runnerd_core/

api.rs

//! The daemon's JSON API, version 1: the request and response types every client deserializes, and the
//! principal a transport authenticates. Plain data only: no I/O, no Docker or GitHub types, no secrets but a
//! [`Pairing`]'s one-time link, which its `Debug` leaves out.
//!
//! Routes, all under the authenticated principal:
//!
//! | Route | Body |
//! |---|---|
//! | `GET /v1/status` | [`Status`] |
//! | `POST /v1/repositories/{owner}/{name}/pause?`[`PauseQuery`] | [`Paused`]; 409 [`Busy`] while it runs a job |
//! | `POST /v1/repositories/{owner}/{name}/resume` | none, 204 |
//! | `POST /v1/repositories/pause?`[`PauseQuery`] | [`Paused`]; 409 [`Busy`] while any runs a job, pausing none |
//! | `POST /v1/repositories/resume` | none, 204: every repository resumed |
//! | `POST /v1/profiles/{name}/reseed` | none, 202; 409 while it reseeds; `cache.reseeded` when done |
//! | `POST /v1/caches/{name}/clean` | none, 204; 409 [`Busy`] while a runner uses it |
//! | `GET /v1/config` | [`ConfigFile`] |
//! | `POST /v1/config/check` | TOML in, [`ConfigCheck`] |
//! | `PUT /v1/config` | TOML in, [`ConfigCheck`]; 422 [`ConfigCheck`] when invalid |
//! | `GET /v1/doctor` | [`Doctor`] |
//! | `POST /v1/shutdown` | [`ShutdownRequest`] in, 202 |
//! | `GET /v1/dashboard` | [`Dashboard`] |
//! | `POST /v1/dashboard/sign-out` | none, 204 |
//! | `POST /v1/dashboard/pairings?`[`PairingQuery`] | [`Pairings`]; 409 when the dashboard is off or has no `[web] origins` |
//! | `GET /v1/jobs?`[`JobQuery`] | [`JobPage`] |
//! | `GET /v1/jobs/{id}` | [`Job`] |
//! | `GET /v1/jobs/{id}/samples` | [`SampleSeries`] |
//! | `GET /v1/jobs/{id}/logs?`[`LogQuery`] | `text/plain`, one line per log line |
//! | `GET /v1/host/samples?`[`HostSampleQuery`] | [`HostSamples`] |
//! | `GET /v1/stats?`[`StatsQuery`] | [`Stats`] |
//! | `GET /v1/activity?`[`ActivityQuery`] | [`Activity`] |
//! | `GET /v1/sizing?`[`SizingQuery`] | [`Sizing`] |
//! | `GET /v1/insights?`[`InsightsQuery`] | [`Insights`] |
//! | `GET /v1/digest` | [`Digest`] |
//! | `GET /v1/savings` | [`Savings`] |
//! | `POST /v1/notify/test?`[`NotifyTestQuery`] | [`NotifyTest`]; 404 without `[notify]` targets or with no such one |
//! | `GET /v1/caches` | [`Caches`] |
//! | `GET /v1/caches/history?`[`CacheHistoryQuery`] | [`CacheHistory`] |
//! | `GET /v1/events?`[`EventQuery`] | `text/event-stream` of [`EventEnvelope`] |
//! | `GET /v1/records` | [`Records`] |
//! | `DELETE /v1/records/{job}` | [`RemovedRecords`]; 409 while a shell is open in it |
//! | `DELETE /v1/records?`[`RemoveRecordsQuery`] | [`RemovedRecords`]; records with an open shell stay |
//! | `POST /v1/records/{job}/shell?`[`ShellQuery`] | `Upgrade:` [`SHELL_PROTOCOL`], 101, then the shell's terminal; 409 when the budget is full |
//!
//! Errors carry an [`ErrorResponse`].

