Added trace to module crash report (#192)

* Added trace to module crash report

The trace provided by Redis is not fully compatible to rust.
The PR adds a section to the crash report (under the module
info section) with the rust trace.

* review fixes

Cargo.toml

@@ -56,6 +56,7 @@ enum-primitive-derive = "^0.1"
 num-traits = "^0.2"
 strum_macros = "0.22"
 #failure = "0.1"
+backtrace = "0.3"
 
 [dev-dependencies]
 anyhow = "1.0.38"

src/lib.rs

@@ -30,8 +30,9 @@ pub use crate::context::thread_safe::{DetachedFromClient, ThreadSafeContext};
 pub use crate::raw::NotifyEvent;
 
 pub use crate::context::Context;
-pub use crate::raw::Status;
+pub use crate::raw::*;
 pub use crate::redismodule::*;
+use backtrace::Backtrace;
 
 /// Ideally this would be `#[cfg(not(test))]`, but that doesn't work:
 /// https://github.com/rust-lang/rust/issues/59168#issuecomment-472653680
@@ -59,3 +60,15 @@ fn from_byte_string(byte_str: *const c_char, length: size_t) -> Result<String, U
 
     String::from_utf8(vec_str).map_err(|e| e.utf8_error())
 }
+
+pub fn base_info_func(ctx: *mut RedisModuleInfoCtx, for_crash_report: bool) {
+    if !for_crash_report {
+        return;
+    }
+    // add rust trace into the crash report
+    if add_info_section(ctx, Some("trace")) == Status::Ok {
+        let current_backtrace = Backtrace::new();
+        let trace = format!("{:?}", current_backtrace);
+        raw::add_info_field_str(ctx, "trace", &trace);
+    }
+}

src/macros.rs

@@ -109,6 +109,13 @@ macro_rules! redis_module {
             ]),* $(,)*
         ])?
     ) => {
+        extern "C" fn __info_func(
+            ctx: *mut $crate::raw::RedisModuleInfoCtx,
+            for_crash_report: i32,
+        ) {
+            $crate::base_info_func(ctx, for_crash_report == 1);
+        }
+
         #[no_mangle]
         #[allow(non_snake_case)]
         pub extern "C" fn RedisModule_OnLoad(
@@ -168,6 +175,8 @@ macro_rules! redis_module {
                 )*
             )?
 
+            raw::register_info_function(ctx, Some(__info_func));
+
             raw::Status::Ok as c_int
         }
 

src/raw.rs

@@ -571,6 +571,40 @@ pub fn subscribe_to_server_event(
     unsafe { RedisModule_SubscribeToServerEvent.unwrap()(ctx, event, callback).into() }
 }
 
+#[allow(clippy::not_unsafe_ptr_arg_deref)]
+pub fn register_info_function(
+    ctx: *mut RedisModuleCtx,
+    callback: RedisModuleInfoFunc,
+) -> Status {
+    unsafe { RedisModule_RegisterInfoFunc.unwrap()(ctx, callback).into() }
+}
+
+#[allow(clippy::not_unsafe_ptr_arg_deref)]
+pub fn add_info_section(
+    ctx: *mut RedisModuleInfoCtx,
+    name: Option<&str>, // assume NULL terminated
+) -> Status {
+    let name = name.map(|n| {
+            CString::new(n).unwrap()
+        });
+    if let Some(n) = name {
+        unsafe { RedisModule_InfoAddSection.unwrap()(ctx, n.as_ptr() as *mut c_char).into() }
+    } else {
+        unsafe { RedisModule_InfoAddSection.unwrap()(ctx, ptr::null_mut()).into() }
+    }
+}
+
+#[allow(clippy::not_unsafe_ptr_arg_deref)]
+pub fn add_info_field_str(
+    ctx: *mut RedisModuleInfoCtx,
+    name: &str, // assume NULL terminated
+    content: &str,
+) -> Status {
+    let name = CString::new(name).unwrap();
+    let content = RedisString::create(ptr::null_mut(), content);
+    unsafe { RedisModule_InfoAddFieldString.unwrap()(ctx, name.as_ptr() as *mut c_char, content.inner).into() }
+}
+
 #[cfg(feature = "experimental-api")]
 pub fn export_shared_api(
     ctx: *mut RedisModuleCtx,