From 5b2f1cdfd54a073596645a6d02d58164ee6c2cee Mon Sep 17 00:00:00 2001
From: Kirill Fomichev <fanatid@ya.ru>
Date: Thu, 22 Apr 2021 02:31:06 +0300
Subject: [PATCH] Add journald support through tracing-journald (#2034)

* Add journald support through tracing-journald

* change journald to use_journald

* more fixes
---
 Cargo.lock                                 | 11 ++++++++++
 book/src/user/tracing.md                   | 11 ++++++++--
 zebrad/Cargo.toml                          |  1 +
 zebrad/src/components/tracing/component.rs | 24 ++++++++++++++++------
 zebrad/src/config.rs                       |  5 +++++
 5 files changed, 44 insertions(+), 8 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index a7284c35..affa54fd 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3738,6 +3738,16 @@ dependencies = [
  "tracing",
 ]
 
+[[package]]
+name = "tracing-journald"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8fe1f0ed2b7a5fcb6da2bc9e783587d9a0c8b9535e50224afe04e543eae8a2d6"
+dependencies = [
+ "tracing-core",
+ "tracing-subscriber 0.2.17",
+]
+
 [[package]]
 name = "tracing-log"
 version = "0.1.2"
@@ -4505,6 +4515,7 @@ dependencies = [
  "tracing-error",
  "tracing-flame",
  "tracing-futures",
+ "tracing-journald",
  "tracing-subscriber 0.2.17",
  "vergen",
  "zebra-chain",
diff --git a/book/src/user/tracing.md b/book/src/user/tracing.md
index be3acf93..620ef406 100644
--- a/book/src/user/tracing.md
+++ b/book/src/user/tracing.md
@@ -12,10 +12,17 @@ if the config had `endpoint_addr = '127.0.0.1:3000'`, then
 
 See the [`filter`][filter] documentation for more details.
 
-Zebra also has support for generating [flamegraphs] of tracing spans,
-configured using the [`flamegraph`][flamegraph] option.
+Zebra also has support for:
+
+* Generating [flamegraphs] of tracing spans, configured using the
+[`flamegraph`][flamegraph] option.
+* Sending tracing spans and events to [systemd-journald][systemd_journald],
+on Linux distributions that use `systemd`. Configured using the
+[`use_journald`][use_journald] option.
 
 [tracing_section]: https://doc.zebra.zfnd.org/zebrad/config/struct.TracingSection.html
 [filter]: https://doc.zebra.zfnd.org/zebrad/config/struct.TracingSection.html#structfield.filter
 [flamegraph]: https://doc.zebra.zfnd.org/zebrad/config/struct.TracingSection.html#structfield.flamegraph
 [flamegraphs]: http://www.brendangregg.com/flamegraphs.html
+[systemd_journald]: https://www.freedesktop.org/software/systemd/man/systemd-journald.service.html
+[use_journald]: https://doc.zebra.zfnd.org/zebrad/config/struct.TracingSection.html#structfield.use_journald
diff --git a/zebrad/Cargo.toml b/zebrad/Cargo.toml
index a5e2cb35..48db2736 100644
--- a/zebrad/Cargo.toml
+++ b/zebrad/Cargo.toml
@@ -34,6 +34,7 @@ thiserror = "1"
 tracing = "0.1"
 tracing-futures = "0.2"
 tracing-flame = "0.1.0"
+tracing-journald = "0.1.0"
 tracing-subscriber = { version = "0.2.17", features = ["tracing-log"] }
 tracing-error = "0.1.2"
 metrics = "0.13.0-alpha.8"
diff --git a/zebrad/src/components/tracing/component.rs b/zebrad/src/components/tracing/component.rs
index c0ac420e..f717787e 100644
--- a/zebrad/src/components/tracing/component.rs
+++ b/zebrad/src/components/tracing/component.rs
@@ -31,17 +31,29 @@ impl Tracing {
             .with_filter_reloading();
         let filter_handle = builder.reload_handle();
 
-        let subscriber = builder.finish().with(ErrorLayer::default());
-
-        let flamegrapher = if let Some(path) = flame_root {
+        let (flamelayer, flamegrapher) = if let Some(path) = flame_root {
             let (flamelayer, flamegrapher) = flame::layer(path);
-            subscriber.with(flamelayer).init();
-            Some(flamegrapher)
+            (Some(flamelayer), Some(flamegrapher))
+        } else {
+            (None, None)
+        };
+
+        let journaldlayer = if config.use_journald {
+            let layer = tracing_journald::layer()
+                .map_err(|e| FrameworkErrorKind::ComponentError.context(e))?;
+            Some(layer)
         } else {
-            subscriber.init();
             None
         };
 
+        let subscriber = builder.finish().with(ErrorLayer::default());
+        match (flamelayer, journaldlayer) {
+            (None, None) => subscriber.init(),
+            (Some(layer1), None) => subscriber.with(layer1).init(),
+            (None, Some(layer2)) => subscriber.with(layer2).init(),
+            (Some(layer1), Some(layer2)) => subscriber.with(layer1).with(layer2).init(),
+        };
+
         Ok(Self {
             filter_handle,
             flamegrapher,
diff --git a/zebrad/src/config.rs b/zebrad/src/config.rs
index d836be15..963c37d4 100644
--- a/zebrad/src/config.rs
+++ b/zebrad/src/config.rs
@@ -105,6 +105,10 @@ pub struct TracingSection {
     /// If you provide a path with an extension the extension will be ignored and
     /// replaced with `.folded` and `.svg` for the respective files.
     pub flamegraph: Option<PathBuf>,
+
+    /// The use_journald flag sends tracing events to systemd-journald, on Linux
+    /// distributions that use systemd.
+    pub use_journald: bool,
 }
 
 impl Default for TracingSection {
@@ -114,6 +118,7 @@ impl Default for TracingSection {
             filter: None,
             endpoint_addr: None,
             flamegraph: None,
+            use_journald: false,
         }
     }
 }