snix/nix/buildkite/default.nix
Ilan Joselevich 91d02d8c84 style: Switch to nixfmt from nixpkgs-fmt
Most of the ecosystem has moved to this formatter,
and many people configured their editors to autoformat it with this formatter.

Closes: https://git.snix.dev/snix/snix/issues/62
Change-Id: Icf39e7836c91fc2ae49fbe22a40a639105bfb0bd
Reviewed-on: https://cl.snix.dev/c/snix/+/30671
Reviewed-by: Florian Klink <flokli@flokli.de>
Tested-by: besadii
Autosubmit: Ilan Joselevich <personal@ilanjoselevich.com>
2025-08-10 13:40:23 +00:00

552 lines
19 KiB
Nix

# Logic for generating Buildkite pipelines from Nix build targets read
# by //nix/readTree.
#
# It outputs a "YAML" (actually JSON) file which is evaluated and
# submitted to Buildkite at the start of each build.
#
# The structure of the file that is being created is documented here:
# https://buildkite.com/docs/pipelines/defining-steps
{ depot, pkgs, ... }:
let
inherit (builtins)
attrValues
concatLists
concatStringsSep
elem
foldl'
hasAttr
hashString
isString
length
listToAttrs
mapAttrs
toJSON
unsafeDiscardStringContext
;
inherit (pkgs) lib runCommand writeText;
inherit (depot.nix.readTree) mkLabel;
inherit (depot.nix) dependency-analyzer;
in
rec {
# Create a unique key for the buildkite pipeline based on the given derivation
# or drvPath. A consequence of using such keys is that every derivation may
# only be exposed as a single, unique step in the pipeline.
keyForDrv =
drvOrPath:
let
drvPath =
if lib.isDerivation drvOrPath then
drvOrPath.drvPath
else if lib.isString drvOrPath then
drvOrPath
else
builtins.throw "keyForDrv: expected string or derivation";
# Only use the drv hash to prevent escaping problems. Buildkite also has a
# limit of 100 characters on keys.
in
"drv-" + (builtins.substring 0 32 (builtins.baseNameOf (unsafeDiscardStringContext drvPath)));
# Given an arbitrary attribute path generate a Nix expression which obtains
# this from the root of depot (assumed to be ./.). Attributes may be any
# Nix strings suitable as attribute names, not just Nix literal-safe strings.
mkBuildExpr =
attrPath:
let
descend = expr: attr: "builtins.getAttr \"${attr}\" (${expr})";
in
foldl' descend "import ./. {}" attrPath;
# Determine whether to skip a target if it has not diverged from the
# HEAD branch.
shouldSkip =
{
parentTargetMap ? { },
label,
drvPath,
}:
if (hasAttr label parentTargetMap) && parentTargetMap."${label}".drvPath == drvPath then
"Target has not changed."
else
false;
# Create build command for an attribute path pointing to a derivation.
mkBuildCommand =
{
attrPath,
drvPath,
outLink ? "result",
}:
concatStringsSep " " [
# If the nix build fails, the Nix command's exit status should be used.
"set -o pipefail;"
# First try to realise the drvPath of the target so we don't evaluate twice.
# Nix has no concept of depending on a derivation file without depending on
# at least one of its `outPath`s, so we need to discard the string context
# if we don't want to build everything during pipeline construction.
#
# To make this more uniform with how nix-build(1) works, we call realpath(1)
# on nix-store(1)'s output since it has the habit of printing the path of the
# out link, not the store path.
"(nix-store --realise '${drvPath}' --add-root '${outLink}' --indirect | xargs -r realpath)"
# Since we don't gcroot the derivation files, they may be deleted by the
# garbage collector. In that case we can reevaluate and build the attribute
# using nix-build.
"|| (test ! -f '${drvPath}' && nix-build -E '${mkBuildExpr attrPath}' --show-trace --out-link '${outLink}')"
];
# Attribute path of a target relative to the depot root. Needs to take into
# account whether the target is a physical target (which corresponds to a path
# in the filesystem) or the subtarget of a physical target.
targetAttrPath =
target: target.__readTree ++ lib.optionals (target ? __subtarget) [ target.__subtarget ];
