#
cargo_test_support/
containers.rs

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    //! Support for testing using Docker containers.
    //!
    //! The [`Container`] type is a builder for configuring a container to run.
    //! After you call `launch`, you can use the [`ContainerHandle`] to interact
    //! with the running container.
    //!
    //! Tests using containers must use `#[cargo_test(container_test)]` to disable
    //! them unless the CARGO_CONTAINER_TESTS environment variable is set.

    use cargo_util::ProcessBuilder;
    use std::collections::HashMap;
    use std::io::Read;
    use std::path::PathBuf;
    use std::process::Command;
    use std::sync::atomic::{AtomicUsize, Ordering};
    use std::sync::Mutex;
    use tar::Header;

    /// A builder for configuring a container to run.
    pub struct Container {
        /// The host directory that forms the basis of the Docker image.
        build_context: PathBuf,
        /// Files to copy over to the image.
        files: Vec<MkFile>,
    }

    /// A handle to a running container.
    ///
    /// You can use this to interact with the container.
    pub struct ContainerHandle {
        /// The name of the container.
        name: String,
        /// The IP address of the container.
        ///
        /// NOTE: This is currently unused, but may be useful so I left it in.
        /// This can only be used on Linux. macOS and Windows docker doesn't allow
        /// direct connection to the container.
        pub ip_address: String,
        /// Port mappings of container_port to host_port for ports exposed via EXPOSE.
        pub port_mappings: HashMap<u16, u16>,
    }

    impl Container {
        pub fn new(context_dir: &str) -> Container {
            assert!(std::env::var_os("CARGO_CONTAINER_TESTS").is_some());
            let mut build_context = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
            build_context.push("containers");
            build_context.push(context_dir);
            Container {
                build_context,
                files: Vec::new(),
            }
        }

        /// Adds a file to be copied into the container.
        pub fn file(mut self, file: MkFile) -> Self {
            self.files.push(file);
            self
        }

        /// Starts the container.
        pub fn launch(mut self) -> ContainerHandle {
            static NEXT_ID: AtomicUsize = AtomicUsize::new(0);

            let id = NEXT_ID.fetch_add(1, Ordering::SeqCst);
            let name = format!("cargo_test_{id}");
            remove_if_exists(&name);
            self.create_container(&name);
            self.copy_files(&name);
            self.start_container(&name);
            let info = self.container_inspect(&name);
            let ip_address = if cfg!(target_os = "linux") {
                info[0]["NetworkSettings"]["IPAddress"]
                    .as_str()
                    .unwrap()
                    .to_string()
            } else {
                // macOS and Windows can't make direct connections to the
                // container. It only works through exposed ports or mapped ports.
                "127.0.0.1".to_string()
            };
            let port_mappings = self.port_mappings(&info);
            self.wait_till_ready(&port_mappings);

            ContainerHandle {
                name,
                ip_address,
                port_mappings,
            }
        }

        fn create_container(&self, name: &str) {
            static BUILD_LOCK: Mutex<()> = Mutex::new(());

            let image_base = self.build_context.file_name().unwrap();
            let image_name = format!("cargo-test-{}", image_base.to_str().unwrap());
            let _lock = BUILD_LOCK
                .lock()
                .map_err(|_| panic!("previous docker build failed, unable to run test"));
            ProcessBuilder::new("docker")
                .args(&["build", "--tag", image_name.as_str()])
                .arg(&self.build_context)
                .exec_with_output()
                .unwrap();

            ProcessBuilder::new("docker")
                .args(&[
                    "container",
                    "create",
                    "--publish-all",
                    "--rm",
                    "--name",
                    name,
                ])
                .arg(image_name)
                .exec_with_output()
                .unwrap();
        }

        fn copy_files(&mut self, name: &str) {
            if self.files.is_empty() {
                return;
            }
            let mut ar = tar::Builder::new(Vec::new());
            ar.sparse(false);
            let files = std::mem::replace(&mut self.files, Vec::new());
            for mut file in files {
                ar.append_data(&mut file.header, &file.path, file.contents.as_slice())
                    .unwrap();
            }
            let ar = ar.into_inner().unwrap();
            ProcessBuilder::new("docker")
                .args(&["cp", "-"])
                .arg(format!("{name}:/"))
                .stdin(ar)
                .exec_with_output()
                .unwrap();
        }

        fn start_container(&self, name: &str) {
            ProcessBuilder::new("docker")
                .args(&["container", "start"])
                .arg(name)
                .exec_with_output()
                .unwrap();
        }

        fn container_inspect(&self, name: &str) -> serde_json::Value {
            let output = ProcessBuilder::new("docker")
                .args(&["inspect", name])
                .exec_with_output()
                .unwrap();
            serde_json::from_slice(&output.stdout).unwrap()
        }