use serde::{Deserialize, Serialize};

mod admission;
mod budget;
mod control;
mod events;
mod insights;
mod jobs;
mod records;
mod results;
mod savings;
mod sizing;
mod slots;
mod stats;
mod storage;
mod tone;
mod units;

pub use admission::{Admission, AdmissionPolicy, Basis, CpuAdmission, JobPeak, cores, cpus};
pub use budget::{
    BudgetParts, ClosedKind, ClosedPart, FreePart, HeldKind, HeldPart, Reading, SlotPart,
};
pub use control::{
    Busy, Check, CheckStatus, ConfigCheck, ConfigFile, Doctor, PauseQuery, Paused, ReplaceQuery,
    RunningJob,
};
pub use events::{Event, EventEnvelope, EventQuery, RunnerFailure};
pub use insights::{
    AutoNote, Delivery, Digest, INSIGHT_DAYS, INSIGHT_DAYS_MAX, Insight, InsightKind, Insights,
    InsightsQuery, LongWait, Notification, NotifyEvent, NotifyTest, NotifyTestQuery, Priority,
    RepositoryWaits, RunLink, Severity, WaitSpread, WeekWaits,
};
pub use jobs::{
    Activity, ActivityQuery, Bucket, BuildCacheCounts, BuildCacheStats, CacheHistory,
    CacheHistoryQuery, CacheKind, CacheSize, CacheVolume, Caches, ChartLine, ChartLineKind,
    ChartLines, Holder, HostMemory, HostSample, HostSampleQuery, HostSamples, Job, JobMetrics,
    JobPage, JobQuery, JobRunner, JobState, JobSummary, JobTitle, Limit, LimitSource, Limits,
    LogQuery, LogSummary, Milestone, Outcome, OutcomeKind, Phase, PhaseKind, Pressure,
    RunComparison, Sample, SampleSeries, SampleUsage, Started, Stats, StatsQuery, StatsRow, Step,
    Timeline, job_title,
};
pub use records::{
    Record, RecordLimits, RecordNote, RecordRemoval, Records, RemoveRecordsQuery, RemovedRecords,
    SHELL_PROTOCOL, ShellQuery,
};
pub use results::{force_pause_consequence, reseed_requested, reseeded};
pub use savings::{
    Period, PricedRun, PricedRunner, Pricing, PricingHistory, SELF_HOSTED_RATE, SavedWindow,
    Savings, Sku, Usd, Visibility, billed_minutes, reads_since,
};
pub use sizing::{
    Advice, AutoPlan, GRANULE, JobSizing, Need, PAGE_CACHE_ROOM, Peaks, ProfilePlan, ProfileSizing,
    Resize, RevertCause, SAMPLE_INTERVAL, Sizing, SizingChange, SizingHold, SizingQuery,
    SizingRefused, SizingRevert, Spread, Starts, need, period, sampled_note,
};
pub use slots::{Health, SlotState};
pub use stats::StatsSummary;
pub use storage::{
    BuildCacheActivity, CacheLimit, RECORDS_NEAR_FULL, RecordState, records_near_full,
};
pub use tone::{Tone, Toned};
#[cfg(feature = "host")]
pub(crate) use units::days_from_civil;
pub use units::{ago, cores_used, cpu_time, duration, in_cores};

/// Who sent a request, as the transport authenticated it. Handlers get it from one place, so a new transport only
/// has to produce one.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "kebab-case", tag = "kind")]
pub enum Principal {
    /// The user the daemon runs as, on the local Unix socket.
    LocalOwner {
        /// The Unix user ID the socket's peer runs as.
        uid: u32,
    },
}

/// `GET /v1/status`: what the daemon serves and runs right now.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct Status {
    /// The daemon's version, from its `Cargo.toml`.
    pub version: String,
    /// Set once the daemon stops polling to shut down.
    pub shutting_down: bool,
    /// The memory budget and what runners use of it.
    pub budget: Budget,
    /// Every configured profile with its slots.
    pub profiles: Vec<ProfileStatus>,
    /// Every configured repository.
    pub repositories: Vec<RepositoryStatus>,
    /// Queued jobs the repositories' runners can take and none holds yet, at the last poll, oldest first. No event
    /// carries the list: `job.queued` announces a job, `job.started` and `job.finished` its leaving the queue.
    /// A repository whose last listing failed, as while GitHub rate-limits runnerd, or that is no longer polled
    /// because runnerd is shutting down, shows no jobs here, while the history keeps its jobs queued.
    pub queued: Vec<QueuedJob>,
}

