refactor: bring metrics to http output (#3247)

* refactor: bring metrics to http output

* chore: remove unwrap

* chore: make walk plan accumulate

* chore: change field name and comment

* chore: add metrics to http resp header

* chore: move PrometheusJsonResponse to a separate file and impl IntoResponse

* chore: put metrics in prometheus resp header too

src/common/plugins/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "common-plugins"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

src/common/plugins/src/consts.rs

@@ -0,0 +1,19 @@
+// Copyright 2023 Greptime Team
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/// Greptime preserved metrics prefix
+pub const GREPTIME_EXEC_PREFIX: &str = "greptime_exec_";
+
+/// Execution cost metrics key
+pub const GREPTIME_EXEC_COST: &str = "greptime_exec_cost";

src/common/plugins/src/lib.rs

@@ -0,0 +1,20 @@
+// Copyright 2023 Greptime Team
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/// This crate is designed to be at the bottom of the depencey tree
+/// to provide common and useful utils and consts to all plugin usage,
+/// since `plugins` crate is at the top depending on crates like `frontend` and `datanode`
+mod consts;
+
+pub use consts::{GREPTIME_EXEC_COST, GREPTIME_EXEC_PREFIX};