Large Payload Service
⚠️ This repository has been open sourced in order to help further discussion in the Temporal community about a proposal for official Temporal large payloads support.
We welcome experimentation and feedback, but please do not use in production. We make no guarantees about backwards compatibility of codecs, the HTTP interface, or storage drivers. If and when the upstream Temporal project includes support for large payloads, this repository will not be maintained.
This repository contains a HTTP service and accompanying Temporal Payload Codec which allows Temporal clients to automatically persist large payloads outside of workflow histories.
Temporal limits payload size to 4MB.
The Large Payload Codec allows Temporal clients to read and write payloads larger than this limit by transparently storing and retrieving them via an HTTP service backed by cloud storage. In essence, the Large Payload Service implements a content addressed storage (CAS) interface for Temporal payloads.
For more details on the motivation, see the talk "Temporal at Datadog" from Replay 2022: https://youtu.be/LxgkAoTSI8Q?t=1686
Usage
This repository does not provide any prebuilt binaries or images.
The recommended approach is to build your own binary and image.
To programmatically build the Large Payload Service, you need to instantiate the driver and then pass it to server.NewHttpHandler
.
For example, to create a Large Payload Service instance backed by an S3 bucket, you would do something along these lines:
package main
import (
"context"
"net/http"
"os"
"github.com/aws/aws-sdk-go-v2/config"
"github.com/DataDog/temporal-large-payload-codec/server"
"github.com/DataDog/temporal-large-payload-codec/server/storage/s3"
...
)
func main() {
region, set := os.LookupEnv("AWS_SDK_REGION")
if !set {
log.Fatal("AWS_REGION environment variable not set")
}
bucket, set := os.LookupEnv("BUCKET")
if !set {
log.Fatal("BUCKET environment variable not set")
}
cfg, err := config.LoadDefaultConfig(context.Background(), config.WithRegion(region))
if err != nil {
log.Fatal(err)
}
driver := s3.New(&s3.Config{
Config: cfg,
Bucket: bucket,
})
mux := http.NewServeMux()
mux.Handle("/", server.NewHttpHandler(driver)))
if err := http.ListenAndServe(":8577", mux); err != nil {
log.Fatal(err)
}
}
On the Temporal side, you need to create the Large Payload Server PayloadCodec
, wrap it in a CodecDataConverter
and pass it to the Temporal client contructor (simplified, without error handling):
opts := client.Options{
...
}
lpsEndpoint, _ := os.LookupEnv("LARGE_PAYLOAD_SERVICE_URL");
lpc, _ := largepayloadcodec.New(largepayloadcodec.WithURL(lpsEndpoint))
opts.DataConverter = converter.NewCodecDataConverter(opts.DataConverter, lpc)
temporalClient, _ := router.NewClient(opts)
Architecture
Architecturally, large payloads are passed through the CodecDataConverter
which in turn uses the large payload codec to en- and decode the payloads.
If the payload size is larger than the configured maximum payload size (default 128KB), the codec will use the Large Payload API to PUT or GET the payload from the Large Payload Service.
flowchart LR
subgraph client["Temporal Client/Worker"]
sdk[Temporal SDK]
codec[[Large Payload<br/>Codec]]
end
subgraph service["Large Payload Service"]
lps[Large Payload<br/>API]
storage[(Cloud Storage)]
end
sdk -- Encode --> codec -. PUT blob .-> lps -. Write blob .-> storage
sdk -- Decode --> codec -. GET blob .-> lps -. Read blob .-> storage
Example Conversion
Given a large input payload where data is larger than 128KB:
{
"metadata": {
"encoding": "text/plain"
},
"data": "..."
}
The large payload codec will encode this payload as follows:
{
"metadata": {
"encoding": "json/plain",
"temporal.io/remote-codec": "v2"
},
"data": {
"metadata": {"encoding": "text/plain"},
"size": 1234567,
"digest": "sha256:deadbeef",
"key": "/blobs/default/sha256:deadbeef"
}
}
- metadata: Original payload's metadata +
temporal.io/remote-codec
metadata header to indicate the use of the remote codec
- size: Size in bytes of data field in original payload
- digest: Digest of data in original payload (for integrity checks)
- key: Key used by the codec retrieve the stored payload
Sequence Diagram for Payload Encoding
sequenceDiagram
autonumber
participant SDK as Temporal SDK
participant Converter as Dataconverter
participant Codec as Large Payload<br/>Codec
participant LPS as Large Payload<br/>Service
participant Storage as Cloud Storage
Note over SDK, Storage: Encoding a Payload
SDK->>+Converter: Serialize Value
Converter->>-SDK: Return Payload
SDK->>+Codec: Encode Payload
Codec->>Codec: Compute payload<br/>length & checksum
Codec->>+LPS: PUT /v2/blobs
LPS->>Storage: Verify checksum<br/>& write blob
LPS->>-Codec: Return blob key
Codec->>-SDK: Return (new) Payload
Sequence Diagram for Payload Decoding
sequenceDiagram
autonumber
participant SDK as Temporal SDK
participant Converter as Dataconverter
participant Codec as Large Payload<br/>Codec
participant LPS as Large Payload<br/>Service
participant Storage as Cloud Storage
Note over SDK, Storage: Decoding a Payload
SDK->>+Codec: Decode Payload
Codec->>+LPS: GET /v2/blobs
LPS->>Storage: Read blob
LPS->>-Codec: Stream blob<br/>bytes
Codec->>Codec: Verify checksum
Codec->>-SDK: Return (original) Payload
SDK->>+Converter: Deserialize Payload
Converter->>-SDK: Return Value
API
The Large Payload Service offers the following API:
-
/v2/health/head
: Health check endpoint using a HEAD
request.
Returns the HTTP response status code 200 if the service is running correctly.
Otherwise, an error code is returned.
-
/v2/blobs/put
: Upload endpoint expecting a PUT
request.
Required headers:
Content-Type
set to application/octet-stream
.
Content-Length
set to the length of payload the data in bytes.
X-Temporal-Metadata
set to the base64 encoded JSON of the Temporal Metadata.
Query parameters:
-
namespace
The Temporal namespace the client using the codec is connected to.
The namespace forms part of the key for retrieval of the payload.
-
digest
Specifies the checksum over the payload data using the format sha256:<sha256_hex_encoded_value>
.
The returned key of the put request needs to be stored and used for later retrieval of the payload.
It is up to the Large Payload Server and the backend driver how to arrange the data in the backing data store.
The server will honor, however, the value of remote-codec/key-prefix
in the Temporal Metadata passed via the X-Temporal-Metadata
header.
It will use the specified string as prefix in the storage path.
-
/v2/blobs/get
: Download endpoint expecting a GET
request.
Required headers:
Content-Type
set to application/octet-stream
.
X-Payload-Expected-Content-Length
set to the expected size of the payload data in bytes.
Query parameters:
key
specifying the key for the payload to retrieve.
Development
Refer to CONTRIBUTING.md for instructions on how to build and test the Large Payload Service and for general contributing guidelines.