/// The memory budget runners and the mirror share, in bytes.
#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize)]
pub struct Budget {
    /// The systemd slice runner containers run in.
    pub slice: String,
    /// The slice's `MemoryMax`; `None` when it is unlimited.
    pub memory_max: Option<u64>,
    /// Memory the running containers reserve: the runners' caps, or under measured admission the larger of each
    /// runner's predicted peak and its last sampled memory, and the caps of the seed containers, shells and the
    /// mirror.
    pub memory_in_use: u64,
    /// What a new runner must fit in beside them.
    pub admission: AdmissionPolicy,
    /// Under measured admission, whether the slice is at the high-water mark, so no runner starts.
    pub held: bool,
    /// The mirror's part of `memory_in_use`: its cap while it is enabled or still running, else 0.
    pub mirror_memory: u64,
    /// The seed containers' part of `memory_in_use`, one per profile that reseeds, by profile name.
    pub seed_memory: Vec<SeedMemory>,
    /// The shells' part of `memory_in_use`, one per shell open in a record, by job.
    pub shell_memory: Vec<ShellMemory>,
    /// What the host's memory leaves runners beside its other programs, from a recent reading of it; absent
    /// without one.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub host: Option<HostBudget>,
    /// The CPU budget, under `[host] cpu_overcommit`. Absent without one.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub cpu: Option<CpuBudget>,
    /// The CPUs the slice may use, in millicores: its `AllowedCPUs` or the host's, less under a lower `CPUQuota`,
    /// whether or not a CPU budget admits runners. The runners' CPU limits are quotas that may add up past it.
    /// Absent when it could not be read.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub slice_cpus: Option<u64>,
}

/// What the host's memory leaves the runners (ADR 0055). New runners fit in the lower of `MemoryMax` and
/// `limit`; running ones are never stopped for it.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct HostBudget {
    /// The reading it comes from.
    pub memory: HostMemory,
    /// What the slice may hold now: what its runners hold without page cache plus the host's `MemAvailable`, less
    /// a margin kept free for the host's page cache.
    pub limit: u64,
    /// What that leaves new runners beside what the running ones reserve, in bytes.
    pub spare: u64,
    /// Whether the host's tasks stall for memory (`full` pressure), so no runner starts until they stop.
    pub stalled: bool,
}

/// Hundredths of a percent as a percentage: `1.5%`, `12%`.
pub fn percent(hundredths: u32) -> String {
    let whole = hundredths / 100;
    match hundredths % 100 / 10 {
        0 => format!("{whole}%"),
        tenth => format!("{whole}.{tenth}%"),
    }
}

/// The CPU budget runners share, in millicores.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq, Serialize, Deserialize)]
pub struct CpuBudget {
    /// The CPUs the slice may use: its `AllowedCPUs` or the host's, less under a lower `CPUQuota`.
    pub cpus: u64,
    /// Those times `cpu_overcommit`: what the runners' reservations must fit.
    pub budget: u64,
    /// What the runners reserve: each its predicted average CPU under measured admission, else its `cpus`.
    pub in_use: u64,
    /// Whether a queued job waits for CPU that memory and a slot have room for.
    pub held: bool,
}

impl CpuBudget {
    /// The budget's line as clients show it beside memory, such as `CPU 4.5 of 32 CPUs reserved` or, while a job
    /// waits for it, `CPU 30 of 32 CPUs reserved; a job waits for CPU`.
    pub fn line(&self) -> String {
        let mut line = format!(
            "CPU {} of {} CPUs reserved",
            cores(self.in_use),
            cores(self.budget)
        );
        if self.held {
            line.push_str("; a job waits for CPU");
        }
        line
    }
}

impl Budget {
    /// How runners are admitted, as clients add it to the budget's line: nothing under caps, else `by predicted
    /// peaks`, and why nothing starts while the slice is at the high-water mark.
    pub fn admission_note(&self) -> Option<&'static str> {
        match (self.admission, self.held) {
            (AdmissionPolicy::Caps, _) => None,
            (AdmissionPolicy::Measured, false) => Some("by predicted peaks"),
            (AdmissionPolicy::Measured, true) => Some(
                "by predicted peaks; the slice is past 90% of its MemoryMax, so no runner starts",
            ),
        }
    }
}

