lib.rs 60.7%

472 of 778 lines run, 69 of 257 functions · run #372 on main · run missed
//! Oxygen Strata: repositories kept on cloud object storage (docs/stores.md).
//!
//! This crate gives `oxy` the stores that need an HTTP client and the
//! providers' signing: Amazon S3 (`s3://BUCKET/PREFIX`), Google Cloud
//! Storage (`gs://BUCKET/PREFIX`) and Azure Blob Storage
//! (`az://ACCOUNT/CONTAINER/PREFIX`), each as a [`Store`] over the
//! `object_store` crate. Credentials come from each provider's standard
//! places, with nothing oxy-specific to set up; a URL may carry settings
//! as query parameters (`?profile=work&region=eu-west-2`), which is where
//! `oxy remote add --profile` keeps them.
//!
//! [`register`] hands these stores to oxy-core's remote opener; a program
//! that links this crate calls it once at start.

mod aws;
mod azure;
mod gcp;
mod http;
mod ini;

use futures::TryStreamExt;
use object_store::path::Path as ObjectPath;
use object_store::{
    GetOptions, ObjectStore, ObjectStoreExt, PutMode, PutOptions, PutPayload, UpdateVersion,
};
use oxy_core::strata::{check_key, Entry, Error, Result, Store, Version};
use std::collections::BTreeMap;
use std::future::Future;
use std::ops::Range;
use std::sync::{Arc, Mutex};

/// Make the cloud stores available to `oxy_core::protocol::open_remote`.
/// Safe to call more than once.
pub fn register() {
    // object_store's reqwest is built with rustls and no bundled crypto
    // provider; oxy links ring already, so that is the one to install.
    let _ = rustls::crypto::ring::default_provider().install_default();
    oxy_core::protocol::register_store_opener(open_url);
}

fn open_url(
    url: &str,
    _options: &oxy_core::protocol::RemoteOptions,
) -> Option<Result<Box<dyn Store>>> {
    let scheme = url.split_once("://")?.0;
    if !matches!(scheme, "s3" | "gs" | "az") {
        return None;
    }
    let lookup = *CREDENTIALS.lock().unwrap_or_else(|p| p.into_inner());
    let given = lookup.and_then(|f| f(url));
    Some(shared(url, given).map(|s| Box::new(Shared(s)) as Box<dyn Store>))
}

/// One client per store and credentials, kept for the life of the process
/// (oxygenhub#234): a server opens a repository for every request, and a
/// new client each time meant a new runtime, new connections and signing
/// in to the provider again before the first byte.
type OpenStores = std::collections::HashMap<(String, Option<Credentials>), Arc<CloudStore>>;

fn shared(url: &str, given: Option<Credentials>) -> Result<Arc<CloudStore>> {
    static OPEN: Mutex<Option<OpenStores>> = Mutex::new(None);
    let key = (url.to_string(), given);
    let mut open = OPEN.lock().unwrap_or_else(|p| p.into_inner());
    let map = open.get_or_insert_with(Default::default);
    if let Some(s) = map.get(&key) {
        return Ok(s.clone());
    }
    let store = Arc::new(CloudStore::open_with(url, key.1.as_ref())?);
    map.insert(key, store.clone());
    Ok(store)
}

/// A shared [`CloudStore`] as a [`Store`].
struct Shared(Arc<CloudStore>);

impl Store for Shared {
    fn describe(&self) -> String {
        self.0.describe()
    }
    fn has(&self, key: &str) -> Result<bool> {
        self.0.has(key)
    }
    fn get(&self, key: &str) -> Result<Vec<u8>> {
        self.0.get(key)
    }
    fn get_range(&self, key: &str, range: Range<u64>) -> Result<Vec<u8>> {
        self.0.get_range(key, range)
    }
    fn put_new(&self, key: &str, bytes: &[u8]) -> Result<()> {
        self.0.put_new(key, bytes)
    }
    fn list(&self, prefix: &str) -> Result<Vec<Entry>> {
        self.0.list(prefix)
    }
    fn stat(&self, key: &str) -> Result<Option<Entry>> {
        self.0.stat(key)
    }
    fn delete(&self, key: &str) -> Result<()> {
        self.0.delete(key)
    }
    fn read_ref(&self, key: &str) -> Result<Option<(Vec<u8>, Version)>> {
        self.0.read_ref(key)
    }
    fn write_ref(&self, key: &str, bytes: &[u8], expected: Option<&Version>) -> Result<Version> {
        self.0.write_ref(key, bytes, expected)
    }
}

static OPENS: std::sync::atomic::AtomicU64 = std::sync::atomic::AtomicU64::new(0);
static CALLS: std::sync::atomic::AtomicU64 = std::sync::atomic::AtomicU64::new(0);
static MICROS: std::sync::atomic::AtomicU64 = std::sync::atomic::AtomicU64::new(0);
static BY_OP: [std::sync::atomic::AtomicU64; Op::ALL.len()] =
    [const { std::sync::atomic::AtomicU64::new(0) }; Op::ALL.len()];

