Upgrade rust/crates/grpcio to 0.8.2 am: 0b6c763777 am: 3adce0c03a am: 1c0bfa292aandroid-12.1.0_r9android-12.1.0_r8android-12.1.0_r7android-12.1.0_r26android-12.1.0_r25android-12.1.0_r24android-12.1.0_r23android-12.1.0_r22android-12.1.0_r21android-12.1.0_r20android-12.1.0_r19android-12.1.0_r18android-12.1.0_r17android-12.1.0_r16android-12.1.0_r15android-12.1.0_r14android-12.1.0_r13android-12.1.0_r12android-12.1.0_r11android-12.1.0_r10android-12.0.0_r32android-12.0.0_r29android-12.0.0_r28android-12.0.0_r27android-12.0.0_r26android-12.0.0_r21android-12.0.0_r20android-12.0.0_r19android-12.0.0_r18android-12.0.0_r16android12L-devandroid12L-d2-s8-releaseandroid12L-d2-s7-releaseandroid12L-d2-s6-releaseandroid12L-d2-s5-releaseandroid12L-d2-s4-releaseandroid12L-d2-s3-releaseandroid12L-d2-s2-releaseandroid12L-d2-s1-releaseandroid12L-d2-releaseandroid12-qpr3-s7-releaseandroid12-qpr3-s6-releaseandroid12-qpr3-s5-releaseandroid12-qpr3-s4-releaseandroid12-qpr3-s3-releaseandroid12-qpr3-s2-releaseandroid12-qpr3-s1-releaseandroid12-qpr3-releaseandroid12-qpr1-releaseandroid12-qpr1-d-s3-releaseandroid12-qpr1-d-s2-releaseandroid12-qpr1-d-s1-releaseandroid12-qpr1-d-releaseandroid12-dev

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/grpcio/+/1662923

Change-Id: I0969f20093796804aad8602c0f9e602623cbc2f1

21 files changed, 287 insertions, 144 deletions

diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
index c4d77c4..05823ce 100644
--- a/.cargo_vcs_info.json
+++ b/.cargo_vcs_info.json
@@ -1,5 +1,5 @@
 {
   "git": {
-    "sha1": "37188956eb8e71631326d708b8afb0940918f5d8"
+    "sha1": "b35467b1bfe58eedf4e77025432074d361be591f"
   }
 }
diff --git a/.clang-tidy b/.clang-tidy
index d217441..752b25e 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -1,6 +1,44 @@
 ---
-Checks: 'modernize-use-nullptr,google-build-namespaces,google-build-explicit-make-pair,readability-function-size,performance-*,bugprone-*'
-WarningsAsErrors: 'modernize-use-nullptr,google-build-namespaces,google-build-explicit-make-pair,readability-function-size,performance-*,bugprone-*'
+# Disable abseil-no-namespace: https://bugs.llvm.org/show_bug.cgi?id=47947
+Checks: '-*,
+  abseil-*,
+  -abseil-no-namespace,
+  bugprone-*,
+  -bugprone-narrowing-conversions,
+  -bugprone-too-small-loop-variable,
+  performance-*,
+  -performance-unnecessary-copy-initialization,
+  -performance-unnecessary-value-param,
+  google-*,
+  -google-runtime-int,
+  -google-runtime-references,
+  misc-definitions-in-headers,
+  misc-static-assert,
+  misc-unconventional-assign-operator,
+  misc-uniqueptr-reset-release,
+  misc-unused-alias-decls,
+  misc-unused-using-decls,
+  modernize-make-unique,
+  -modernize-redundant-void-arg,
+  modernize-replace-auto-ptr,
+  modernize-shrink-to-fit,
+  modernize-use-bool-literals,
+  modernize-use-nullptr,
+  modernize-use-override,
+  readability-container-size-empty,
+  readability-deleted-default,
+  readability-function-size,
+  readability-inconsistent-declaration-parameter-name,
+  readability-redundant-control-flow,
+  readability-redundant-smartptr-get,
+  readability-string-compare'
+WarningsAsErrors: '*'
 CheckOptions:
   - key:    readability-function-size.StatementThreshold
     value:  '450'
+  - key:    modernize-make-unique.MakeSmartPtrFunction
+    value:  'absl::make_unique'
+  - key:    modernize-make-unique.MakeSmartPtrFunctionHeader
+    value:  'absl/memory/memory.h'
+  - key:    google-readability-braces-around-statements.ShortStatementLines
+    value:  1
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 1c42285..3731f9e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -39,6 +39,7 @@ jobs:
     - run: cargo build --no-default-features
     - run: cargo build --no-default-features --features protobuf-codec
     - run: cargo build --no-default-features --features prost-codec
+    - run: cd proto && cargo build --no-default-features --features prost-codec
     - run: cargo build
     - run: cargo test --all
 
