage.tigris.dev"}
   :x-ray? false})

(def store (k/create-store config {:sync? true}))

For API usage (assoc-in, get-in, delete-store, etc.), see the konserve documentation.

Multiple Stores in Same Bucket

S3 supports multiple independent stores within the same bucket by using different :id values:

;; Store 1
(def store1-config
  {:backend :s3
   :region "us-west-1"
   :bucket "my-bucket"
   :id #uuid "11111111-1111-1111-1111-111111111111"})

;; Store 2 - same bucket, different ID
(def store2-config
  {:backend :s3
   :region "us-west-1"
   :bucket "my-bucket"
   :id #uuid "22222222-2222-2222-2222-222222222222"})

(def store1 (k/create-store store1-config {:sync? true}))
(def store2 (k/create-store store2-config {:sync? true}))

;; Each store maintains its own isolated namespace within the bucket

Listing Stores in a Bucket

You can discover all konserve stores in a bucket using list-stores:

(require '[konserve-s3.core :as s3])

;; List all store IDs in a bucket
(def bucket-config
  {:region "us-west-1"
   :bucket "my-bucket"})

(s3/list-stores bucket-config :opts {:sync? true})
;; => #{#uuid "11111111-1111-1111-1111-111111111111"
;;      #uuid "22222222-2222-2222-2222-222222222222"}

Optimistic Locking for Distributed Updates

konserve-s3 supports optimistic concurrency control using S3's ETag-based conditional writes. This enables safe concurrent updates from multiple machines without distributed locks.

;; Enable optimistic locking with up to 10 retries on conflict
(def config
  {:backend :s3
   :region "us-west-1"
   :bucket "my-bucket"
   :id #uuid "550e8400-e29b-41d4-a716-446655440000"
   :config {:optimistic-locking-retries 10}})

(def store (k/create-store config {:sync? true}))

;; Now update-in is safe across multiple machines!
;; Each machine can run this concurrently:
(k/update-in store [:counter] (fnil inc 0) {:sync? true})

How it works:

1. When reading a key, konserve-s3 captures the object's ETag (a hash of the content)
2. When writing, it uses S3's If-Match header with the captured ETag
3. If another process modified the object, S3 returns HTTP 412 (Precondition Failed)
4. konserve automatically retries: re-reads the new value, re-applies your update function, and writes again
5. This continues until the write succeeds or max retries is exceeded

This is particularly useful for:

• Counters and metrics aggregation across distributed workers
• Shared configuration that multiple services update
• Any read-modify-write pattern in distributed systems

Note: Without optimistic locking enabled, concurrent update-in calls from different machines may lose updates (last-write-wins). With optimistic locking, all updates are preserved through automatic retry.

Notes

Note that you do not need full S3 rights if you manage the bucket outside, i.e. create it before and delete it after usage form a privileged account. Connection will otherwise create a bucket and all files created by konserve (with suffix ".ksv", ".ksv.new" or ".ksv.backup") will be deleted by delete-store, but the bucket needs to be separately deleted by delete-bucket. You can activate Amazon X-Ray by setting :x-ray? to true in the S3 spec.

Authentication

A common approach to manage AWS credentials is to put them into the environment variables as AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY to avoid storing them in plain text or code files. Alternatively you can provide the credentials in the s3-spec as :access-key and :secret.

License

Copyright © 2023-2026 Christian Weilbach

Licensed under Eclipse Public License (see LICENSE).