Implement async Azure Functions.

This commit implements support for async Azure Functions. The feature is behind the `unstable` feature for the azure-functions crate. Additionally, users must have a dependency on `futures-preview` for the generated code to build. Part of this work was refactoring the worker code out of the run command and into its own file. The thread-local invocation context also needed to be refactored to better support a futures-based invocation. This is a breaking change as `Context` is no longer a binding type; instead, users use `Context::current` to get the current invocation context. Closes #270.
peterhuene · Jul 8, 2019 · d329c54 · d329c54
1 parent 1b5d1e6
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diff --git a/Cargo.lock b/Cargo.lock
diff --git a/README.md b/README.md
@@ -21,21 +21,44 @@ in [Rust](https://www.rust-lang.org/).
 A simple HTTP-triggered Azure Function:
 
 ```rust
-use azure_functions::bindings::{HttpRequest, HttpResponse};
-use azure_functions::func;
+use azure_functions::{
+    bindings::{HttpRequest, HttpResponse},
+    func,
+};
 
 #[func]
 pub fn greet(req: HttpRequest) -> HttpResponse {
-    // Log the message with the Azure Functions Host
-    info!("Request: {:?}", req);
-
     format!(
         "Hello from Rust, {}!\n",
         req.query_params().get("name").map_or("stranger", |x| x)
-    ).into()
+    )
+    .into()
+}
+```
+
+Azure Functions for Rust supports [async](https://rust-lang.github.io/rfcs/2394-async_await.html) functions when compiled with a nightly compiler and with the `unstable` feature enabled:
+
+```rust
+use azure_functions::{
+    bindings::{HttpRequest, HttpResponse},
+    func,
+};
+use futures::future::ready;
+
+#[func]
+pub async fn greet_async(req: HttpRequest) -> HttpResponse {
+    // Use ready().await to simply demonstrate the async/await feature
+    ready(format!(
+        "Hello from Rust, {}!\n",
+        req.query_params().get("name").map_or("stranger", |x| x)
+    ))
+    .await
+    .into()
 }
 ```
 
+See [Building an async Azure Functions application](#building-an-async-azure-functions-application) for more information.
+
 ## Get Started
 
 - [More Examples](https://github.com/peterhuene/azure-functions-rs/tree/master/examples)
@@ -54,6 +77,7 @@ pub fn greet(req: HttpRequest) -> HttpResponse {
 - [Creating a new Azure Functions application](#creating-a-new-azure-functions-application)
 - [Adding a simple HTTP-triggered application](#adding-a-simple-http-triggered-application)
 - [Building the Azure Functions application](#building-the-azure-functions-application)
+- [Building an async Azure Functions application](#building-an-async-azure-functions-application)
 - [Running the Azure Functions application](#running-the-azure-functions-application)
 - [Debugging the Azure Functions application](#debugging-the-azure-functions-application)
 - [Deploying the Azure Functions application](#deploying-the-azure-functions-application)
@@ -138,6 +162,24 @@ cargo build --features unstable
 
 This enables Azure Functions for Rust to emit diagnostic messages that will include the position of an error within an attribute.
 
+## Building an async Azure Functions application
+
+To build with support for async Azure Functions, add the following to your `Cargo.toml`:
+
+```toml
+[dependencies]
+futures-preview = { version = "0.3.0-alpha.17", optional = true }
+
+[features]
+unstable = ["azure-functions/unstable", "futures-preview"]
+```
+
+And then build with the `unstable` feature:
+
+```bash
+cargo build --features unstable
+```
+
 ## Running the Azure Functions application
 
