8 files changed, 299 insertions, 0 deletions
diff --git a/third_party/rust/interrupt-support/.cargo-checksum.json b/third_party/rust/interrupt-support/.cargo-checksum.json
new file mode 100644
index 0000000000..a106d68b82
--- /dev/null
+++ b/third_party/rust/interrupt-support/.cargo-checksum.json
@@ -0,0 +1 @@
+{"files":{"Cargo.toml":"0d4ed8e02406a7c9a4f7219b5da2de5afc9357264c5d8b66c57d25c45be714ed","README.md":"7f1418b4a7c138ba20bcaea077fe6cf0d6ffbaf6df6b90c80efc52aa0d0e2e9f","src/error.rs":"b83cbe8abd22a9d687508d236a2a77e28b3fc6c39673633e5820cc0e3fc86cba","src/interruptee.rs":"c56f9ac610d0b24a128a907266432287558c4b73f6c24b82674ca7894181d18f","src/lib.rs":"cf44a84310913be5264e1c4a3e004a9f7a6cd82d01a109bb6ac4d6002b5dd560","src/shutdown.rs":"b9dfdb717932301035001a0398967384f1b993e14505860415d023febbe82d63","src/sql.rs":"7e050313884a281e6b3fc7a4514374e08cb9e5f3c5aefb873be92e56f30af660"},"package":null}
+\ No newline at end of file
diff --git a/third_party/rust/interrupt-support/Cargo.toml b/third_party/rust/interrupt-support/Cargo.toml
new file mode 100644
index 0000000000..8a19048949
--- /dev/null
+++ b/third_party/rust/interrupt-support/Cargo.toml
@@ -0,0 +1,31 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2021"
+name = "interrupt-support"
+version = "0.1.0"
+authors = ["application-services@mozilla.com"]
+readme = "README.md"
+license = "MPL-2.0"
+
+[dependencies]
+lazy_static = "1.4"
+parking_lot = ">=0.11,<=0.12"
+
+[dependencies.rusqlite]
+version = "0.28.0"
+features = [
+    "functions",
+    "limits",
+    "bundled",
+    "unlock_notify",
+]
diff --git a/third_party/rust/interrupt-support/README.md b/third_party/rust/interrupt-support/README.md
new file mode 100644
index 0000000000..5a9fbe5f39
--- /dev/null
+++ b/third_party/rust/interrupt-support/README.md
@@ -0,0 +1,4 @@
+## Interrupt crate
+
+This create exposes traits and errors to allow for interrupt support across
+the various crates in this repository.
diff --git a/third_party/rust/interrupt-support/src/error.rs b/third_party/rust/interrupt-support/src/error.rs
new file mode 100644
index 0000000000..6718a16480
--- /dev/null
+++ b/third_party/rust/interrupt-support/src/error.rs
@@ -0,0 +1,15 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+License, v. 2.0. If a copy of the MPL was not distributed with this
+* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/// The error returned by err_if_interrupted.
+#[derive(Debug, Clone)]
+pub struct Interrupted;
+
+impl std::fmt::Display for Interrupted {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str("The operation was interrupted")
+    }
+}
+
+impl std::error::Error for Interrupted {}
diff --git a/third_party/rust/interrupt-support/src/interruptee.rs b/third_party/rust/interrupt-support/src/interruptee.rs
new file mode 100644
index 0000000000..3ee6eadfe6
--- /dev/null
+++ b/third_party/rust/interrupt-support/src/interruptee.rs
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+License, v. 2.0. If a copy of the MPL was not distributed with this
+* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::Interrupted;
+
+/// Represents the state of something that may be interrupted. Decoupled from
+/// the interrupt mechanics so that things which want to check if they have been
+/// interrupted are simpler.
+pub trait Interruptee {
+    fn was_interrupted(&self) -> bool;
+
+    fn err_if_interrupted(&self) -> Result<(), Interrupted> {
+        if self.was_interrupted() {
+            return Err(Interrupted);
+        }
+        Ok(())
+    }
+}
+
+/// A convenience implementation, should only be used in tests.