/// A shell container's memory cap: its record's profile's limit when the shell opened.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct ShellMemory {
    /// The job whose record the shell runs.
    pub job: u64,
    /// Its cap in bytes.
    pub memory: u64,
}

/// A seed container's memory cap: its profile's limit when the reseed started, or, for a requested reseed whose
/// profile drained, the room it holds until it starts.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct SeedMemory {
    /// The profile it reseeds.
    pub profile: String,
    /// Its cap in bytes.
    pub memory: u64,
}

/// A runner profile and what runs in its slots.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct ProfileStatus {
    /// The name under `[profiles]` in `runnerd.toml`.
    pub name: String,
    /// The image its runners run, such as `runnerd-runner:base`.
    pub image: String,
    /// CPUs per slot.
    pub cpus: u32,
    /// Bytes per slot.
    pub memory: u64,
    /// Set while slot 1's layers become the profile's snapshot.
    pub reseeding: bool,
    /// Index 0 is slot 1.
    pub slots: Vec<SlotStatus>,
}

/// One slot of a profile: room for one job.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct SlotStatus {
    /// 1-based.
    pub slot: usize,
    /// `None` when the slot is free.
    pub runner: Option<RunnerStatus>,
}

/// A runner registered for one job, in its container.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct RunnerStatus {
    /// `owner/name` the runner is registered on.
    pub repository: String,
    /// The runner's name, also its container's.
    pub name: String,
    /// The runner's ID on GitHub.
    pub runner_id: u64,
    /// The Docker container ID.
    pub container: String,
    /// Whether it runs a job, as GitHub or its log reports it: its log names the job before GitHub lists it busy.
    pub busy: bool,
    /// Seconds since the Unix epoch.
    pub started_at: u64,
    /// What it takes of the budget: its cap under caps; under measured admission the larger of its predicted peak
    /// and its last sampled memory.
    pub reserved: u64,
    /// A warm runner: idle, and no queued job of its repository waits for it; it takes the next one GitHub hands
    /// out.
    pub warm: bool,
}

/// A configured repository and its queue.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct RepositoryStatus {
    /// `owner/name` on GitHub.
    pub name: String,
    /// Its first pool's profile, which 0.0.19's TUI and dashboard colour it by. Read `pools`; it goes when the wire
    /// check moves past 0.0.19 (ADR 0073).
    pub profile: String,
    /// Its first pool's labels, for 0.0.19's clients as `profile` is.
    pub labels: Vec<String>,
    /// Its pools in config order, one per `[[repositories]]` entry: a job runs in the one whose labels match it
    /// (ADR 0058).
    pub pools: Vec<PoolStatus>,
    /// Paused repositories get no new runners; their running jobs finish.
    pub paused: bool,
    /// Its jobs in `Status::queued`: queued ones none of its runners took yet, those no pool serves too.
    pub queued_jobs: usize,
}

/// One of a repository's pools: its runners in one profile.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct PoolStatus {
    /// The profile its jobs run in.
    pub profile: String,
    /// The labels its runners register with.
    pub labels: Vec<String>,
    /// Its jobs in `Status::queued`: those its labels match.
    pub queued_jobs: usize,
}

