Hyperledger Sawtooth

Every devops engineer knows the importance of continuous integration (CI) testing. It’s vital to prevent regressions, as well as maintain performance, security, and supportability. At Bitwise IO, we are experimenting with Kubernetes as an automated CI deployment tool. We like the simplicity of extending tests with deployments on Kubernetes. We think Kubernetes has compelling potential for use in the CI workflow.

Figure 1: The main tools in our CI workflow

This blog post explains how Kubernetes fits into our CI workflow for Hyperledger Sawtooth. We don’t go into detail, but we provide links so you can learn more about Kubernetes and the other tools we use.

Building Sawtooth

Hyperledger Sawtooth uses Jenkins to automate builds of around 20 GitHub repositories. Each new or merged pull request in the master branch initiates a build that contains project-specific tests. The next logical step is to deploy into a test environment.

We have two deployment methods: Debian packages and Docker images. We install the Debian packages inside the Docker deployment image to ensure both that the binaries are tested and that the packages are installable.

Using Docker’s multi-stage build capability, an intermediate build container makes the deployment image smaller and narrows its exposed attack surface (possible vulnerabilities).

Handing off Docker Images with Docker Registry

Jenkins is a great place for build artifacts, but Docker has its own way to easily retrieve images. Docker Registry allows you to push your newly created images and easily retrieve them with Docker, Kubernetes, or anything else that uses the Docker Registry model.

This example shows how to tag an image with the URL of an internal registry, then upload the image to that registry.

$ docker build -f Dockerfile -t registry.url/repo/image_name:${tag} .
$ docker push registry.url/repo/image_name:${tag}

We also use Portus, because Docker Registry does not provide user and access management on its own. The Portus project makes it simple to place an authentication layer over Docker Registry. Now, any authenticated user can pull and deploy the same images that are being deployed into the test environment.

Kubernetes: Simulating Scaled Deployments

Kubernetes excels at creating deployments within and across abstracted infrastructures. We have done our experiments on local (“on-prem”) hardware with a cluster of small Kubernetes nodes dedicated to Sawtooth deployments. Each deployment consists of several pods partitioned in a namespace, which allows us to run multiple networks based on the same deployment file. (Without namespaces, Kubernetes would think we are updating the deployment.) A pod represents a Sawtooth node and contains several containers, each running a specific Sawtooth component: validator, transaction processor, REST API, and so on. Each namespace can have independent quotas for resources such as CPU time, memory, and storage, which prevents a misbehaving network from impacting another network.

Figure 2: Containerized services grouped together in pods.

Because we use Kubernetes, these deployments are portable. We can use them on any cloud infrastructure that supports Kubernetes.

Kubernetes also allows us to scale the number of CI test deployments. With an elastic cloud infrastructure, Kubernetes provides effortless testing on a large number of virtual systems (limited only by the cost of cloud hosting). This solves the issue of limited hardware resources, where each additional deployment will stress existing deployments when they share a node’s resources.

Workload Generation: Deploying Changes Under Load

Deploying Sawtooth is the first step, but you need to give it something to do—better yet, lots to do. Sawtooth includes several workload generators and corresponding transaction processors. In our Kubernetes environment, we deploy intkey_workload and smallbank_workload at rates slightly above what we think the hardware can handle for shorter runs.

Modifying workload rates is as simple as editing the deployment file, changing the rate settings, and reapplying with kubectl. When Kubernetes detects that the pod’s configuration has changed, it terminates the existing workload pod and creates a new one with the changed settings.

This example shows a container definition for an intkey workload pod.

containers:
  - name: sawtooth-intkey-workload
    image: registry.url/repo/sawtooth-intkey-workload:latest
    resources:
      limits:
        memory: "1Gi"
    command:
      - bash
    args:
      - -c
      - |
         intkey-workload \
           --rate 10 \
           --urls ...

Retaining Data with Kubernetes: Logging and Graphing

All this testing isn’t much use if you can’t troubleshoot issues when they arise. Kubernetes can streamline deployments, but it can also frustrate your attempts to gather logs and data embedded inside Docker containers after a pod has failed or stopped. Luckily, Sawtooth provides real-time metrics (which we view with Grafana) and remote logging through syslog. We actively collect logs and metrics from the Sawtooth networks, even down to syslog running on the hardware, then carefully match the logging and metrics artifacts to the testing instance. In the end, we can provide a comprehensive set of log data and system metrics for each code change.