/// The kinds of request a cloud store makes, counted apart so a server can
/// tell which of them its time goes to.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Op {
    /// `has` that found the object.
    Has,
    /// `has` that did not: an absent object is never cached.
    HasMissing,
    Get,
    Range,
    Put,
    List,
    /// A listing of a repository's packs, sent.
    ListPacks,
    /// A listing answered from [`Listings`], not sent.
    ListKept,
    Delete,
    ReadRef,
    /// A read of a repository's journal of signatures and index entries
    /// (`pack-entries`, spec §13.7): one per open of a folded store, in
    /// place of a listing per lookup.
    ReadJournal,
    WriteRef,
}

impl Op {
    pub const ALL: [Op; 12] = [
        Op::Has,
        Op::HasMissing,
        Op::Get,
        Op::Range,
        Op::Put,
        Op::List,
        Op::ListPacks,
        Op::ListKept,
        Op::Delete,
        Op::ReadRef,
        Op::ReadJournal,
        Op::WriteRef,
    ];

    pub fn name(self) -> &'static str {
        match self {
            Op::Has => "has",
            Op::HasMissing => "has_missing",
            Op::Get => "get",
            Op::Range => "range",
            Op::Put => "put",
            Op::List => "list",
            Op::ListPacks => "list_packs",
            Op::ListKept => "list_kept",
            Op::Delete => "delete",
            Op::ReadRef => "read_ref",
            Op::ReadJournal => "read_journal",
            Op::WriteRef => "write_ref",
        }
    }
}

fn counted(op: Op) {
    BY_OP[op as usize].fetch_add(1, std::sync::atomic::Ordering::Relaxed);
}

/// What the cloud stores have done since the process started: clients
/// opened, requests made and the time spent in them, for a server to show
/// (a hub's /health).
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub struct Stats {
    pub opens: u64,
    pub calls: u64,
    pub millis: u64,
    /// Requests by kind, in [`Op::ALL`]'s order.
    pub by_op: [u64; Op::ALL.len()],
}

impl Stats {
    /// Each kind of request with how many were made.
    pub fn ops(&self) -> impl Iterator<Item = (&'static str, u64)> + '_ {
        Op::ALL
            .iter()
            .map(|op| (op.name(), self.by_op[*op as usize]))
    }
}

pub fn stats() -> Stats {
    use std::sync::atomic::Ordering::Relaxed;
    Stats {
        opens: OPENS.load(Relaxed),
        calls: CALLS.load(Relaxed),
        millis: MICROS.load(Relaxed) / 1000,
        by_op: std::array::from_fn(|i| BY_OP[i].load(Relaxed)),
    }
}

/// Credentials a program keeps itself and hands over, instead of the
/// provider's usual places: a hub keeps each repository's sealed. When a
/// store is opened with them, nothing from the environment or the
/// provider's files is used.
#[derive(Clone, PartialEq, Eq, Hash)]
pub enum Credentials {
    /// An S3 access key.
    Aws {
        access_key_id: String,
        secret_access_key: String,
        session_token: Option<String>,
    },
    /// A Google Cloud service account key, as the JSON Google issues.
    Gcp { service_account_key: String },
    /// An Azure service principal.
    Azure {
        tenant_id: String,
        client_id: String,
        client_secret: String,
    },
}

impl std::fmt::Debug for Credentials {
    /// Names the kind and the public part only: never the secret.
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Credentials::Aws { access_key_id, .. } => {
                write!(f, "Aws({access_key_id}, secret hidden)")
            }
            Credentials::Gcp { .. } => write!(f, "Gcp(service account key hidden)"),
            Credentials::Azure { client_id, .. } => write!(f, "Azure({client_id}, secret hidden)"),
        }
    }
}

impl Credentials {
    /// The scheme of the stores these are for.
    pub fn scheme(&self) -> &'static str {
        match self {
            Credentials::Aws { .. } => "s3",
            Credentials::Gcp { .. } => "gs",
            Credentials::Azure { .. } => "az",
        }
    }

    /// As JSON, for keeping (sealed) and reading back with [`Credentials::from_json`].
    pub fn to_json(&self) -> String {
        let v = match self {
            Credentials::Aws {
                access_key_id,
                secret_access_key,
                session_token,
            } => serde_json::json!({
                "kind": "aws", "access_key_id": access_key_id, "secret_access_key": secret_access_key,
                "session_token": session_token,
            }),
            Credentials::Gcp {
                service_account_key,
            } => {
                serde_json::json!({ "kind": "gcp", "service_account_key": service_account_key })
            }
            Credentials::Azure {
                tenant_id,
                client_id,
                client_secret,
            } => serde_json::json!({
                "kind": "azure", "tenant_id": tenant_id, "client_id": client_id, "client_secret": client_secret,
            }),
        };
        v.to_string()
    }

