[performance] update remaining worker pools to use queues (#2865)

* start replacing client + federator + media workers with new worker + queue types

* refactor federatingDB.Delete(), drop queued messages when deleting account / status

* move all queue purging to the processor workers

* undo toolchain updates

* code comments, ensure dereferencer worker pool gets started

* update gruf libraries in readme

* start the job scheduler separately to the worker pools

* reshuffle ordering or server.go + remove duplicate worker start / stop

* update go-list version

* fix vendoring

* move queue invalidation to before wipeing / deletion, to ensure queued work not dropped

* add logging to worker processing functions in testrig, don't start workers in unexpected places

* update go-structr to add (+then rely on) QueueCtx{} type

* ensure more worker pools get started properly in tests

* fix remaining broken tests relying on worker queue logic

* fix account test suite queue popping logic, ensure noop workers do not pull from queue

* move back accidentally shuffled account deletion order

* ensure error (non nil!!) gets passed in refactored federatingDB{}.Delete()

* silently drop deletes from accounts not permitted to

* don't warn log on forwarded deletes

* make if else clauses easier to parse

* use getFederatorMsg()

* improved code comment

* improved code comment re: requesting account delete checks

* remove boolean result from worker start / stop since false = already running or already stopped

* remove optional passed-in http.client

* remove worker starting from the admin CLI commands (we don't need to handle side-effects)

* update prune cli to start scheduler but not all of the workers

* fix rebase issues

* remove redundant return statements

* i'm sorry sir linter

2 files changed, 157 insertions, 34 deletions

diff --git a/internal/queue/simple.go b/internal/queue/simple.go
new file mode 100644
index 000000000..9307183f2
--- /dev/null
+++ b/internal/queue/simple.go
@@ -0,0 +1,141 @@
+// 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 (
+	"context"
+	"sync"
+
+	"codeberg.org/gruf/go-list"
+)
+
+// SimpleQueue provides a simple concurrency safe
+// queue using generics and a memory pool of list
+// elements to reduce overall memory usage.
+type SimpleQueue[T any] struct {
+	l list.List[T]
+	p []*list.Elem[T]
+	w chan struct{}
+	m sync.Mutex
+}
+
+// Push will push given value to the queue.
+func (q *SimpleQueue[T]) Push(value T) {
+	q.m.Lock()
+	elem := q.alloc()
+	elem.Value = value
+	q.l.PushElemFront(elem)
+	if q.w != nil {
+		close(q.w)
+		q.w = nil
+	}
+	q.m.Unlock()
+}
+
+// Pop will attempt to pop value from the queue.
+func (q *SimpleQueue[T]) Pop() (value T, ok bool) {
+	q.m.Lock()
+	if ok = (q.l.Tail != nil); ok {
+		tail := q.l.Tail
+		value = tail.Value
+		q.l.Remove(tail)
+		q.free(tail)
+	}
+	q.m.Unlock()
+	return
+}
+
+// PopCtx will attempt to pop value from queue, else blocking on context.
+func (q *SimpleQueue[T]) PopCtx(ctx context.Context) (value T, ok bool) {
+
+	// Acquire lock.
+	q.m.Lock()
+
+	var elem *list.Elem[T]
+
+	for {
+		// Get next elem.
+		elem = q.l.Tail
+		if ok = (elem != nil); ok {
+			break
+		}
+
+		if q.w == nil {
+			// Create new wait channel.
+			q.w = make(chan struct{})
+		}
+
+		// Get current
+		// ch pointer.
+		ch := q.w
+
+		// Done with lock.
+		q.m.Unlock()
+
+		select {
+		// Context canceled.
+		case <-ctx.Done():
+			return
+
+		// Pushed!
+		case <-ch:
+		}
+
+		// Relock queue.
+		q.m.Lock()
+	}
+
+	// Extract value.
+	value = elem.Value
+
+	// Remove element.
+	q.l.Remove(elem)
+	q.free(elem)
+
+	// Done with lock.
+	q.m.Unlock()
+
+	return
+}
+
+// Len returns the current length of the queue.
+func (q *SimpleQueue[T]) Len() int {
+	q.m.Lock()
+	l := q.l.Len()
+	q.m.Unlock()
+	return l
+}
+
+// alloc will allocate new list element (relying on memory pool).
+func (q *SimpleQueue[T]) alloc() *list.Elem[T] {
+	if len(q.p) > 0 {
+		elem := q.p[len(q.p)-1]
+		q.p = q.p[:len(q.p)-1]
+		return elem
+	}
+	return new(list.Elem[T])
+}
+
+// free will free list element and release to pool.
+func (q *SimpleQueue[T]) free(elem *list.Elem[T]) {
+	var zero T
+	elem.Next = nil
+	elem.Prev = nil
+	elem.Value = zero
+	q.p = append(q.p, elem)
+}
diff --git a/internal/queue/wrappers.go b/internal/queue/struct.go
index e07984f84..27139daec 100644
--- a/internal/queue/wrappers.go
+++ b/internal/queue/struct.go
@@ -18,7 +18,7 @@
 package queue
 
 import (
-	"sync/atomic"
+	"context"
 
 	"codeberg.org/gruf/go-structr"
 )
@@ -26,15 +26,14 @@ import (
 // StructQueue wraps a structr.Queue{} to
 // provide simple index caching by name.
 type StructQueue[StructType any] struct {
-	queue structr.Queue[StructType]
+	queue structr.QueueCtx[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 = structr.QueueCtx[T]{}
 	q.queue.Init(config)
 	for _, cfg := range config.Indices {
 		q.index[cfg.Fields] = q.queue.Index(cfg.Fields)
@@ -43,13 +42,22 @@ func (q *StructQueue[T]) Init(config structr.QueueConfig[T]) {
 
 // Pop: see structr.Queue{}.PopFront().
 func (q *StructQueue[T]) Pop() (value T, ok bool) {
-	return q.queue.PopFront()
+	values := q.queue.PopFrontN(1)
+	if ok = (len(values) > 0); !ok {
+		return
+	}
+	value = values[0]
+	return
+}
+
+// PopCtx: see structr.QueueCtx{}.PopFront().
+func (q *StructQueue[T]) PopCtx(ctx context.Context) (value T, ok bool) {
+	return q.queue.PopFront(ctx)
 }
 
-// Push wraps structr.Queue{}.PushBack() to awaken those blocking on <-.Wait().
+// Push: see structr.Queue.PushBack().
 func (q *StructQueue[T]) Push(values ...T) {
 	q.queue.PushBack(values...)
-	q.broadcast()
 }
 
 // Delete pops (and drops!) all queued entries under index with key.
@@ -66,31 +74,5 @@ func (q *StructQueue[T]) Len() int {
 // 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)
-	}
+	return q.queue.Wait()
 }