1+ //! Connection pooling module for SSH connections.
2+ //!
3+ //! NOTE: This is a placeholder implementation. The async-ssh2-tokio Client
4+ //! doesn't support connection reuse or cloning, so actual pooling is not
5+ //! currently possible. This module provides the infrastructure for future
6+ //! connection pooling when the underlying library supports it.
7+ //!
8+ //! The current implementation always creates new connections but provides
9+ //! the API surface for connection pooling to minimize future refactoring.
10+
11+ // Copyright 2025 Lablup Inc. and Jeongkyu Shin
12+ //
13+ // Licensed under the Apache License, Version 2.0 (the "License");
14+ // you may not use this file except in compliance with the License.
15+ // You may obtain a copy of the License at
16+ //
17+ // http://www.apache.org/licenses/LICENSE-2.0
18+ //
19+ // Unless required by applicable law or agreed to in writing, software
20+ // distributed under the License is distributed on an "AS IS" BASIS,
21+ // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
22+ // See the License for the specific language governing permissions and
23+ // limitations under the License.
24+
25+ use anyhow:: Result ;
26+ use async_ssh2_tokio:: Client ;
27+ use std:: sync:: Arc ;
28+ use std:: time:: Duration ;
29+ use tokio:: sync:: RwLock ;
30+ use tracing:: { debug, trace} ;
31+
32+ #[ derive( Debug , Clone , Hash , Eq , PartialEq ) ]
33+ struct ConnectionKey {
34+ host : String ,
35+ port : u16 ,
36+ user : String ,
37+ }
38+
39+ /// Connection pool for SSH connections.
40+ ///
41+ /// Currently a placeholder implementation due to async-ssh2-tokio limitations.
42+ /// Always creates new connections regardless of the `enabled` flag.
43+ pub struct ConnectionPool {
44+ /// Placeholder for future connection storage
45+ _connections : Arc < RwLock < Vec < ConnectionKey > > > ,
46+ ttl : Duration ,
47+ enabled : bool ,
48+ max_connections : usize ,
49+ }
50+
51+ impl ConnectionPool {
52+ /// Create a new connection pool.
53+ ///
54+ /// Note: Pooling is not actually implemented due to library limitations.
55+ pub fn new ( ttl : Duration , max_connections : usize , enabled : bool ) -> Self {
56+ Self {
57+ _connections : Arc :: new ( RwLock :: new ( Vec :: new ( ) ) ) ,
58+ ttl,
59+ enabled,
60+ max_connections,
61+ }
62+ }
63+
64+ pub fn disabled ( ) -> Self {
65+ Self :: new ( Duration :: from_secs ( 0 ) , 0 , false )
66+ }
67+
68+ pub fn with_defaults ( ) -> Self {
69+ Self :: new (
70+ Duration :: from_secs ( 300 ) , // 5 minutes TTL
71+ 50 , // max 50 connections
72+ false , // disabled by default
73+ )
74+ }
75+
76+ /// Get or create a connection.
77+ ///
78+ /// Currently always creates a new connection due to async-ssh2-tokio limitations.
79+ /// The Client type doesn't support cloning or connection reuse.
80+ pub async fn get_or_create < F > (
81+ & self ,
82+ host : & str ,
83+ port : u16 ,
84+ user : & str ,
85+ create_fn : F ,
86+ ) -> Result < Client >
87+ where
88+ F : FnOnce ( ) -> std:: pin:: Pin < Box < dyn std:: future:: Future < Output = Result < Client > > + Send > > ,
89+ {
90+ let _key = ConnectionKey {
91+ host : host. to_string ( ) ,
92+ port,
93+ user : user. to_string ( ) ,
94+ } ;
95+
96+ if self . enabled {
97+ trace ! ( "Connection pooling enabled (placeholder mode)" ) ;
98+ // In the future, we would check for existing connections here
99+ // For now, we always create new connections
100+ } else {
101+ trace ! ( "Connection pooling disabled" ) ;
102+ }
103+
104+ // Always create new connection (pooling not possible with current library)
105+ debug ! ( "Creating new SSH connection to {}@{}:{}" , user, host, port) ;
106+ create_fn ( ) . await
107+ }
108+
109+ /// Return a connection to the pool.
110+ ///
111+ /// Currently a no-op due to connection reuse limitations.
112+ pub async fn return_connection (
113+ & self ,
114+ _host : & str ,
115+ _port : u16 ,
116+ _user : & str ,
117+ _client : Client ,
118+ ) {
119+ // No-op: Client cannot be reused
120+ if self . enabled {
121+ trace ! ( "Connection return requested (no-op in placeholder mode)" ) ;
122+ }
123+ }
124+
125+ /// Clean up expired connections.
126+ ///
127+ /// Currently a no-op.
128+ pub async fn cleanup_expired ( & self ) {
129+ if self . enabled {
130+ trace ! ( "Cleanup requested (no-op in placeholder mode)" ) ;
131+ }
132+ }
133+
134+ /// Clear all connections from the pool.
135+ ///
136+ /// Currently a no-op.
137+ pub async fn clear ( & self ) {
138+ if self . enabled {
139+ trace ! ( "Clear requested (no-op in placeholder mode)" ) ;
140+ }
141+ }
142+
143+ /// Get the number of pooled connections.
144+ ///
145+ /// Always returns 0 in the current implementation.
146+ pub async fn size ( & self ) -> usize {
147+ 0 // No actual pooling
148+ }
149+
150+ pub fn is_enabled ( & self ) -> bool {
151+ self . enabled
152+ }
153+
154+ pub fn enable ( & mut self ) {
155+ self . enabled = true ;
156+ debug ! ( "Connection pooling enabled" ) ;
157+ }
158+
159+ pub fn disable ( & mut self ) {
160+ self . enabled = false ;
161+ debug ! ( "Connection pooling disabled" ) ;
162+ }
163+ }
164+
165+ impl Default for ConnectionPool {
166+ fn default ( ) -> Self {
167+ Self :: with_defaults ( )
168+ }
169+ }
170+
171+ #[ cfg( test) ]
172+ mod tests {
173+ use super :: * ;
174+
175+ #[ tokio:: test]
176+ async fn test_pool_disabled_by_default ( ) {
177+ let pool = ConnectionPool :: with_defaults ( ) ;
178+ assert ! ( !pool. is_enabled( ) ) ;
179+ assert_eq ! ( pool. size( ) . await , 0 ) ;
180+ }
181+
182+ #[ tokio:: test]
183+ async fn test_pool_cleanup ( ) {
184+ let pool = ConnectionPool :: new ( Duration :: from_millis ( 100 ) , 10 , true ) ;
185+
186+ // Pool starts empty
187+ assert_eq ! ( pool. size( ) . await , 0 ) ;
188+
189+ // Cleanup should work even on empty pool
190+ pool. cleanup_expired ( ) . await ;
191+ assert_eq ! ( pool. size( ) . await , 0 ) ;
192+ }
193+
194+ #[ tokio:: test]
195+ async fn test_pool_clear ( ) {
196+ let pool = ConnectionPool :: new ( Duration :: from_secs ( 60 ) , 10 , true ) ;
197+
198+ pool. clear ( ) . await ;
199+ assert_eq ! ( pool. size( ) . await , 0 ) ;
200+ }
201+ }
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