Sftp refactor

internal/impl/sftp/client_pool.go

@@ -0,0 +1,126 @@
+// Copyright 2024 Redpanda Data, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package sftp
+
+import (
+	"errors"
+	"io/fs"
+	"sync"
+
+	"github.com/pkg/sftp"
+)
+
+func newClientPool(newClient func() (*sftp.Client, error)) (*clientPool, error) {
+	client, err := newClient()
+	if err != nil {
+		return nil, err
+	}
+	return &clientPool{
+		newClient: newClient,
+		client:    client,
+	}, nil
+}
+
+type clientPool struct {
+	newClient func() (*sftp.Client, error)
+
+	lock   sync.Mutex
+	client *sftp.Client
+	closed bool
+}
+
+func (c *clientPool) Open(path string) (*sftp.File, error) {
+	return clientPoolDoReturning(c, func(client *sftp.Client) (*sftp.File, error) {
+		return client.Open(path)
+	})
+}
+
+func (c *clientPool) Glob(path string) ([]string, error) {
+	return clientPoolDoReturning(c, func(client *sftp.Client) ([]string, error) {
+		return client.Glob(path)
+	})
+}
+
+func (c *clientPool) Stat(path string) (fs.FileInfo, error) {
+	return clientPoolDoReturning(c, func(client *sftp.Client) (fs.FileInfo, error) {
+		return client.Stat(path)
+	})
+}
+
+func (c *clientPool) Remove(path string) error {
+	return clientPoolDo(c, func(client *sftp.Client) error {
+		return client.Remove(path)
+	})
+}
+
+func (c *clientPool) Close() error {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	if c.closed {
+		return nil
+	}
+	c.closed = true
+
+	if c.client != nil {
+		err := c.client.Close()
+		c.client = nil
+		return err
+	}
+	return nil
+}
+
+func clientPoolDo(c *clientPool, fn func(*sftp.Client) error) error {
+	_, err := clientPoolDoReturning(c, func(client *sftp.Client) (struct{}, error) {
+		err := fn(client)
+		return struct{}{}, err
+	})
+	return err
+}
+
+func clientPoolDoReturning[T any](c *clientPool, fn func(*sftp.Client) (T, error)) (T, error) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	var zero T
+
+	// In the case that the clientPool is used from an AckFn after the input is
+	// closed, we create temporary client to fulfil the operation, then
+	// immediately close it.
+	if c.closed {
+		client, err := c.newClient()
+		if err != nil {
+			return zero, err
+		}
+		result, err := fn(client)
+		_ = client.Close()
+		return result, err
+	}
+
+	if c.client == nil {
+		client, err := c.newClient()
+		if err != nil {
+			return zero, err
+		}
+		c.client = client
+	}
+
+	result, err := fn(c.client)
+	if errors.Is(err, sftp.ErrSSHFxConnectionLost) {
+		_ = c.client.Close()
+		c.client = nil
+	}
+	return result, err
+}