/// A queued job runners of this daemon can take, as GitHub listed it at the last poll.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct QueuedJob {
    /// GitHub's job ID.
    pub id: u64,
    /// The repository whose runners can take it, `owner/name`.
    pub repository: String,
    /// The profile of its repository's pool whose labels match it; `None` when no pool's do.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub profile: Option<String>,
    /// The workflow run it belongs to.
    pub run_id: u64,
    /// 1 for the first attempt of the run, higher for re-runs.
    pub run_attempt: u32,
    /// The workflow's name.
    pub workflow: Option<String>,
    /// The job's name in the workflow.
    pub name: String,
    /// The branch the run is for.
    pub branch: Option<String>,
    /// The job's page on GitHub.
    pub url: Option<String>,
    /// When GitHub queued it, in seconds since the Unix epoch; 0 if GitHub did not say.
    pub queued_at: u64,
    /// Why no runner has it yet, as the last plan saw it. `None` before the daemon has planned with it, and while
    /// it shuts down.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub waiting: Option<Waiting>,
}

/// The slot of an idle runner of `job`'s repository, in its pool's profile when known, such as `jvm 2`.
fn starting_for(job: &QueuedJob, status: &Status) -> Option<String> {
    status
        .profiles
        .iter()
        .filter(|profile| job.profile.as_ref().is_none_or(|own| *own == profile.name))
        .find_map(|profile| {
            profile
                .slots
                .iter()
                .find(|slot| {
                    slot.runner
                        .as_ref()
                        .is_some_and(|runner| runner.repository == job.repository && !runner.busy)
                })
                .map(|slot| format!("{}\u{a0}{}", profile.name, slot.slot))
        })
}

impl QueuedJob {
    /// Where it runs, as every client names it: its repository, and its pool's profile when the repository has
    /// several pools in `status`, such as `halyard/ledger · light`.
    pub fn place(&self, status: &Status) -> String {
        let pools = status
            .repositories
            .iter()
            .find(|repository| repository.name == self.repository)
            .map_or(0, |repository| repository.pools.len());
        match self.profile.as_deref().filter(|_| pools > 1) {
            Some(profile) => format!("{}\u{a0}· {profile}", self.repository),
            None => self.repository.clone(),
        }
    }
}

impl RepositoryStatus {
    /// The profile of its first pool, which every client colours it by.
    pub fn first_profile(&self) -> &str {
        self.pools.first().map_or("", |pool| pool.profile.as_str())
    }

    /// Its pools' profiles, as every client lists them on one line: `jvm` or `jvm + light`.
    pub fn profiles(&self) -> String {
        self.pools
            .iter()
            .map(|pool| pool.profile.as_str())
            .collect::<Vec<_>>()
            .join(" + ")
    }

    /// The profile of its pool whose labels match a job asking for `labels`, as the daemon picks it.
    pub fn pool_for(&self, labels: &[String]) -> Option<String> {
        self.pools
            .iter()
            .find(|pool| crate::config::labels_match(labels, &pool.labels))
            .map(|pool| pool.profile.clone())
    }
}

/// What failed, that holds a repository's runners back for a while.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "kebab-case")]
pub enum HoldCause {
    /// Its runners ended without taking a job.
    NoJob,
    /// Its runners ended without a job after waiting for one, twice in a row.
    IdleExits,
    /// GitHub did not register its runner.
    Register,
    /// Docker did not start its runner's container.
    Start,
}

