[performance] ffmpeg ffprobe wrapper improvements (#3225)

* use a single instance of wazero runtime and compiled modules

* remove test output 🤦

* undo process-{media,emoji} changes

* update test runner to include wazero compilation cache

* sign drone.yml

---------

Co-authored-by: tobi <tobi.smethurst@protonmail.com>

internal/media/ffmpeg/runner.go

@@ -0,0 +1,70 @@
+// 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 ffmpeg
+
+import (
+	"context"
+
+	"github.com/tetratelabs/wazero"
+)
+
+// runner simply abstracts away the complexities
+// of limiting the number of concurrent running
+// instances of a particular WebAssembly module.
+type runner struct{ pool chan struct{} }
+
+// Init initializes the runner to
+// only allow 'n' concurrently running
+// instances. Special cases include 0
+// which clamps to 1, and < 0 which
+// disables the limit alltogether.
+func (r *runner) Init(n int) {
+
+	// Reset pool.
+	r.pool = nil
+
+	// Clamp to 1.
+	if n <= 0 {
+		n = 1
+	}
+
+	// Allocate new pool channel.
+	r.pool = make(chan struct{}, n)
+	for i := 0; i < n; i++ {
+		r.pool <- struct{}{}
+	}
+}
+
+// Run will attempt to pass the given compiled WebAssembly module with args to run(), waiting on
+// the receiving runner until a free slot is available to run an instance, (if a limit is enabled).
+func (r *runner) Run(ctx context.Context, cmod wazero.CompiledModule, args Args) (uint32, error) {
+	select {
+	// Context canceled.
+	case <-ctx.Done():
+		return 0, ctx.Err()
+
+	// Slot acquired.
+	case <-r.pool:
+	}
+
+	// Release slot back to pool on end.
+	defer func() { r.pool <- struct{}{} }()
+
+	// Pass to main module runner.
+	return run(ctx, cmod, args)
+}