Cache postgres build and cargo deps in CI builds

Now most of CI check time is spent during dependencies installation and compilation (~ 10min total). Use actions/cache@v2 to cache things between checks. This commit sets up two caching targets:

* ./tmp_install with postgres build files and installed binaries uses $runner.os-pg-$pg_submodule_revision as a cache key and will be rebuilt only if linked submodule revision changes.

* ./target with cargo dependencies. That one uses hash(Cargo.lock) as a caching key and will be rebuilt only on deps update.

Also add tg notifications in a passing.

.github/workflows/testing.yml

@@ -1,6 +1,6 @@
 name: regression check
 
-on: [push, pull_request]
+on: [push]
 
 jobs:
   regression-check:
@@ -8,16 +8,57 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+
       - name: Checkout
         uses: actions/checkout@v2
         with:
           submodules: true
+          fetch-depth: 2
+
+      - name: Form variables for notification message
+        id: git_info_grab
+        run: |
+          git_stat=$(git show --stat=50)
+          git_stat="${git_stat//'%'/'%25'}"
+          git_stat="${git_stat//$'\n'/'%0A'}"
+          git_stat="${git_stat//$'\r'/'%0D'}"
+          git_stat="${git_stat// / }" # space -> 'Space En', as github tends to eat ordinary spaces
+          echo "::set-output name=git_stat::$git_stat"
+          echo "::set-output name=sha_short::$(git rev-parse --short HEAD)"
+          echo "##[set-output name=git_branch;]$(echo ${GITHUB_REF#refs/heads/})"
+
+      - name: Send notification
+        uses: appleboy/telegram-action@master
+        with:
+          to: ${{ secrets.TELEGRAM_TO }}
+          token: ${{ secrets.TELEGRAM_TOKEN }}
+          format: markdown
+          args: |
+            *@${{ github.actor }} pushed to* [${{ github.repository }}:${{steps.git_info_grab.outputs.git_branch}}](github.com/${{ github.repository }}/commit/${{steps.git_info_grab.outputs.sha_short }})
+
+            ```
+            ${{ steps.git_info_grab.outputs.git_stat }}
+            ```
 
       - name: Install postgres dependencies
         run: |
+          sudo apt update
           sudo apt install build-essential libreadline-dev zlib1g-dev flex bison libxml2-dev libcurl4-openssl-dev
 
+      - name: Set pg revision for caching
+        id: pg_ver
+        run: echo ::set-output name=pg_rev::$(git rev-parse HEAD:vendor/postgres)
+
+      - name: Cache postgres build
+        id: cache_pg
+        uses: actions/cache@v2
+        with:
+          path: |
+            tmp_install/
+          key: ${{ runner.os }}-pg-${{ steps.pg_ver.outputs.pg_rev }}
+
       - name: Build postgres
+        if: steps.cache_pg.outputs.cache-hit != 'true'
         run: |
           ./pgbuild.sh
 
@@ -25,6 +66,23 @@ jobs:
         run: |
           sudo apt install -y cargo
 
+      - name: Cache cargo deps
+        id: cache_cargo
+        uses: actions/cache@v2
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+
+      # That build is only to build dependencies and can be skipped if Cargo.lock
+      # wasn't changed. Next steps need their own build
+      - name: Install cargo deps
+        if: steps.cache_cargo.outputs.cache-hit != 'true'
+        run: |
+          cargo build
+
       - name: Run test
         run: |
           cargo test --test test_pageserver -- --nocapture --test-threads=1

src/page_service.rs

@@ -7,6 +7,7 @@
 //     *status* -- show actual info about this pageserver,
 //     *pagestream* -- enter mode where smgr and pageserver talk with their
 //  custom protocol.
+//     *callmemaybe $url* -- ask pageserver to start walreceiver on $url
 //
 
 use tokio::net::{TcpListener, TcpStream};
@@ -499,8 +500,6 @@ impl Connection {
         loop {
             let message = self.read_message().await?;
 
-            // XXX: none seems to appear a lot in log.
-            // Do we have conditions for busy-loop here?
             if let Some(m) = &message {
                 info!("query({}): {:?}", sysid, m);
             };