diesel/connection/instrumentation.rs
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use downcast_rs::Downcast;
use std::fmt::{Debug, Display};
use std::num::NonZeroU32;
use std::ops::{Deref, DerefMut};
static GLOBAL_INSTRUMENTATION: std::sync::RwLock<fn() -> Option<Box<dyn Instrumentation>>> =
std::sync::RwLock::new(|| None);
/// A helper trait for opaque query representations
/// which allows to get a `Display` and `Debug`
/// representation of the underlying type without
/// exposing type specific details
pub trait DebugQuery: Debug + Display {}
impl<T, DB> DebugQuery for crate::query_builder::DebugQuery<'_, T, DB> where Self: Debug + Display {}
/// A helper type that allows printing out str slices
///
/// This type is necessary because it's not possible
/// to cast from a reference of a unsized type like `&str`
/// to a reference of a trait object even if that
/// type implements all necessary traits
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
pub(crate) struct StrQueryHelper<'query> {
s: &'query str,
}
impl<'query> StrQueryHelper<'query> {
/// Construct a new `StrQueryHelper`
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
#[cfg(any(
feature = "postgres",
feature = "sqlite",
feature = "mysql",
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
))]
pub(crate) fn new(s: &'query str) -> Self {
Self { s }
}
}
impl Debug for StrQueryHelper<'_> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
Debug::fmt(self.s, f)
}
}
impl Display for StrQueryHelper<'_> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
Display::fmt(&self.s, f)
}
}
impl DebugQuery for StrQueryHelper<'_> {}
/// This enum describes possible connection events
/// that can be handled by an [`Instrumentation`] implementation
///
/// Some fields might contain sensitive information, like login
/// details for the database.
///
/// Diesel does not guarantee that future versions will
/// emit the same events in the same order or timing.
/// In addition the output of the [`Debug`] and [`Display`]
/// implementation of the enum itself and any of its fields
/// is not guarantee to be stable.
//
// This type is carefully designed
// to avoid any potential overhead by
// taking references for all things
// and by not performing any additional
// work until required.
// In addition it's carefully designed
// not to be dependent on the actual backend
// type, as that makes it easier to reuse
// `Instrumentation` implementations in
// a different context
#[derive(Debug)]
#[non_exhaustive]
pub enum InstrumentationEvent<'a> {
/// An event emitted by before starting
/// establishing a new connection
#[non_exhaustive]
StartEstablishConnection {
/// The database url the connection
/// tries to connect to
///
/// This might contain sensitive information
/// like the database password
url: &'a str,
},
/// An event emitted after establishing a
/// new connection
#[non_exhaustive]
FinishEstablishConnection {
/// The database url the connection
/// tries is connected to
///
/// This might contain sensitive information
/// like the database password
url: &'a str,
/// An optional error if the connection failed
error: Option<&'a crate::result::ConnectionError>,
},
/// An event that is emitted before executing
/// a query
#[non_exhaustive]
StartQuery {
/// A opaque representation of the query
///
/// This type implements [`Debug`] and [`Display`],
/// but should be considered otherwise as opaque.
///
/// The exact output of the [`Debug`] and [`Display`]
/// implementation is not considered as part of the
/// stable API.
query: &'a dyn DebugQuery,
},
/// An event that is emitted when a query
/// is cached in the connection internal
/// prepared statement cache
#[non_exhaustive]
CacheQuery {
/// SQL string of the cached query
sql: &'a str,
},
/// An event that is emitted after executing
/// a query
#[non_exhaustive]
FinishQuery {
/// A opaque representation of the query
///
/// This type implements [`Debug`] and [`Display`],
/// but should be considered otherwise as opaque.