 To build and run your Azure Functions application, use `cargo func run`:
@@ -146,6 +188,12 @@ To build and run your Azure Functions application, use `cargo func run`:
 cargo func run
 ```
 
+If you need to enable the `unstable` feature, pass the `--features` option to cargo:
+
+```bash
+cargo func run -- --features unstable
+```
+
 The `cargo func run` command builds and runs your application locally using the Azure Function Host that was
 installed by the Azure Functions Core Tools.
 
@@ -228,9 +276,6 @@ The current list of supported bindings:
 | [Table](https://docs.rs/azure-functions/latest/azure_functions/bindings/struct.Table.html)                                 | Input and Ouput Table               | in, out        | No      |
 | [TimerInfo](https://docs.rs/azure-functions/latest/azure_functions/bindings/struct.TimerInfo.html)                         | Timer Trigger                       | in             | No      |
 | [TwilioSmsMessage](https://docs.rs/azure-functions/latest/azure_functions/bindings/struct.TwilioSmsMessage.html)           | Twilio SMS Message Output | out     | Yes            | Yes     |
-| [Context](https://docs.rs/azure-functions/latest/azure_functions/struct.Context.html)*                                     | Invocation Context                  | N/A            | N/A     |
-
-\****Note: the `Context` binding is not an Azure Functions binding; it is used to pass information about the function being invoked.***
 
 More bindings will be implemented in the future, including support for retreiving data from custom bindings.
 
@@ -358,4 +403,3 @@ pub fn example(...) -> ((), Blob) {
 ```
 
 For the above example, there is no `$return` binding and the Azure Function "returns" no value.  Instead, a single output binding named `output1` is used.
-
diff --git a/azure-functions-codegen/src/func.rs b/azure-functions-codegen/src/func.rs
@@ -7,7 +7,7 @@ use azure_functions_shared::codegen::{
         Binding, BindingFactory, INPUT_BINDINGS, INPUT_OUTPUT_BINDINGS, OUTPUT_BINDINGS, TRIGGERS,
         VEC_INPUT_BINDINGS, VEC_OUTPUT_BINDINGS,
     },
-    get_string_value, iter_attribute_args, last_segment_in_path, macro_panic, Function,
+    get_string_value, iter_attribute_args, last_segment_in_path, macro_panic, Function, InvokerFn,
 };
 use invoker::Invoker;
 use output_bindings::OutputBindings;
@@ -23,7 +23,6 @@ use syn::{
 
 pub const OUTPUT_BINDING_PREFIX: &str = "output";
 const RETURN_BINDING_NAME: &str = "$return";
-const CONTEXT_TYPE_NAME: &str = "Context";
 
 fn validate_function(func: &ItemFn) {
     match func.vis {
@@ -224,19 +223,6 @@ fn bind_input_type(
     has_trigger: bool,
     binding_args: &mut HashMap<String, (AttributeArgs, Span)>,
 ) -> Binding {
-    let last_segment = last_segment_in_path(&tp.path);
-    let type_name = last_segment.ident.to_string();
-
-    if type_name == CONTEXT_TYPE_NAME {
-        if let Some(m) = mutability {
-            macro_panic(
-                m.span(),
-                "context bindings cannot be passed by mutable reference",
-            );
-        }
-        return Binding::Context;
-    }
-
     let factory = get_input_binding_factory(tp, mutability, has_trigger);
 
     match pattern {
@@ -498,7 +484,27 @@ pub fn func_impl(
         func.name = Cow::Owned(target_name.clone());
     }
 
-    func.invoker_name = Some(Cow::Owned(invoker.name()));
+    match target.asyncness {
+        Some(asyncness) => {
+            if cfg!(feature = "unstable") {
+                func.invoker = Some(azure_functions_shared::codegen::Invoker {
+                    name: Cow::Owned(invoker.name()),
+                    invoker_fn: InvokerFn::Async(None),
+                });
+            } else {
+                macro_panic(
+                    asyncness.span(),
+                    "async Azure Functions require a nightly compiler with the 'unstable' feature enabled",
+                );
+            }
+        }
+        None => {
+            func.invoker = Some(azure_functions_shared::codegen::Invoker {
+                name: Cow::Owned(invoker.name()),
+                invoker_fn: InvokerFn::Sync(None),
+            });
+        }
+    }
 
     let const_name = Ident::new(
         &format!("__{}_FUNCTION", target_name.to_uppercase()),