# Given a derivation (identified by drvPath) that is part of the list of
# targets passed to mkPipeline, determine all derivations that it depends on
# and are also part of the pipeline. Finally, return the keys of the steps
# that build them. This is used to populate `depends_on` in `mkStep`.
#
# See //nix/dependency-analyzer for documentation on the structure of `targetDepMap`.
getTargetPipelineDeps =
targetDepMap: drvPath: builtins.map keyForDrv (targetDepMap.${drvPath}.knownDeps or [ ]);
# Create a pipeline step from a single target.
mkStep =
{
headBranch,
parentTargetMap,
targetDepMap,
target,
cancelOnBuildFailing,
}:
let
label = mkLabel target;
drvPath = unsafeDiscardStringContext target.drvPath;
in
{
label = ":nix: " + label;
key = keyForDrv target;
skip = shouldSkip { inherit label drvPath parentTargetMap; };
command = mkBuildCommand {
attrPath = targetAttrPath target;
inherit drvPath;
};
env.READTREE_TARGET = label;
cancel_on_build_failing = cancelOnBuildFailing;
# Add a dependency on the initial static pipeline step which
# always runs. This allows build steps uploaded in batches to
# start running before all batches have been uploaded.
depends_on = [
":init:"
]
++ getTargetPipelineDeps targetDepMap drvPath
++ lib.optionals (target ? meta.ci.buildkiteExtraDeps) target.meta.ci.buildkiteExtraDeps;
}
// lib.optionalAttrs (target ? meta.timeout) {
timeout_in_minutes = target.meta.timeout / 60;
# Additional arguments to set on the step.
# Keep in mind these *overwrite* existing step args, not extend. Use with caution.
}
// lib.optionalAttrs (
target ? meta.ci.buildkiteExtraStepArgs
) target.meta.ci.buildkiteExtraStepArgs;
# Helper function to inelegantly divide a list into chunks of at
# most n elements.
#
# This works by assigning each element a chunk ID based on its
# index, and then grouping all elements by their chunk ID.
chunksOf =
n: list:
let
chunkId = idx: toString (idx / n + 1);
assigned = lib.imap1 (idx: value: {
inherit value;
chunk = chunkId idx;
}) list;
unchunk = mapAttrs (_: elements: map (e: e.value) elements);
in
unchunk (lib.groupBy (e: e.chunk) assigned);
# Define a build pipeline chunk as a JSON file, using the pipeline
# format documented on
# https://buildkite.com/docs/pipelines/defining-steps.
makePipelineChunk = name: chunkId: chunk: rec {
filename = "${name}-chunk-${chunkId}.json";
path = writeText filename (toJSON {
steps = chunk;
});
};
# Split the pipeline into chunks of at most 192 steps at once, which
# are uploaded sequentially. This is because of a limitation in the
# Buildkite backend which struggles to process more than a specific
# number of chunks at once.
pipelineChunks = name: steps: attrValues (mapAttrs (makePipelineChunk name) (chunksOf 192 steps));
# Create a pipeline structure for the given targets.
mkPipeline =
{
# HEAD branch of the repository on which release steps, GC
# anchoring and other "mainline only" steps should run.
headBranch,
# List of derivations as read by readTree (in most cases just the
# output of readTree.gather) that should be built in Buildkite.
#
# These are scheduled as the first build steps and run as fast as
# possible, in order, without any concurrency restrictions.
drvTargets,
# Derivation map of a parent commit. Only targets which no longer
# correspond to the content of this map will be built. Passing an
# empty map will always build all targets.
parentTargetMap ? { },
# A list of plain Buildkite step structures to run alongside the
# build for all drvTargets, but before proceeding with any
# post-build actions such as status reporting.
#
# Can be used for things like code formatting checks.
additionalSteps ? [ ],
# A list of plain Buildkite step structures to run after all
# previous steps succeeded.
#
# Can be used for status reporting steps and the like.
postBuildSteps ? [ ],
# The list of phases known by the current Buildkite
# pipeline. Dynamic pipeline chunks for each phase are uploaded
# to Buildkite on execution of static part of the
# pipeline. Phases selection is hard-coded in the static
# pipeline.
#
# Pipeline generation will fail when an extra step with
# unregistered phase is added.
#
# Common scenarios for different phase:
# - "build" - main phase for building all Nix targets
# - "release" - pushing artifacts to external repositories
# - "deploy" - updating external deployment configurations
phases ? [
"build"
"release"
