Improve available capacity checking (#240)

* Improve available capacity checking

* Fixed expression

README.md

@@ -8,6 +8,22 @@ Built by CI engineers for your automation needs. Here are some highlights of Tar
 * Use Tart Packer Plugin to automate VM creation.
 * Built-in CI integration.
 
+*Tart* is already adopted by several automation services:
+
+<p align="center">
+  <a href="https://cirrus-ci.org/guide/macOS/" target=_blank>
+    <img src="https://github.com/cirruslabs/tart/raw/main/Resources/Users/CirrusCI.png" height="65"/>
+  </a>
+  <a href="https://codemagic.io/" target=_blank>
+    <img src="https://github.com/cirruslabs/tart/raw/main/Resources/Users/Codemagic.png" height="65"/>
+  </a>
+  <a href="https://testingbot.com/" target=_blank>
+    <img src="https://github.com/cirruslabs/tart/raw/main/Resources/Users/TestingBot.png" height="65"/>
+  </a>
+</p>
+
+## Usage
+
 Try running a Tart VM on your Apple Silicon device running macOS Monterey or later (will download a 25 GB image):
 
 ```shell
@@ -252,3 +268,21 @@ This invocation calls the `tart pull` implicitly (if the image is not being pres
   Tart is limited by functionality of Apple's `Virtualization.Framework`. At the moment `Virtualization.Framework`
   doesn't support nested virtualization.
 </details>
+
+<details>
+  <summary>Changing the default NAT subnet</summary>
+
+  To change the default network to `192.168.77.1`:
+
+  ```
+  sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.vmnet.plist Shared_Net_Address -string 192.168.77.1
+  ```
+
+  Note that even through a network would normally be specified as `192.168.77.0`, the [vmnet framework](https://developer.apple.com/documentation/vmnet) seems to treat this as a starting address too and refuses to pick up such network-like values.
+
+  The default subnet mask `255.255.255.0` should suffice for most use-cases, however, you can also change it to `255.255.0.0`, for example:
+
+  ```
+  sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.vmnet.plist Shared_Net_Mask -string 255.255.0.0
+  ```
+</details>

Resources/Users/CirrusCI.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:dbcf6f65f26c0e17b2fe55a9712fc783315cd64905a0febce758b31d7e4e923b
+size 6787

Resources/Users/Codemagic.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:4239996f30145992936cfc8faa0232fa8904aedf4de61e30ef4c4fc86cad587f
+size 14588

Resources/Users/TestingBot.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:227192fcd215c9cc05b1ebcd2616bd1f8c95be184726f64d91fc4507a88c66e1
+size 18393

Sources/tart/Commands/Clone.swift

@@ -32,12 +32,22 @@ struct Clone: AsyncParsableCommand {
       }
 
       let sourceVM = try VMStorageHelper.open(sourceName)
-      let generateMAC = try localStorage.hasVMsWithMACAddress(macAddress: sourceVM.macAddress())
 
       let tmpVMDir = try VMDirectory.temporary()
+
+      // Lock the temporary VM directory to prevent it's garbage collection
+      let tmpVMDirLock = try FileLock(lockURL: tmpVMDir.baseURL)
+      try tmpVMDirLock.lock()
+
       try await withTaskCancellationHandler(operation: {
+        let lock = try FileLock(lockURL: Config().tartHomeDir)
+        try lock.lock()
+
+        let generateMAC = try localStorage.hasVMsWithMACAddress(macAddress: sourceVM.macAddress())
         try sourceVM.clone(to: tmpVMDir, generateMAC: generateMAC)
         try localStorage.move(newName, from: tmpVMDir)
+
+        try lock.unlock()
       }, onCancel: {
         try? FileManager.default.removeItem(at: tmpVMDir.baseURL)
       })

Sources/tart/Commands/Create.swift

@@ -27,6 +27,11 @@ struct Create: AsyncParsableCommand {
   func run() async throws {
     do {
       let tmpVMDir = try VMDirectory.temporary()
+
+      // Lock the temporary VM directory to prevent it's garbage collection
+      let tmpVMDirLock = try FileLock(lockURL: tmpVMDir.baseURL)
+      try tmpVMDirLock.lock()
+
       try await withTaskCancellationHandler(operation: {
         if let fromIPSW = fromIPSW {
           if fromIPSW == "latest" {

Sources/tart/Commands/Prune.swift

@@ -101,7 +101,7 @@ struct Prune: AsyncParsableCommand {
         break
       }
 
-      cacheReclaimedBytes -= try prunable.sizeBytes()
+      cacheReclaimedBytes += try prunable.sizeBytes()
       try prunable.delete()
     }
   }

Sources/tart/Commands/Run.swift

@@ -47,8 +47,10 @@ struct Run: AsyncParsableCommand {
   @Option(help: ArgumentHelp("""
                              Additional directory shares with an optional read-only specifier\n(e.g. --dir=\"build:~/src/build\" --dir=\"sources:~/src/sources:ro\")
                              """, discussion: """
+                                              Requires host to be macOS 13.0 (Ventura) or newer.