///
/// The exact output of the [`Debug`] and [`Display`]
/// implementation is not considered as part of the
/// stable API.
query: &'a dyn DebugQuery,
/// An optional error if the connection failed
error: Option<&'a crate::result::Error>,
},
/// An event that is emitted while
/// starting a new transaction
#[non_exhaustive]
BeginTransaction {
/// Transaction level of the newly started
/// transaction
depth: NonZeroU32,
},
/// An event that is emitted while
/// committing a transaction
#[non_exhaustive]
CommitTransaction {
/// Transaction level of the to be committed
/// transaction
depth: NonZeroU32,
},
/// An event that is emitted while
/// rolling back a transaction
#[non_exhaustive]
RollbackTransaction {
/// Transaction level of the to be rolled
/// back transaction
depth: NonZeroU32,
},
}
// these constructors exist to
// keep `#[non_exhaustive]` on all the variants
// and to gate the constructors on the unstable feature
#[cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes")]
impl<'a> InstrumentationEvent<'a> {
/// Create a new `InstrumentationEvent::StartEstablishConnection` event
#[cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes")]
pub fn start_establish_connection(url: &'a str) -> Self {
Self::StartEstablishConnection { url }
}
/// Create a new `InstrumentationEvent::FinishEstablishConnection` event
#[cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes")]
pub fn finish_establish_connection(
url: &'a str,
error: Option<&'a crate::result::ConnectionError>,
) -> Self {
Self::FinishEstablishConnection { url, error }
}
/// Create a new `InstrumentationEvent::StartQuery` event
#[cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes")]
pub fn start_query(query: &'a dyn DebugQuery) -> Self {
Self::StartQuery { query }
}
/// Create a new `InstrumentationEvent::CacheQuery` event
#[cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes")]
pub fn cache_query(sql: &'a str) -> Self {
Self::CacheQuery { sql }
}
/// Create a new `InstrumentationEvent::FinishQuery` event
#[cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes")]
pub fn finish_query(
query: &'a dyn DebugQuery,
error: Option<&'a crate::result::Error>,
) -> Self {
Self::FinishQuery { query, error }
}
/// Create a new `InstrumentationEvent::BeginTransaction` event
#[cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes")]
pub fn begin_transaction(depth: NonZeroU32) -> Self {
Self::BeginTransaction { depth }
}
/// Create a new `InstrumentationEvent::RollbackTransaction` event
#[cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes")]
pub fn rollback_transaction(depth: NonZeroU32) -> Self {
Self::RollbackTransaction { depth }
}
/// Create a new `InstrumentationEvent::CommitTransaction` event
#[cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes")]
pub fn commit_transaction(depth: NonZeroU32) -> Self {
Self::CommitTransaction { depth }
}
}
/// A type that provides an connection `Instrumentation`
///
/// This trait is the basic building block for logging or
/// otherwise instrumenting diesel connection types. It
/// acts as callback that receives information about certain
/// important connection states
///
/// For simple usages this trait is implemented for closures
/// accepting a [`InstrumentationEvent`] as argument.
///
/// More complex usages and integrations with frameworks like
/// `tracing` and `log` are supposed to be part of their own
/// crates.
