Changelog

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All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

[0.5.0] - 2026-06-26

Changed

  • grpc 1.0 support. Bumped grpc to ~> 1.0 (was 0.11.5). grpc 1.0 is client-only (GRPC.Server was removed) and makes :gun optional, so gun ~> 2.2 is now a direct dependency (the pool uses the default Gun adapter). :public_key and :ssl are declared in extra_applications (used by Config).
  • BREAKING (telemetry): the [:grpc_connection_pool, :channel, :gun_down] and [:grpc_connection_pool, :channel, :gun_error] events were removed. Under grpc 1.0 the Gun adapter owns the socket in its own process, so those gun messages never reach the pool. A single adapter-agnostic [:grpc_connection_pool, :channel, :connection_down] event (metadata pool_name, reason) is emitted instead. :disconnected and :reconnect_scheduled are unchanged. Consumers handling :gun_down/:gun_error should switch to :connection_down (or :disconnected).
  • Disconnect detection reworked. grpc 1.0's Gun adapter keeps the live connection inside its own ConnectionProcess, which lingers as a zombie after a drop, so the old gun_down/gun_error message handlers were dead code. The worker now monitors the inner gun process and pairs it with adapter_opts: [retry: 0] so gun fails fast on a drop and the pool's own Backoff governs reconnection. This also restores fast-fail connects (a dead endpoint now errors in ~0ms instead of stalling ~5s per attempt).

Fixed

  • License declaration now correctly reports Apache-2.0 (matching the committed LICENSE file) instead of MIT in mix.exs and README — resolves the Hex.pm mismatch (#6).

[0.4.0] - 2026-06-01

Changed

  • Security: production configs now default to verifying TLS. Config.production/1 sets verify: :verify_peer, and a :production endpoint built without ssl/credentials no longer silently downgrades to plaintext h2c — it raises a clear configuration error.
  • Narrowed several broad rescue/catch clauses (Pool.scale_up/scale_down, Worker.send_ping, TelemetryReporter) so unexpected errors surface instead of being swallowed; demoted expected reconnect/retry logs to :debug.

Fixed

  • Documentation: replaced README examples referencing a non-existent GrpcConnectionPool.execute/1 with the real get_channel/1 + stub-call pattern; corrected the stale install snippet and the :get_channel telemetry/strategy docs.

[0.3.5] - 2026-06-01

Fixed

  • Slot-claim race in the hot path — slot claim/release are now serialized through PoolState (register_channel/3, unregister_channel/2). Concurrent worker connects/disconnects could previously collide on a slot, leaving :channel_count higher than the populated channels so get_channel/1 returned :not_connected on a healthy pool.
  • get_channel/1 now returns {:error, :not_connected} (instead of raising) when the pool is not started or PoolState is restarting.

Changed

  • Hot-path performance: collapsed the per-call ETS table-name rebuild + two persistent_term lookups into one combined term; RoundRobin uses unsigned atomics (no abs/1); PowerOfTwo now tracks load in lock-free :atomics counters (least-frequently-used) instead of writing a timestamp to ETS on every selection.
  • Per-call :get_channel telemetry is configurable via telemetry_sample_rate (default 1 = emit every call; 0 disables; N samples ~1-in-N).
  • The pid => slot map moved from ETS into PoolState state (slot claim is now O(1)).

[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] - 2026-01-29

Added

  • Enhanced telemetry events for better observability:
    • [:grpc_connection_pool, :pool, :init] - Pool initialization with size and endpoint
    • [:grpc_connection_pool, :channel, :ping] - Ping health check with duration and result
    • [:grpc_connection_pool, :channel, :gun_down] - Gun connection down events with reason and protocol
    • [:grpc_connection_pool, :channel, :gun_error] - Gun error events with reason
    • [:grpc_connection_pool, :channel, :reconnect_scheduled] - Reconnection scheduling with delay and attempt count
  • Reconnect attempt tracking in worker state
  • Comprehensive telemetry documentation in README
  • Telemetry test suite

[0.2.2] - 2026-01-29

Added

  • Support for gRPC client interceptors in endpoint configuration (thanks @arctarus)
  • Comprehensive tests for interceptors feature
  • CHANGELOG.md file

[0.2.1] - 2025-11-22

Fixed

  • Handle GRPC v0.11.5 FunctionClauseError during disconnect

[0.2.0] - 2025-11-22

Added

  • Dynamic pool scaling feature

[0.1.6] - 2025-11-22

Fixed

  • Handle GenServer exit gracefully in connection cleanup

[0.1.5] - 2025-11-21

Changed

  • Refactored to replace Poolex with DynamicSupervisor
  • Added conn_grpc features
  • Fixed documentation LICENSE reference warnings

[0.1.4] - 2025-11-19

Changed

  • Updated dependencies: poolex to 1.4.2, grpc to 0.11.5
  • Changed gRPC connection logs from info to debug level

Added

  • suppress_connection_errors config option for GCP endpoints

[0.1.3] - 2025-11-18

Added

  • License file

[0.1.2] - 2025-11-18

Added

  • Comprehensive README with complete configuration examples and architecture details

[0.1.0] - 2025-11-18

Added

  • Initial release: Complete GrpcConnectionPool library
  • Configuration module with support for production, local, and custom environments
  • Connection pooling with DynamicSupervisor
  • Automatic connection warming and health monitoring
  • Retry logic with exponential backoff and jitter
  • Telemetry integration for metrics