/// Why a queued job has no runner of its own yet. Jobs are served oldest first; each takes the first of these that
/// holds for it.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "kebab-case", tag = "kind")]
pub enum Waiting {
    /// Its repository is paused.
    Paused,
    /// Runners of its repository failed, so none starts before `until` (seconds since the Unix epoch).
    Backoff {
        /// When runners may start again.
        until: u64,
        /// What failed.
        cause: HoldCause,
    },
    /// A runner started for it and waits for GitHub to hand it the job: a runner takes any job its labels match,
    /// so not necessarily this one.
    RunnerStarting,
    /// Slot 1 of its profile is becoming the profile's snapshot, so none of the profile's slots starts.
    Reseeding {
        /// The profile.
        profile: String,
    },
    /// Its profile's image is being pulled, so none of the profile's slots starts.
    PullingImage {
        /// The profile.
        profile: String,
    },
    /// Every slot of its profile holds a runner.
    NoSlot {
        /// The profile.
        profile: String,
    },
    /// What its runner would reserve does not fit the memory budget left. Under measured admission, `free` is 0
    /// while the slice is at the high-water mark (`Budget::held`).
    Memory {
        /// What its runner would reserve, in bytes.
        needs: u64,
        /// What the budget has left, in bytes.
        free: u64,
    },
    /// What its runner would reserve does not fit what the host's memory has to spare beside its other programs
    /// (`HostBudget::spare`), though it fits the slice's budget. `free` is 0 while the host's tasks stall for memory
    /// (`HostBudget::stalled`).
    HostMemory {
        /// What its runner would reserve, in bytes.
        needs: u64,
        /// What the host has to spare, in bytes.
        free: u64,
    },
    /// What its runner would reserve does not fit the CPU budget left, in millicores.
    Cpu {
        /// What its runner would reserve.
        needs: u64,
        /// What the CPU budget has left.
        free: u64,
    },
    /// An older job has waited long enough for CPU that no younger one takes CPU before it.
    BehindCpu {
        /// The older job's ID.
        job: u64,
    },
    /// An older job is about to have a runner start for it, which takes the slot, memory or CPU this one would
    /// otherwise start with: what holds it is that start, not what runs now.
    BehindStart {
        /// The older job's ID.
        job: u64,
    },
    /// No pool of its repository has every label it asks for, so no runner of this daemon can take it (ADR 0058).
    NoPool {
        /// The labels it asks for.
        labels: Vec<String>,
    },
    /// A reason from a newer daemon than this client knows, so a reason added later does not keep the client from
    /// reading the status.
    #[serde(other)]
    Unknown,
}

/// What a [`Waiting`] reason waits on, which clients draw it by.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum WaitKind {
    /// Something the owner can act on: a pause, runners that failed to take a job, or labels no pool serves.
    Act,
    /// Something that clears by itself shortly: a runner starting, a reseed, an image pull, an older job's start.
    Soon,
    /// Room: a slot, memory or CPU that a running job holds.
    Full,
    /// A reason this client does not know (`Waiting::Unknown`), drawn neutral.
    Other,
}

impl Waiting {
    /// What it waits on.
    pub fn kind(&self) -> WaitKind {
        match self {
            Waiting::Paused | Waiting::Backoff { .. } | Waiting::NoPool { .. } => WaitKind::Act,
            Waiting::Unknown => WaitKind::Other,
            Waiting::RunnerStarting
            | Waiting::Reseeding { .. }
            | Waiting::PullingImage { .. }
            | Waiting::BehindStart { .. } => WaitKind::Soon,
            Waiting::NoSlot { .. }
            | Waiting::Memory { .. }
            | Waiting::HostMemory { .. }
            | Waiting::Cpu { .. }
            | Waiting::BehindCpu { .. } => WaitKind::Full,
        }
    }