+pub struct NeverInterrupts;
+
+impl Interruptee for NeverInterrupts {
+    #[inline]
+    fn was_interrupted(&self) -> bool {
+        false
+    }
+}
diff --git a/third_party/rust/interrupt-support/src/lib.rs b/third_party/rust/interrupt-support/src/lib.rs
new file mode 100644
index 0000000000..6d2ef8f8e5
--- /dev/null
+++ b/third_party/rust/interrupt-support/src/lib.rs
@@ -0,0 +1,16 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#![allow(unknown_lints)]
+#![warn(rust_2018_idioms)]
+
+mod error;
+mod interruptee;
+mod shutdown;
+mod sql;
+
+pub use error::Interrupted;
+pub use interruptee::*;
+pub use shutdown::*;
+pub use sql::*;
diff --git a/third_party/rust/interrupt-support/src/shutdown.rs b/third_party/rust/interrupt-support/src/shutdown.rs
new file mode 100644
index 0000000000..9c64df27e8
--- /dev/null
+++ b/third_party/rust/interrupt-support/src/shutdown.rs
@@ -0,0 +1,81 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+License, v. 2.0. If a copy of the MPL was not distributed with this
+* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/// Shutdown handling for database operations
+///
+/// This module allows us to enter shutdown mode, causing all `SqlInterruptScope` instances that opt-in to
+/// to be permanently interrupted.  This means:
+///
+///   - All current scopes will be interrupted
+///   - Any attempt to create a new scope will be interrupted
+///
+/// Here's how add shutdown support to a component:
+///
+///   - Use `SqlInterruptScope::new_with_shutdown_check()` to create a new
+///     `SqlInterruptScope`
+///   - Database connections need to be wrapped in a type that:
+///      - Implements `AsRef<SqlInterruptHandle>`.
+///      - Gets wrapped in an `Arc<>`.  This is needed so the shutdown code can get a weak reference to
+///        the instance.
+///      - Calls `register_interrupt()` on creation
+///
+///  See `PlacesDb::begin_interrupt_scope()` and `PlacesApi::new_connection()` for an example of
+///  how this works.
+use crate::Interruptee;
+use parking_lot::Mutex;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Weak;
+
+use crate::SqlInterruptHandle;
+
+// Bool that tracks if we're in shutdown mode or not.  We use Ordering::Relaxed to read/write to
+// variable.  It's just a flag so we don't need stronger synchronization guarentees.
+static IN_SHUTDOWN: AtomicBool = AtomicBool::new(false);
+
+// `SqlInterruptHandle` instances to interrupt when we shutdown
+lazy_static::lazy_static! {
+   static ref REGISTERED_INTERRUPTS: Mutex<Vec<Weak<dyn AsRef<SqlInterruptHandle> + Send + Sync>>> = Mutex::new(Vec::new());
+}
+
+/// Initiate shutdown mode
+pub fn shutdown() {
+    IN_SHUTDOWN.store(true, Ordering::Relaxed);
+    for weak in REGISTERED_INTERRUPTS.lock().iter() {
+        if let Some(interrupt) = weak.upgrade() {
+            interrupt.as_ref().as_ref().interrupt()
+        }
+    }
+}
+
+/// Check if we're currently in shutdown mode
+pub fn in_shutdown() -> bool {
+    IN_SHUTDOWN.load(Ordering::Relaxed)
+}
+
+/// Register a ShutdownInterrupt implementation
+///
+/// Call this function to ensure that the `SqlInterruptHandle::interrupt()` method will be called
+/// at shutdown.
+pub fn register_interrupt(interrupt: Weak<dyn AsRef<SqlInterruptHandle> + Send + Sync>) {
+    // Try to find an existing entry that's been dropped to replace.  This keeps the vector growth
+    // in check
+    let mut interrupts = REGISTERED_INTERRUPTS.lock();
+    for weak in interrupts.iter_mut() {
+        if weak.strong_count() == 0 {
+            *weak = interrupt;
+            return;
+        }
+    }
+    // No empty slots, push the new value
+    interrupts.push(interrupt);
+}
+
+// Implements Interruptee by checking if we've entered shutdown mode
+pub struct ShutdownInterruptee;
+impl Interruptee for ShutdownInterruptee {
+    #[inline]
+    fn was_interrupted(&self) -> bool {
+        in_shutdown()
+    }
+}
diff --git a/third_party/rust/interrupt-support/src/sql.rs b/third_party/rust/interrupt-support/src/sql.rs
new file mode 100644
index 0000000000..6f361013fc
--- /dev/null
+++ b/third_party/rust/interrupt-support/src/sql.rs
@@ -0,0 +1,122 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::{in_shutdown, Interrupted, Interruptee};
+use rusqlite::{Connection, InterruptHandle};
+use std::fmt;
+use std::sync::{
+    atomic::{AtomicUsize, Ordering},
+    Arc,
+};
+
+/// Interrupt operations that use SQL
+///
+/// Typical usage of this type:
+///   - Components typically create a wrapper class around an `rusqlite::Connection`
+///     (`PlacesConnection`, `LoginStore`, etc.)