@@ -75,9 +76,9 @@ jobs:
     - uses: actions/checkout@v2
     - run: which go && go version && which cargo && cargo version && clang --version && openssl version
     - run: scripts/reset-submodule.cmd
-    - run: cargo build --no-default-features
-    - run: cargo build --no-default-features --features protobuf-codec
-    - run: cargo build --no-default-features --features prost-codec
+    - run: cargo build --no-default-features --features use-bindgen
+    - run: cargo build --no-default-features --features "protobuf-codec use-bindgen"
+    - run: cargo build --no-default-features --features "prost-codec use-bindgen"
     - run: cargo build
     - run: cargo test --all
 
@@ -95,6 +96,8 @@ jobs:
   Win:
     name: Windows
     runs-on: windows-latest
+    env:
+      LIBCLANG_PATH: 'C:\Program Files\LLVM\bin'
     steps:
     - uses: actions/checkout@v2
     - run: choco install -y llvm
diff --git a/.travis.yml b/.travis.yml
index 822e0f1..9cc0821 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,7 +1,7 @@
 # Travis is only used to test ARM64 Linux
 
 dist: focal
-sudo: false
+sudo: true
 language: rust
 git:
   submodules: false
@@ -26,12 +26,12 @@ addons:
 jobs:
   include:
   - os: linux
-    arch: arm64
+    arch: arm64-graviton2
+    vm: virt
     before_script:
       - scripts/reset-submodule.cmd
-      - export GRPC_VERSION=1.33.1
+      - export GRPC_VERSION=1.35.0
       - export PATH="$PATH:$HOME/.cache/bin:$HOME/.cargo/bin"
-      - sudo apt-get update && sudo apt-get -y install libssl-dev
       - which cmake && cmake --version && openssl version
       - eval "$(gimme stable)"
     script:
@@ -44,5 +44,16 @@ jobs:
       - cargo build --no-default-features --features protobuf-codec
       - cargo build --no-default-features --features prost-codec
       - cargo build
-      - cargo test --release --all
-      - cargo test --release --features "openssl-vendored" --all
+      - travis_wait 40 cargo test --release --all
+  - os: linux
+    arch: arm64-graviton2
+    vm: virt
+    before_script:
+      - scripts/reset-submodule.cmd
+      - export GRPC_VERSION=1.35.0
+      - export PATH="$PATH:$HOME/.cache/bin:$HOME/.cargo/bin"
+      - sudo apt-get update && sudo apt-get -y install libssl-dev
+      - which cmake && cmake --version && openssl version
+      - eval "$(gimme stable)"
+    script:
+      - travis_wait 40 cargo test --release --features "openssl-vendored" --all
diff --git a/Android.bp b/Android.bp
index ef9f992..44ad1a2 100644
--- a/Android.bp
+++ b/Android.bp
@@ -1,4 +1,5 @@
 // This file is generated by cargo2android.py --run --device --dependencies --features=protobuf,protobuf-codec.
+// Do not modify this file as changes will be overridden on upgrade.
 
 package {
     default_applicable_licenses: ["external_rust_crates_grpcio_license"],
@@ -38,59 +39,40 @@ rust_library {
 }
 
