[Libguestfs] ANNOUNCE: nbdkit 1.18 - high performance NBD server

I'm pleased to announce the release of nbdkit 1.18, a high performance plugin-based Network Block Device (NBD) server. Key features of nbdkit: * Multithreaded NBD server written in C with good performance. * Minimal dependencies for the basic server. * Liberal license (BSD) allows nbdkit to be linked to proprietary libraries or included in proprietary code. * Well-documented, simple plugin API with a stable ABI guarantee. Lets you export “unconventional” block devices easily. * You can write plugins in C, Lua, Perl, Python, OCaml, Ruby, Rust, shell script or Tcl. * Filters can be stacked in front of plugins to transform the output. Git: https://github.com/libguestfs/nbdkit Download: http://download.libguestfs.org/nbdkit/1.18-stable/ Fedora: https://koji.fedoraproject.org/koji/packageinfo?packageID=16469 Rich. Release notes (http://libguestfs.org/nbdkit-release-notes-1.18.1.html) These are the release notes for nbdkit stable release 1.18. This describes the major changes since 1.16. nbdkit 1.18.0 was released on 27th February 2020. Security There were no security issues found. All past security issues and information about how to report new ones can be found in nbdkit-security(1). Plugins New nbdkit-eval-plugin(1) lets you write a plugin entirely on a single command line. It is similar to nbdkit-sh-plugin(3). nbdkit-ext2-plugin(1) is deprecated and will be removed in the next release after this one (nbdkit 1.20). As a replacement use nbdkit-ext2-filter(1) like this: nbdkit --filter=ext2 file fs.img ext2file=/disks/disk.raw nbdkit-python-plugin(3) now offers a version 2 API which avoids copying the data buffer, improving performance. The original protocol (now retrospectively called version 1) is still supported for backwards compatibility. The version 1 protocol was also enhanced to support the buffer protocol for the pread method, and memoryview for pwrite, improving performance by reducing copies (Nir Soffer). The Python plugin now prints readable stack traces when an exception is thrown (Nir Soffer). New methods implemented in the Python plugin: cache, can_cache, can_zero, can_fast_zero, can_multi_conn, can_fua. In nbdkit-curl-plugin(1), new options "cainfo" and "capath" (Wiktor Gołgowski). nbdkit-split-plugin(1) now supports extents (Eric Blake). In nbdkit-vddk-plugin(1), "file=" is now a magic config key, meaning it can be omitted in most circumstances (Eric Blake). The VDDK plugin now no longer needs $LD_LIBRARY_PATH to be set. The correct library load path is automatically inferred from the "libdir" parameter (Eric Blake). Verbose messages about calls to VDDK functions Read and Write can now be suppressed by setting -D vddk.datapath=0. Filters New nbdkit-ext2-filter(1), which replaces the deprecated nbdkit-ext2-plugin. This filter allows you to read and write files inside ext2, ext3 or ext4 filesystems. The new filter has the same features as the plugin, and one enhancement: optionally the name of the file to serve can be picked from the client-supplied exportname. The old plugin will be removed in nbdkit 1.20 (Eric Blake). New nbdkit-extentlist-filter(1) lets you specify a static list of extents from a file which can be placed on top of plugins which don't export extent information. New nbdkit-ip-filter(1) lets you allow and deny incoming connections by client IP address, similar to TCP wrappers or a firewall. New nbdkit-nofilter-filter(1) is a null filter, used for testing. The stats filter now collects time elapsed per operation, per operation and total rates, and adds stats for the flush method. The output is shown in human sizes making it easier to understand. (Nir Soffer). Server New --swap option which allows nbdkit to be safely used to serve swap space to the same machine. Debug flags (-D) can now be applied to the server core (using -D nbdkit.*). Underscores in debug flags can now be replaced by dots, allowing a kind of namespacing. Debug flags which are not consumed now no longer give an error, so you can use them without needing to detect if the plugin supports them. New server debug flags -D nbdkit.backend.controlpath=0 and -D nbdkit.backend.datapath=0 were added to suppress some very verbose messages when verbose mode is enabled. API There is a new ".get_ready" method which is called after ".config_complete" and before the server forks or changes directory. It is the last chance to do any global preparation that is needed to serve connections. Plugins have previously done this work in ".config_complete", but by splitting this into a new method it makes the API clearer. (Note that existing plugins may continue to use ".config_complete" for this work if they prefer.) There is a new ".preconnect" method available which is called just after the client makes a connection but before any NBD negotiation or TLS authentication is done. It can be used for early whitelisting or rate limiting of connections, and in particular is used by the new nbdkit-ip-filter(1). Bug fixes In nbdkit-curl-plugin(1), "CURLINFO_CONTENT_LENGTH_DOWNLOAD_T" is used (if available) so that file sizes up to 63 bits should now work on all platforms (Pino Toscano and Adrian Ambrożewicz). nbdkit is now compatible with OCaml 4.10. nbdkit-memory-plugin(1) now supports "size=0" (Eric Blake). Documentation Plugins which were actually added in nbdkit 1.0.0 are now documented as such properly. Improved methods for probing plugins and filters are documented in nbdkit-probing(1). Tests Old plugins from nbdkit 1.0, 1.2, 1.8 and 1.12 are now bundled with the nbdkit sources and tested to try to ensure that they do not accidentally regress. Note these are included as binary blobs. See tests/old-plugins/README for more information about this, including how to delete these tests. Various tests, especially ones which rely on timeouts, have been made more stable so they should not fail on slow or overloaded machines. Many tests now use libnbd and nbdsh (instead of libguestfs and guestfish) as the test client. This should improve the performance of the tests for most people. The --vsock option (added in nbdkit 1.16) can now be tested if the host is running Linux ≥ 5.6 (Stefano Garzarella). Build You can use "./configure --disable-nbd-plugin" to completely disable the NBD plugin. The automake feature "subdir-objects" is no longer used, which may improve compatibility on platforms with ancient and buggy automake (RHEL 7 being one such platform). Internals The explicit connection parameter passed around many functions in the server is now fetched from thread-local storage. The server no longer calls the finalize method if prepare fails. Also failing to reopen the plugin from nbdkit-retry-filter(1) no longer hangs (Eric Blake). "git.orderfile" was enhanced to make patches easier to read (Eric Blake). Internal calls to methods like get_size, can_write will now no longer produce debug messages if the data is simply being returned from the internal cache (but calls into the plugin are still logged). SEE ALSO nbdkit(1). AUTHORS Authors of nbdkit 1.18: Adrian Ambrożewicz (1 commit) Eric Blake (30 commits) Wiktor Gołgowski (1 commit) Richard W.M. Jones (130 commits) Nir Soffer (11 commits) Pino Toscano (1 commit) -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-builder quickly builds VMs from scratch http://libguestfs.org/virt-builder.1.html