],
# Build phases that are active for this invocation (i.e. their
# steps should be generated).
#
# This can be used to disable outputting parts of a pipeline if,
# for example, build and release phases are created in separate
# eval contexts.
#
# TODO(tazjin): Fail/warn if unknown phase is requested.
activePhases ? phases,
# Setting this attribute to true cancels dynamic pipeline steps
# as soon as the build is marked as failing.
#
# To enable this feature one should enable "Fail Fast" setting
# at Buildkite pipeline or on organization level.
cancelOnBuildFailing ? false,
}:
let
# List of phases to include.
enabledPhases = lib.intersectLists activePhases phases;
# Is the 'build' phase included? This phase is treated specially
# because it always contains the plain Nix builds, and some
# logic/optimisation depends on knowing whether is executing.
buildEnabled = elem "build" enabledPhases;
# Dependency relations between the `drvTargets`. See also //nix/dependency-analyzer.
targetDepMap =
let
# Only calculate dependencies between drvTargets that were not part of
# the previous pipeline (per parentTargetMap). Unchanged targets will
# be skipped (assumed already built), so it's useless to emit deps
# on their steps.
changedDrvTargets = builtins.filter (
target: parentTargetMap.${mkLabel target}.drvPath or null != target.drvPath
) drvTargets;
in
dependency-analyzer (dependency-analyzer.drvsToPaths changedDrvTargets);
# Convert a target into all of its steps, separated by build
# phase (as phases end up in different chunks).
targetToSteps =
target:
let
mkStepArgs = {
inherit
headBranch
parentTargetMap
targetDepMap
target
cancelOnBuildFailing
;
};
step = mkStep mkStepArgs;
# Same step, but with an override function applied. This is
# used in mkExtraStep if the extra step needs to modify the
# parent derivation somehow.
#
# Note that this will never affect the label.
overridable = f: mkStep (mkStepArgs // { target = (f target); });
# Split extra steps by phase.
splitExtraSteps = lib.groupBy ({ phase, ... }: phase) (
attrValues (mapAttrs (normaliseExtraStep phases overridable) (target.meta.ci.extraSteps or { }))
);
extraSteps = mapAttrs (
_: steps: map (mkExtraStep (targetAttrPath target) buildEnabled) steps
) splitExtraSteps;
in
if !buildEnabled then
extraSteps
else
extraSteps
// {
build = [ step ] ++ (extraSteps.build or [ ]);
};
# Combine all target steps into step lists per phase.
#
# TODO(tazjin): Refactor when configurable phases show up.
globalSteps = {
build = additionalSteps;
release = postBuildSteps;
};
phasesWithSteps = lib.zipAttrsWithNames enabledPhases (_: concatLists) (
(map targetToSteps drvTargets) ++ [ globalSteps ]
);
# Generate pipeline chunks for each phase.
chunks = foldl' (
acc: phase:
let
phaseSteps = phasesWithSteps.${phase} or [ ];
in
if phaseSteps == [ ] then acc else acc ++ (pipelineChunks phase phaseSteps)
) [ ] enabledPhases;
in
runCommand "buildkite-pipeline" { } ''
mkdir $out
echo "Generated ${toString (length chunks)} pipeline chunks"
${lib.concatMapStringsSep "\n" (chunk: "cp ${chunk.path} $out/${chunk.filename}") chunks}
'';
# Create a drvmap structure for the given targets, containing the
# mapping of all target paths to their derivations. The mapping can
# be persisted for future use.
mkDrvmap =
drvTargets:
writeText "drvmap.json" (
toJSON (
listToAttrs (
map (target: {
name = mkLabel target;
value = {
drvPath = unsafeDiscardStringContext target.drvPath;
# Include the attrPath in the output to reconstruct the drv
# without parsing the human-readable label.
attrPath = targetAttrPath target;
};
}) drvTargets
)
)
);