 // dependent_library ["feature_list"]
-//   aho-corasick-0.7.15 "default,std"
-//   bindgen-0.51.1
-//   bitflags-1.2.1 "default"
-//   boringssl-src-0.1.0
-//   cc-1.0.66
-//   cexpr-0.3.6
-//   cfg-if-0.1.10
+//   boringssl-src-0.2.0
+//   cc-1.0.67
 //   cfg-if-1.0.0
-//   clang-sys-0.28.1 "clang_6_0,gte_clang_3_6,gte_clang_3_7,gte_clang_3_8,gte_clang_3_9,gte_clang_4_0,gte_clang_5_0,gte_clang_6_0,libloading,runtime"
 //   cmake-0.1.45
-//   futures-0.3.8 "alloc,async-await,default,executor,futures-executor,std"
-//   futures-channel-0.3.8 "alloc,futures-sink,sink,std"
-//   futures-core-0.3.8 "alloc,std"
-//   futures-executor-0.3.8 "std"
-//   futures-io-0.3.8 "std"
-//   futures-macro-0.3.8
-//   futures-sink-0.3.8 "alloc,std"
-//   futures-task-0.3.8 "alloc,once_cell,std"
-//   futures-util-0.3.8 "alloc,async-await,async-await-macro,channel,futures-channel,futures-io,futures-macro,futures-sink,io,memchr,proc-macro-hack,proc-macro-nested,sink,slab,std"
-//   glob-0.3.0
-//   grpcio-sys-0.7.2 "default"
+//   futures-0.3.13 "alloc,async-await,default,executor,futures-executor,std"
+//   futures-channel-0.3.13 "alloc,futures-sink,sink,std"
+//   futures-core-0.3.13 "alloc,std"
+//   futures-executor-0.3.13 "std"
+//   futures-io-0.3.13 "std"
+//   futures-macro-0.3.13
+//   futures-sink-0.3.13 "alloc,std"
+//   futures-task-0.3.13 "alloc,std"
+//   futures-util-0.3.13 "alloc,async-await,async-await-macro,channel,futures-channel,futures-io,futures-macro,futures-sink,io,memchr,proc-macro-hack,proc-macro-nested,sink,slab,std"
+//   grpcio-sys-0.8.1
 //   instant-0.1.9
-//   lazy_static-1.4.0
-//   libc-0.2.81 "default,std"
-//   libloading-0.5.2
+//   libc-0.2.92 "default,std"
 //   libz-sys-1.1.2 "default,libc,static,stock-zlib"
 //   lock_api-0.4.2
-//   log-0.4.11
-//   memchr-2.3.4 "default,std,use_std"
-//   nom-4.2.3 "alloc,default,std,verbose-errors"
-//   once_cell-1.5.2 "alloc,std"
+//   log-0.4.14
+//   memchr-2.3.4 "default,std"
 //   parking_lot-0.11.1 "default"
-//   parking_lot_core-0.8.1
-//   peeking_take_while-0.1.2
-//   pin-project-1.0.2
-//   pin-project-internal-1.0.2
+//   parking_lot_core-0.8.3
+//   pin-project-lite-0.2.6
 //   pin-utils-0.1.0
 //   pkg-config-0.3.19
 //   proc-macro-hack-0.5.19
-//   proc-macro-nested-0.1.6
-//   proc-macro2-1.0.24 "default,proc-macro"
-//   protobuf-2.18.1
-//   quote-1.0.7 "default,proc-macro"
-//   regex-1.4.2 "aho-corasick,default,memchr,perf,perf-cache,perf-dfa,perf-inline,perf-literal,std,thread_local,unicode,unicode-age,unicode-bool,unicode-case,unicode-gencat,unicode-perl,unicode-script,unicode-segment"
-//   regex-syntax-0.6.21 "default,unicode,unicode-age,unicode-bool,unicode-case,unicode-gencat,unicode-perl,unicode-script,unicode-segment"
-//   rustc-hash-1.1.0 "default,std"
+//   proc-macro-nested-0.1.7
+//   proc-macro2-1.0.26 "default,proc-macro"
+//   protobuf-2.22.1
+//   quote-1.0.9 "default,proc-macro"
 //   same-file-1.0.6
 //   scopeguard-1.1.0
-//   shlex-0.1.1
 //   slab-0.4.2
-//   smallvec-1.5.1
-//   syn-1.0.54 "clone-impls,default,derive,full,parsing,printing,proc-macro,quote,visit-mut"
-//   thread_local-1.0.1
+//   smallvec-1.6.1
+//   syn-1.0.68 "clone-impls,default,derive,full,parsing,printing,proc-macro,quote"
 //   unicode-xid-0.2.1 "default"
-//   version_check-0.1.5
-//   walkdir-2.3.1
+//   walkdir-2.3.2
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6a6dfdb..f928b24 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,23 @@
+# 0.8.2 - 2012-03-10
+
+- Fix send requirement in connectivity APIs (#516)
+
+# 0.8.1 - 2021-03-05
+
+- Support watch connectivity state (#513)
+- Fix prost build of grpcio-proto (#515)
+
+# grpcio-sys 0.8.1 - 2021-03-02
+
+- Detect changes ahead to ease pain of upgrading compiler (#511)
+
+# 0.8.0 - 2021-02-19
+
+- Fix clippy warnings (#504)
+- Add a way to not use bindgen (#499)
+- Update gRPC C core to 1.35.0 (#506)
+- Update bindgen to 0.57.0 (#507)
+
 # 0.7.1 - 2020-12-18
 
 - Allow CXX environment variable to override g++ for musl build (#500)
diff --git a/Cargo.toml b/Cargo.toml
index b03eb7c..c8ccf28 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,7 +13,7 @@
 [package]
 edition = "2018"
 name = "grpcio"
-version = "0.7.1"
+version = "0.8.2"
 authors = ["The TiKV Project Developers"]
 autoexamples = false
 description = "The rust language implementation of gRPC, base on the gRPC c core library."
@@ -29,14 +29,15 @@ all-features = true
 [profile.release]
 debug = true
 [dependencies.bytes]
-version = "0.5"
+version = "1.0"
 optional = true
 
 [dependencies.futures]
 version = "0.3"
 
 [dependencies.grpcio-sys]
-version = "0.7"
+version = "0.8"
+default-features = false
 
 [dependencies.libc]
 version = "0.2"
@@ -48,7 +49,7 @@ version = "0.4"
 version = "0.11"
 
 [dependencies.prost]
-version = "0.6"
+version = "0.7"
 optional = true
 
 [dependencies.protobuf]
@@ -56,12 +57,13 @@ version = "2.0"
 optional = true
 
 [features]
-default = ["protobuf-codec", "secure"]
+default = ["protobuf-codec", "secure", "use-bindgen"]
 no-omit-frame-pointer = ["grpcio-sys/no-omit-frame-pointer"]
 openssl = ["secure", "grpcio-sys/openssl"]
 openssl-vendored = ["secure", "grpcio-sys/openssl-vendored"]
 prost-codec = ["prost", "bytes"]
 protobuf-codec = ["protobuf"]
 secure = ["grpcio-sys/secure"]
+use-bindgen = ["grpcio-sys/use-bindgen"]
 [badges.travis-ci]
 repository = "tikv/grpc-rs"
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
index 7daa61e..8938f97 100644
--- a/Cargo.toml.orig
+++ b/Cargo.toml.orig
@@ -1,6 +1,6 @@
 [package]
 name = "grpcio"
-version = "0.7.1"
+version = "0.8.2"
 edition = "2018"
 authors = ["The TiKV Project Developers"]
 license = "Apache-2.0"
@@ -17,12 +17,12 @@ autoexamples = false
 all-features = true
 