    pub fn from_json(text: &str) -> Result<Credentials> {
        let v: serde_json::Value = serde_json::from_str(text)
            .map_err(|e| Error::Backend(format!("credentials are not JSON: {e}")))?;
        let field = |k: &str| -> Result<String> {
            v.get(k)
                .and_then(|x| x.as_str())
                .filter(|x| !x.trim().is_empty())
                .map(|x| x.trim().to_string())
                .ok_or_else(|| Error::Backend(format!("credentials need {k}")))
        };
        match v.get("kind").and_then(|k| k.as_str()) {
            Some("aws") => Ok(Credentials::Aws {
                access_key_id: field("access_key_id")?,
                secret_access_key: field("secret_access_key")?,
                session_token: field("session_token").ok(),
            }),
            Some("gcp") => {
                let key = field("service_account_key")?;
                let parsed: serde_json::Value = serde_json::from_str(&key).map_err(|_| {
                    Error::Backend("the service account key is not the JSON Google issues".into())
                })?;
                if parsed.get("type").and_then(|t| t.as_str()) != Some("service_account") {
                    return Err(Error::Backend(
                        "the key is not a service account key (its type is not service_account)"
                            .into(),
                    ));
                }
                Ok(Credentials::Gcp {
                    service_account_key: key,
                })
            }
            Some("azure") => Ok(Credentials::Azure {
                tenant_id: field("tenant_id")?,
                client_id: field("client_id")?,
                client_secret: field("client_secret")?,
            }),
            _ => Err(Error::Backend(
                "credentials need a kind: aws, gcp or azure".into(),
            )),
        }
    }
}

/// Finds the credentials a program keeps for a store URL.
pub type CredentialsLookup = fn(&str) -> Option<Credentials>;

static CREDENTIALS: Mutex<Option<CredentialsLookup>> = Mutex::new(None);

/// Have stores opened by URL (as a repository's `storage.url` is) use the
/// credentials `lookup` finds for it, where it finds any.
pub fn set_credentials_lookup(lookup: CredentialsLookup) {
    *CREDENTIALS.lock().unwrap_or_else(|p| p.into_inner()) = Some(lookup);
}

/// A parsed store URL: `SCHEME://HOST/PATH?PARAMS`.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct StoreUrl {
    pub scheme: String,
    /// The bucket (S3, GCS) or the storage account (Azure).
    pub host: String,
    /// The path under the host, without leading or trailing slashes; for
    /// Azure the container is its first segment.
    pub path: String,
    pub params: BTreeMap<String, String>,
}

impl StoreUrl {
    pub fn parse(url: &str) -> Result<StoreUrl> {
        let bad = |why: &str| Error::Backend(format!("{url}: {why}"));
        let (scheme, rest) = url.split_once("://").ok_or_else(|| bad("not a URL"))?;
        let (rest, query) = match rest.split_once('?') {
            Some((r, q)) => (r, Some(q)),
            None => (rest, None),
        };
        let (host, path) = match rest.split_once('/') {
            Some((h, p)) => (h, p.trim_matches('/')),
            None => (rest, ""),
        };
        if host.is_empty() {
            return Err(bad("names no bucket"));
        }
        let mut params = BTreeMap::new();
        for pair in query.unwrap_or("").split('&').filter(|p| !p.is_empty()) {
            let (k, v) = pair.split_once('=').unwrap_or((pair, ""));
            params.insert(k.to_string(), percent_decode(v));
        }
        Ok(StoreUrl {
            scheme: scheme.to_string(),
            host: host.to_string(),
            path: path.to_string(),
            params,
        })
    }

    /// The URL without its parameters, for messages.
    pub fn plain(&self) -> String {
        if self.path.is_empty() {
            format!("{}://{}", self.scheme, self.host)
        } else {
            format!("{}://{}/{}", self.scheme, self.host, self.path)
        }
    }

    pub fn param(&self, name: &str) -> Option<&str> {
        self.params.get(name).map(String::as_str)
    }
}

fn percent_decode(s: &str) -> String {
    let bytes = s.as_bytes();
    let mut out = Vec::with_capacity(bytes.len());
    let mut i = 0;
    while i < bytes.len() {
        if bytes[i] == b'%' && i + 2 < bytes.len() {
            if let Ok(v) = u8::from_str_radix(&s[i + 1..i + 3], 16) {
                out.push(v);
                i += 3;
                continue;
            }
        }
        out.push(bytes[i]);
        i += 1;
    }
    String::from_utf8_lossy(&out).into_owned()
}

/// A store on a cloud provider: the provider's client, the prefix every
/// key goes under, and a runtime to run the client on.
pub struct CloudStore {
    inner: Arc<dyn ObjectStore>,
    prefix: String,
    name: String,
    hint: &'static str,
    /// Always there until the store is dropped: two workers, so the
    /// requests of a shared store run side by side.
    runtime: Option<tokio::runtime::Runtime>,
    /// Keys `has` found missing lately (see [`Misses`]).
    misses: Misses,
    /// Pack listings, kept a moment (see [`Listings`]).
    listings: Listings,
}

/// How long a key found missing is taken as missing without asking again.
const MISS_FOR: std::time::Duration = std::time::Duration::from_secs(30);

