Performance optimization: zero GenServer.call hot path, pluggable strategies, CI/CD

.github/workflows/ci.yml

@@ -0,0 +1,192 @@
+name: CI
+
+on:
+  push:
+    branches: [master]
+    tags: ["v*"]
+  pull_request:
+    branches: [master]
+
+permissions:
+  contents: read
+
+env:
+  FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
+  MIX_ENV: test
+  ELIXIR_VERSION: "1.18.3"
+  OTP_VERSION: "27.2"
+
+jobs:
+  compile:
+    name: Compile & Warnings
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: erlef/setup-beam@v1
+        with:
+          elixir-version: ${{ env.ELIXIR_VERSION }}
+          otp-version: ${{ env.OTP_VERSION }}
+
+      - name: Cache deps & build
+        uses: actions/cache@v5
+        with:
+          path: |
+            deps
+            _build
+          key: ${{ runner.os }}-mix-${{ env.ELIXIR_VERSION }}-${{ env.OTP_VERSION }}-${{ hashFiles('mix.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-mix-${{ env.ELIXIR_VERSION }}-${{ env.OTP_VERSION }}-
+
+      - run: mix deps.get
+      - run: mix deps.compile
+
+      - name: Compile with warnings as errors
+        run: mix compile --warnings-as-errors
+
+  format:
+    name: Formatting
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: erlef/setup-beam@v1
+        with:
+          elixir-version: ${{ env.ELIXIR_VERSION }}
+          otp-version: ${{ env.OTP_VERSION }}
+
+      - name: Cache deps
+        uses: actions/cache@v5
+        with:
+          path: deps
+          key: ${{ runner.os }}-mix-${{ env.ELIXIR_VERSION }}-${{ env.OTP_VERSION }}-${{ hashFiles('mix.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-mix-${{ env.ELIXIR_VERSION }}-${{ env.OTP_VERSION }}-
+
+      - run: mix deps.get
+      - run: mix format --check-formatted
+
+  credo:
+    name: Credo
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: erlef/setup-beam@v1
+        with:
+          elixir-version: ${{ env.ELIXIR_VERSION }}
+          otp-version: ${{ env.OTP_VERSION }}
+
+      - name: Cache deps & build
+        uses: actions/cache@v5
+        with:
+          path: |
+            deps
+            _build
+          key: ${{ runner.os }}-mix-${{ env.ELIXIR_VERSION }}-${{ env.OTP_VERSION }}-${{ hashFiles('mix.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-mix-${{ env.ELIXIR_VERSION }}-${{ env.OTP_VERSION }}-
+
+      - run: mix deps.get
+      - run: mix credo --strict
+
+  test:
+    name: Tests (${{ matrix.os }} / OTP ${{ matrix.otp }} / Elixir ${{ matrix.elixir }})
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: ubuntu-latest
+            elixir: "1.18.3"
+            otp: "27.2"
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: erlef/setup-beam@v1
+        with:
+          elixir-version: ${{ matrix.elixir }}
+          otp-version: ${{ matrix.otp }}
+
+      - name: Cache deps & build
+        uses: actions/cache@v5
+        with:
+          path: |
+            deps
+            _build
+          key: ${{ runner.os }}-mix-${{ matrix.elixir }}-${{ matrix.otp }}-${{ hashFiles('mix.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-mix-${{ matrix.elixir }}-${{ matrix.otp }}-
+
+      - run: mix deps.get
+      - run: mix deps.compile
+      - run: mix compile
+      - run: mix test --exclude emulator
+
+  dialyzer:
+    name: Dialyzer
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: erlef/setup-beam@v1
+        with:
+          elixir-version: ${{ env.ELIXIR_VERSION }}
+          otp-version: ${{ env.OTP_VERSION }}
+
+      - name: Cache deps & build
+        uses: actions/cache@v5
+        with:
+          path: |
+            deps
+            _build
+          key: ${{ runner.os }}-mix-${{ env.ELIXIR_VERSION }}-${{ env.OTP_VERSION }}-${{ hashFiles('mix.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-mix-${{ env.ELIXIR_VERSION }}-${{ env.OTP_VERSION }}-
+
+      - name: Cache PLTs
+        uses: actions/cache@v5
+        with:
+          path: priv/plts
+          key: ${{ runner.os }}-plt-${{ env.ELIXIR_VERSION }}-${{ env.OTP_VERSION }}-${{ hashFiles('mix.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-plt-${{ env.ELIXIR_VERSION }}-${{ env.OTP_VERSION }}-
+
+      - run: mix deps.get
+      - run: mix deps.compile
+      - run: mix compile
+      - run: mix dialyzer
+
+  publish:
+    name: Publish to Hex
+    runs-on: ubuntu-latest
+    needs: [compile, format, credo, test, dialyzer]
+    if: startsWith(github.ref, 'refs/tags/v')
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: erlef/setup-beam@v1
+        with:
+          elixir-version: ${{ env.ELIXIR_VERSION }}
+          otp-version: ${{ env.OTP_VERSION }}
+
+      - name: Set version from tag
+        env:
+          TAG_REF: ${{ github.ref }}
+        run: |
+          TAG_VERSION="${TAG_REF#refs/tags/v}"
+          sed -i "s/@version \".*\"/@version \"${TAG_VERSION}\"/" mix.exs
+          grep '@version' mix.exs
+
+      - run: mix deps.get
+        env:
+          MIX_ENV: dev
+      - run: mix compile
+        env:
+          MIX_ENV: dev
+
+      - name: Publish to Hex
+        run: mix hex.publish --yes
+        env:
+          MIX_ENV: dev
+          HEX_API_KEY: ${{ secrets.HEX_API_KEY }}

