breaking(diagnostics): make zebrad diagnostics into optional compile-time features (#4539)

* Disable the flamegraph feature by default at compile time

* Disable the journald feature by default at compile time

* Also disable inferno dependency, and rearrange features

* Disable the prometheus feature by default at compile time

* Disable the tracing filter reload feature by default at compile time

* Disable tests when corresponding features are disabled

* Add compile-time tracing features to user docs

* Add compile-time features to the metrics user docs

* Document diagnostics as part of the start command tasks and services

* breaking(diagnostics): rename "enable-sentry" feature to "sentry" (#4623)

* Also skip conflict tests when those ports are disabled

* breaking(diagnostics): rename "enable-sentry" feature to "sentry"

This is mostly:
```sh
fastmod enable-sentry sentry
```

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

book/src/user/metrics.md

@@ -1,6 +1,7 @@
 # Zebra Metrics
 
-Zebra has support for Prometheus, configured using the [`MetricsSection`][metrics_section].
+Zebra has support for Prometheus, configured using the `prometheus` compile-time feature,
+and the [`MetricsSection`][metrics_section] runtime configuration.
 
 This requires supporting infrastructure to collect and visualize metrics, for example:
 

book/src/user/requirements.md

@@ -26,7 +26,7 @@ tested its exact limits yet.
 
 ## Sentry Production Monitoring
 
-Compile Zebra with `--features enable-sentry` to monitor it using Sentry in production.
+Compile Zebra with `--features sentry` to monitor it using Sentry in production.
 
 ## Lightwalletd Test Requirements
 

book/src/user/tracing.md

@@ -1,7 +1,12 @@
 # Tracing Zebra
 
+## Dynamic Tracing
+
 Zebra supports dynamic tracing, configured using the config's 
-[`TracingSection`][tracing_section] and (optionally) an HTTP RPC endpoint.
+[`TracingSection`][tracing_section] and an HTTP RPC endpoint.
+
+Activate this feature using the `filter-reload` compile-time feature,
+and the [`filter`][filter] and `endpoint_addr` runtime config options.
 
 If the `endpoint_addr` is specified, `zebrad` will open an HTTP endpoint
 allowing dynamic runtime configuration of the tracing filter. For instance,
@@ -12,13 +17,20 @@ 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:
+## `journald` Logging
 
-* Generating [flamegraphs] of tracing spans, configured using the
+Zebra can send tracing spans and events to [systemd-journald][systemd_journald],
-[`flamegraph`][flamegraph] option.
+on Linux distributions that use `systemd`.
-* Sending tracing spans and events to [systemd-journald][systemd_journald],
+
-on Linux distributions that use `systemd`. Configured using the
+Activate `journald` logging using the `journald` compile-time feature,
-[`use_journald`][use_journald] option.
+and the [`use_journald`][use_journald] runtime config option.
+
+## Flamegraphs
+
+Zebra can generate [flamegraphs] of tracing spans.
+
+Activate flamegraphs using the `flamegraph` compile-time feature,
+and the [`flamegraph`][flamegraph] runtime config 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

docker/Dockerfile

@@ -100,7 +100,7 @@ COPY --from=us-docker.pkg.dev/zealous-zebra/zebra/lightwalletd /lightwalletd /us
 # This is the caching Docker layer for Rust!
 #
 # TODO: is it faster to use --tests here?
-RUN cargo chef cook --release --features enable-sentry,lightwalletd-grpc-tests --workspace --recipe-path recipe.json
+RUN cargo chef cook --release --features sentry,lightwalletd-grpc-tests --workspace --recipe-path recipe.json
 
 COPY . .
 RUN cargo test --locked --release --features lightwalletd-grpc-tests --workspace --no-run
@@ -118,11 +118,11 @@ CMD [ "cargo"]
 # `test` stage. This step is a dependency for the `runtime` stage, which uses the resulting
 # zebrad binary from this step.
 FROM deps AS release
-RUN cargo chef cook --release --features enable-sentry --recipe-path recipe.json
+RUN cargo chef cook --release --features sentry --recipe-path recipe.json
 
 COPY . .
 # Build zebra
-RUN cargo build --locked --release --features enable-sentry --package zebrad --bin zebrad
+RUN cargo build --locked --release --features sentry --package zebrad --bin zebrad
 