    /// Why `job` waits, in the owner's words with the numbers that hold it, as every client says it: such as
    /// `All 2 node slots are busy` or `Needs 9G of memory; 2.5G of the budget is free`. `status` is the one `job`
    /// is queued in, which names the slot of a starting runner and the older job one waits behind.
    pub fn reason(&self, job: &QueuedJob, status: &Status, now: u64) -> String {
        let size = |bytes: u64| crate::config::ByteSize(bytes).to_string();
        let older_name = |id: u64| {
            status
                .queued
                .iter()
                .find(|candidate| candidate.id == id)
                .map_or_else(|| "an older job".to_owned(), |older| older.name.clone())
        };
        match self {
            Waiting::Paused => format!("{} is paused", job.repository),
            Waiting::Unknown => "Waits for a reason this client does not know yet".to_owned(),
            Waiting::NoPool { labels } if labels.is_empty() => {
                "It asks for no labels, so no profile serves it".to_owned()
            }
            Waiting::NoPool { labels } => format!(
                "No profile serves the {} {}",
                if labels.len() == 1 { "label" } else { "labels" },
                labels.join(", ")
            ),
            Waiting::Backoff { until, cause } => format!(
                "{}; retrying in {}",
                match cause {
                    HoldCause::NoJob => "Runners failed to take a job",
                    HoldCause::IdleExits => "Runners ended without a job after waiting for one",
                    HoldCause::Register => "Runners cannot register with GitHub",
                    HoldCause::Start => "Runners cannot start",
                },
                duration(until.saturating_sub(now))
            ),
            Waiting::RunnerStarting => match starting_for(job, status) {
                Some(slot) => format!("A runner is starting for it in {slot}"),
                None => "A runner is starting for it".to_owned(),
            },
            Waiting::Reseeding { profile } => format!("{profile} is rebuilding its snapshot"),
            Waiting::PullingImage { profile } => format!("Pulling {profile}'s image"),
            Waiting::NoSlot { profile } => {
                let slots = status
                    .profiles
                    .iter()
                    .find(|candidate| &candidate.name == profile)
                    .map_or(0, |profile| profile.slots.len());
                if slots == 1 {
                    format!("The {profile} slot is busy")
                } else {
                    format!("All {slots} {profile} slots are busy")
                }
            }
            Waiting::Memory { .. } if status.budget.held => {
                "The slice is past 90% of its MemoryMax, so nothing starts".to_owned()
            }
            Waiting::Memory { needs, free } => format!(
                "Needs {} of memory; {} of the budget is free",
                size(*needs),
                size(*free)
            ),
            Waiting::HostMemory { needs, free } => {
                let host = status.budget.host.as_ref();
                let reason = if host.is_some_and(|host| host.stalled) {
                    "The host is short of memory: its programs stall waiting for it, so nothing starts"
                        .to_owned()
                } else {
                    format!(
                        "The host is short of memory: needs {}; the host has {} to spare",
                        size(*needs),
                        size(*free)
                    )
                };
                match host {
                    Some(host) => format!("{reason}; {}", host.memory.outside_line()),
                    None => reason,
                }
            }
            Waiting::Cpu { needs, free } => {
                format!(
                    "Needs {}; {} are free",
                    cpus(*needs),
                    admission::free_cores(*free)
                )
            }
            Waiting::BehindCpu { job: older } => {
                format!("Behind {}, which waits for CPU", older_name(*older))
            }
            Waiting::BehindStart { job: older } => {
                format!(
                    "Next after {}, whose runner starts first",
                    older_name(*older)
                )
            }
        }
    }
}

/// `GET /v1/dashboard`: the dashboard's `[web]` settings, as the daemon read them when it started.
#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize)]
pub struct Dashboard {
    /// `[web] open`: the one of `[web] origins` that `runnerctl web` opens the dashboard on; the loopback address
    /// when none.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub open: Option<String>,
}

/// `POST /v1/dashboard/pairings`: which of `[web] origins` to make a link for.
#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize)]
pub struct PairingQuery {
    /// One of `[web] origins`; each of them when none.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub origin: Option<String>,
}

/// `POST /v1/dashboard/pairings`: fresh one-time links that sign a device in to the dashboard.
#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize)]
pub struct Pairings {
    /// One per origin asked for.
    pub links: Vec<Pairing>,
}

/// A link that signs one device in to the dashboard on `origin`, and nowhere else, within `lifetime`.
#[derive(Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct Pairing {
    /// One of `[web] origins`.
    pub origin: String,
    /// The link with its one-time code: a credential, which `Debug` leaves out.
    pub url: String,
    /// Seconds it works for from when it was made.
    pub lifetime: u64,
}

impl std::fmt::Debug for Pairing {
    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        formatter
            .debug_struct("Pairing")
            .field("origin", &self.origin)
            .field("lifetime", &self.lifetime)
            .finish_non_exhaustive()
    }
}

/// `POST /v1/shutdown`.
#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize)]
pub struct ShutdownRequest {
    /// Kill running jobs and delete their runners instead of waiting for them.
    #[serde(default)]
    pub force: bool,
}

/// The body of every error response.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct ErrorResponse {
    /// What went wrong, for people to read.
    pub message: String,
}