access-log: Add JSON support

Cargo.lock

@@ -207,6 +207,26 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "crossbeam-channel"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "06ed27e177f16d65f0f0c22a213e17c696ace5dd64b14258b52f9417ccb52db4"
+dependencies = [
+ "cfg-if",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.8.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d82cfc11ce7f2c3faef78d8a684447b40d503d9681acebed6cb728d45940c4db"
+dependencies = [
+ "cfg-if",
+ "lazy_static",
+]
+
 [[package]]
 name = "data-encoding"
 version = "2.3.2"
@@ -1625,6 +1645,7 @@ dependencies = [
  "linkerd-error",
  "tokio",
  "tracing",
+ "tracing-appender",
  "tracing-log",
  "tracing-subscriber",
 ]
@@ -2353,6 +2374,16 @@ dependencies = [
  "once_cell",
 ]
 
+[[package]]
+name = "time"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "99beeb0daeac2bd1e86ac2c21caddecb244b39a093594da1a661ec2060c7aedd"
+dependencies = [
+ "itoa 0.4.8",
+ "libc",
+]
+
 [[package]]
 name = "tinyvec"
 version = "1.5.1"
@@ -2572,6 +2603,17 @@ dependencies = [
  "tracing-core",
 ]
 
+[[package]]
+name = "tracing-appender"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "94571df2eae3ed4353815ea5a90974a594a1792d8782ff2cbcc9392d1101f366"
+dependencies = [
+ "crossbeam-channel",
+ "time",
+ "tracing-subscriber",
+]
+
 [[package]]
 name = "tracing-attributes"
 version = "0.1.18"

linkerd/tracing/Cargo.toml

@@ -14,6 +14,7 @@ ansi = ["tracing-subscriber/ansi"]
 linkerd-error = { path = "../error" }
 tokio = { version = "1", features = ["time"] }
 tracing = "0.1.29"
+tracing-appender = "0.2"
 tracing-log = "0.1.2"
 
 [dependencies.tracing-subscriber]

linkerd/tracing/src/access_log.rs

@@ -10,8 +10,10 @@ use tracing_subscriber::{
 
 pub const TRACE_TARGET: &str = "_access_log";
 
-pub(super) type AccessLogLayer<S> = Filtered<Writer, FilterFn, S>;
+pub(super) type AccessLogLayer<S> =
+    Filtered<Box<dyn Layer<S> + Send + Sync + 'static>, FilterFn, S>;
 
+#[derive(Default)]
 pub(super) struct Writer<F = ApacheCommon> {
     formatter: F,
 }
@@ -21,16 +23,27 @@ pub(super) struct ApacheCommon {
     _p: (),
 }
 
+#[derive(Copy, Clone, Debug)]
+pub(super) enum Format {
+    Apache,
+    Json,
+}
+
 struct ApacheCommonVisitor<'writer> {
     res: fmt::Result,
     writer: format::Writer<'writer>,
 }
 
-pub(super) fn build<S>() -> (AccessLogLayer<S>, Directive)
+pub(super) fn build<S>(format: Format) -> (AccessLogLayer<S>, Directive)
 where
     S: Subscriber + for<'span> LookupSpan<'span>,
 {
-    let writer = Writer::new().with_filter(
+    let writer: Box<dyn Layer<S> + Send + Sync + 'static> = match format {
+        Format::Apache => Box::new(Writer::<ApacheCommon>::default()),
+        Format::Json => Box::new(Writer::<format::JsonFields>::default()),
+    };
+
+    let writer = writer.with_filter(
         FilterFn::new(
             (|meta| meta.level() == &Level::INFO && meta.target().starts_with(TRACE_TARGET))
                 as fn(&Metadata<'_>) -> bool,
@@ -49,14 +62,6 @@ where
 
 // === impl Writer ===
 
-impl Writer {
-    pub fn new() -> Self {
-        Self {
-            formatter: Default::default(),
-        }
-    }
-}
-
 impl<S, F> Layer<S> for Writer<F>
 where
     S: Subscriber + for<'span> LookupSpan<'span>,
@@ -154,3 +159,17 @@ impl field::Visit for ApacheCommonVisitor<'_> {
         }
     }
 }
+
+// === impl Format ===
+
+impl std::str::FromStr for Format {
+    type Err = &'static str;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            s if s.eq_ignore_ascii_case("json") => Ok(Self::Json),
+            // Default to the Apache Common Log Format if another format isn't
+            // specified.
+            _ => Ok(Self::Apache),
+        }
+    }
+}

linkerd/tracing/src/lib.rs

@@ -1,4 +1,4 @@
-#![deny(warnings, rust_2018_idioms, clippy::disallowed_method)]
+#![deny(warnings, rust_2018_idioms)]
 #![forbid(unsafe_code)]
 
 pub mod access_log;
@@ -29,7 +29,7 @@ const DEFAULT_LOG_FORMAT: &str = "PLAIN";
 pub struct Settings {
     filter: Option<String>,
     format: Option<String>,
-    access_log: bool,
+    access_log: Option<access_log::Format>,
     is_test: bool,
 }
 
@@ -81,16 +81,18 @@ impl Settings {
         Some(Self {
             filter,
             format: std::env::var(ENV_LOG_FORMAT).ok(),
-            access_log: std::env::var(ENV_ACCESS_LOG).is_ok(),
+            access_log: std::env::var(ENV_ACCESS_LOG)
+                .ok()
+                .and_then(|env| env.parse().ok()),
             is_test: false,
         })
     }
 
-    fn for_test(filter: String, format: String) -> Self {
+    fn for_test(filter: String, format: String, access_log: Option<String>) -> Self {
         Self {
             filter: Some(filter),
             format: Some(format),
-            access_log: false,
+            access_log: access_log.and_then(|env| env.parse().ok()),
             is_test: true,
         }
     }
@@ -154,8 +156,8 @@ impl Settings {
         let mut filter = EnvFilter::new(log_level);
 
         // If access logging is enabled, build the access log layer.
-        let access_log = if self.access_log {
-            let (access_log, directive) = access_log::build();
+        let access_log = if let Some(format) = self.access_log {
+            let (access_log, directive) = access_log::build(format);
             filter = filter.add_directive(directive);
             Some(access_log)
         } else {

linkerd/tracing/src/test.rs

@@ -15,7 +15,12 @@ pub fn trace_subscriber(default: impl ToString) -> (Dispatch, Handle) {
     // This may fail, since the global log compat layer may have been
     // initialized by another test.
     let _ = init_log_compat();
-    Settings::for_test(log_level, log_format).build()
+    Settings::for_test(
+        log_level,
+        log_format,
+        env::var("LINKERD2_PROXY_ACCESS_LOG").ok(),
+    )
+    .build()
 }
 
 pub fn with_default_filter(