/// Keys found missing in the last [`MISS_FOR`], so a server answering the
/// same question again and again does not send a request each time
/// (oxygenhub#228: a client's negotiate asked about ~190 objects the hub
/// lacked every 8 s, 45 ms a request). This process forgets a key the
/// moment it writes it, so its own writes are never hidden; another writer
/// to the same keys is seen within `MISS_FOR`.
#[derive(Default)]
struct Misses(Mutex<std::collections::HashMap<String, std::time::Instant>>);

impl Misses {
    /// At most this many kept; past it the oldest half is let go.
    const MAX: usize = 100_000;

    fn known(&self, key: &str) -> bool {
        let map = self.0.lock().unwrap_or_else(|p| p.into_inner());
        map.get(key).is_some_and(|t| t.elapsed() < MISS_FOR)
    }

    fn missed(&self, key: &str) {
        let mut map = self.0.lock().unwrap_or_else(|p| p.into_inner());
        if map.len() >= Self::MAX {
            map.retain(|_, t| t.elapsed() < MISS_FOR / 2);
            if map.len() >= Self::MAX {
                map.clear();
            }
        }
        map.insert(key.to_string(), std::time::Instant::now());
    }

    fn written(&self, key: &str) {
        self.0.lock().unwrap_or_else(|p| p.into_inner()).remove(key);
    }
}

/// Listings kept for [`MISS_FOR`] (oxygen#116): the `pack-` keys, which
/// every open of a repository's store lists, so a forge serving a
/// repository from a bucket lists them once a while rather than once a
/// request. Like [`Misses`], this process forgets a listing the moment it
/// writes or deletes a key under it; another writer's pack is seen within
/// `MISS_FOR`, as a missing key is.
#[derive(Default)]
struct Listings(Mutex<std::collections::HashMap<String, (std::time::Instant, Vec<Entry>)>>);

impl Listings {
    /// The prefixes kept: those every open lists.
    fn kept(prefix: &str) -> bool {
        prefix == "pack-"
    }

    fn get(&self, prefix: &str) -> Option<Vec<Entry>> {
        if !Self::kept(prefix) {
            return None;
        }
        let map = self.0.lock().unwrap_or_else(|p| p.into_inner());
        map.get(prefix)
            .filter(|(t, _)| t.elapsed() < MISS_FOR)
            .map(|(_, e)| e.clone())
    }

    fn put(&self, prefix: &str, entries: &[Entry]) {
        if Self::kept(prefix) {
            self.0.lock().unwrap_or_else(|p| p.into_inner()).insert(
                prefix.to_string(),
                (std::time::Instant::now(), entries.to_vec()),
            );
        }
    }

    fn written(&self, key: &str) {
        self.0
            .lock()
            .unwrap_or_else(|p| p.into_inner())
            .retain(|prefix, _| !key.starts_with(prefix.as_str()));
    }
}

/// Run a request that writes or deletes `key`, forgetting what the caches
/// hold for it both before it is sent and after it completes, whatever it
/// returns: a listing or a miss taken by another thread while the request
/// was in flight may predate it, and would otherwise be kept for
/// `MISS_FOR` (oxygenhub#249).
fn writing<T>(misses: &Misses, listings: &Listings, key: &str, request: impl FnOnce() -> T) -> T {
    misses.written(key);
    listings.written(key);
    let out = request();
    misses.written(key);
    listings.written(key);
    out
}

impl Drop for CloudStore {
    /// Without waiting, so a store can be dropped inside a runtime too.
    fn drop(&mut self) {
        if let Some(rt) = self.runtime.take() {
            rt.shutdown_background();
        }
    }
}

impl CloudStore {
    /// Open the store a URL names. Nothing is sent yet: credentials are
    /// resolved here, but the bucket is first spoken to on the first call.
    pub fn open(url: &str) -> Result<CloudStore> {
        Self::open_with(url, None)
    }