 # This stage is only used when deploying nodes or when only the resulting zebrad binary is needed
 #

docker/zcash-params/Dockerfile

@@ -23,7 +23,7 @@ RUN apt-get -qq update && \
 
 ENV CARGO_HOME /app/.cargo/
 # Build dependencies - this is the caching Docker layer!
-RUN cargo chef cook --release --features enable-sentry --package zebrad --recipe-path recipe.json
+RUN cargo chef cook --release --features sentry --package zebrad --recipe-path recipe.json
 
 ARG RUST_BACKTRACE=0
 ENV RUST_BACKTRACE ${RUST_BACKTRACE}
@@ -36,4 +36,4 @@ ENV COLORBT_SHOW_HIDDEN ${COLORBT_SHOW_HIDDEN}
 
 COPY . .
 # Pre-download Zcash Sprout and Sapling parameters
-RUN cargo run --locked --release --features enable-sentry --package zebrad --bin zebrad download
+RUN cargo run --locked --release --features sentry --package zebrad --bin zebrad download

zebrad/Cargo.toml

@@ -17,7 +17,13 @@ default-run = "zebrad"
 default = ["release_max_level_info"]
 
 # Production features that activate extra dependencies
-enable-sentry = ["sentry", "sentry-tracing"]
+
+sentry = ["dep:sentry", "sentry-tracing"]
+flamegraph = ["tracing-flame", "inferno"]
+journald = ["tracing-journald"]
+filter-reload = ["hyper"]
+
+prometheus = ["metrics-exporter-prometheus"]
 
 # Production features that modify dependency behaviour
 
@@ -78,7 +84,6 @@ lazy_static = "1.4.0"
 serde = { version = "1.0.137", features = ["serde_derive"] }
 toml = "0.5.9"
 
-hyper = { version = "0.14.19", features = ["full"] }
 futures = "0.3.21"
 tokio = { version = "1.19.2", features = ["time", "rt-multi-thread", "macros", "tracing", "signal"] }
 tower = { version = "0.4.12", features = ["hedge", "limit"] }
@@ -87,27 +92,36 @@ pin-project = "1.0.10"
 color-eyre = { version = "0.6.1", default_features = false, features = ["issue-url"] }
 thiserror = "1.0.31"
 
-tracing-flame = "0.2.0"
-tracing-journald = "0.3.0"
 tracing-subscriber = { version = "0.3.11", features = ["env-filter"] }
 tracing-error = "0.2.0"
 tracing-futures = "0.2.5"
 tracing = "0.1.31"
 
 metrics = "0.18.1"
-metrics-exporter-prometheus = { version = "0.9.0", default-features = false, features = ["http-listener"] }
 
 dirs = "4.0.0"
-inferno = { version = "0.11.4", default-features = false }
 atty = "0.2.14"
 
 num-integer = "0.1.45"
 rand = { version = "0.8.5", package = "rand" }
 
-# prod feature enable-sentry
+# prod feature sentry
 sentry-tracing = { version = "0.26.0", optional = true }
 sentry = { version = "0.26.0", default-features = false, features = ["backtrace", "contexts", "reqwest", "rustls"], optional = true }
 
+# prod feature flamegraph
+tracing-flame = { version = "0.2.0", optional = true }
+inferno = { version = "0.11.4", default-features = false, optional = true }
+
+# prod feature journald
+tracing-journald = { version = "0.3.0", optional = true }
+
+# prod feature filter-reload
+hyper = { version = "0.14.19", features = ["http1", "http2", "server"], optional = true }
+
+# prod feature prometheus
+metrics-exporter-prometheus = { version = "0.9.0", default-features = false, features = ["http-listener"], optional = true }
+
 # prod feature release_max_level_info
 #
 # zebrad uses tracing for logging,
@@ -132,12 +146,15 @@ abscissa_core = { version = "0.5", features = ["testing"] }
 hex = "0.4.3"
 once_cell = "1.12.0"
 regex = "1.5.6"
-reqwest = "0.11.11"
 semver = "1.0.10"
+
 # zebra-rpc needs the preserve_order feature, it also makes test results more stable
 serde_json = { version = "1.0.81", features = ["preserve_order"] }
 tempfile = "3.3.0"
 