 [dependencies]
-grpcio-sys = { path = "grpc-sys", version = "0.7" }
+grpcio-sys = { path = "grpc-sys", version = "0.8", default-features = false }
 libc = "0.2"
 futures = "0.3"
 protobuf = { version = "2.0", optional = true }
-prost = { version = "0.6", optional = true }
-bytes = { version = "0.5", optional = true }
+prost = { version = "0.7", optional = true }
+bytes = { version = "1.0", optional = true }
 log = "0.4"
 parking_lot = "0.11"
 
@@ -30,13 +30,14 @@ parking_lot = "0.11"
 members = ["proto", "benchmark", "compiler", "interop", "tests-and-examples"]
 
 [features]
-default = ["protobuf-codec", "secure"]
+default = ["protobuf-codec", "secure", "use-bindgen"]
 protobuf-codec = ["protobuf"]
 prost-codec = ["prost", "bytes"]
 secure = ["grpcio-sys/secure"]
 openssl = ["secure", "grpcio-sys/openssl"]
 openssl-vendored = ["secure", "grpcio-sys/openssl-vendored"]
 no-omit-frame-pointer = ["grpcio-sys/no-omit-frame-pointer"]
+use-bindgen = ["grpcio-sys/use-bindgen"]
 
 [profile.release]
 debug = true
@@ -45,4 +46,4 @@ debug = true
 travis-ci = { repository = "tikv/grpc-rs" }
 
 [patch.crates-io]
-grpcio-compiler = { path = "compiler", version = "0.7.0", default-features = false }
+grpcio-compiler = { path = "compiler", version = "0.8.0", default-features = false }
diff --git a/METADATA b/METADATA
index ab343d9..a81517a 100644
--- a/METADATA
+++ b/METADATA
@@ -7,13 +7,13 @@ third_party {
   }
   url {
     type: ARCHIVE
-    value: "https://static.crates.io/crates/grpcio/grpcio-0.7.1.crate"
+    value: "https://static.crates.io/crates/grpcio/grpcio-0.8.2.crate"
   }
-  version: "0.7.1"
+  version: "0.8.2"
   license_type: NOTICE
   last_upgrade_date {
-    year: 2020
-    month: 12
-    day: 18
+    year: 2021
+    month: 4
+    day: 1
   }
 }
diff --git a/README.md b/README.md
index 03f4e19..d4d384a 100644
--- a/README.md
+++ b/README.md
@@ -31,7 +31,7 @@ This project is still under development. The following features with the check m
 - LLVM and Clang >= 3.9 if you need to generate bindings at compile time.
 - By default, the [secure feature](#feature-secure) is provided by boringssl. You can also use openssl instead by enabling [openssl feature](#feature-openssl).
 
-For Linux and MacOS, you also need to install gcc (or clang) too.
+For Linux and MacOS, you also need to install gcc 4.9+ (or clang) too.
 
 Bindings are pre-generated for x86_64/arm64 Linux. For other platforms, bindings are generated at compile time.
 
diff --git a/scripts/generate-bindings.sh b/scripts/generate-bindings.sh
index 462b2fa..81a043e 100755
--- a/scripts/generate-bindings.sh
+++ b/scripts/generate-bindings.sh
@@ -11,5 +11,5 @@ export UPDATE_BIND=1
 cargo build -p grpcio-sys --target ${ARCH}-unknown-linux-gnu
 rustfmt grpc-sys/bindings/*
 if [ "$(uname -s)" == "Linux" ]; then
-  sed -i '/pub type .*= ::std::os::raw::.*/d' grpc-sys/bindings/*
+  sed -i '/^pub type .*= ::std::os::raw::.*/d' grpc-sys/bindings/*
 fi
diff --git a/src/buf.rs b/src/buf.rs
index d51f274..de8fe54 100644
--- a/src/buf.rs
+++ b/src/buf.rs
@@ -427,7 +427,7 @@ impl bytes::Buf for GrpcByteBufferReader {
         self.remain
     }
 
