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Version: 2.0.x

S3 Connector


libraryDependencies += "dev.zio" %% "zio-connect-s3" % "0.4.4"

How to use it?

All available S3Connector combinators and operations are available in the package object zio.connect.s3, you only need to import zio.connect.s3._

First, you must configure the underlying S3 connection provided by zio-aws you can read more about how to configure it here If you have default credentials in the system environment typically at ~/.aws/credentials or as env variables the following configuration will likely work.

import zio._
import zio.connect.s3._

lazy val zioAwsConfig = NettyHttpClient.default >>> AwsConfig.default

Now let's create a bucket:

val bucketName = BucketName("this-very-charming-bucket-name") // BucketName is a zio prelude newtype of String

val program1: ZIO[S3Connector, S3Exception, Unit] =
for {
_ <- ZStream(bucketName) >>> createBucket
} yield ()

The way to understand this is to recognize that createBucket is a ZSink that expects elements of type BucketName as its streamed input. In this case we have a ZStream with a single element of type BucketName but we could have an arbitrary number of buckets and the code would look and work virtually the same.

Okay, let's put some readable bytes into that bucket:

val objectKey = ObjectKey("my-object") // ObjectKey is a zio prelude newtype of String

val program2: ZIO[S3Connector, S3Exception, Unit] =
for {
content <- Random.nextString(100).map(_.getBytes).map(Chunk.fromArray)
_ <- ZStream.fromChunk(content) >>> putObject(bucketName, objectKey)
} yield ()

Here a stream of chunks of bytes are streamed into the putObject sink. The sink takes two arguments, the bucket name and the object key to associate with the data being streamed in.

Let's list objects in the bucket:

val program3: ZIO[S3Connector, S3Exception, Chunk[ObjectKey]] =
for {
keys <- listObjects(bucketName).runCollect
} yield keys

listObjects is a ZStream that emits elements of type ObjectKey and we can use the runCollect operator to collect all the elements into a Chunk.

Here's what it looks like to get an object put earlier:

val program5: ZIO[S3Connector, Object, String] =
for {
content <- getObject(bucketName, objectKey) >>> ZPipeline.utf8Decode >>> ZSink.mkString
} yield content

Finally, let's look at how to run one of these programs:

def run = program1.provide(zioAwsConfig,, s3ConnectorLiveLayer)

You need to provide the configuration layer for zio-aws, the S3 layer from zio-aws and the s3ConnectorLiveLayer which is the live implementation of the S3Connector interface.

Test / Stub

A stub implementation of S3Connector is provided for testing purposes via the TestS3Connector.layer. It uses internally an TRef[Map[BucketName, S3Bucket]] instead of talking to S3. You can create the test harness as follows:

import zio.connect.s3._

object MyTestSpec extends ZIOSpecDefault {

override def spec =


Operators & Examples

The following operators are available:


Copy an object from one bucket to another

ZStream(CopyObject(bucket1, objectKey, bucket2)) >>> copyObject


Creates S3 buckets

ZStream(bucketName1, bucketName2) >>> createBucket


Deletes empty S3 buckets

ZStream(bucketName1, bucketName2) >>> deleteEmptyBucket

The buckets must be empty, if they are not you will get an BucketsNotEmptyException from S3


Deletes objects from an S3 bucket

ZStream(objectKey1, objectKey2) >>> deleteObjects(bucketName)

Does not result in an error, if object keys do not exist


Checks if a bucket exists

ZStream(bucketName1, bucketName2) >>> existsBucket


Checks if an object exists in an s3 bucket

ZStream(objectKey1, objectKey2) >>> existsObject(bucketName)

It expects the bucket to exist and will return a NoSuchBucketException if the bucket does not


Gets an object from an S3 bucket

getObject(bucket2, objectKey) >>> ZPipeline.utf8Decode >>> ZSink.mkString

You will receive the objects as a stream of bytes, parsing/decoding of course depends on the object contents. The example here assumes you have a stream of utf-8 encoded bytes and you want to decode them into a string.


Lists all buckets in the account

listBuckets >>> ZSink.collectAll

Currently, gets ALL buckets, there is no pagination support yet. You may want to use some other ZStream combinators to filter the lists prior to collecting bucket names


Lists all objects keys in a bucket takes a BucketName as an argument

listObjects(bucketName) >>> ZSink.collectAll

Currently, gets ALL objects in the bucket, there is no pagination support yet. You may want to use some other ZStream combinators to filter the lists prior to collecting object keys


Move an object from one bucket to another

ZStream(MoveObject(sourceBucket, sourceKey, targetBucket, targetKey)) >>> moveObject

The sourceBucket, sourceKey, and targetBucket must exist. If the targetKey exists, it will be overwritten.


Puts an object into an S3 bucket

ZStream.fromChunk(content) >>> putObject(bucketName, objectKey)

Expects as stream of bytes, returns a Unit if successful.