servo/components/constellation/logging.rs

/* 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 https://mozilla.org/MPL/2.0/. */

//! The constellation uses logging to perform crash reporting.
//! The constellation receives all `warn!`, `error!` and `panic!` messages,
//! and generates a crash report when it receives a panic.

use std::borrow::ToOwned;
use std::sync::Arc;
use std::thread;

use backtrace::Backtrace;
use base::id::{ScriptEventLoopId, TEST_PIPELINE_ID, TEST_WEBVIEW_ID};
use constellation_traits::{
    EmbedderToConstellationMessage, LogEntry, ScriptToConstellationMessage,
    ScriptToConstellationSender,
};
use crossbeam_channel::Sender;
use log::{Level, LevelFilter, Log, Metadata, Record};
use parking_lot::ReentrantMutex;

/// A logger directed at the constellation from content processes
/// #[derive(Clone)]
pub struct FromScriptLogger {
    /// A channel to the constellation
    pub script_to_constellation_sender: Arc<ReentrantMutex<ScriptToConstellationSender>>,
}

/// A logger directed at the constellation from content processes
impl FromScriptLogger {
    /// Create a new constellation logger.
    pub fn new(script_to_constellation_chan: ScriptToConstellationSender) -> FromScriptLogger {
        FromScriptLogger {
            script_to_constellation_sender: Arc::new(ReentrantMutex::new(
                script_to_constellation_chan,
            )),
        }
    }

    /// The maximum log level the constellation logger is interested in.
    pub fn filter(&self) -> LevelFilter {
        LevelFilter::Warn
    }
}

impl Log for FromScriptLogger {
    fn enabled(&self, metadata: &Metadata) -> bool {
        metadata.level() <= Level::Warn
    }

    fn log(&self, record: &Record) {
        if let Some(entry) = log_entry(record) {
            let thread_name = thread::current().name().map(ToOwned::to_owned);
            let _ = self.script_to_constellation_sender.lock().send(
                // TODO: The WebViewId and PipelineId are unused for the `LogEntry` method, but it
                // would probably be better to have an entirely new message variant or sender for
                // messages that definitely do not need these fields to avoid having to use the
                // TEST_* values here.
                (
                    TEST_WEBVIEW_ID,
                    TEST_PIPELINE_ID,
                    ScriptToConstellationMessage::LogEntry(
                        ScriptEventLoopId::installed(),
                        thread_name,
                        entry,
                    ),
                ),
            );
        }
    }

    fn flush(&self) {}
}

/// A logger directed at the constellation from `Paint`.
#[derive(Clone)]
pub struct FromEmbedderLogger {
    /// A channel to the constellation
    pub constellation_chan: Arc<ReentrantMutex<Sender<EmbedderToConstellationMessage>>>,
}

impl FromEmbedderLogger {
    /// Create a new constellation logger.
    pub fn new(constellation_chan: Sender<EmbedderToConstellationMessage>) -> FromEmbedderLogger {
        FromEmbedderLogger {
            constellation_chan: Arc::new(ReentrantMutex::new(constellation_chan)),
        }
    }

    /// The maximum log level the constellation logger is interested in.
    pub fn filter(&self) -> LevelFilter {
        LevelFilter::Warn
    }
}

impl Log for FromEmbedderLogger {
    fn enabled(&self, metadata: &Metadata) -> bool {
        metadata.level() <= Level::Warn
    }

    fn log(&self, record: &Record) {
        if let Some(entry) = log_entry(record) {
            let event_loop_id = ScriptEventLoopId::installed();
            let thread_name = thread::current().name().map(ToOwned::to_owned);
            let msg = EmbedderToConstellationMessage::LogEntry(event_loop_id, thread_name, entry);
            let chan = self.constellation_chan.lock();
            let _ = chan.send(msg);
        }
    }

    fn flush(&self) {}
}

/// Rust uses `Record` for storing logging, but servo converts that to
/// a `LogEntry`. We do this so that we can record panics as well as log
/// messages, and because `Record` does not implement serde (de)serialization,
/// so cannot be used over an IPC channel.
fn log_entry(record: &Record) -> Option<LogEntry> {
    match record.level() {
        Level::Error if thread::panicking() => Some(LogEntry::Panic(
            format!("{}", record.args()),
            format!("{:?}", Backtrace::new()),
        )),
        Level::Error => Some(LogEntry::Error(format!("{}", record.args()))),
        Level::Warn => Some(LogEntry::Warn(format!("{}", record.args()))),
        _ => None,
    }
}