-    fn bytes(&self) -> &[u8] {
+    fn chunk(&self) -> &[u8] {
         // This is similar but not identical to `BuffRead::fill_buf`, since `self`
         // is not mutable, we can only return bytes up to the end of the current
         // slice.
@@ -595,7 +595,7 @@ mod tests {
                 let mut count = 100;
                 while reader.remaining() > 0 {
                     assert_eq!(remaining, reader.remaining());
-                    let bytes = Buf::bytes(&reader);
+                    let bytes = Buf::chunk(&reader);
                     bytes.iter().for_each(|b| assert_eq!(*b, len as u8));
                     let mut read = bytes.len();
                     // We don't have to advance by the whole amount we read.
diff --git a/src/call/client.rs b/src/call/client.rs
index 279e619..d1047bf 100644
--- a/src/call/client.rs
+++ b/src/call/client.rs
@@ -399,7 +399,7 @@ impl<Req> Sink<(Req, WriteFlags)> for StreamingCallSink<Req> {
             t.close_f = Some(close_f);
         }
 
-        if let Poll::Pending = Pin::new(t.close_f.as_mut().unwrap()).poll(cx)? {
+        if Pin::new(t.close_f.as_mut().unwrap()).poll(cx)?.is_pending() {
             // if call is finished, can return early here.
             call.check_alive()?;
             return Poll::Pending;
diff --git a/src/call/mod.rs b/src/call/mod.rs
index a06e003..7f1582f 100644
--- a/src/call/mod.rs
+++ b/src/call/mod.rs
@@ -33,9 +33,9 @@ impl From<i32> for RpcStatusCode {
     }
 }
 
-impl Into<i32> for RpcStatusCode {
-    fn into(self) -> i32 {
-        self.0
+impl From<RpcStatusCode> for i32 {
+    fn from(code: RpcStatusCode) -> i32 {
+        code.0
     }
 }
 
@@ -533,7 +533,7 @@ impl StreamingBase {
         if !skip_finish_check {
             let mut finished = false;
             if let Some(close_f) = &mut self.close_f {
-                if let Poll::Ready(_) = Pin::new(close_f).poll(cx)? {
+                if Pin::new(close_f).poll(cx)?.is_ready() {
                     // Don't return immediately, there may be pending data.
                     finished = true;
                 }
diff --git a/src/call/server.rs b/src/call/server.rs
index 875555e..0fed656 100644
--- a/src/call/server.rs
+++ b/src/call/server.rs
@@ -3,6 +3,7 @@
 use std::ffi::CStr;
 use std::pin::Pin;
 use std::sync::Arc;
+use std::time::Duration;
 use std::{result, slice};
 
 use crate::grpc_sys::{
@@ -30,8 +31,10 @@ use crate::server::{BoxHandler, RequestCallContext};
 use crate::task::{BatchFuture, CallTag, Executor, Kicker};
 use crate::CheckResult;
 
+/// A time point that an rpc or operation should finished before it.
+#[derive(Clone, Copy)]
 pub struct Deadline {
-    spec: gpr_timespec,
+    pub(crate) spec: gpr_timespec,
 }
 
 impl Deadline {
@@ -44,12 +47,27 @@ impl Deadline {
         }
     }
 
-    pub fn exceeded(&self) -> bool {
+    /// Checks if the deadline is exceeded.
+    pub fn exceeded(self) -> bool {
         unsafe {
             let now = grpc_sys::gpr_now(gpr_clock_type::GPR_CLOCK_REALTIME);
             grpc_sys::gpr_time_cmp(now, self.spec) >= 0
         }
     }
+
+    pub(crate) fn spec(self) -> gpr_timespec {
+        self.spec
+    }
+}
+
+impl From<Duration> for Deadline {
+    /// Build a deadline from given duration.
+    ///
+    /// The deadline will be `now + duration`.
+    #[inline]
+    fn from(dur: Duration) -> Deadline {
+        Deadline::new(dur.into())
+    }
 }
 
 /// Context for accepting a request.
@@ -626,8 +644,8 @@ impl<'a> RpcContext<'a> {
         self.ctx.host()
     }
 
-    pub fn deadline(&self) -> &Deadline {
-        &self.deadline
+    pub fn deadline(&self) -> Deadline {
+        self.deadline
     }
 
     /// Get the initial metadata sent by client.
diff --git a/src/channel.rs b/src/channel.rs
index a33a4be..c8c67b1 100644
--- a/src/channel.rs
+++ b/src/channel.rs
@@ -4,12 +4,14 @@ use std::borrow::Cow;
 use std::collections::hash_map::Entry;
 use std::collections::HashMap;
 use std::ffi::{CStr, CString};
+use std::future::Future;
 use std::sync::Arc;
 use std::time::Duration;
 use std::{cmp, i32, ptr};
 
-use crate::grpc_sys::{
-    self, gpr_timespec, grpc_arg_pointer_vtable, grpc_channel, grpc_channel_args,
+use crate::{
+    grpc_sys::{self, gpr_timespec, grpc_arg_pointer_vtable, grpc_channel, grpc_channel_args},
+    Deadline,
 };
 use libc::{self, c_char, c_int};
 
@@ -17,6 +19,7 @@ use crate::call::{Call, Method};
 use crate::cq::CompletionQueue;
 use crate::env::Environment;
 use crate::error::Result;
+use crate::task::CallTag;
 use crate::task::Kicker;
 use crate::CallOption;
 use crate::ResourceQuota;
@@ -28,7 +31,7 @@ pub use crate::grpc_sys::{
 