Try It Out!

The Sawtooth documentation can help you get started: See Using Kubernetes for Your Development Environment and Kubernetes: Start a Multiple-node Sawtooth Network.

To configure Grafana, see Using Grafana to Display Sawtooth Metrics.

See these links for more information about each tool in our CI workflow:

• Jenkins
• Docker multi-stage builds
• Docker Registry
• Portus
• Kubernetes basics
• Grafana

About the Authors

Richard Berg is a Senior Systems Engineer at Bitwise IO. He has several years’ experience in sysadmin and devops roles. When not behind a terminal, Richard can be found in the woods with his snow-loving adventure cat.

Ben Betts is a Senior Systems Engineer at Bitwise IO. Ben has lots of experience with deploying, monitoring, coordinating, and supporting large systems and with writing long lists of experiences. He only uses Oxford commas because he has to.

It has been a busy two weeks at Digital Asset… first, we announced that we have open-sourced DAML under the Apache 2.0 license and that the DAML SDK is available to all. Five days later, ISDA (the standards body for the derivatives market) announced DAML as an available smart contract language for their Common Domain Model, and we open-sourced a reference library and application. Next up, we announced that we’ve been working with the team at VMware to integrate DAML with their enterprise blockchain platform, VMware Blockchain.

Today, we’re delighted to share that we have been working with fellow Hyperledger members, Blockchain Technology Partners (BTP), to integrate the DAML runtime with Hyperledger Sawtooth! In this blog post, I’ll describe why we believe it’s important to architect a DLT application independently of the platform, why a new language is needed for smart contracts, and why we are working with BTP to integrate it with Hyperledger Sawtooth.

“Following the recent announcement that DAML has been open-sourced, we are delighted that work is already underway to integrate the DAML runtime with Hyperledger Sawtooth. This demonstrates the power of the open source community to enable collaboration and give developers the freedom required to truly move the industry forward.”

Brian Behlendorf, Executive Director of Hyperledger

One language for multiple platforms

As you all know, the enterprise blockchain space is fairly nascent and highly competitive. There are multiple platforms and protocols battling it out to be the “one true blockchain,” each with their own version of maximalists. Hyperledger alone has six distinct frameworks, each tailored to different needs, making necessary trade-offs to solve different problems. The field is rapidly evolving and we are all learning from the contributions of others to better the industry as a whole. One thing all these platforms have in common: Their purpose is to execute multi-party business processes. The differences arise in how a given platform deals with data representation and privacy, transaction authorization, progressing the state of an agreement, and so on.

And so each platform has its own patterns for writing distributed ledger applications, typically in a general-purpose language such as Java, JavaScript, Kotlin, Go, Python, and C++. The result of this is that developers must pick which framework they want to use and then develop their application specifically for that platform. Their application is now tightly coupled to the underlying architecture of that ledger and if a better alternative arises for their needs, that likely results in a wholesale rewrite.

One of the primary goals of DAML was to decouple smart contracts, the business logic itself, from the ledger by defining an abstraction over implementation details such as data distribution, cryptography, notifications, and the underlying shared store. This provides a clean ledger model accessible via a well specified API. With a mapping between this abstraction layer and the specifics of a given platform, as BTP is developing for Hyperledger Sawtooth, DAML applications can be ported from platform to platform without complex rewrites.

Why do smart contracts need a new language?

DAML’s deep abstraction doesn’t just enable the portability of applications—it greatly improves the productivity of the developer by delivering language-level constructs that deal with boilerplate concerns like signatures, data schemas, and privacy. Blockchain applications are notoriously difficult to get right. Libraries and packages can help improve productivity in some cases, but the application will remain bound to a given platform. Even Solidity, the language of choice for writing to an Ethereum Virtual Machine (EVM), exposes elements of the Ethereum platform directly to the developer. And we’ve seen several examples of how damaging a bug in a smart contract, or even the language itself, can be.

Abstracting away the underlying complexities of blockchains allows you to focus only on the business logic of your project and leave lower-level issues to the platform.

For example, when a contract involves many parties and data types it can be extremely difficult to define fine-grained data permissions in a general-purpose language. DAML allows you to define explicitly in code who is able to see which parts of your model, and who is allowed to perform which updates to it.