+hyper = { version = "0.14.18", features = ["http1", "http2", "server"]}
+reqwest = "0.11.11"
+
 tokio = { version = "1.19.2", features = ["full", "tracing", "test-util"] }
 tokio-stream = "0.1.9"
 

zebrad/src/application.rs

@@ -314,7 +314,7 @@ impl Application for ZebradApp {
 
         // The Sentry default config pulls in the DSN from the `SENTRY_DSN`
         // environment variable.
-        #[cfg(feature = "enable-sentry")]
+        #[cfg(feature = "sentry")]
         let guard = sentry::init(sentry::ClientOptions {
             debug: true,
             release: Some(app_version().to_string().into()),
@@ -325,7 +325,7 @@ impl Application for ZebradApp {
             let panic_report = panic_hook.panic_report(panic_info);
             eprintln!("{}", panic_report);
 
-            #[cfg(feature = "enable-sentry")]
+            #[cfg(feature = "sentry")]
             {
                 let event = crate::sentry::panic_event_from(panic_report);
                 sentry::capture_event(event);

zebrad/src/commands/start.rs

@@ -58,6 +58,12 @@
 //!  * JSON-RPC Service
 //!    * answers RPC client requests using the State Service and Mempool Service
 //!    * submits client transactions to the node's mempool
+//!
+//! Zebra also has diagnostic support
+//! * [metrics](https://github.com/ZcashFoundation/zebra/blob/main/book/src/user/metrics.md)
+//! * [tracing](https://github.com/ZcashFoundation/zebra/blob/main/book/src/user/tracing.md)
+//!
+//! Some of the diagnostic features are optional, and need to be enabled at compile-time.
 
 use std::{cmp::max, ops::Add, time::Duration};
 

zebrad/src/components/metrics.rs

@@ -10,6 +10,7 @@ pub struct MetricsEndpoint {}
 
 impl MetricsEndpoint {
     /// Create the component.
+    #[cfg(feature = "prometheus")]
     pub fn new(config: &ZebradConfig) -> Result<Self, FrameworkError> {
         if let Some(addr) = config.metrics.endpoint_addr {
             info!("Trying to open metrics endpoint at {}...", addr);
@@ -38,6 +39,21 @@ impl MetricsEndpoint {
                 ),
             }
         }
+
+        Ok(Self {})
+    }
+
+    /// Create the component.
+    #[cfg(not(feature = "prometheus"))]
+    pub fn new(config: &ZebradConfig) -> Result<Self, FrameworkError> {
+        if let Some(addr) = config.metrics.endpoint_addr {
+            warn!(
+                ?addr,
+                "unable to activate configured metrics endpoint: \
+                 enable the 'prometheus' feature when compiling zebrad",
+            );
+        }
+
         Ok(Self {})
     }
 }

zebrad/src/components/tracing.rs

@@ -2,8 +2,12 @@
 
 mod component;
 mod endpoint;
+
+#[cfg(feature = "flamegraph")]
 mod flame;
 
 pub use component::Tracing;
 pub use endpoint::TracingEndpoint;
+
+#[cfg(feature = "flamegraph")]
 pub use flame::{layer, Grapher};

zebrad/src/components/tracing/component.rs

@@ -1,6 +1,6 @@
 //! The Abscissa component for Zebra's `tracing` implementation.
 
-use abscissa_core::{Component, FrameworkError, FrameworkErrorKind, Shutdown};
+use abscissa_core::{Component, FrameworkError, Shutdown};
 use tracing_error::ErrorLayer;
 use tracing_subscriber::{
     fmt::Formatter, layer::SubscriberExt, reload::Handle, util::SubscriberInitExt, EnvFilter,
@@ -8,6 +8,7 @@ use tracing_subscriber::{
 
 use crate::{application::app_version, config::TracingSection};
 
+#[cfg(feature = "flamegraph")]
 use super::flame;
 
 /// Abscissa component for initializing the `tracing` subsystem
@@ -21,6 +22,7 @@ pub struct Tracing {
     initial_filter: String,
 
     /// The installed flame graph collector, if enabled.
+    #[cfg(feature = "flamegraph")]
     flamegrapher: Option<flame::Grapher>,
 }
 
@@ -35,7 +37,9 @@ impl Tracing {
         let use_color =
             config.force_use_color || (config.use_color && atty::is(atty::Stream::Stdout));
 
-        // Construct a format subscriber with the supplied global logging filter, and enable reloading.
+        // Construct a format subscriber with the supplied global logging filter,
+        // and optionally enable reloading.
+        //
         // TODO: when fmt::Subscriber supports per-layer filtering, always enable this code
         #[cfg(not(all(feature = "tokio-console", tokio_unstable)))]
         let (subscriber, filter_handle) = {
@@ -43,13 +47,22 @@ impl Tracing {
 
             let logger = FmtSubscriber::builder()
                 .with_ansi(use_color)
-                .with_env_filter(&filter)
+                .with_env_filter(&filter);
-                .with_filter_reloading();
+
+            // Enable reloading if that feature is selected.
+            #[cfg(feature = "filter-reload")]
+            let (filter_handle, logger) = {
+                let logger = logger.with_filter_reloading();
+
+                (Some(logger.reload_handle()), logger)
+            };
+
+            #[cfg(not(feature = "filter-reload"))]
+            let filter_handle = None;
 