    /// [`CloudStore::open`] with credentials given, which must be for
    /// the URL's kind of store; then only they are used.
    pub fn open_with(url: &str, given: Option<&Credentials>) -> Result<CloudStore> {
        let parsed = StoreUrl::parse(url)?;
        if let Some(c) = given.filter(|c| c.scheme() != parsed.scheme) {
            return Err(Error::Backend(format!(
                "{}: the credentials given are for {}:// stores",
                parsed.plain(),
                c.scheme()
            )));
        }
        let aws_keys = match given {
            Some(Credentials::Aws {
                access_key_id,
                secret_access_key,
                session_token,
            }) => Some((
                access_key_id.as_str(),
                secret_access_key.as_str(),
                session_token.as_deref(),
            )),
            _ => None,
        };
        let gcp_key = match given {
            Some(Credentials::Gcp {
                service_account_key,
            }) => Some(service_account_key.as_str()),
            _ => None,
        };
        let principal = match given {
            Some(Credentials::Azure {
                tenant_id,
                client_id,
                client_secret,
            }) => Some((
                tenant_id.as_str(),
                client_id.as_str(),
                client_secret.as_str(),
            )),
            _ => None,
        };
        OPENS.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
        let runtime = tokio::runtime::Builder::new_multi_thread()
            .worker_threads(2)
            .thread_name("oxy-strata")
            .enable_all()
            .build()
            .map_err(|e| Error::Backend(format!("starting the HTTP runtime: {e}")))?;
        let (inner, prefix, hint): (Arc<dyn ObjectStore>, String, &'static str) =
            match parsed.scheme.as_str() {
                "s3" => (
                    Arc::new(aws::open(&parsed, aws_keys)?),
                    parsed.path.clone(),
                    aws::HINT,
                ),
                "gs" => (
                    Arc::new(gcp::open(&parsed, gcp_key)?),
                    parsed.path.clone(),
                    gcp::HINT,
                ),
                "az" => {
                    let (store, prefix) = azure::open(&parsed, principal)?;
                    (Arc::new(store), prefix, azure::HINT)
                }
                other => {
                    return Err(Error::Backend(format!(
                        "{url}: {other}:// is not a store oxy knows (s3://, gs://, az://, dir://)"
                    )))
                }
            };
        Ok(CloudStore {
            inner,
            prefix,
            name: parsed.plain(),
            hint,
            runtime: Some(runtime),
            misses: Misses::default(),
            listings: Listings::default(),
        })
    }

    /// Run a request to completion. Called from a thread that is itself
    /// driving async tasks (a server's handler), where blocking on another
    /// runtime is not allowed, the request runs on a thread of its own.
    fn block<F>(&self, f: F) -> F::Output
    where
        F: Future + Send,
        F::Output: Send,
    {
        let runtime = self
            .runtime
            .as_ref()
            .expect("the runtime lives as long as the store");
        let started = std::time::Instant::now();
        let out = if tokio::runtime::Handle::try_current().is_ok() {
            std::thread::scope(|s| {
                s.spawn(|| runtime.block_on(f))
                    .join()
                    .unwrap_or_else(|p| std::panic::resume_unwind(p))
            })
        } else {
            runtime.block_on(f)
        };
        CALLS.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
        MICROS.fetch_add(
            started.elapsed().as_micros() as u64,
            std::sync::atomic::Ordering::Relaxed,
        );
        out
    }

    fn path(&self, key: &str) -> Result<ObjectPath> {
        check_key(key)?;
        let full = if self.prefix.is_empty() {
            key.to_string()
        } else {
            format!("{}/{key}", self.prefix)
        };
        ObjectPath::parse(&full).map_err(|e| Error::Backend(format!("{full}: {e}")))
    }

    /// Our error for the provider's, with what to do next where it helps.
    fn map(&self, e: object_store::Error, key: &str) -> Error {
        use object_store::Error as E;
        match e {
            E::NotFound { .. } => Error::NotFound(key.to_string()),
            E::AlreadyExists { .. } => Error::Exists(key.to_string()),
            E::Precondition { .. } | E::NotModified { .. } => Error::Conflict(key.to_string()),
            other => {
                let text = other.to_string();
                let lower = text.to_ascii_lowercase();
                let advice = if lower.contains("403")
                    || lower.contains("accessdenied")
                    || lower.contains("forbidden")
                    || lower.contains("authorizationpermissionmismatch")
                {
                    format!(
                        ": access denied; the credentials in use may not do this on {}: {}",
                        self.name, self.hint
                    )
                } else if lower.contains("credential") || lower.contains("no valid credentials") {
                    format!(": no usable credentials: {}", self.hint)
                } else if lower.contains("nosuchbucket")
                    || lower.contains("bucketnotfound")
                    || lower.contains("containernotfound")
                {
                    format!(
                        ": {} does not exist, or the credentials cannot see it",
                        self.name
                    )
                } else if lower.contains("dns")
                    || lower.contains("connect")
                    || lower.contains("timed out")
                {
                    ": cannot reach the service; check the network, the endpoint and the region"
                        .to_string()
                } else {
                    String::new()
                };
                Error::Backend(format!("{}: {text}{advice}", self.name))
            }
        }
    }

    fn version_of(e_tag: Option<String>, version: Option<String>) -> Version {
        Version(format!(
            "{}\t{}",
            e_tag.unwrap_or_default(),
            version.unwrap_or_default()
        ))
    }

    fn update_version(v: &Version) -> UpdateVersion {
        let (e_tag, version) = v.0.split_once('\t').unwrap_or((v.0.as_str(), ""));
        UpdateVersion {
            e_tag: (!e_tag.is_empty()).then(|| e_tag.to_string()),
            version: (!version.is_empty()).then(|| version.to_string()),
        }
    }
}

impl Store for CloudStore {
    fn describe(&self) -> String {
        self.name.clone()
    }

    fn has(&self, key: &str) -> Result<bool> {
        let path = self.path(key)?;
        if self.misses.known(key) {
            return Ok(false);
        }
        match self.block(self.inner.head(&path)) {
            Ok(_) => {
                counted(Op::Has);
                Ok(true)
            }
            Err(object_store::Error::NotFound { .. }) => {
                counted(Op::HasMissing);
                self.misses.missed(key);
                Ok(false)
            }
            Err(e) => Err(self.map(e, key)),
        }
    }

