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Diffstat (limited to 'nix/buildkite/default.nix')
| -rw-r--r-- | nix/buildkite/default.nix | 335 |
1 files changed, 335 insertions, 0 deletions
diff --git a/nix/buildkite/default.nix b/nix/buildkite/default.nix new file mode 100644 index 000000000000..6a0e9d246dab --- /dev/null +++ b/nix/buildkite/default.nix @@ -0,0 +1,335 @@ +# 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 + concatMap + concatStringsSep + filter + foldl' + getEnv + hasAttr + hashString + isNull + isString + length + listToAttrs + mapAttrs + partition + pathExists + toJSON + unsafeDiscardStringContext; + + inherit (pkgs) lib runCommandNoCC writeText; + inherit (depot.nix.readTree) mkLabel; +in +rec { + # Creates a Nix expression that yields the target at the specified + # location in the repository. + # + # This makes a distinction between normal targets (which physically + # exist in the repository) and subtargets (which are "virtual" + # targets exposed by a physical one) to make it clear in the build + # output which is which. + mkBuildExpr = target: + let + descend = expr: attr: "builtins.getAttr \"${attr}\" (${expr})"; + targetExpr = foldl' descend "import ./. {}" target.__readTree; + subtargetExpr = descend targetExpr target.__subtarget; + in + if target ? __subtarget then subtargetExpr else targetExpr; + + # Determine whether to skip a target if it has not diverged from the + # HEAD branch. + shouldSkip = parentTargetMap: label: drvPath: + if (hasAttr label parentTargetMap) && parentTargetMap."${label}".drvPath == drvPath + then "Target has not changed." + else false; + + # Create build command for a derivation target. + mkBuildCommand = target: drvPath: concatStringsSep " " [ + # First try to realise the drvPath of the target so we don't evaluate twice. + # Nix has no concept of depending on a derivation file without depending on + # at least one of its `outPath`s, so we need to discard the string context + # if we don't want to build everything during pipeline construction. + "(nix-store --realise '${drvPath}' --add-root result --indirect && readlink result)" + + # 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 target}' --show-trace)" + ]; + + # Create a pipeline step from a single target. + mkStep = headBranch: parentTargetMap: target: + let + label = mkLabel target; + drvPath = unsafeDiscardStringContext target.drvPath; + shouldSkip' = shouldSkip parentTargetMap; + in + { + label = ":nix: " + label; + key = hashString "sha1" label; + skip = shouldSkip' label drvPath; + command = mkBuildCommand target drvPath; + env.READTREE_TARGET = label; + + # 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:"; + }; + + # 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 256 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 ? [ ] + }: + let + # Convert a target into all of its build and post-build steps, + # treated separately as they need to be in different chunks. + targetToSteps = target: + let + step = mkStep headBranch parentTargetMap target; + + # 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 headBranch parentTargetMap (f target); + + # Split build/post-build steps + splitExtraSteps = partition ({ postStep, ... }: postStep) + (attrValues (mapAttrs + (name: value: { + inherit name value; + postStep = (value ? prompt) || (value.postBuild or false); + }) + (target.meta.ci.extraSteps or { }))); + + mkExtraStep' = { name, value, ... }: mkExtraStep overridable name value; + extraBuildSteps = map mkExtraStep' splitExtraSteps.wrong; # 'wrong' -> no prompt + extraPostSteps = map mkExtraStep' splitExtraSteps.right; # 'right' -> has prompt + in + { + buildSteps = [ step ] ++ extraBuildSteps; + postSteps = extraPostSteps; + }; + + # Combine all target steps into separate build and post-build step lists. + steps = foldl' + (acc: t: { + buildSteps = acc.buildSteps ++ t.buildSteps; + postSteps = acc.postSteps ++ t.postSteps; + }) + { buildSteps = [ ]; postSteps = [ ]; } + (map targetToSteps drvTargets); + + buildSteps = + # Add build steps for each derivation target and their extra + # steps. + steps.buildSteps + + # Add additional steps (if set). + ++ additionalSteps; + + postSteps = + # Add post-build steps for each derivation target. + steps.postSteps + + # Add any globally defined post-build steps. + ++ postBuildSteps; + + buildChunks = pipelineChunks "build" buildSteps; + postBuildChunks = pipelineChunks "post" postSteps; + chunks = buildChunks ++ postBuildChunks; + in + runCommandNoCC "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 = target.__readTree ++ lib.optionals (target ? __subtarget) [ + target.__subtarget + ]; + }; + }) + 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. + # + # postBuild (optional): If set to true, this step will run after + # all primary build steps (that is, after status has been reported + # back to CI). + # + # 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 (step) branches; + inherit prompt; + 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" ]) + ]; + }; + + # Create the Buildkite configuration for an extra step, optionally + # wrapping it in a gate group. + mkExtraStep = overridableParent: key: + { command + , label ? key + , prompt ? false + , needsOutput ? false + , parentOverride ? (x: x) + , branches ? null + , alwaysRun ? false + , postBuild ? false + }@cfg: + let + parent = overridableParent parentOverride; + parentLabel = parent.env.READTREE_TARGET; + + step = { + label = ":gear: ${label} (from ${parentLabel})"; + skip = if alwaysRun then false else parent.skip or false; + depends_on = lib.optional (!alwaysRun && !needsOutput) parent.key; + branches = if branches != null then lib.concatStringsSep " " branches else null; + + command = pkgs.writeShellScript "${key}-script" '' + set -ueo pipefail + ${lib.optionalString needsOutput "echo '~~~ Preparing build output of ${parentLabel}'"} + ${lib.optionalString needsOutput parent.command} + echo '+++ Running extra step command' + exec ${command} + ''; + }; + in + if (isString prompt) + then + mkGatedStep + { + inherit step label parent prompt; + } + else step; +} |