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Massimiliano Culpo authored
This fixes a fork bomb in `spack versions`. Recursive generation of pools
to scrape URLs in `_spider` was creating large numbers of processes.
Instead of recursively creating process pools, we now use a single
`ThreadPool` with a concurrency limit.

More on the issue: having ~10 users running at the same time spack
versions on front-end nodes caused kernel lockup due to the high number
of sockets opened (sys-admin reports ~210k distributed over 3 nodes).
Users were internal, so they had ulimit -n set to ~70k.

The forking behavior could be observed by just running:

    $ spack versions boost

and checking the number of processes spawned. Number of processes
per se was not the issue, but each one of them opens a socket
which can stress `iptables`.

In the original issue the kernel watchdog was reporting:

    Message from syslogd@login03 at May 19 12:01:30 ...
    kernel:Watchdog CPU:110 Hard LOCKUP
    Message from syslogd@login03 at May 19 12:01:31 ...
    kernel:watchdog: BUG: soft lockup - CPU#110 stuck for 23s! [python3:2756]
    Message from syslogd@login03 at May 19 12:01:31 ...
    kernel:watchdog: BUG: soft lockup - CPU#94 stuck for 22s! [iptables:5603]
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Spack Spack

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Spack is a multi-platform package manager that builds and installs multiple versions and configurations of software. It works on Linux, macOS, and many supercomputers. Spack is non-destructive: installing a new version of a package does not break existing installations, so many configurations of the same package can coexist.

Spack offers a simple "spec" syntax that allows users to specify versions and configuration options. Package files are written in pure Python, and specs allow package authors to write a single script for many different builds of the same package. With Spack, you can build your software all the ways you want to.

See the Feature Overview for examples and highlights.

To install spack and your first package, make sure you have Python. Then:

$ git clone https://github.com/spack/spack.git
$ cd spack/bin
$ ./spack install zlib

Documentation

Full documentation is available, or run spack help or spack help --all.

Tutorial

We maintain a hands-on tutorial. It covers basic to advanced usage, packaging, developer features, and large HPC deployments. You can do all of the exercises on your own laptop using a Docker container.

Feel free to use these materials to teach users at your organization about Spack.

Community

Spack is an open source project. Questions, discussion, and contributions are welcome. Contributions can be anything from new packages to bugfixes, documentation, or even new core features.

Resources:

Contributing

Contributing to Spack is relatively easy. Just send us a pull request. When you send your request, make develop the destination branch on the Spack repository.

Your PR must pass Spack's unit tests and documentation tests, and must be PEP 8 compliant. We enforce these guidelines with Travis CI. To run these tests locally, and for helpful tips on git, see our Contribution Guide.

Spack uses a rough approximation of the Git Flow branching model. The develop branch contains the latest contributions, and master is always tagged and points to the latest stable release.

Code of Conduct

Please note that Spack has a Code of Conduct. By participating in the Spack community, you agree to abide by its rules.

Authors

Many thanks go to Spack's contributors.

Spack was created by Todd Gamblin, tgamblin@llnl.gov.

Citing Spack

If you are referencing Spack in a publication, please cite the following paper:

License

Spack is distributed under the terms of both the MIT license and the Apache License (Version 2.0). Users may choose either license, at their option.

All new contributions must be made under both the MIT and Apache-2.0 licenses.

See LICENSE-MIT, LICENSE-APACHE, COPYRIGHT, and NOTICE for details.

SPDX-License-Identifier: (Apache-2.0 OR MIT)

LLNL-CODE-647188