    fn get(&self, key: &str) -> Result<Vec<u8>> {
        let path = self.path(key)?;
        counted(Op::Get);
        self.block(async {
            let r = self.inner.get(&path).await?;
            r.bytes().await
        })
        .map(|b| b.to_vec())
        .map_err(|e| self.map(e, key))
    }

    fn get_range(&self, key: &str, range: Range<u64>) -> Result<Vec<u8>> {
        let path = self.path(key)?;
        if range.start > range.end {
            return Err(Error::Backend(format!(
                "{key}: bytes {}..{} is not a range",
                range.start, range.end
            )));
        }
        if range.is_empty() {
            return Ok(Vec::new());
        }
        let want = (range.end - range.start) as usize;
        counted(Op::Range);
        let bytes = self
            .block(self.inner.get_range(&path, range.clone()))
            .map_err(|e| self.map(e, key))?;
        if bytes.len() != want {
            return Err(Error::Backend(format!(
                "{key}: bytes {}..{} asked, {} returned: the object is shorter",
                range.start,
                range.end,
                bytes.len()
            )));
        }
        Ok(bytes.to_vec())
    }

    fn put_new(&self, key: &str, bytes: &[u8]) -> Result<()> {
        let path = self.path(key)?;
        let opts = PutOptions {
            mode: PutMode::Create,
            ..Default::default()
        };
        counted(Op::Put);
        writing(&self.misses, &self.listings, key, || {
            self.block(
                self.inner
                    .put_opts(&path, PutPayload::from(bytes.to_vec()), opts),
            )
        })
        .map(|_| ())
        .map_err(|e| self.map(e, key))
    }

    fn list(&self, prefix: &str) -> Result<Vec<Entry>> {
        if let Some(kept) = self.listings.get(prefix) {
            counted(Op::ListKept);
            return Ok(kept);
        }
        // Providers list by whole path segments; the asked prefix may end
        // mid-segment, so list its directory and filter here.
        let dir = prefix.rsplit_once('/').map(|(d, _)| d).unwrap_or("");
        let full_dir = match (self.prefix.as_str(), dir) {
            ("", "") => None,
            ("", d) => Some(d.to_string()),
            (p, "") => Some(p.to_string()),
            (p, d) => Some(format!("{p}/{d}")),
        };
        let full_dir = full_dir
            .map(|d| ObjectPath::parse(&d).map_err(|e| Error::Backend(format!("{d}: {e}"))))
            .transpose()?;
        counted(if Listings::kept(prefix) {
            Op::ListPacks
        } else {
            Op::List
        });
        let metas: Vec<object_store::ObjectMeta> = self
            .block(self.inner.list(full_dir.as_ref()).try_collect())
            .map_err(|e| self.map(e, prefix))?;
        let strip = if self.prefix.is_empty() {
            String::new()
        } else {
            format!("{}/", self.prefix)
        };
        let mut out: Vec<Entry> = metas
            .into_iter()
            .filter_map(|m| {
                let loc = m.location.to_string();
                let key = loc.strip_prefix(&strip)?;
                key.starts_with(prefix).then(|| Entry {
                    key: key.to_string(),
                    size: m.size,
                    modified_ms: u64::try_from(m.last_modified.timestamp_millis()).ok(),
                })
            })
            .collect();
        out.sort_by(|a, b| a.key.cmp(&b.key));
        self.listings.put(prefix, &out);
        Ok(out)
    }

    /// A HEAD of the key, not a listing of its directory (oxygen#116).
    fn stat(&self, key: &str) -> Result<Option<Entry>> {
        let path = self.path(key)?;
        counted(Op::Has);
        match self.block(self.inner.head(&path)) {
            Ok(m) => Ok(Some(Entry {
                key: key.to_string(),
                size: m.size,
                modified_ms: u64::try_from(m.last_modified.timestamp_millis()).ok(),
            })),
            Err(object_store::Error::NotFound { .. }) => Ok(None),
            Err(e) => Err(self.map(e, key)),
        }
    }

    fn delete(&self, key: &str) -> Result<()> {
        let path = self.path(key)?;
        counted(Op::Delete);
        match writing(&self.misses, &self.listings, key, || {
            self.block(self.inner.delete(&path))
        }) {
            Ok(()) | Err(object_store::Error::NotFound { .. }) => Ok(()),
            Err(e) => Err(self.map(e, key)),
        }
    }

    fn read_ref(&self, key: &str) -> Result<Option<(Vec<u8>, Version)>> {
        let path = self.path(key)?;
        counted(if key == oxy_core::store::JOURNAL_KEY {
            Op::ReadJournal
        } else {
            Op::ReadRef
        });
        let got = self.block(async {
            let r = self.inner.get_opts(&path, GetOptions::default()).await?;
            let meta = r.meta.clone();
            let bytes = r.bytes().await?;
            Ok::<_, object_store::Error>((bytes, meta))
        });
        match got {
            Ok((bytes, meta)) => Ok(Some((
                bytes.to_vec(),
                Self::version_of(meta.e_tag, meta.version),
            ))),
            Err(object_store::Error::NotFound { .. }) => Ok(None),
            Err(e) => Err(self.map(e, key)),
        }
    }

