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JaewonHurJaewonHur
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Fix directory watcher (#1234)
- Current DirectoryWatcher fails if `/etc/resolver` does not exist. This PR fixes DirectoryWatcher to handle non-existing `/etc/resolver` directory. If that directory does not exist, it first watches `/etc` directory to check if `/etc/resolver` directory is created later. Once it detects new `/etc/resolver` directory, it starts watching new DNS resolver files there. - This PR also fixes to log the exception thrown by API server's tasks. - Closes #1207
1 parent 339a389 commit 0760791

6 files changed

Lines changed: 377 additions & 120 deletions

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‎Package.swift‎

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Original file line numberDiff line numberDiff line change
@@ -42,6 +42,7 @@ let package = Package(
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.library(name: "ContainerPlugin", targets: ["ContainerPlugin"]),
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.library(name: "ContainerVersion", targets: ["ContainerVersion"]),
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.library(name: "ContainerXPC", targets: ["ContainerXPC"]),
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.library(name: "ContainerOS", targets: ["ContainerOS"]),
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.library(name: "SocketForwarder", targets: ["SocketForwarder"]),
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.library(name: "TerminalProgress", targets: ["TerminalProgress"]),
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],
@@ -142,6 +143,7 @@ let package = Package(
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"ContainerResource",
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"ContainerVersion",
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"ContainerXPC",
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"ContainerOS",
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"DNSServer",
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],
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path: "Sources/Helpers/APIServer"
@@ -400,6 +402,14 @@ let package = Package(
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"CAuditToken",
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]
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),
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.target(
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name: "ContainerOS",
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dependencies: [
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.product(name: "Containerization", package: "containerization"),
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.product(name: "ContainerizationOS", package: "containerization"),
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],
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path: "Sources/ContainerOS"
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),
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.target(
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name: "TerminalProgress",
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dependencies: [
@@ -418,6 +428,7 @@ let package = Package(
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.product(name: "DNSClient", package: "DNSClient"),
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.product(name: "DNS", package: "DNS"),
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.product(name: "Logging", package: "swift-log"),
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.product(name: "ContainerizationOS", package: "containerization"),
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]
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),
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.testTarget(
@@ -427,6 +438,12 @@ let package = Package(
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"DNSServer",
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]
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),
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.testTarget(
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name: "ContainerOSTests",
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dependencies: [
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"ContainerOS"
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]
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),
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.target(
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name: "SocketForwarder",
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dependencies: [

‎Sources/ContainerOS/DirectoryWatcher.swift‎

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@@ -0,0 +1,138 @@
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//===----------------------------------------------------------------------===//
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// Copyright © 2026 Apple Inc. and the container project authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//===----------------------------------------------------------------------===//
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import ContainerizationError
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import ContainerizationOS
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import Foundation
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import Logging
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import Synchronization
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/// Watches a directory for changes and invokes a handler when the contents change.
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///
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/// `DirectoryWatcher` uses `DispatchSource` file system events to monitor a directory.
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/// If the target directory does not exist yet, it polls until the directory is created.
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/// the target is created, then transitions to watching the target directly.
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///
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/// Example usage:
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/// ```swift
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/// let watcher = DirectoryWatcher(directoryURL: myURL, log: logger)
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/// try watcher.startWatching { urls in
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/// print("Directory contents changed: \(urls)")
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/// }
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/// ```
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public actor DirectoryWatcher {
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public static let watchPeriod = Duration.seconds(1)
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/// The URL of the directory being watched.
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public let directoryURL: URL
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private var task: Task<Void, any Error>?
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private let monitorQueue: DispatchQueue
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private let source: Mutex<DispatchSourceFileSystemObject?>
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private let log: Logger?
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/// Creates a new `DirectoryWatcher` for the given directory URL.
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///
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/// - Parameters:
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/// - directoryURL: The URL of the directory to watch.
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/// - log: An optional logger for diagnostic messages.
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public init(directoryURL: URL, log: Logger?) {
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self.directoryURL = directoryURL
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self.monitorQueue = DispatchQueue(label: "monitor:\(directoryURL.path)")
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self.log = log
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self.source = Mutex(nil)
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}
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/// Starts watching the directory for changes.
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///
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/// - Parameters:
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/// - handler: handler to run on directory state change.
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public func startWatching(handler: @Sendable @escaping ([URL]) throws -> Void) {
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self.task = Task {
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var exists: Bool
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var isDir: ObjCBool = false
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while true {
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do {
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exists = FileManager.default.fileExists(atPath: self.directoryURL.path, isDirectory: &isDir)
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if exists && isDir.boolValue && self.source.withLock({ $0 }) == nil {
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try _startWatching(handler: handler)
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}
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} catch {
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log?.error("failed to start watching", metadata: ["error": "\(error)"])
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}
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79+
try await Task.sleep(for: Self.watchPeriod)
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}
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}
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}
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private func _startWatching(
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handler: @escaping ([URL]) throws -> Void
86+
) throws {
87+
let descriptor = open(directoryURL.path, O_EVTONLY)
88+
guard descriptor > 0 else {
89+
throw ContainerizationError(.internalError, message: "cannot open \(directoryURL.path), descriptor=\(descriptor)")
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}
91+
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do {
93+
let files = try FileManager.default.contentsOfDirectory(atPath: directoryURL.path)
94+
try handler(files.map { directoryURL.appending(path: $0) })
95+
} catch {
96+
throw ContainerizationError(.internalError, message: "failed to run handler for \(directoryURL.path)")
97+
}
98+
99+
log?.info("starting directory watcher", metadata: ["path": "\(directoryURL.path)"])
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101+
let dispatchSource = DispatchSource.makeFileSystemObjectSource(
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fileDescriptor: descriptor,
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eventMask: [.delete, .write],
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queue: monitorQueue
105+
)
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107+
dispatchSource.setCancelHandler {
108+
close(descriptor)
109+
}
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111+
dispatchSource.setEventHandler { [weak self] in
112+
guard let self else { return }
113+
114+
guard !dispatchSource.data.contains(.delete) else {
115+
dispatchSource.cancel()
116+
self.source.withLock { $0 = nil }
117+
return
118+
}
119+
120+
do {
121+
let files = try FileManager.default.contentsOfDirectory(atPath: directoryURL.path)
122+
try handler(files.map { directoryURL.appending(path: $0) })
123+
} catch {
124+
self.log?.error(
125+
"failed to run watch handler",
126+
metadata: ["error": "\(error)", "path": "\(directoryURL.path)"])
127+
}
128+
}
129+
130+
source.withLock { $0 = dispatchSource }
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dispatchSource.resume()
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}
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134+
deinit {
135+
self.task?.cancel()
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source.withLock { $0?.cancel() }
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}
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}