-            let filter_handle = logger.reload_handle();
             let subscriber = logger.finish().with(ErrorLayer::default());
 
-            (subscriber, Some(filter_handle))
+            (subscriber, filter_handle)
         };
 
         // Construct a tracing registry with the supplied per-layer logging filter,
@@ -82,6 +95,7 @@ impl Tracing {
         // Add optional layers based on dynamic and compile-time configs
 
         // Add a flamegraph
+        #[cfg(feature = "flamegraph")]
         let (flamelayer, flamegrapher) = if let Some(path) = flame_root {
             let (flamelayer, flamegrapher) = flame::layer(path);
 
@@ -89,9 +103,13 @@ impl Tracing {
         } else {
             (None, None)
         };
+        #[cfg(feature = "flamegraph")]
         let subscriber = subscriber.with(flamelayer);
 
+        #[cfg(feature = "journald")]
         let journaldlayer = if config.use_journald {
+            use abscissa_core::FrameworkErrorKind;
+
             let layer = tracing_journald::layer()
                 .map_err(|e| FrameworkErrorKind::ComponentError.context(e))?;
 
@@ -107,9 +125,10 @@ impl Tracing {
         } else {
             None
         };
+        #[cfg(feature = "journald")]
         let subscriber = subscriber.with(journaldlayer);
 
-        #[cfg(feature = "enable-sentry")]
+        #[cfg(feature = "sentry")]
         let subscriber = subscriber.with(sentry_tracing::layer());
 
         // spawn the console server in the background, and apply the console layer
@@ -127,14 +146,33 @@ impl Tracing {
             LOG_STATIC_MAX_LEVEL = ?log::STATIC_MAX_LEVEL,
             "started tracing component",
         );
+
         if flame_root.is_some() {
-            info!("installed flamegraph tracing layer");
+            if cfg!(feature = "flamegraph") {
+                info!(flamegraph = ?flame_root, "installed flamegraph tracing layer");
+            } else {
+                warn!(
+                    flamegraph = ?flame_root,
+                    "unable to activate configured flamegraph: \
+                     enable the 'flamegraph' feature when compiling zebrad",
+                );
+            }
         }
+
         if config.use_journald {
-            info!(?filter, "installed journald tracing layer");
+            if cfg!(feature = "journald") {
+                info!("installed journald tracing layer");
+            } else {
+                warn!(
+                    "unable to activate configured journald tracing: \
+                     enable the 'journald' feature when compiling zebrad",
+                );
+            }
         }
-        #[cfg(feature = "enable-sentry")]
+
+        #[cfg(feature = "sentry")]
         info!("installed sentry tracing layer");
+
         #[cfg(all(feature = "tokio-console", tokio_unstable))]
         info!(
             TRACING_STATIC_MAX_LEVEL = ?tracing::level_filters::STATIC_MAX_LEVEL,
@@ -145,6 +183,7 @@ impl Tracing {
         Ok(Self {
             filter_handle,
             initial_filter: filter,
+            #[cfg(feature = "flamegraph")]
             flamegrapher,
         })
     }
@@ -204,12 +243,17 @@ impl<A: abscissa_core::Application> Component<A> for Tracing {
     }
 
     fn before_shutdown(&self, _kind: Shutdown) -> Result<(), FrameworkError> {
+        #[cfg(feature = "flamegraph")]
         if let Some(ref grapher) = self.flamegrapher {
+            use abscissa_core::FrameworkErrorKind;
+
             info!("writing flamegraph");
+
             grapher
                 .write_flamegraph()
                 .map_err(|e| FrameworkErrorKind::ComponentError.context(e))?
         }
+
         Ok(())
     }
 }

zebrad/src/components/tracing/endpoint.rs

@@ -3,20 +3,27 @@
 use std::net::SocketAddr;
 
 use abscissa_core::{Component, FrameworkError};
-use hyper::service::{make_service_fn, service_fn};
-use hyper::{Body, Request, Response, Server};
 
