For most blockchain clients it is essential to keep track of transaction nonces that protect against duplicate transactions and replay attacks.

You can read more about nonces here.

Normally, a non-partitioned client application, like your mobile wallet app or MetaMask will easily do this for you, but tracking nonces gets trickier once your application needs to split-brain and run in a distributed fashion. Check MetaMask's nonce-tracker implementation here.

dinonce is a nonce ticketing service which we use at welthee to process transactions(tx) with multiple tx executors, making sure that we avoid:

• double spending
• filling a network's tx pool by having gaps in our nonce sequences

dinonce is designed to support ticketing for multiple nonce sequences in parallel.

An identity on a given blockchain should have it's own sequence of nonces. dinonce defines such a sequence as a lineage.

For each lineage a dinonce client can get a leased nonce ticket for a transcation, and should specify a ticket externalId which should be unique for a transaction for a given lineage. In other words, it should uniquely identify a natural transaction in the calling system.

If the operation succeeds, dinonce will reserve hold a lease for the tx's newly associated nonce.

Since most tx executors (dinonce's clients) operate with an at-least-once semantics, it is possible that the tx will:

• complete (a.k.a will be mined on the blockchain)
• will fail for non-transient reasons

If the tx completes successfully, then the client is expected to close the ticket, marking it unlease-able forever. If the tx fails, the client is expected to notify dinonce to release the ticket. In this case, it should be assigned to the next lease request, and be re-used as soon as possible, to avoid filling node tx pools on the blockchain network.

dinonce is built using a contract first approach with OpenAPI 3.0. The API definition can be found here.

You can generate a client library for the language of your choice using the openapi-generator.

dinonce is packaged as a Docker container and pushed automatically to Docker Hub. If you're interested, check out the Dockerfile that generates the image here.

Since we are fans of both Kubernetes and Terraform we have created a Helm Chart to easy deployment to Kubernetes. The user is responsible to create the ConfigMap dinonce config, which should contain a single config.yaml data entry and have the structure similar to this example.

We like to thing about the services we run as self-contained Terraform projects with clear external dependencies, so we've created a handy Terraform module directory to help with deployments.

Currently there is just one module that you can use, called helm-aws-rds-psql, which will create a managed AWS RDS Aurora PostgreSQL database, create a namespace in kubernetes and deploy the aforementioned Helm Chart to your cluster.

See a usage example here.

dinonce is designed to support multiple storage backends as long as they respect the above described semantics.

The initial backend we are launching is PostgreSQL. If you'd like to implement a new backend, feel free to do so and open a pull request.