 /// Ref: http://www.grpc.io/docs/guides/wire.html#user-agents
 fn format_user_agent_string(agent: &str) -> CString {
-    let version = "0.7.1";
+    let version = "0.8.2";
     let trimed_agent = agent.trim();
     let val = if trimed_agent.is_empty() {
         format!("grpc-rust/{}", version)
@@ -589,12 +592,66 @@ impl Channel {
         }
     }
 
-    // If try_to_connect is true, the channel will try to establish a connection, potentially
-    // changing the state.
+    /// If try_to_connect is true, the channel will try to establish a connection, potentially
+    /// changing the state.
     pub fn check_connectivity_state(&self, try_to_connect: bool) -> ConnectivityState {
         self.inner.check_connectivity_state(try_to_connect)
     }
 
+    /// Blocking wait for channel state change or deadline expiration.
+    ///
+    /// `check_connectivity_state` needs to be called to get the current state. Returns false
+    /// means deadline excceeds before observing any state changes.
+    pub fn wait_for_state_change(
+        &self,
+        last_observed: ConnectivityState,
+        deadline: impl Into<Deadline>,
+    ) -> impl Future<Output = bool> {
+        let (cq_f, prom) = CallTag::action_pair();
+        let prom_box = Box::new(prom);
+        let tag = Box::into_raw(prom_box);
+        let should_wait = if let Ok(cq_ref) = self.cq.borrow() {
+            unsafe {
+                grpcio_sys::grpc_channel_watch_connectivity_state(
+                    self.inner.channel,
+                    last_observed,
+                    deadline.into().spec(),
+                    cq_ref.as_ptr(),
+                    tag as *mut _,
+                )
+            }
+            true
+        } else {
+            // It's already shutdown.
+            false
+        };
+        async move { should_wait && cq_f.await.unwrap() }
+    }
+
+    /// Wait for this channel to be connected.
+    ///
+    /// Returns false means deadline excceeds before connection is connected.
+    pub async fn wait_for_connected(&self, deadline: impl Into<Deadline>) -> bool {
+        // Fast path, it's probably connected.
+        let mut state = self.check_connectivity_state(true);
+        if ConnectivityState::GRPC_CHANNEL_READY == state {
+            return true;
+        }
+        let deadline = deadline.into();
+        loop {
+            if self.wait_for_state_change(state, deadline).await {
+                state = self.check_connectivity_state(true);
+                match state {
+                    ConnectivityState::GRPC_CHANNEL_READY => return true,
+                    ConnectivityState::GRPC_CHANNEL_SHUTDOWN => return false,
+                    _ => (),
+                }
+                continue;
+            }
+            return false;
+        }
+    }
+
     /// Create a Kicker.
     pub(crate) fn create_kicker(&self) -> Result<Kicker> {
         let cq_ref = self.cq.borrow()?;
diff --git a/src/cq.rs b/src/cq.rs
index 60b6bb3..58d6d6b 100644
--- a/src/cq.rs
+++ b/src/cq.rs
@@ -36,35 +36,39 @@ impl CompletionQueueHandle {
     }
 
     fn add_ref(&self) -> Result<()> {
+        let mut cnt = self.ref_cnt.load(Ordering::SeqCst);
         loop {
-            let cnt = self.ref_cnt.load(Ordering::SeqCst);
             if cnt <= 0 {
                 // `shutdown` has been called, reject any requests.
                 return Err(Error::QueueShutdown);
             }
             let new_cnt = cnt + 1;
-            if cnt
-                == self
-                    .ref_cnt
-                    .compare_and_swap(cnt, new_cnt, Ordering::SeqCst)
-            {
-                return Ok(());
+            match self.ref_cnt.compare_exchange_weak(
+                cnt,
+                new_cnt,
+                Ordering::SeqCst,
+                Ordering::SeqCst,
+            ) {
+                Ok(_) => return Ok(()),
+                Err(c) => cnt = c,
             }
         }
     }
 
     fn unref(&self) {
+        let mut cnt = self.ref_cnt.load(Ordering::SeqCst);
         let shutdown = loop {
-            let cnt = self.ref_cnt.load(Ordering::SeqCst);
             // If `shutdown` is not called, `cnt` > 0, so minus 1 to unref.
             // If `shutdown` is called, `cnt` < 0, so plus 1 to unref.
             let new_cnt = cnt - cnt.signum();
-            if cnt
-                == self
-                    .ref_cnt
-                    .compare_and_swap(cnt, new_cnt, Ordering::SeqCst)
-            {
-                break new_cnt == 0;
+            match self.ref_cnt.compare_exchange_weak(
+                cnt,
+                new_cnt,
+                Ordering::SeqCst,
+                Ordering::SeqCst,
+            ) {
+                Ok(_) => break new_cnt == 0,
+                Err(c) => cnt = c,
             }
         };
         if shutdown {
@@ -75,8 +79,8 @@ impl CompletionQueueHandle {
     }
 