                                               All shared directories are automatically mounted to "/Volumes/My Shared Files" directory on macOS,
                                               while on Linux you have to do it manually: "mount -t virtiofs com.apple.virtio-fs.automount /mount/point".
+                                              For macOS guests, they must be running macOS 13.0 (Ventura) or newer.
                                               """, valueName: "name:path[:ro]"))
   var dir: [String] = []
 
@@ -126,8 +128,9 @@ struct Run: AsyncParsableCommand {
   func additionalDiskAttachments() throws -> [VZDiskImageStorageDeviceAttachment] {
     var result: [VZDiskImageStorageDeviceAttachment] = []
     let readOnlySuffix = ":ro"
+    let expandedDiskPaths = disk.map { NSString(string:$0).expandingTildeInPath }
 
-    for rawDisk in disk {
+    for rawDisk in expandedDiskPaths {
       if rawDisk.hasSuffix(readOnlySuffix) {
         result.append(try VZDiskImageStorageDeviceAttachment(
           url: URL(fileURLWithPath: String(rawDisk.prefix(rawDisk.count - readOnlySuffix.count))),
@@ -166,7 +169,7 @@ struct Run: AsyncParsableCommand {
 
       let (name, path) = (String(splits[0]), String(splits[1]))
 
-      result.append(DirectoryShare(name: name, path: URL(fileURLWithPath: path), readOnly: readOnly))
+      result.append(DirectoryShare(name: name, path: URL(fileURLWithPath: NSString(string: path).expandingTildeInPath), readOnly: readOnly))
     }
 
     return result

Sources/tart/Config.swift

@@ -3,8 +3,9 @@ import Foundation
 struct Config {
   let tartHomeDir: URL
   let tartCacheDir: URL
+  let tartTmpDir: URL
 
-  init() {
+  init() throws {
     var tartHomeDir: URL
 
     if let customTartHome = ProcessInfo.processInfo.environment["TART_HOME"] {
@@ -14,9 +15,27 @@ struct Config {
               .homeDirectoryForCurrentUser
               .appendingPathComponent(".tart", isDirectory: true)
     }
-
     self.tartHomeDir = tartHomeDir
+
     tartCacheDir = tartHomeDir.appendingPathComponent("cache", isDirectory: true)
+    try FileManager.default.createDirectory(at: tartCacheDir, withIntermediateDirectories: true)
+
+    tartTmpDir = tartHomeDir.appendingPathComponent("tmp", isDirectory: true)
+    try FileManager.default.createDirectory(at: tartTmpDir, withIntermediateDirectories: true)
+  }
+
+  func gc() throws {
+    for entry in try FileManager.default.contentsOfDirectory(at: tartTmpDir,
+        includingPropertiesForKeys: [], options: []) {
+      let lock = try FileLock(lockURL: entry)
+      if try !lock.trylock() {
+        continue
+      }
+
+      try FileManager.default.removeItem(at: entry)
+
+      try lock.unlock()
+    }
   }
 
   static func jsonEncoder() -> JSONEncoder {

Sources/tart/FileLock.swift

@@ -0,0 +1,48 @@
+import Foundation
+import System
+
+enum FileLockError: Error, Equatable {
+    case Failed(_ message: String)
+    case AlreadyLocked
+}
+
+class FileLock {
+    let url: URL
+    let fd: Int32
+
+    init(lockURL: URL) throws {
+        url = lockURL
+        fd = open(lockURL.path, 0)
+    }
+
+    deinit {
+        close(fd)
+    }
+
+    func trylock() throws -> Bool {
+        try flockWrapper(LOCK_EX | LOCK_NB)
+    }
+
+    func lock() throws {
+        _ = try flockWrapper(LOCK_EX)
+    }
+
+    func unlock() throws {
+        _ = try flockWrapper(LOCK_UN)
+    }
+
+    func flockWrapper(_ operation: Int32) throws -> Bool {
+        let ret = flock(fd, operation)
+        if ret != 0 {
+            let details = Errno(rawValue: CInt(errno))