.gitignore

@@ -21,3 +21,4 @@ grpc_connection_pool-*.tar
 
 # Temporary files, for example, from tests.
 /tmp/
+priv/plts/

CHANGELOG.md

@@ -5,6 +5,37 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.3.0] - 2026-03-24
+
+### Added
+- **Zero GenServer.call hot path** — channels stored directly in ETS for O(1) indexed access, eliminating the GenServer.call bottleneck on every `get_channel` request
+- **Pluggable connection strategies** via `GrpcConnectionPool.Strategy` behaviour:
+  - `:round_robin` (default) — lock-free atomics-based round-robin
+  - `:random` — random selection, good for avoiding hot-spotting
+  - `:power_of_two` — power-of-two-choices with least-recently-used tiebreak
+  - Custom strategies supported via behaviour implementation
+- **`:persistent_term` for pool config** — zero-copy reads for configuration data
+- **ETS with read/write concurrency** — optimized concurrent access flags
+- **`PoolState` GenServer** — dedicated ETS table owner for crash resilience
+- **`TelemetryReporter` GenServer** — replaced recursive `:timer.sleep` telemetry loop with a proper GenServer using `Process.send_after`
+- **`await_ready/2`** — blocks until at least one channel is connected or timeout, useful for application startup
+- **Stale scaling lock detection** — scaling locks older than 30 seconds are automatically released
+- **`max_reconnect_attempts` config** — workers crash after N consecutive connection failures instead of the fragile `crash_after_reconnect_attempt` timer
+- **Benchee benchmarks** — `bench/get_channel_bench.exs` for measuring hot path performance
+- **Strategy tests** — comprehensive tests for all three built-in strategies
+- **CI/CD pipeline** — GitHub Actions with compile, format, credo, test, dialyzer, and auto-publish to Hex on tag push
+
+### Changed
+- **4.3x–5.8x faster `get_channel`** — single-process throughput improved from ~470K ips to ~2M ips
+- **O(n) scaling eliminated** — pool_size=25 was 38% slower than pool_size=5, now only 2% slower
+- **44–58% lower latency under concurrency** — 100 concurrent callers: median 553μs → 312μs, p99 1035μs → 439μs
+- **28–56% less memory per call** — memory now constant regardless of pool size (was O(n))
+- **Pool.status 2.5x faster** — reads from ETS channel_count instead of Registry.lookup
+- Pool supervision tree restructured: PoolState starts first, then Registry, DynamicSupervisor, workers, and TelemetryReporter
+
+### Removed
+- `crash_after_reconnect_attempt` message — replaced by `max_reconnect_attempts` config with clean `{:stop, reason, state}` on exhaustion
+
 ## [0.2.3] - 2025-01-29
 
 ### Added