     fn shutdown(&self) {
+        let mut cnt = self.ref_cnt.load(Ordering::SeqCst);
         let shutdown = loop {
-            let cnt = self.ref_cnt.load(Ordering::SeqCst);
             if cnt <= 0 {
                 // `shutdown` is called, skipped.
                 return;
@@ -85,12 +89,14 @@ impl CompletionQueueHandle {
             // Because `cnt` is initialized to 1, so minus 1 to make it reach
             // toward 0. That is `new_cnt = -(cnt - 1) = -cnt + 1`.
             let new_cnt = -cnt + 1;
-            if cnt
-                == self
-                    .ref_cnt
-                    .compare_and_swap(cnt, new_cnt, Ordering::SeqCst)
-            {
-                break new_cnt == 0;
+            match self.ref_cnt.compare_exchange_weak(
+                cnt,
+                new_cnt,
+                Ordering::SeqCst,
+                Ordering::SeqCst,
+            ) {
+                Ok(_) => break new_cnt == 0,
+                Err(c) => cnt = c,
             }
         };
         if shutdown {
diff --git a/src/metadata.rs b/src/metadata.rs
index 746b593..893f6e2 100644
--- a/src/metadata.rs
+++ b/src/metadata.rs
@@ -16,11 +16,11 @@ fn normalize_key(key: &str, binary: bool) -> Result<Cow<'_, str>> {
     let mut is_upper_case = false;
     for b in key.as_bytes() {
         let b = *b;
-        if b >= b'A' && b <= b'Z' {
+        if (b'A'..=b'Z').contains(&b) {
             is_upper_case = true;
             continue;
-        } else if b >= b'a' && b <= b'z'
-            || b >= b'0' && b <= b'9'
+        } else if (b'a'..=b'z').contains(&b)
+            || (b'0'..=b'9').contains(&b)
             || b == b'_'
             || b == b'-'
             || b == b'.'
@@ -83,10 +83,10 @@ impl MetadataBuilder {
             }
         }
         let key = normalize_key(key, false)?;
-        self.add_metadata(&key, value.as_bytes())
+        Ok(self.add_metadata(&key, value.as_bytes()))
     }
 
-    fn add_metadata(&mut self, key: &str, value: &[u8]) -> Result<&mut MetadataBuilder> {
+    fn add_metadata(&mut self, key: &str, value: &[u8]) -> &mut MetadataBuilder {
         unsafe {
             grpc_sys::grpcwrap_metadata_array_add(
                 &mut self.arr.0,
@@ -96,7 +96,7 @@ impl MetadataBuilder {
                 value.len(),
             )
         }
-        Ok(self)
+        self
     }
 
     /// Add a metadata holding a binary value.
@@ -104,7 +104,7 @@ impl MetadataBuilder {
     /// `key` needs to have suffix (-bin) indicating a binary valued metadata entry.
     pub fn add_bytes(&mut self, key: &str, value: &[u8]) -> Result<&mut MetadataBuilder> {
         let key = normalize_key(key, true)?;
-        self.add_metadata(&key, value)
+        Ok(self.add_metadata(&key, value))
     }
 
     /// Create `Metadata` with configured entries.
@@ -221,7 +221,7 @@ impl Clone for Metadata {
         let mut builder = MetadataBuilder::with_capacity(self.len());
         for (k, v) in self.iter() {
             // use `add_metadata` to skip validation.
-            builder.add_metadata(k, v).unwrap();
+            builder.add_metadata(k, v);
         }
         builder.build()
     }
diff --git a/src/server.rs b/src/server.rs
index 0f01690..a612b13 100644
--- a/src/server.rs
+++ b/src/server.rs
@@ -11,6 +11,7 @@ use std::sync::Arc;
 
 use crate::grpc_sys::{self, grpc_call_error, grpc_server};
 use futures::future::Future;
+use futures::ready;
 use futures::task::{Context, Poll};
 
 use crate::call::server::*;
@@ -523,14 +524,19 @@ pub fn request_call(ctx: RequestCallContext, cq: &CompletionQueue) {
 
 /// A `Future` that will resolve when shutdown completes.
 pub struct ShutdownFuture {
-    cq_f: CqFuture<()>,
+    /// `true` means the future finishes successfully.
+    cq_f: CqFuture<bool>,
 }
 
 impl Future for ShutdownFuture {
     type Output = Result<()>;
 
     fn poll(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
-        Pin::new(&mut self.cq_f).poll(cx)
+        match ready!(Pin::new(&mut self.cq_f).poll(cx)) {
+            Ok(true) => Poll::Ready(Ok(())),
+            Ok(false) => Poll::Ready(Err(Error::ShutdownFailed)),
+            Err(e) => unreachable!("action future should never resolve to error: {}", e),
+        }
     }
 }
 