As a very simple illustration, consider the model for a cash transfer. DAML’s powerful type system makes it easy to model data schemas—even far more complex schemas than this—directly in the application.

DAML data model

Built-in language elements simplify the specification of which party or parties need to sign a given contract, who can see it, and who is allowed to perform actions on it. These permissions can be specified on a very fine-grained, sub-transaction basis. For example, the issuer of cash does not need to know who owns that currency or what they do with it.

DAML permissions

DAML provides a very clean syntax for describing the actions available on a contract, together with their parameters, assertions, and precise consequences.

DAML business logic

What you won’t find in DAML are low-level, platform-specific concerns like hashing, cryptography, and consensus protocols. You define the rules in DAML, and the runtime enforces the rules that you set out.

If you refer to the examples in the DAML SDK documentation, or the open source code for the set of complete sample applications we’ve provided, you’ll really come to appreciate the full richness of DAML and the simplifying effect it can have on complicated workflows.

Why Hyperledger Sawtooth?

Digital Asset has a long history with Hyperledger, being founding premier members and serving as both the Chairs of the Governing Board and Marketing Committees. In fact, we donated code to the initial implementation of Hyperledger Fabric and the trademark “Hyperledger” itself! I personally worked with Jim Zemlin and team at the Linux Foundation to establish the project and co-founded the company Hyperledger with my colleague Daniel Feichtinger back in early 2014.

We have clearly always believed in the need for an organization such as Hyperledger to exist, to create an open source foundation of common components that can serve as the underlying plumbing for the future of global commerce.

Hyperledger Sawtooth has quickly been emerging as an enterprise-grade platform that exemplifies the umbrella strategy that Brian laid out in his first blog post after joining as executive director. It has an extremely modular architecture that lends itself well to the plug-and-play composability that Hyperledger set out to achieve.

An example of this is that Hyperledger Sawtooth originally only offered support for the Proof of Elapsed Time, or PoET, consensus algorithm; consensus is now a pluggable feature. This modularity is accompanied by a very clean separation of business logic from platform logic, offering developers a degree of ‘future-proofing’ by limiting the amount of code that needs to be changed should a core component such as consensus be replaced.

Modularity also makes Hyperledger Sawtooth very amenable to plugging in new language runtimes. We’ve already seen this in action with Hyperledger Burrow, which integrates an Ethereum Virtual Machine into Hyperledger Sawtooth to support contracts written in Solidity. Incorporating the DAML runtime into Hyperledger Sawtooth similarly enables support for contracts written in DAML as an enterprise-grade alternative to Solidity.

Finally, from a ledger model point of view, many of the Hyperledger Sawtooth characteristics already map well to what DAML expects. Hyperledger Sawtooth’s Transaction Processor has a very flexible approach towards roles and permissions, for example, and is based on a very natural DLT network topology of fully distributed peers. DAML is based on a permissioned architecture and Hyperledger Sawtooth can be configured to be permissioned without requiring special nodes.

What comes next?

Digital Asset and BTP will soon be submitting the DAML Integration to the upstream Hyperledger Sawtooth framework, fully open sourcing our work.

The integration will also be commercially supported by BTP’s blockchain management platform, Sextant, which provides application developers with a cloud-ready instance of Hyperledger Sawtooth. Sextant is already available on the AWS Marketplace for Containers, and DAML support for Sextant will be added in July. BTP expects to support Sextant on other cloud provider support soon thereafter.

BTP is one of Digital Asset’s first partners to use the DAML Integration Toolkit, a new tool designed to enable developers and partners to easily integrate our open source DAML runtime with their own products, immediately offering the benefits of the best in class smart contract language to their end customers. We look forward to any collaboration that brings DAML to even more platforms, including the other frameworks in the Hyperledger family!

To learn more, download the DAML SDK today and start building your applications for Hyperledger Sawtooth!

As interest in Hyperledger Sawtooth grows, robust SDKs continue to be important for helping developers innovate on this blockchain platform. Since mobile is one of the most popular application platforms, it is crucial to extend Sawtooth to support native iOS and Android application development.

Additionally, the introduction of Hyperledger Grid has expanded the possibility of supply chain products for the Sawtooth platform. Many of these uses are well suited to mobile clients, allowing on-site professionals at manufacturing or logistics facilities to interact with a Sawtooth application.