diff --git a/azure-functions-codegen/src/func/invoker.rs b/azure-functions-codegen/src/func/invoker.rs
@@ -1,4 +1,4 @@
-use crate::func::{get_generic_argument_type, OutputBindings, CONTEXT_TYPE_NAME};
+use crate::func::{get_generic_argument_type, OutputBindings};
 use azure_functions_shared::codegen::{bindings::TRIGGERS, last_segment_in_path};
 use azure_functions_shared::util::to_camel_case;
 use proc_macro2::TokenStream;
@@ -21,10 +21,24 @@ impl<'a> Invoker<'a> {
         }
     }
 
+    fn is_trigger_type(ty: &Type) -> bool {
+        match Invoker::deref_arg_type(ty) {
+            Type::Path(tp) => {
+                TRIGGERS.contains_key(last_segment_in_path(&tp.path).ident.to_string().as_str())
+            }
+            Type::Paren(tp) => Invoker::is_trigger_type(&tp.elem),
+            _ => false,
+        }
+    }
+}
+
+struct CommonInvokerTokens<'a>(pub &'a ItemFn);
+
+impl<'a> CommonInvokerTokens<'a> {
     fn get_input_args(&self) -> (Vec<&'a Ident>, Vec<&'a Type>) {
         self.iter_args()
             .filter_map(|(name, arg_type)| {
-                if Invoker::is_context_type(arg_type) | Invoker::is_trigger_type(arg_type) {
+                if Invoker::is_trigger_type(arg_type) {
                     return None;
                 }
 
@@ -36,7 +50,7 @@ impl<'a> Invoker<'a> {
     fn get_input_assignments(&self) -> Vec<TokenStream> {
         self.iter_args()
             .filter_map(|(_, arg_type)| {
-                if Invoker::is_context_type(arg_type) | Invoker::is_trigger_type(arg_type) {
+                if Invoker::is_trigger_type(arg_type) {
                     return None;
                 }
 
@@ -66,13 +80,6 @@ impl<'a> Invoker<'a> {
     fn get_args_for_call(&self) -> Vec<::proc_macro2::TokenStream> {
         self.iter_args()
             .map(|(name, arg_type)| {
-                if Invoker::is_context_type(arg_type) {
-                    if let Type::Reference(_) = arg_type {
-                        return quote!(&__ctx)
-                    }
-                    return quote!(__ctx.clone());
-                }
-
                 let name_str = name.to_string();
 
                 if let Type::Reference(tr) = arg_type {
@@ -99,32 +106,10 @@ impl<'a> Invoker<'a> {
             _ => panic!("expected captured arguments"),
         })
     }
-
-    fn is_context_type(ty: &Type) -> bool {
-        match Invoker::deref_arg_type(ty) {
-            Type::Path(tp) => last_segment_in_path(&tp.path).ident == CONTEXT_TYPE_NAME,
-            Type::Paren(tp) => Invoker::is_context_type(&tp.elem),
-            _ => false,
-        }
-    }
-
-    fn is_trigger_type(ty: &Type) -> bool {
-        match Invoker::deref_arg_type(ty) {
-            Type::Path(tp) => {
-                TRIGGERS.contains_key(last_segment_in_path(&tp.path).ident.to_string().as_str())
-            }
-            Type::Paren(tp) => Invoker::is_trigger_type(&tp.elem),
-            _ => false,
-        }
-    }
 }
 
-impl ToTokens for Invoker<'_> {
+impl ToTokens for CommonInvokerTokens<'_> {
     fn to_tokens(&self, tokens: &mut ::proc_macro2::TokenStream) {
-        let invoker = Ident::new(
-            &format!("{}{}", INVOKER_PREFIX, self.0.ident.to_string()),
-            self.0.ident.span(),
-        );
         let target = &self.0.ident;
 
         let (args, types) = self.get_input_args();
@@ -139,13 +124,7 @@ impl ToTokens for Invoker<'_> {
 
         let args_for_call = self.get_args_for_call();
 
