Verdi

A framework for formally verifying distributed systems implementations in Coq.

Requirements

Framework:

• Coq (8.7 or later)
• StructTact
• InfSeqExt
• Cheerios

Runtime:

• OCaml 4.02.3 (or later)
• verdi-runtime

Building

We recommend installing Verdi via OPAM, which will automatically build and install its dependencies:

opam repo add coq-extra-dev https://coq.inria.fr/opam/extra-dev
opam install coq-verdi

To build Verdi manually, it is a good idea to first consult the opam file for exact requirements.

Then, run ./configure in the Verdi root directory. This will check for the appropriate version of Coq and ensure all necessary dependencies can be located. By default, the script assumes that StructTact, InfSeqExt, and Cheerios are installed in Coq's user-contrib directory, but this can be overridden by setting the StructTact_PATH, InfSeqExt_PATH, and Cheerios_PATH environment variables.

Finally, run make in the Verdi root directory. This will compile the framework's core specifications and proofs, as well as some simple example systems and their correctness proofs.

Runtime Library

To run Verdi systems on real hardware, event handler code must be extracted to OCaml and linked with one of the shims in the Verdi runtime library that handles low-level network communication.

To install the runtime library via OPAM, use the following commands:

opam repo add distributedcomponents-dev http://opam-dev.distributedcomponents.net
opam install verdi-runtime

Getting Started

To set up your own Verdi-based distributed systems verification project, we recommend basing it on Verdi LockServ.

Verdi LockServ contains a minimalistic implementation of a message-passing lock server and a proof that it maintains mutual exclusion between client nodes. At build time, extracted OCaml code is linked to a runtime library shim to produce an executable program that can be run in a cluster. There is also a simple script to interface with cluster nodes.

Documentation

In addition to the example verified systems listed below, see the scientific papers and blog posts listed at the Verdi website.

Files

• Core Verdi files:
  • Verdi.v: exporting of core Verdi theories, imported by systems
  • Net.v: core (unlabeled) network semantics
  • LabeledNet.v: labeled network semantics, for use in liveness reasoning
  • HandlerMonad.v: a monad for writing network/input handlers
  • StatePacketPacket.v: a technique for writing easily decomposable invariants
• Example systems:
  • Counter.v: counting server with backup
  • LockServ.v: lock server with proof of safety
  • LiveLockServ.v: lock server with proof of liveness
  • VarD.v: vard, a key-value store
• Verified system transformers:
  • SeqNum.v and SeqNumCorrect.v, a system transformer implementing sequence numbering
    • LockServSeqNum.v, the sequence numbering transformer applied to the lock server
  • PrimaryBackup.v, a system transformer implementing asynchronous primary-backup replication
    • VarDPrimaryBackup.v, the primary-backup transformer applied to the key-value store

Projects using Verdi

• Verdi Raft: a verified implementation of the Raft distributed consensus protocol