@@ -549,7 +555,7 @@ pub struct Server {
 impl Server {
     /// Shutdown the server asynchronously.
     pub fn shutdown(&mut self) -> ShutdownFuture {
-        let (cq_f, prom) = CallTag::shutdown_pair();
+        let (cq_f, prom) = CallTag::action_pair();
         let prom_box = Box::new(prom);
         let tag = Box::into_raw(prom_box);
         unsafe {
diff --git a/src/task/mod.rs b/src/task/mod.rs
index f151d0e..53369f1 100644
--- a/src/task/mod.rs
+++ b/src/task/mod.rs
@@ -14,7 +14,7 @@ use parking_lot::Mutex;
 
 use self::callback::{Abort, Request as RequestCallback, UnaryRequest as UnaryRequestCallback};
 use self::executor::SpawnTask;
-use self::promise::{Batch as BatchPromise, Shutdown as ShutdownPromise};
+use self::promise::{Action as ActionPromise, Batch as BatchPromise};
 use crate::call::server::RequestContext;
 use crate::call::{BatchContext, Call, MessageReader};
 use crate::cq::CompletionQueue;
@@ -113,7 +113,7 @@ pub enum CallTag {
     Request(RequestCallback),
     UnaryRequest(UnaryRequestCallback),
     Abort(Abort),
-    Shutdown(ShutdownPromise),
+    Action(ActionPromise),
     Spawn(Arc<SpawnTask>),
 }
 
@@ -131,11 +131,12 @@ impl CallTag {
         CallTag::Request(RequestCallback::new(ctx))
     }
 
-    /// Generate a Future/CallTag pair for shutdown call.
-    pub fn shutdown_pair() -> (CqFuture<()>, CallTag) {
+    /// Generate a Future/CallTag pair for action call that only cares if the result is
+    /// successful.
+    pub fn action_pair() -> (CqFuture<bool>, CallTag) {
         let inner = new_inner();
-        let shutdown = ShutdownPromise::new(inner.clone());
-        (CqFuture::new(inner), CallTag::Shutdown(shutdown))
+        let action = ActionPromise::new(inner.clone());
+        (CqFuture::new(inner), CallTag::Action(action))
     }
 
     /// Generate a CallTag for abort call before handler is called.
@@ -175,7 +176,7 @@ impl CallTag {
             CallTag::Request(cb) => cb.resolve(cq, success),
             CallTag::UnaryRequest(cb) => cb.resolve(cq, success),
             CallTag::Abort(_) => {}
-            CallTag::Shutdown(prom) => prom.resolve(success),
+            CallTag::Action(prom) => prom.resolve(success),
             CallTag::Spawn(notify) => self::executor::resolve(notify, success),
         }
     }
@@ -188,7 +189,7 @@ impl Debug for CallTag {
             CallTag::Request(_) => write!(f, "CallTag::Request(..)"),
             CallTag::UnaryRequest(_) => write!(f, "CallTag::UnaryRequest(..)"),
             CallTag::Abort(_) => write!(f, "CallTag::Abort(..)"),
-            CallTag::Shutdown(_) => write!(f, "CallTag::Shutdown"),
+            CallTag::Action(_) => write!(f, "CallTag::Action"),
             CallTag::Spawn(_) => write!(f, "CallTag::Spawn"),
         }
     }
@@ -208,8 +209,8 @@ mod tests {
     fn test_resolve() {
         let env = Environment::new(1);
 
-        let (cq_f1, tag1) = CallTag::shutdown_pair();
-        let (cq_f2, tag2) = CallTag::shutdown_pair();
+        let (cq_f1, tag1) = CallTag::action_pair();
+        let (cq_f2, tag2) = CallTag::action_pair();
         let (tx, rx) = mpsc::channel();
 
         let handler = thread::spawn(move || {
@@ -224,8 +225,8 @@ mod tests {
         assert_eq!(rx.try_recv().unwrap_err(), TryRecvError::Empty);
         tag2.resolve(&env.pick_cq(), false);
         match rx.recv() {
-            Ok(Err(Error::ShutdownFailed)) => {}
-            res => panic!("expect shutdown failed, but got {:?}", res),
+            Ok(Ok(false)) => {}
+            res => panic!("expect Ok(false), but got {:?}", res),
         }
 
         handler.join().unwrap();
diff --git a/src/task/promise.rs b/src/task/promise.rs
index 02e9419..50add06 100644
--- a/src/task/promise.rs
+++ b/src/task/promise.rs
@@ -104,24 +104,22 @@ impl Debug for Batch {
     }
 }
 
-/// A promise used to resolve async shutdown result.
-pub struct Shutdown {
-    inner: Arc<Inner<()>>,
+/// A promise used to resolve async action status.
+///
+/// The action can only succeed or fail without extra error hint.
+pub struct Action {
+    inner: Arc<Inner<bool>>,
 }
 
-impl Shutdown {
-    pub fn new(inner: Arc<Inner<()>>) -> Shutdown {
-        Shutdown { inner }
+impl Action {
+    pub fn new(inner: Arc<Inner<bool>>) -> Action {
+        Action { inner }
     }
 
     pub fn resolve(self, success: bool) {
         let task = {
             let mut guard = self.inner.lock();
-            if success {
-                guard.set_result(Ok(()))
-            } else {
-                guard.set_result(Err(Error::ShutdownFailed))
-            }
+            guard.set_result(Ok(success))
         };
         task.map(|t| t.wake());
     }