        /// Returns the mapping of container_port->host_port for ports that were
        /// exposed with EXPOSE.
        fn port_mappings(&self, info: &serde_json::Value) -> HashMap<u16, u16> {
            info[0]["NetworkSettings"]["Ports"]
                .as_object()
                .unwrap()
                .iter()
                .map(|(key, value)| {
                    let key = key
                        .strip_suffix("/tcp")
                        .expect("expected TCP only ports")
                        .parse()
                        .unwrap();
                    let values = value.as_array().unwrap();
                    let value = values
                        .iter()
                        .find(|value| value["HostIp"].as_str().unwrap() == "0.0.0.0")
                        .expect("expected localhost IP");
                    let host_port = value["HostPort"].as_str().unwrap().parse().unwrap();
                    (key, host_port)
                })
                .collect()
        }

        fn wait_till_ready(&self, port_mappings: &HashMap<u16, u16>) {
            for port in port_mappings.values() {
                let mut ok = false;
                for _ in 0..30 {
                    match std::net::TcpStream::connect(format!("127.0.0.1:{port}")) {
                        Ok(_) => {
                            ok = true;
                            break;
                        }
                        Err(e) => {
                            if e.kind() != std::io::ErrorKind::ConnectionRefused {
                                panic!("unexpected localhost connection error: {e:?}");
                            }
                            std::thread::sleep(std::time::Duration::new(1, 0));
                        }
                    }
                }
                if !ok {
                    panic!("no listener on localhost port {port}");
                }
            }
        }
    }

    impl ContainerHandle {
        /// Executes a program inside a running container.
        pub fn exec(&self, args: &[&str]) -> std::process::Output {
            ProcessBuilder::new("docker")
                .args(&["container", "exec", &self.name])
                .args(args)
                .exec_with_output()
                .unwrap()
        }

        /// Returns the contents of a file inside the container.
        pub fn read_file(&self, path: &str) -> String {
            let output = ProcessBuilder::new("docker")
                .args(&["cp", &format!("{}:{}", self.name, path), "-"])
                .exec_with_output()
                .unwrap();
            let mut ar = tar::Archive::new(output.stdout.as_slice());
            let mut entry = ar.entries().unwrap().next().unwrap().unwrap();
            let mut contents = String::new();
            entry.read_to_string(&mut contents).unwrap();
            contents
        }
    }

    impl Drop for ContainerHandle {
        fn drop(&mut self) {
            // To help with debugging, this will keep the container alive.
            if std::env::var_os("CARGO_CONTAINER_TEST_KEEP").is_some() {
                return;
            }
            remove_if_exists(&self.name);
        }
    }

    fn remove_if_exists(name: &str) {
        if let Err(e) = Command::new("docker")
            .args(&["container", "rm", "--force", name])
            .output()
        {
            panic!("failed to run docker: {e}");
        }
    }

    /// Builder for configuring a file to copy into a container.
    pub struct MkFile {
        path: String,
        contents: Vec<u8>,
        header: Header,
    }

    impl MkFile {
        /// Defines a file to add to the container.
        ///
        /// This should be passed to `Container::file`.
        ///
        /// The path is the path inside the container to create the file.
        pub fn path(path: &str) -> MkFile {
            MkFile {
                path: path.to_string(),
                contents: Vec::new(),
                header: Header::new_gnu(),
            }
        }

        pub fn contents(mut self, contents: impl Into<Vec<u8>>) -> Self {
            self.contents = contents.into();
            self.header.set_size(self.contents.len() as u64);
            self
        }

        pub fn mode(mut self, mode: u32) -> Self {
            self.header.set_mode(mode);
            self
        }

        pub fn uid(mut self, uid: u64) -> Self {
            self.header.set_uid(uid);
            self
        }

        pub fn gid(mut self, gid: u64) -> Self {
            self.header.set_gid(gid);
            self
        }
    }