+///   - The wrapper stores an `Arc<SqlInterruptHandle>`
+///   - The wrapper has a method that clones and returns that `Arc`.  This allows passing the interrupt
+///     handle to a different thread in order to interrupt a particular operation.
+///   - The wrapper calls `begin_interrupt_scope()` at the start of each operation.  The code that
+///     performs the operation periodically calls `err_if_interrupted()`.
+///   - Finally, the wrapper class implements `AsRef<SqlInterruptHandle>` and calls
+///     `register_interrupt()`.  This causes all operations to be interrupted when we enter
+///     shutdown mode.
+pub struct SqlInterruptHandle {
+    db_handle: InterruptHandle,
+    // Counter that we increment on each interrupt() call.
+    // We use Ordering::Relaxed to read/write to this variable.  This is safe because we're
+    // basically using it as a flag and don't need stronger synchronization guarentees.
+    interrupt_counter: Arc<AtomicUsize>,
+}
+
+impl SqlInterruptHandle {
+    #[inline]
+    pub fn new(conn: &Connection) -> Self {
+        Self {
+            db_handle: conn.get_interrupt_handle(),
+            interrupt_counter: Arc::new(AtomicUsize::new(0)),
+        }
+    }
+
+    /// Begin an interrupt scope that will be interrupted by this handle
+    ///
+    /// Returns Err(Interrupted) if we're in shutdown mode
+    #[inline]
+    pub fn begin_interrupt_scope(&self) -> Result<SqlInterruptScope, Interrupted> {
+        if in_shutdown() {
+            Err(Interrupted)
+        } else {
+            Ok(SqlInterruptScope::new(Arc::clone(&self.interrupt_counter)))
+        }
+    }
+
+    /// Interrupt all interrupt scopes created by this handle
+    #[inline]
+    pub fn interrupt(&self) {
+        self.interrupt_counter.fetch_add(1, Ordering::Relaxed);
+        self.db_handle.interrupt();
+    }
+}
+
+impl fmt::Debug for SqlInterruptHandle {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("SqlInterruptHandle")
+            .field(
+                "interrupt_counter",
+                &self.interrupt_counter.load(Ordering::Relaxed),
+            )
+            .finish()
+    }
+}
+
+/// Check if an operation has been interrupted
+///
+/// This is used by the rust code to check if an operation should fail because it was interrupted.
+/// It handles the case where we get interrupted outside of an SQL query.
+#[derive(Debug)]
+pub struct SqlInterruptScope {
+    start_value: usize,
+    interrupt_counter: Arc<AtomicUsize>,
+}
+
+impl SqlInterruptScope {
+    fn new(interrupt_counter: Arc<AtomicUsize>) -> Self {
+        let start_value = interrupt_counter.load(Ordering::Relaxed);
+        Self {
+            start_value,
+            interrupt_counter,
+        }
+    }
+
+    // Create an `SqlInterruptScope` that's never interrupted.
+    //
+    // This should only be used for testing purposes.
+    pub fn dummy() -> Self {
+        Self::new(Arc::new(AtomicUsize::new(0)))
+    }
+
+    /// Check if scope has been interrupted
+    #[inline]
+    pub fn was_interrupted(&self) -> bool {
+        self.interrupt_counter.load(Ordering::Relaxed) != self.start_value
+    }
+
+    /// Return Err(Interrupted) if we were interrupted
+    #[inline]
+    pub fn err_if_interrupted(&self) -> Result<(), Interrupted> {
+        if self.was_interrupted() {
+            Err(Interrupted)
+        } else {
+            Ok(())
+        }
+    }
+}
+
+impl Interruptee for SqlInterruptScope {
+    #[inline]
+    fn was_interrupted(&self) -> bool {
+        self.was_interrupted()
+    }
+}