pub trait Instrumentation: Downcast + Send + 'static {
/// The function that is invoked for each event
fn on_connection_event(&mut self, event: InstrumentationEvent<'_>);
}
downcast_rs::impl_downcast!(Instrumentation);
/// Get an instance of the default [`Instrumentation`]
///
/// This function is mostly useful for crates implementing
/// their own connection types
pub fn get_default_instrumentation() -> Option<Box<dyn Instrumentation>> {
match GLOBAL_INSTRUMENTATION.read() {
Ok(f) => (*f)(),
Err(_) => None,
}
}
/// Set a custom constructor for the default [`Instrumentation`]
/// used by new connections
///
/// ```rust
/// use diesel::connection::{set_default_instrumentation, Instrumentation, InstrumentationEvent};
///
/// // a simple logger that prints all events to stdout
/// fn simple_logger() -> Option<Box<dyn Instrumentation>> {
/// // we need the explicit argument type there due
/// // to bugs in rustc
/// Some(Box::new(|event: InstrumentationEvent<'_>| {
/// println!("{event:?}")
/// }))
/// }
///
/// set_default_instrumentation(simple_logger);
/// ```
pub fn set_default_instrumentation(
default: fn() -> Option<Box<dyn Instrumentation>>,
) -> crate::QueryResult<()> {
match GLOBAL_INSTRUMENTATION.write() {
Ok(mut l) => {
*l = default;
Ok(())
}
Err(e) => Err(crate::result::Error::DatabaseError(
crate::result::DatabaseErrorKind::Unknown,
Box::new(e.to_string()),
)),
}
}
impl<F> Instrumentation for F
where
F: FnMut(InstrumentationEvent<'_>) + Send + 'static,
{
fn on_connection_event(&mut self, event: InstrumentationEvent<'_>) {
(self)(event)
}
}
impl Instrumentation for Box<dyn Instrumentation> {
fn on_connection_event(&mut self, event: InstrumentationEvent<'_>) {
self.deref_mut().on_connection_event(event)
}
}
impl<T> Instrumentation for Option<T>
where
T: Instrumentation,
{
fn on_connection_event(&mut self, event: InstrumentationEvent<'_>) {
if let Some(i) = self {
i.on_connection_event(event)
}
}
}
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
/// An optional dyn instrumentation.
///
/// For ease of use, this type implements [`Deref`] and [`DerefMut`] to `&dyn Instrumentation`,
/// falling back to a no-op implementation if no instrumentation is set.
///
/// The DynInstrumentation type is useful because without it we actually did tend to return
/// (accidentally) &mut Option<Box> as &mut dyn Instrumentation from connection.instrumentation(),
/// so downcasting would have to be done in these two steps by the user, which is counter-intuitive.
pub(crate) struct DynInstrumentation {
/// zst
no_instrumentation: NoInstrumentation,
inner: Option<Box<dyn Instrumentation>>,
}
impl Deref for DynInstrumentation {
type Target = dyn Instrumentation;
fn deref(&self) -> &Self::Target {
self.inner.as_deref().unwrap_or(&self.no_instrumentation)
}
}
impl DerefMut for DynInstrumentation {
fn deref_mut(&mut self) -> &mut Self::Target {
self.inner
.as_deref_mut()
.unwrap_or(&mut self.no_instrumentation)
}
}
impl DynInstrumentation {
/// Create a instance of the default instrumentation provider
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
pub(crate) fn default_instrumentation() -> Self {
Self {
inner: get_default_instrumentation(),
no_instrumentation: NoInstrumentation,
}
}
/// Create a noop instrumentation provider instance
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
pub(crate) fn none() -> Self {
Self {
inner: None,
no_instrumentation: NoInstrumentation,
}
}
/// register an event with the given instrumentation implementation
#[diesel_derives::__diesel_public_if(
feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
)]
pub(crate) fn on_connection_event(&mut self, event: InstrumentationEvent<'_>) {
// This implementation is not necessary to be able to call this method on this object
// because of the already existing Deref impl.
// However it allows avoiding the dynamic dispatch to the stub value
if let Some(inner) = self.inner.as_deref_mut() {
inner.on_connection_event(event)
}
}
}
impl<I: Instrumentation> From<I> for DynInstrumentation {
fn from(instrumentation: I) -> Self {
Self {
inner: Some(unpack_instrumentation(Box::new(instrumentation))),
no_instrumentation: NoInstrumentation,
}
}
}
struct NoInstrumentation;
impl Instrumentation for NoInstrumentation {
fn on_connection_event(&mut self, _: InstrumentationEvent<'_>) {}
}
/// Unwrap unnecessary boxing levels
fn unpack_instrumentation(
mut instrumentation: Box<dyn Instrumentation>,
) -> Box<dyn Instrumentation> {
loop {
match instrumentation.downcast::<Box<dyn Instrumentation>>() {
Ok(extra_boxed_instrumentation) => instrumentation = *extra_boxed_instrumentation,
Err(not_extra_boxed_instrumentation) => {
break not_extra_boxed_instrumentation;
}
}
}
}