Feature: add feature-flag: bt enables backtrace

`--features bt` enables backtrace when generating errors.
By default errors does not contain backtrace info.

Thus openraft can be built on stable rust by default.

To use on stable rust with backtrace, set `RUSTC_BOOTSTRAP=1`, e.g.:
```
RUSTUP_TOOLCHAIN=stable RUSTC_BOOTSTRAP=1 make test
```

.github/workflows/ci.yaml

@@ -55,6 +55,56 @@ jobs:
           args: --all-targets -- -D warnings -A clippy::bool-assert-comparison
 
 
+      - name: Upload artifact
+        uses: actions/upload-artifact@v2
+        if: failure()
+        with:
+          path: |
+            openraft/_log/
+
+  ut-on-stable-rust:
+    name: unittest on stable rust
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Setup | Checkout
+        uses: actions/checkout@v2
+
+      - name: Setup | Toolchain
+        uses: actions-rs/toolchain@v1.0.6
+        with:
+          toolchain: "stable"
+          override: true
+          components: rustfmt, clippy
+
+      - name: Unit Tests
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
+        env:
+          # Parallel tests block each other and result in timeout.
+          RUST_TEST_THREADS: 2
+          RUST_LOG: debug
+          RUST_BACKTRACE: full
+
+
+      - name: Build | Release Mode | No features
+        uses: actions-rs/cargo@v1
+        with:
+          command: build
+          args: --release
+
+
+      - name: Build | Release Mode | No features
+        uses: actions-rs/cargo@v1
+        with:
+          command: build
+          args: --release --all-features
+        env:
+          # Enable unstable feature on stalbe rust.
+          RUSTC_BOOTSTRAP: 1
+
+
       - name: Upload artifact
         uses: actions/upload-artifact@v2
         if: failure()

memstore/Cargo.toml

@@ -16,7 +16,7 @@ repository = "https://github.com/datafuselabs/openraft"
 readme = "README.md"
 
 [dependencies]
-anyerror = { version = "0.1.1", features=["anyhow"]}
+anyerror = { version = "0.1.6", features = ["anyhow"]}
 anyhow = "1.0.32"
 openraft = { version="0.7.0", path= "../openraft" }
 async-trait = "0.1.36"

memstore/src/lib.rs

@@ -1,5 +1,3 @@
-#![feature(backtrace)]
-
 #[cfg(test)]
 mod test;
 
@@ -11,13 +9,13 @@ use std::ops::RangeBounds;
 use std::sync::Arc;
 use std::sync::Mutex;
 
-use anyerror::AnyError;
 use openraft::async_trait::async_trait;
 use openraft::raft::Entry;
 use openraft::raft::EntryPayload;
 use openraft::storage::HardState;
 use openraft::storage::LogState;
 use openraft::storage::Snapshot;
+use openraft::AnyError;
 use openraft::AppData;
 use openraft::AppDataResponse;
 use openraft::EffectiveMembership;

openraft/Cargo.toml

@@ -17,7 +17,7 @@ readme = "../README.md"
 
 [dependencies]
 anyhow = "1.0.32"
-anyerror = { version = "0.1.1", features=["anyhow"]}
+anyerror = { version = "0.1.6", features = ["anyhow"]}
 async-trait = "0.1.36"
 byte-unit = "4.0.12"
 bytes = "1.0"
@@ -44,5 +44,9 @@ tracing-subscriber = { version = "0.3.3",  features=["env-filter"] }
 [features]
 docinclude = [] # Used only for activating `doc(include="...")` on nightly.
 
+# Enable backtrace when generating an error.
+# Stable rust does not support backtrace.
+bt  = ["anyerror/backtrace", "anyhow/backtrace"]
+
 [package.metadata.docs.rs]
 features = ["docinclude"] # Activate `docinclude` during docs.rs build.

openraft/src/core/mod.rs

@@ -491,7 +491,8 @@ impl<D: AppData, R: AppDataResponse, N: RaftNetwork<D>, S: RaftStorage<D, R>> Ra
                     Ok(res) => match res {
                         Ok(snapshot) => {
                             let _ = tx_compaction.try_send(SnapshotUpdate::SnapshotComplete(snapshot.meta.last_log_id));
-                            let _ = chan_tx.send(snapshot.meta.last_log_id); // This will always succeed.
+                            // This will always succeed.
+                            let _ = chan_tx.send(snapshot.meta.last_log_id);
                         }
                         Err(err) => {
                             tracing::error!({error=%err}, "error while generating snapshot");

openraft/src/error.rs

@@ -198,7 +198,7 @@ pub enum ReplicationError {
 
     #[error(transparent)]
     IO {
-        #[backtrace]
+        #[cfg_attr(feature = "bt", backtrace)]
         #[from]
         source: std::io::Error,
     },
@@ -212,7 +212,7 @@ pub enum ReplicationError {
 
     #[error(transparent)]
     Network {
-        #[backtrace]
+        #[cfg_attr(feature = "bt", backtrace)]
         source: anyhow::Error,
     },
 }

openraft/src/lib.rs

@@ -1,5 +1,11 @@
 #![doc = include_str!("../README.md")]
-#![feature(backtrace)]
+#![cfg_attr(feature = "bt", feature(backtrace))]
+
+//! # Feature flags
+//!
+//! - `bt`: Enable backtrace: generate backtrace for errors. This requires a unstable feature `backtrace` thus it can
+//!   not be used with stable rust, unless explicity allowing using unstable features in stable rust with
+//!   `RUSTC_BOOTSTRAP=1`.
 
 mod config;
 mod core;
@@ -24,6 +30,8 @@ pub mod types;
 mod metrics_wait_test;
 mod storage_helper;
 
+pub use anyerror;
+pub use anyerror::AnyError;
 pub use async_trait;
 
 pub use crate::config::Config;

openraft/src/storage_error.rs

@@ -1,4 +1,3 @@
-use std::backtrace::Backtrace;
 use std::fmt::Formatter;
 
 use anyerror::AnyError;
@@ -15,7 +14,7 @@ impl DefensiveError {
         DefensiveError {
             subject,
             violation,
-            backtrace: format!("{:?}", Backtrace::capture()),
+            backtrace: anyerror::backtrace_str(),
         }
     }
 }
@@ -59,8 +58,7 @@ impl StorageIOError {
             subject,
             verb,
             source,
-            // TODO: use crate backtrace instead of std::backtrace.
-            backtrace: format!("{:?}", Backtrace::capture()),
+            backtrace: anyerror::backtrace_str(),
         }
     }
 }

openraft/src/types/v070/storage_error.rs

@@ -18,7 +18,7 @@ pub struct DefensiveError {
     /// The description of the violation.
     pub violation: Violation,
 
-    pub backtrace: String,
+    pub backtrace: Option<String>,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
@@ -116,15 +116,15 @@ pub enum StorageError {
     #[error(transparent)]
     Defensive {
         #[from]
-        #[backtrace]
+        #[cfg_attr(feature = "bt", backtrace)]
         source: DefensiveError,
     },
 
     /// An error raised by io operation.
     #[error(transparent)]
     IO {
         #[from]
-        #[backtrace]
+        #[cfg_attr(feature = "bt", backtrace)]
         source: StorageIOError,
     },
 }
@@ -135,5 +135,5 @@ pub struct StorageIOError {
     pub(crate) subject: ErrorSubject,
     pub(crate) verb: ErrorVerb,
     pub(crate) source: AnyError,
-    pub(crate) backtrace: String,
+    pub(crate) backtrace: Option<String>,
 }