witchcraft-server 6.4.0

// Copyright 2022 Palantir Technologies, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! Health checks.
pub use api::objects::HealthState;
use conjure_object::Any;
pub use registry::HealthCheckRegistry;
use serde::Serialize;
use staged_builder::staged_builder;
use std::any::TypeId;
use std::collections::BTreeMap;
use std::sync::Arc;

#[allow(warnings)]
#[rustfmt::skip]
pub(crate) mod api;
pub(crate) mod config_reload;
pub(crate) mod endpoint_500s;
pub(crate) mod minidump;
pub(crate) mod panics;
mod registry;
pub(crate) mod service_dependency;

mod private {
    pub struct PrivacyToken;
}

/// A health check.
pub trait HealthCheck: 'static + Sync + Send {
    /// Returns the check's type.
    ///
    /// The type must be `SCREAMING_SNAKE_CASE`.
    fn type_(&self) -> &str;

    /// Performs the check, returning its result.
    fn result(&self) -> HealthCheckResult;

    // PrivacyToken can't be named outside of this crate, so it prevents anyone from overriding this
    // default implementation in another crate. That allows us to trust it to be correct in the
    // downcast methods below.
    #[doc(hidden)]
    fn __private_api_type_id(&self, _: private::PrivacyToken) -> TypeId
    where
        Self: 'static,
    {
        TypeId::of::<Self>()
    }
}

impl dyn HealthCheck {
    /// Returns `true` if the health check's type is `T`.
    pub fn is<T>(&self) -> bool
    where
        T: HealthCheck,
    {
        self.__private_api_type_id(private::PrivacyToken) == TypeId::of::<T>()
    }

    /// Attempts to downcast the health check to the type `T` if it is that type.
    pub fn downcast_ref<T>(&self) -> Option<&T>
    where
        T: HealthCheck,
    {
        if self.is::<T>() {
            unsafe { Some(&*(self as *const dyn HealthCheck as *const T)) }
        } else {
            None
        }
    }

    /// Attempts to downcast the health check to the type `T` if it is that type.
    pub fn downcast_arc<T>(self: Arc<Self>) -> Result<Arc<T>, Arc<Self>>
    where
        T: HealthCheck,
    {
        if self.is::<T>() {
            unsafe { Ok(Arc::from_raw(Arc::into_raw(self).cast::<T>())) }
        } else {
            Err(self)
        }
    }
}

/// The result of a health check.
#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
#[staged_builder]
pub struct HealthCheckResult {
    state: HealthState,
    #[builder(default, into)]
    message: Option<String>,
    #[builder(map(key(type = String, into), value(custom(type = impl Serialize, convert = serialize))))]
    params: BTreeMap<String, Any>,
}

fn serialize(arg: impl Serialize) -> Any {
    Any::new(arg).expect("value failed to serialize")
}

impl HealthCheckResult {
    /// Health state of the check.
    #[inline]
    pub fn state(&self) -> &HealthState {
        &self.state
    }

    /// Text describing the state of the check which should provide enough information for the check to be actionable
    /// when included in an alert.
    #[inline]
    pub fn message(&self) -> Option<&str> {
        self.message.as_deref()
    }

    /// Additional redacted information on the nature of the health check.
    #[inline]
    pub fn params(&self) -> &BTreeMap<String, Any> {
        &self.params
    }
}