This blog post describes the first native mobile client applications for Hyperledger Sawtooth, which we have developed using the Sawtooth Java SDK as well as a new Sawtooth Swift SDK. These first example applications showcase a client for the XO transaction processor that, although simple, opens up possibilities for Sawtooth mobile applications moving forward.

Sawtooth Java and Swift SDKs

The Sawtooth Java SDK is already familiar to many Hyperledger Sawtooth developers; no changes are needed to make it compatible with an Android project. The SDK works similarly in Java-native projects or in Android projects in Java or Kotlin. The Sawtooth Java SDK documentation describes how to import the SDK into an Android project and includes example code for writing a client application in Kotlin.

The new Sawtooth Swift SDK supports iOS applications on the Hyperledger Sawtooth platform and provides a way for an application to sign transactions before submitting them to the blockchain. This SDK implements the same functionality present in other Sawtooth SDKs. Cocoa/Cocoa Touch projects can import the SawtoothSigning framework via Carthage, an iOS dependency manager. The Sawtooth Swift documentation includes instructions for using the SawtoothSigning framework.

Example XO Mobile Apps

Our example mobile applications use the XO transaction processor, which allows two users to play tic-tac-toe on the blockchain. (For the details of XO, see the XO CLI tutorial and transaction family specification.)

Both applications implement most of the functionality from the XO transaction processor. The applications open to a landing screen with tabs to navigate between games to play, games to watch, and finished games.

The Play tab lists the current games that a user is able to join. In the following figures, the iOS example (using Swift) is on the left, and the Android example (using Kotlin) is on the right.

 .                        

Figure 1. Play screen

The Create Game screen lets the user enter a unique name for a new game. The new game will appear on the Play screen once this transaction has been successfully submitted.

                         

Figure 2. Create Game screen

The Game Board screen allows the user to submit their moves, with Player 1 as ‘X’ and Player 2 as ‘O’.

                         

Figure 3. New game board (iOS) and finished game board (Android).

Running the Sawtooth Mobile Apps

If you want to try out these apps, you can find them in the Sawtooth Java SDK and Sawtooth Swift SDK repositories.

1. Check out the repositories and open the project on Android Studio or Xcode to run the apps on a simulator or on your device.
2. The application needs to communicate with a Sawtooth validator connected to an XO transaction processor. To start a local Docker network with the validator, XO transaction processor, and Sawtooth REST API, run docker-compose up in the examples/xo_ios folder in the Sawtooth Swift SDK project or examples/xo_android_client in the Sawtooth Java SDK. This will allow your application to send transactions to the validator.

Further Development

We have proposed a new Sawtooth Swift SDK, using the Hyperledger Sawtooth Request for Comments (RFC) process. Once that process is completed, a new GitHub Hyperledger repository will host the Sawtooth Swift SDK. We have already implemented part of that SDK and will contribute the code to the Hyperledger repository once the RFC has been approved. At this moment, the only framework available with the SDK is SawtoothSigning, which can be used to sign create private/public key pairs and sign transactions. In the future, we plan to implement a framework help generate Sawtooth protobuf messages.

Summary

Native mobile applications are a logical step for Hyperledger Sawtooth development. With projects such as Hyperledger Grid encouraging a larger suite of technologies to be used for supply chain solutions, flexibility in the interactions with the Hyperledger Sawtooth platform is critical. Native mobile applications make interactions with Hyperledger Sawtooth more convenient and comfortable.

The Sawtooth Java and Swift SDKs, along with the example XO client application, provide a solid foundation for getting Sawtooth mobile. Using the Sawtooth Java SDK and a new Sawtooth Swift SDK, native mobile applications allow developers and users to unlock the full potential of Sawtooth applications wherever they go.

Want to Learn More?

To learn more about mobile development in Sawtooth, see the source code and the documentation in the Sawtooth Java SDK and Sawtooth Swift SDK git repositories. These repositories include the source code for the example XO client and documentation with details on how to import the modules and how to use the SDKs to write clients.

You can also join the Sawtooth SDK development community in the #sawtooth-sdk-dev channel on chat.hyperledger.org.

About the Authors

Darian Plumb (Senior Software Engineer), Eloá Verona (Software Engineer) and Shannyn Telander (Software Engineer) work on Hyperledger Sawtooth projects at Bitwise IO. They recently worked together on the first venture into native mobile applications for Hyperledger Sawtooth.