Validate XML against XML Schema using Rust

Prerequisites

Cargo for Rust is required.

libxml2 needs to be installed.

Installation

$ cargo install --path .

will install validate-xml into $HOME/.cargo/bin.

Usage

Basic usage:

$ validate-xml root_dir 2> log.txt

Detailed usage:

$ validate-xml --help
Validate XML files concurrently and downloading remote XML Schemas only once.

Usage:
  validate-xml [--extension=<extension>] <dir>
  validate-xml (-h | --help)
  validate-xml --version

Options:
  -h --help                Show this screen.
  --version                Show version.
  --extension=<extension>  File extension of XML files [default: cmdi].

Performance

This was written to be super fast:

• Concurrency, using number of cores available.
• Use of C FFI with libxml2 library.
• Downloading of remote XML Schema files only once per run, and caching to memory.
• Caching of libxml2 schema data structure for reuse in multiple concurrent parses.

On my machine, it takes a few seconds to validate a sample set of 20,000 XML files. This is hundreds of times faster than the first attempt, which was a shell script that sequentially runs xmllint (after first pre-downloading remote XML Schema files and passing the local files to xmllint with --schema). The concurrency is a big win, as is the reuse of the libxml2 schema data structure across threads and avoiding having to spawn xmllint as a heavyweight process.

Comparison

If I had known about Python's lxml binding to C libxml2, I might not have bothered this Rust program. I found out about it and wrote the Python version of this program, which looks very similar (but without all the types): https://github.com/FranklinChen/validate-xml-python

However, as the Rust ecosystem fills in gaps in available libraries, I think I would actually be pretty happy to write in Rust instead of Python.