+
+            if (operation & LOCK_NB) != 0 && details == .wouldBlock {
+                return false
+            }
+
+            throw FileLockError.Failed("failed to lock \(url): \(details)")
+        }
+
+        return true
+    }
+}

Sources/tart/IPSWCache.swift

@@ -5,7 +5,7 @@ class IPSWCache: PrunableStorage {
   let baseURL: URL
 
   init() throws {
-    baseURL = Config().tartCacheDir.appendingPathComponent("IPSWs", isDirectory: true)
+    baseURL = try Config().tartCacheDir.appendingPathComponent("IPSWs", isDirectory: true)
     try FileManager.default.createDirectory(at: baseURL, withIntermediateDirectories: true)
   }
 

Sources/tart/Root.swift

@@ -36,6 +36,9 @@ struct Root: AsyncParsableCommand {
     do {
       var command = try parseAsRoot()
 
+      // Run garbage-collection before each command (shouldn't take too long)
+      try Config().gc()
+
       if var asyncCommand = command as? AsyncParsableCommand {
         try await asyncCommand.run()
       } else {

Sources/tart/VM.swift

@@ -14,7 +14,7 @@ struct UnsupportedOSError: Error, CustomStringConvertible {
   let description: String
 
   init(_ what: String, _ plural: String) {
-    description = "error: \(what) \(plural) only supported on macOS 13.0 (Ventura) or newer"
+    description = "error: \(what) \(plural) only supported on hosts running macOS 13.0 (Ventura) or newer"
   }
 }
 

Sources/tart/VMDirectory.swift

@@ -29,7 +29,7 @@ struct VMDirectory: Prunable {
   }
 
   static func temporary() throws -> VMDirectory {
-    let tmpDir = FileManager.default.temporaryDirectory.appendingPathComponent(UUID().uuidString)
+    let tmpDir = try Config().tartTmpDir.appendingPathComponent(UUID().uuidString)
     try FileManager.default.createDirectory(at: tmpDir, withIntermediateDirectories: false)
 
     return VMDirectory(baseURL: tmpDir)

Sources/tart/VMStorageLocal.swift

@@ -1,7 +1,7 @@
 import Foundation
 
 class VMStorageLocal {
-  let baseURL: URL = Config().tartHomeDir.appendingPathComponent("vms", isDirectory: true)
+  let baseURL: URL = try! Config().tartHomeDir.appendingPathComponent("vms", isDirectory: true)
 
   private func vmURL(_ name: String) -> URL {
     baseURL.appendingPathComponent(name, isDirectory: true)

Sources/tart/VMStorageOCI.swift

@@ -1,12 +1,16 @@
 import Foundation
 
 class VMStorageOCI: PrunableStorage {
-  let baseURL = Config().tartCacheDir.appendingPathComponent("OCIs", isDirectory: true)
+  let baseURL = try! Config().tartCacheDir.appendingPathComponent("OCIs", isDirectory: true)
 
   private func vmURL(_ name: RemoteName) -> URL {
     baseURL.appendingRemoteName(name)
   }
 
+  private func hostDirectoryURL(_ name: RemoteName) -> URL {
+    baseURL.appendingHost(name)
+  }
+
   func exists(_ name: RemoteName) -> Bool {
     VMDirectory(baseURL: vmURL(name)).initialized
   }
@@ -125,17 +129,41 @@ class VMStorageOCI: PrunableStorage {
     let digestName = RemoteName(host: name.host, namespace: name.namespace,
             reference: Reference(digest: Digest.hash(manifestData)))
 
+    // Ensure that host directory for given RemoteName exists in OCI storage
+    let hostDirectoryURL = hostDirectoryURL(digestName)
+    try FileManager.default.createDirectory(at: hostDirectoryURL, withIntermediateDirectories: true)
+
+    // Acquire a lock on it to prevent concurrent pulls for a single host
+    let lock = try FileLock(lockURL: hostDirectoryURL)
+
+    let sucessfullyLocked = try lock.trylock()
+    if !sucessfullyLocked {
+      print("waiting for lock...")