‎Sources/Helpers/APIServer/APIServer+Start.swift‎

Lines changed: 39 additions & 22 deletions
Original file line numberDiff line numberDiff line change
@@ -91,10 +91,15 @@ extension APIServer {
9191
$0[$1.key.rawValue] = $1.value
9292
}), log: log)
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94-
await withThrowingTaskGroup(of: Void.self) { group in
94+
await withTaskGroup(of: Result<Void, Error>.self) { group in
9595
group.addTask {
9696
log.info("starting XPC server")
97-
try await server.listen()
97+
do {
98+
try await server.listen()
99+
return .success(())
100+
} catch {
101+
return .failure(error)
102+
}
98103
}
99104

100105
// start up host table DNS
@@ -111,35 +116,47 @@ extension APIServer {
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"port": "\(Self.dnsPort)",
112117
]
113118
)
114-
try await dnsServer.run(host: Self.listenAddress, port: Self.dnsPort)
119+
do {
120+
try await dnsServer.run(host: Self.listenAddress, port: Self.dnsPort)
121+
return .success(())
122+
} catch {
123+
return .failure(error)
124+
}
115125

116126
}
117127

118128
// start up realhost DNS
119-
/*
120129
group.addTask {
121-
let localhostResolver = LocalhostDNSHandler(log: log)
122130
do {
123-
try localhostResolver.monitorResolvers()
131+
let localhostResolver = LocalhostDNSHandler(log: log)
132+
await localhostResolver.monitorResolvers()
133+
134+
let nxDomainResolver = NxDomainResolver()
135+
let compositeResolver = CompositeResolver(handlers: [localhostResolver, nxDomainResolver])
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let hostsQueryValidator = StandardQueryValidator(handler: compositeResolver)
137+
let dnsServer: DNSServer = DNSServer(handler: hostsQueryValidator, log: log)
138+
log.info(
139+
"starting DNS resolver for localhost",
140+
metadata: [
141+
"host": "\(Self.listenAddress)",
142+
"port": "\(Self.localhostDNSPort)",
143+
]
144+
)
145+
try await dnsServer.run(host: Self.listenAddress, port: Self.localhostDNSPort)
146+
return .success(())
124147
} catch {
125-
log.error("could not initialize resolver monitor", metadata: ["error": "\(error)"])
126-
throw error
148+
return .failure(error)
149+
}
150+
}
151+
152+
for await result in group {
153+
switch result {
154+
case .success():
155+
continue
156+
case .failure(let error):
157+
log.error("API server task failed: \(error)")
127158
}
128-
129-
let nxDomainResolver = NxDomainResolver()
130-
let compositeResolver = CompositeResolver(handlers: [localhostResolver, nxDomainResolver])
131-
let hostsQueryValidator = StandardQueryValidator(handler: compositeResolver)
132-
let dnsServer: DNSServer = DNSServer(handler: hostsQueryValidator, log: log)
133-
log.info(
134-
"starting DNS resolver for localhost",
135-
metadata: [
136-
"host": "\(Self.listenAddress)",
137-
"port": "\(Self.localhostDNSPort)",
138-
]
139-
)
140-
try await dnsServer.run(host: Self.listenAddress, port: Self.localhostDNSPort)
141159
}
142-
*/
143160
}
144161
} catch {
145162
log.error(

‎Sources/Helpers/APIServer/DirectoryWatcher.swift‎

Lines changed: 0 additions & 89 deletions
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