[performance] massively improved ActivityPub delivery worker efficiency (#2812)

* add delivery worker type that pulls from queue to httpclient package

* finish up some code commenting, bodge a vendored activity library change, integrate the deliverypool changes into transportcontroller

* hook up queue deletion logic

* support deleting queued http requests by target ID

* don't index APRequest by hostname in the queue

* use gorun

* use the original context's values when wrapping msg type as delivery{}

* actually log in the AP delivery worker ...

* add uncommitted changes

* use errors.AsV2()

* use errorsv2.AsV2()

* finish adding some code comments, add bad host handling to delivery workers

* slightly tweak deliveryworkerpool API, use advanced sender multiplier

* remove PopCtx() method, let others instead rely on Wait()

* shuffle things around to move delivery stuff into transport/ subpkg

* remove dead code

* formatting

* validate request before queueing for delivery

* finish adding code comments, fix up backoff code

* finish adding more code comments

* clamp minimum no. senders to 1

* add start/stop logging to delivery worker, some slight changes

* remove double logging

* use worker ptrs

* expose the embedded log fields in httpclient.Request{}

* ensure request context values are preserved when updating ctx

* add delivery worker tests

* fix linter issues

* ensure delivery worker gets inited in testrig

* fix tests to delivering messages to check worker delivery queue

* update error type to use ptr instead of value receiver

* fix test calling Workers{}.Start() instead of testrig.StartWorkers()

* update docs for advanced-sender-multiplier

* update to the latest activity library version

* add comment about not using httptest.Server{}

internal/queue/wrappers.go

@@ -0,0 +1,96 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package queue
+
+import (
+	"sync/atomic"
+
+	"codeberg.org/gruf/go-structr"
+)
+
+// StructQueue wraps a structr.Queue{} to
+// provide simple index caching by name.
+type StructQueue[StructType any] struct {
+	queue structr.Queue[StructType]
+	index map[string]*structr.Index
+	wait  atomic.Pointer[chan struct{}]
+}
+
+// Init initializes queue with structr.QueueConfig{}.
+func (q *StructQueue[T]) Init(config structr.QueueConfig[T]) {
+	q.index = make(map[string]*structr.Index, len(config.Indices))
+	q.queue = structr.Queue[T]{}
+	q.queue.Init(config)
+	for _, cfg := range config.Indices {
+		q.index[cfg.Fields] = q.queue.Index(cfg.Fields)
+	}
+}
+
+// Pop: see structr.Queue{}.PopFront().
+func (q *StructQueue[T]) Pop() (value T, ok bool) {
+	return q.queue.PopFront()
+}
+
+// Push wraps structr.Queue{}.PushBack() to awaken those blocking on <-.Wait().
+func (q *StructQueue[T]) Push(values ...T) {
+	q.queue.PushBack(values...)
+	q.broadcast()
+}
+
+// Delete pops (and drops!) all queued entries under index with key.
+func (q *StructQueue[T]) Delete(index string, key ...any) {
+	i := q.index[index]
+	_ = q.queue.Pop(i, i.Key(key...))
+}
+
+// Len: see structr.Queue{}.Len().
+func (q *StructQueue[T]) Len() int {
+	return q.queue.Len()
+}
+
+// Wait returns current wait channel, which may be
+// blocked on to awaken when new value pushed to queue.
+func (q *StructQueue[T]) Wait() <-chan struct{} {
+	var ch chan struct{}
+
+	for {
+		// Get channel ptr.
+		ptr := q.wait.Load()
+		if ptr != nil {
+			return *ptr
+		}
+
+		if ch == nil {
+			// Allocate new channel.
+			ch = make(chan struct{})
+		}
+
+		// Try set the new wait channel ptr.
+		if q.wait.CompareAndSwap(ptr, &ch) {
+			return ch
+		}
+	}
+}
+
+// broadcast safely closes wait channel if
+// currently set, releasing waiting goroutines.
+func (q *StructQueue[T]) broadcast() {
+	if ptr := q.wait.Swap(nil); ptr != nil {
+		close(*ptr)
+	}
+}