-        let output_bindings = OutputBindings(self.0);
-
-        quote!(#[allow(dead_code)]
-        fn #invoker(
-            __name: &str,
-            __req: ::azure_functions::rpc::InvocationRequest,
-        ) -> ::azure_functions::rpc::InvocationResponse {
+        quote!(
             use azure_functions::{IntoVec, FromVec};
 
             let mut #trigger_arg: Option<#trigger_type> = None;
@@ -155,33 +134,87 @@ impl ToTokens for Invoker<'_> {
 
             for __param in __req.input_data.into_iter() {
                 match __param.name.as_str() {
-                   #trigger_name => #trigger_arg = Some(
-                       #trigger_type::new(
-                           __param.data.expect("expected parameter binding data"),
-                           __metadata.take().expect("expected only one trigger")
+                    #trigger_name => #trigger_arg = Some(
+                        #trigger_type::new(
+                            __param.data.expect("expected parameter binding data"),
+                            __metadata.take().expect("expected only one trigger")
                         )
                     ),
-                   #(#arg_names => #args_for_match = Some(#arg_assignments),)*
+                    #(#arg_names => #args_for_match = Some(#arg_assignments),)*
                     _ => panic!(format!("unexpected parameter binding '{}'", __param.name)),
                 };
             }
 
-            let __ctx = ::azure_functions::Context::new(&__req.invocation_id, &__req.function_id, __name);
             let __ret = #target(#(#args_for_call,)*);
+        )
+        .to_tokens(tokens);
+    }
+}
 
-            let mut __res = ::azure_functions::rpc::InvocationResponse {
-                invocation_id: __req.invocation_id,
-                result: Some(::azure_functions::rpc::StatusResult {
-                    status: ::azure_functions::rpc::status_result::Status::Success as i32,
-                    ..Default::default()
-                }),
-                ..Default::default()
-            };
+impl ToTokens for Invoker<'_> {
+    fn to_tokens(&self, tokens: &mut ::proc_macro2::TokenStream) {
+        let ident = Ident::new(
+            &format!("{}{}", INVOKER_PREFIX, self.0.ident.to_string()),
+            self.0.ident.span(),
+        );
+
+        let common_tokens = CommonInvokerTokens(&self.0);
 
-            #output_bindings
+        let output_bindings = OutputBindings(self.0);
+
+        if self.0.asyncness.is_some() {
+            quote!(
+                #[allow(dead_code)]
+                fn #ident(
+                    __req: ::azure_functions::rpc::InvocationRequest,
+                ) -> ::azure_functions::codegen::InvocationFuture {
+                    #common_tokens
+
+                    use futures::future::FutureExt;
+
+                    let __id = __req.invocation_id;
+
+                    Box::pin(
+                        __ret.then(move |__ret| {
+                            let mut __res = ::azure_functions::rpc::InvocationResponse {
+                                invocation_id: __id,
+                                result: Some(::azure_functions::rpc::StatusResult {
+                                    status: ::azure_functions::rpc::status_result::Status::Success as i32,
+                                    ..Default::default()
+                                }),
+                                ..Default::default()
+                            };
+
+                            #output_bindings
+
+                            ::futures::future::ready(__res)
+                        })
+                    )
+                }
+            ).to_tokens(tokens);
+        } else {
+            quote!(
+                #[allow(dead_code)]
+                fn #ident(
+                    __req: ::azure_functions::rpc::InvocationRequest,
+                ) -> ::azure_functions::rpc::InvocationResponse {
+                    #common_tokens
+
+                    let mut __res = ::azure_functions::rpc::InvocationResponse {
+                        invocation_id: __req.invocation_id,
+                        result: Some(::azure_functions::rpc::StatusResult {
+                            status: ::azure_functions::rpc::status_result::Status::Success as i32,
+                            ..Default::default()
+                        }),
+                        ..Default::default()
+                    };
 
-            __res
+                    #output_bindings
 
-        }).to_tokens(tokens);
+                    __res
+                }
+            )
+            .to_tokens(tokens);
+        }
     }
 }