    fn write_ref(&self, key: &str, bytes: &[u8], expected: Option<&Version>) -> Result<Version> {
        let path = self.path(key)?;
        let mode = match expected {
            None => PutMode::Create,
            Some(v) => PutMode::Update(Self::update_version(v)),
        };
        let opts = PutOptions {
            mode,
            ..Default::default()
        };
        counted(Op::WriteRef);
        let put = writing(&self.misses, &self.listings, key, || {
            self.block(
                self.inner
                    .put_opts(&path, PutPayload::from(bytes.to_vec()), opts),
            )
        })
        .map_err(|e| match self.map(e, key) {
            // A record that exists when none was expected is a lost
            // race too, not a misuse of put_new.
            Error::Exists(k) => Error::Conflict(k),
            other => other,
        })?;
        Ok(Self::version_of(put.e_tag, put.version))
    }
}

#[cfg(test)]
mod tests {

    /// A miss is remembered until the key is written, or for MISS_FOR.
    #[test]
    fn a_miss_is_remembered_until_written() {
        let m = super::Misses::default();
        assert!(!m.known("loose/ab/cd"));
        m.missed("loose/ab/cd");
        assert!(m.known("loose/ab/cd") && !m.known("loose/ab/ce"));
        m.written("loose/ab/cd");
        assert!(!m.known("loose/ab/cd"), "a write forgets the miss");
        m.missed("old");
        m.0.lock()
            .unwrap()
            .insert("old".into(), std::time::Instant::now() - super::MISS_FOR);
        assert!(!m.known("old"), "a miss expires");
    }

    /// Every kind of request is reported, once and by its own name.
    /// The pack listing is kept until a pack key is written or deleted
    /// here, or for MISS_FOR; other prefixes are never kept (oxygen#116).
    #[test]
    fn the_pack_listing_is_kept_until_a_pack_is_written() {
        let l = super::Listings::default();
        let e = |k: &str| oxy_core::strata::Entry {
            key: k.into(),
            size: 1,
            modified_ms: None,
        };
        l.put("pack-", &[e("pack-1.idx")]);
        assert_eq!(l.get("pack-").map(|v| v.len()), Some(1));
        l.put("loose/", &[e("loose/ab")]);
        assert!(l.get("loose/").is_none(), "only the pack listing is kept");
        l.written("loose/cd");
        assert!(l.get("pack-").is_some(), "a loose object leaves it");
        l.written("pack-2.pack");
        assert!(l.get("pack-").is_none(), "a new pack forgets it");
        l.put("pack-", &[e("pack-1.idx")]);
        l.0.lock().unwrap().get_mut("pack-").unwrap().0 -= super::MISS_FOR;
        assert!(l.get("pack-").is_none(), "and it ages out");
    }

    /// A listing or miss taken by another thread while a write is in
    /// flight is forgotten when the write completes, not kept stale for
    /// MISS_FOR (oxygenhub#249), whether the write succeeded or not.
    #[test]
    fn a_listing_taken_during_a_write_is_forgotten_after_it() {
        let (m, l) = (super::Misses::default(), super::Listings::default());
        let e = |k: &str| oxy_core::strata::Entry {
            key: k.into(),
            size: 1,
            modified_ms: None,
        };
        l.put("pack-", &[e("pack-1.idx")]);
        let got = super::writing(&m, &l, "pack-2.idx", || {
            assert!(l.get("pack-").is_none(), "forgotten before it is sent");
            // Another thread lists, and misses, mid-request.
            l.put("pack-", &[e("pack-1.idx")]);
            m.missed("pack-2.idx");
            7
        });
        assert_eq!(got, 7);
        assert!(l.get("pack-").is_none(), "the mid-request listing is gone");
        assert!(!m.known("pack-2.idx"), "and the miss");
        // A delete that fails is treated the same.
        l.put("pack-", &[e("pack-1.idx")]);
        let r: std::result::Result<(), &str> = super::writing(&m, &l, "pack-1.idx", || {
            l.put("pack-", &[e("pack-1.idx")]);
            Err("network")
        });
        assert!(r.is_err() && l.get("pack-").is_none());
        // Other prefixes' writes leave the pack listing.
        l.put("pack-", &[e("pack-1.idx")]);
        super::writing(&m, &l, "loose/ab/cd", || ());
        assert!(l.get("pack-").is_some());
    }

    #[test]
    fn stats_name_every_kind_of_request() {
        let names: Vec<&str> = super::stats().ops().map(|(n, _)| n).collect();
        assert_eq!(names.len(), super::Op::ALL.len());
        let mut unique = names.clone();
        unique.sort();
        unique.dedup();
        assert_eq!(unique.len(), names.len());
        assert!(names.contains(&"has_missing") && names.contains(&"range"));
    }

