This project evaluates nix attributes sets in parallel with a streamable json output. This is useful for time and memory-intensive evaluations such as nixos machines i.e. in a CI context. Evaluation happens with a controlable number of threads that are restarted if their memory consumption grows beyond a threshold.
For ease of integration nix-eval-jobs creates garbage collection roots for each evaluated derivation (drv file not the build) inside the supplied attribute. This prevent race conditions between nix garbage collection service and nix builds processes started by the user.
- Faster evaluation due the use of threads
- Memory used for evaluation is reclaimed after nix-eval-jobs is finished so that the build can use it.
- Evaluation of jobs can fail individually
In the following example we evaluate the hydraJobs attribute of the patchelf flake:
$ nix-eval-jobs --gc-roots-dir $(pwd)/gcroot --flake 'github:NixOS/patchelf#hydraJobs'
{"attr":"build-sanitized-clang.aarch64-linux","drvPath":"/nix/store/361mr6bzzwcv65sp0bhbakaa21fj4p1b-patchelf-0.13.20210926.18a389b.drv","name":"patchelf-0.13.20210926.18a389b","system":"x86_64-linux"}
{"attr":"build-sanitized-clang.i686-linux","drvPath":"/nix/store/ial7z46jy8kivmq5dz6f9vqr0b70jqkd-patchelf-0.13.20210926.18a389b.drv","name":"patchelf-0.13.20210926.18a389b","system":"x86_64-linux"}
{"attr":"build-sanitized-clang.x86_64-linux","drvPath":"/nix/store/h2m3k085m21gd3cxc4n1wzhcjv3iap9m-patchelf-0.13.20210926.18a389b.drv","name":"patchelf-0.13.20210926.18a389b","system":"x86_64-linux"}
{"attr":"build-sanitized.aarch64-linux","drvPath":"/nix/store/m9jl25lcwvdk8rz79ibzd55wqfaxhdxx-patchelf-0.13.20210926.18a389b.drv","name":"patchelf-0.13.20210926.18a389b","system":"aarch64-linux"}
{"attr":"build-sanitized.i686-linux","drvPath":"/nix/store/0njjscgha4smzd9qsi4839pbsyqs18zl-patchelf-0.13.20210926.18a389b.drv","name":"patchelf-0.13.20210926.18a389b","system":"i686-linux"}
{"attr":"build-sanitized.x86_64-linux","drvPath":"/nix/store/cp8z7idqzf2cvfj9lzyr3xqll26bbz76-patchelf-0.13.20210926.18a389b.drv","name":"patchelf-0.13.20210926.18a389b","system":"x86_64-linux"}
{"attr":"build.aarch64-linux","drvPath":"/nix/store/rsgwdq3503ibln8hwilbl8ifjhrlb9mv-patchelf-0.13.20210926.18a389b.drv","name":"patchelf-0.13.20210926.18a389b","system":"aarch64-linux"}
{"attr":"build.i686-linux","drvPath":"/nix/store/l5k6ma3lrb2rmbw50s8s8x4c4wvj35s7-patchelf-0.13.20210926.18a389b.drv","name":"patchelf-0.13.20210926.18a389b","system":"i686-linux"}
{"attr":"build.x86_64-linux","drvPath":"/nix/store/lmhpwvj4y9ypz5rgp0y1jbw2vqryc80l-patchelf-0.13.20210926.18a389b.drv","name":"patchelf-0.13.20210926.18a389b","system":"x86_64-linux"}
{"attr":"coverage","drvPath":"/nix/store/hlh7x41c2nnklbnhrc41wm2rir0l3zq3-patchelf-coverage-0.13.20210926.18a389b.drv","name":"patchelf-coverage-0.13.20210926.18a389b","system":"x86_64-linux"}
{"attr":"release","drvPath":"/nix/store/b1jfn3pjdhq1ds4d52sj8k2z33lmb3jk-patchelf-0.13.20210926.18a389b.drv","name":"patchelf-0.13.20210926.18a389b","system":"x86_64-linux"}
{"attr":"tarball","drvPath":"/nix/store/jcharij3ylh36hvszb48j2pzjas9hmx1-patchelf-tarball-0.13.20210926.18a389b.drv","name":"patchelf-tarball-0.13.20210926.18a389b","system":"x86_64-linux"}The output here newline-seperated json according to https://jsonlines.org/
The code is derived from hydra's eval-jobs executable.
$ nix-eval-jobs --help
USAGE: nix-eval-jobs [options] expr
--arg Pass the value *expr* as the argument *name* to Nix functions.
--argstr Pass the string *string* as the argument *name* to Nix functions.
--debug Set the logging verbosity level to 'debug'.
--eval-store The Nix store to use for evaluations.
--flake build a flake
--gc-roots-dir garbage collector roots directory
--help show usage information
--impure set evaluation mode
--include Add *path* to the list of locations used to look up `<...>` file names.
--log-format Set the format of log output; one of `raw`, `internal-json`, `bar` or `bar-with-logs`.
--max-memory-size maximum evaluation memory size
--meta include derivation meta field in output
--option Set the Nix configuration setting *name* to *value* (overriding `nix.conf`).
--override-flake Override the flake registries, redirecting *original-ref* to *resolved-ref*.
--quiet Decrease the logging verbosity level.
--verbose Increase the logging verbosity level.
--workers number of evaluate workersFaster evaluator in deployment tools. When evaluating nixos machines evaluation can take several minutes when performed on a single core. This limits the scalability for large deployment with deployment tools such as NixOps. Faster evaluator in CI. In addition to evaluation speed for CIs it is also useful if evaluation of individual jobs can fail in CIs in contrast to failing the whole jobset. Furthermore for CIs that allow to create dynamic build steps, one can leverage the fact that nix-eval-jobs outputs derivation path seperatly. This allows to have seperate logs and success status per job rather than one big log file.