+      try lock.lock()
+    }
+    defer { try! lock.unlock() }
+
+    if Task.isCancelled {
+      throw CancellationError()
+    }
+
     if !exists(digestName) {
       let tmpVMDir = try VMDirectory.temporary()
 
+      // Lock the temporary VM directory to prevent it's garbage collection
+      let tmpVMDirLock = try FileLock(lockURL: tmpVMDir.baseURL)
+      try tmpVMDirLock.lock()
+
       // Try to reclaim some cache space if we know the VM size in advance
       if let uncompressedDiskSize = manifest.uncompressedDiskSize() {
         let requiredCapacityBytes = UInt64(uncompressedDiskSize + 128 * 1024 * 1024)
 
-        let attrs = try tmpVMDir.baseURL.resourceValues(forKeys: [.volumeAvailableCapacityForImportantUsageKey])
-        let availableCapacityBytes = UInt64(attrs.volumeAvailableCapacityForImportantUsage!)
+        let attrs = try Config().tartCacheDir.resourceValues(forKeys: [.volumeAvailableCapacityForImportantUsageKey, .volumeAvailableCapacityKey])
+        let availableCapacityBytes = max(UInt64(attrs.volumeAvailableCapacityForImportantUsage!), UInt64(attrs.volumeAvailableCapacity!))
 
-        if availableCapacityBytes < requiredCapacityBytes {
+        // There is a suspicious that occasionally capacity is returned as zero which can't be true.
+        // Let's validate to avoid unnecessary pruning.
+        if 0 < availableCapacityBytes && availableCapacityBytes < requiredCapacityBytes {
           try Prune.pruneReclaim(reclaimBytes: requiredCapacityBytes - availableCapacityBytes)
         }
       }
@@ -181,4 +209,8 @@ extension URL {
 
     return result
   }
+
+  func appendingHost(_ name: RemoteName) -> URL {
+    self.appendingPathComponent(name.host, isDirectory: true)
+  }
 }

Tests/TartTests/FileLockTests.swift

@@ -0,0 +1,34 @@
+import XCTest
+@testable import tart
+
+final class FileLockTests: XCTestCase {
+    func testSimple() throws {
+        // Create a temporary file that will be used as a lock
+        let url = temporaryFile()
+
+        // Make sure this file can be locked and unlocked
+        let lock = try FileLock(lockURL: url)
+        try lock.lock()
+        try lock.unlock()
+    }
+
+    func testDoubleLockResultsInError() throws {
+        // Create a temporary file that will be used as a lock
+        let url = temporaryFile()
+
+        // Create two locks on a same file and ensure one of them fails
+        let firstLock = try FileLock(lockURL: url)
+        try firstLock.lock()
+
+        let secondLock = try! FileLock(lockURL: url)
+        XCTAssertFalse(try secondLock.trylock())
+    }
+
+    private func temporaryFile() -> URL {
+        let url = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(UUID().uuidString)
+
+        FileManager.default.createFile(atPath: url.path, contents: nil)
+
+        return url
+    }
+}