    /// One client per store and credentials (oxygenhub#234): opening the
    /// same again shares it, and only a new one counts as opened.
    #[test]
    fn a_store_opened_again_shares_its_client() {
        let creds = |k: &str| Credentials::Aws {
            access_key_id: k.into(),
            secret_access_key: "s".into(),
            session_token: None,
        };
        let url = "s3://oxy-shared-test/repos/a?region=eu-west-2";
        let before = super::stats().opens;
        let a = super::shared(url, Some(creds("one"))).unwrap();
        let b = super::shared(url, Some(creds("one"))).unwrap();
        assert!(std::sync::Arc::ptr_eq(&a, &b));
        let other_keys = super::shared(url, Some(creds("two"))).unwrap();
        assert!(
            !std::sync::Arc::ptr_eq(&a, &other_keys),
            "other credentials, another client"
        );
        assert!(
            super::stats().opens - before >= 2,
            "two clients opened (other tests may open more)"
        );
    }

    #[tokio::test]
    async fn a_store_can_be_used_from_inside_a_runtime() {
        // As a server's handler would: blocking on the store's own runtime
        // from here must neither panic nor deadlock, and nor must dropping it.
        let store = CloudStore::open(
            "s3://oxy-no-such-bucket/p?region=eu-west-2&endpoint=http://127.0.0.1:9",
        )
        .unwrap();
        assert_eq!(store.block(async { 7 }), 7);
        drop(store);
    }

    #[test]
    fn credentials_round_trip_and_never_show_their_secret() {
        let aws = Credentials::Aws {
            access_key_id: "AKIDEXAMPLE".into(),
            secret_access_key: "wJalrXUtnFEMI".into(),
            session_token: None,
        };
        assert_eq!(Credentials::from_json(&aws.to_json()).unwrap(), aws);
        assert_eq!(format!("{aws:?}"), "Aws(AKIDEXAMPLE, secret hidden)");
        let az = Credentials::Azure {
            tenant_id: "t".into(),
            client_id: "c".into(),
            client_secret: "s3cr3t".into(),
        };
        assert_eq!(Credentials::from_json(&az.to_json()).unwrap(), az);
        assert!(!format!("{az:?}").contains("s3cr3t"));
        let key = r#"{"type":"service_account","client_email":"x@y","private_key":"k"}"#;
        let gcp = Credentials::Gcp {
            service_account_key: key.into(),
        };
        assert_eq!(Credentials::from_json(&gcp.to_json()).unwrap(), gcp);
        assert!(!format!("{gcp:?}").contains("private_key"));
        for (bad, why) in [
            (r#"{"kind":"aws","access_key_id":"a"}"#, "secret_access_key"),
            (
                r#"{"kind":"gcp","service_account_key":"{\"type\":\"authorized_user\"}"}"#,
                "not a service account key",
            ),
            (r#"{"kind":"ftp"}"#, "aws, gcp or azure"),
            ("nope", "not JSON"),
        ] {
            let e = Credentials::from_json(bad).unwrap_err().to_string();
            assert!(e.contains(why), "{bad}: {e}");
        }
        let e = CloudStore::open_with("gs://bucket/p", Some(&aws))
            .err()
            .unwrap()
            .to_string();
        assert!(e.contains("are for s3:// stores"), "{e}");
    }

    use super::*;

    #[test]
    fn urls_parse_with_their_parameters() {
        let u =
            StoreUrl::parse("s3://my-bucket/repos/oxygen?profile=work&region=eu-west-2").unwrap();
        assert_eq!(u.scheme, "s3");
        assert_eq!(u.host, "my-bucket");
        assert_eq!(u.path, "repos/oxygen");
        assert_eq!(u.param("profile"), Some("work"));
        assert_eq!(u.param("region"), Some("eu-west-2"));
        assert_eq!(u.plain(), "s3://my-bucket/repos/oxygen");
        let u = StoreUrl::parse("gs://bucket").unwrap();
        assert_eq!((u.host.as_str(), u.path.as_str()), ("bucket", ""));
        assert_eq!(u.plain(), "gs://bucket");
        let u = StoreUrl::parse("az://acct/container/a/b/?endpoint=http%3A%2F%2F127.0.0.1%3A10000")
            .unwrap();
        assert_eq!(u.path, "container/a/b");
        assert_eq!(u.param("endpoint"), Some("http://127.0.0.1:10000"));
        assert!(StoreUrl::parse("s3://").is_err());
        assert!(StoreUrl::parse("nonsense").is_err());
    }

    #[test]
    fn versions_carry_both_an_etag_and_a_generation() {
        let v = CloudStore::version_of(Some("\"abc\"".into()), Some("17".into()));
        let u = CloudStore::update_version(&v);
        assert_eq!(u.e_tag.as_deref(), Some("\"abc\""));
        assert_eq!(u.version.as_deref(), Some("17"));
        let u = CloudStore::update_version(&CloudStore::version_of(None, Some("3".into())));
        assert_eq!((u.e_tag, u.version.as_deref()), (None, Some("3")));
    }
}
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