# Implementation of extra step logic.
#
# Each target extra step is an attribute specified in
# `meta.ci.extraSteps`. Its attribute name will be used as the step
# name on Buildkite.
#
# command (required): A command that will be run in the depot
# checkout when this step is executed. Should be a derivation
# resulting in a single executable file, e.g. through
# pkgs.writeShellScript.
#
# label (optional): Human-readable label for this step to display
# in the Buildkite UI instead of the attribute name.
#
# prompt (optional): Setting this blocks the step until confirmed
# by a human. Should be a string which is displayed for
# confirmation. These steps always run after the main build is
# done and have no influence on CI status.
#
# needsOutput (optional): If set to true, the parent derivation
# will be built in the working directory before running the
# command. Output will be available as 'result'.
# TODO: Figure out multiple-output derivations.
#
# parentOverride (optional): A function (drv -> drv) to override
# the parent's target definition when preparing its output. Only
# used in extra steps that use needsOutput.
#
# branches (optional): Git references (branches, tags ... ) on
# which this step should be allowed to run. List of strings.
#
# alwaysRun (optional): If set to true, this step will always run,
# even if its parent has not been rebuilt.
#
# Note that gated steps are independent of each other.
# Create a gated step in a step group, independent from any other
# steps.
mkGatedStep =
{
step,
label,
parent,
prompt,
}:
{
inherit (step) depends_on;
group = label;
skip = parent.skip or false;
steps = [
{
inherit prompt;
branches = step.branches or [ ];
block = ":radio_button: Run ${label}? (from ${parent.env.READTREE_TARGET})";
}
# The explicit depends_on of the wrapped step must be removed,
# otherwise its dependency relationship with the gate step will
# break.
(builtins.removeAttrs step [ "depends_on" ])
];
};
# Validate and normalise extra step configuration before actually
# generating build steps, in order to use user-provided metadata
# during the pipeline generation.
normaliseExtraStep =
phases: overridableParent: key:
{
command,
label ? key,
needsOutput ? false,
parentOverride ? (x: x),
branches ? null,
alwaysRun ? false,
prompt ? false,
softFail ? false,
phase ? "build",
skip ? false,
agents ? null,
}:
let
parent = overridableParent parentOverride;
parentLabel = parent.env.READTREE_TARGET;
validPhase = lib.throwIfNot (elem phase phases) ''
In step '${label}' (from ${parentLabel}):
Phase '${phase}' is not valid.
Known phases: ${concatStringsSep ", " phases}
'' phase;
in
{
inherit
alwaysRun
branches
command
key
label
needsOutput
parent
parentLabel
softFail
skip
agents
;
phase = validPhase;
prompt = lib.throwIf (prompt != false && phase == "build") ''
In step '${label}' (from ${parentLabel}):
The 'prompt' feature can not be used by steps in the "build"
phase, because CI builds should not be gated on manual human
approvals.
'' prompt;
};
# Create the Buildkite configuration for an extra step, optionally
# wrapping it in a gate group.
mkExtraStep =
parentAttrPath: buildEnabled: cfg:
let
# ATTN: needs to match an entry in .gitignore so that the tree won't get dirty
commandScriptLink = "nix-buildkite-extra-step-command-script";
step = {
key = "extra-step-" + hashString "sha1" "${cfg.label}-${cfg.parentLabel}";
label = ":gear: ${cfg.label} (from ${cfg.parentLabel})";
skip =
let
# When parent doesn't have skip attribute set, default to false
parentSkip = cfg.parent.skip or false;
# Extra step skip parameter can be string explaining the
# skip reason.
extraStepSkip = if builtins.isString cfg.skip then true else cfg.skip;
# Don't run if extra step is explicitly set to skip. If
# parameter is not set or equal to false, follow parent behavior.
skip' = if extraStepSkip then cfg.skip else parentSkip;
in
if cfg.alwaysRun then false else skip';
depends_on = lib.optional (buildEnabled && !cfg.alwaysRun && !cfg.needsOutput) cfg.parent.key;
command = ''
set -ueo pipefail
${lib.optionalString cfg.needsOutput "echo '~~~ Preparing build output of ${cfg.parentLabel}'"}
${lib.optionalString cfg.needsOutput cfg.parent.command}
echo '--- Building extra step script'
command_script="$(${
# Using command substitution in this way assumes the script drv only has one output
assert builtins.length cfg.command.outputs == 1;
mkBuildCommand {
# script is exposed at <parent>.meta.ci.extraSteps.<key>.command
attrPath = parentAttrPath ++ [
"meta"
"ci"
"extraSteps"
cfg.key
"command"
];
drvPath = unsafeDiscardStringContext cfg.command.drvPath;
# make sure it doesn't conflict with result (from needsOutput)
outLink = commandScriptLink;
}
})"
echo '+++ Running extra step script'
# ATTN: buildkite substitutes this variable outside of the execution for some reason
exec "\$command_script"
'';
soft_fail = cfg.softFail;
}
// (lib.optionalAttrs (cfg.agents != null) { inherit (cfg) agents; })
// (lib.optionalAttrs (cfg.branches != null) {
branches = lib.concatStringsSep " " cfg.branches;
});
in
if (isString cfg.prompt) then
mkGatedStep {
inherit step;
inherit (cfg) label parent prompt;
}
else
step;
}