-use crate::{components::tokio::TokioComponent, config::ZebradConfig, prelude::*};
+use crate::config::ZebradConfig;
 
-use super::Tracing;
+#[cfg(feature = "filter-reload")]
+use hyper::{Body, Request, Response};
+
+#[cfg(feature = "filter-reload")]
+use crate::{components::tokio::TokioComponent, prelude::*};
 
 /// Abscissa component which runs a tracing filter endpoint.
 #[derive(Debug, Component)]
-#[component(inject = "init_tokio(zebrad::components::tokio::TokioComponent)")]
+#[cfg_attr(
+    feature = "filter-reload",
+    component(inject = "init_tokio(zebrad::components::tokio::TokioComponent)")
+)]
 pub struct TracingEndpoint {
+    #[allow(dead_code)]
     addr: Option<SocketAddr>,
 }
 
+#[cfg(feature = "filter-reload")]
 async fn read_filter(req: Request<Body>) -> Result<String, String> {
     std::str::from_utf8(
         &hyper::body::to_bytes(req.into_body())
@@ -30,12 +37,25 @@ async fn read_filter(req: Request<Body>) -> Result<String, String> {
 impl TracingEndpoint {
     /// Create the component.
     pub fn new(config: &ZebradConfig) -> Result<Self, FrameworkError> {
+        if !cfg!(feature = "filter-reload") {
+            warn!(addr = ?config.tracing.endpoint_addr,
+                  "unable to activate configured tracing filter endpoint: \
+                   enable the 'filter-reload' feature when compiling zebrad",
+            );
+        }
+
         Ok(Self {
             addr: config.tracing.endpoint_addr,
         })
     }
 
+    #[cfg(feature = "filter-reload")]
     pub fn init_tokio(&mut self, tokio_component: &TokioComponent) -> Result<(), FrameworkError> {
+        use hyper::{
+            service::{make_service_fn, service_fn},
+            Server,
+        };
+
         let addr = if let Some(addr) = self.addr {
             addr
         } else {
@@ -75,10 +95,13 @@ impl TracingEndpoint {
     }
 }
 
+#[cfg(feature = "filter-reload")]
 #[instrument]
 async fn request_handler(req: Request<Body>) -> Result<Response<Body>, hyper::Error> {
     use hyper::{Method, StatusCode};
 
+    use super::Tracing;
+
     let rsp = match (req.method(), req.uri().path()) {
         (&Method::GET, "/") => Response::new(Body::from(
             r#"

zebrad/src/lib.rs

@@ -37,5 +37,5 @@ pub mod components;
 pub mod config;
 pub mod prelude;
 
-#[cfg(feature = "enable-sentry")]
+#[cfg(feature = "sentry")]
 pub mod sentry;

zebrad/tests/acceptance.rs

@@ -103,7 +103,7 @@
 //!
 //! Please refer to the documentation of each test for more information.
 
-use std::{collections::HashSet, convert::TryInto, env, path::PathBuf};
+use std::{collections::HashSet, env, path::PathBuf};
 
 use color_eyre::{
     eyre::{Result, WrapErr},
@@ -866,6 +866,7 @@ fn full_sync_testnet() -> Result<()> {
     full_sync_test(Testnet, "FULL_SYNC_TESTNET_TIMEOUT_MINUTES")
 }
 
+#[cfg(feature = "prometheus")]
 #[tokio::test]
 async fn metrics_endpoint() -> Result<()> {
     use hyper::Client;
@@ -921,6 +922,7 @@ async fn metrics_endpoint() -> Result<()> {
     Ok(())
 }
 
+#[cfg(feature = "filter-reload")]
 #[tokio::test]
 async fn tracing_endpoint() -> Result<()> {
     use hyper::{Body, Client, Request};
@@ -1386,6 +1388,7 @@ fn zebra_zcash_listener_conflict() -> Result<()> {
 /// exclusive use of the port. The second node will panic with the Zcash metrics
 /// conflict hint added in #1535.
 #[test]
+#[cfg(feature = "prometheus")]
 fn zebra_metrics_conflict() -> Result<()> {
     zebra_test::init();
 
@@ -1414,6 +1417,7 @@ fn zebra_metrics_conflict() -> Result<()> {
 /// exclusive use of the port. The second node will panic with the Zcash tracing
 /// conflict hint added in #1535.
 #[test]
+#[cfg(feature = "filter-reload")]
 fn zebra_tracing_conflict() -> Result<()> {
     zebra_test::init();