Server Stats Collection (#1834)

* Server Stats Collection

Motivation:

In order to implement the 'runServer' RPC on the WorkerService we need to capture a snapshot with the resorces usage for the server
and compute the difference between 2 of these snapshots.

Modifications:

- Created the ServerStats struct that contains all stats needed in the QPS benchmarking from the server
- Implemented the init() that collects all these stats
- Implemented the function that computes the differences between 2 snapshots of ServerStats

Result:

We will be able to implement the `runServer` RPC.

Package.swift

@@ -32,7 +32,7 @@ let includeNIOSSL = ProcessInfo.processInfo.environment["GRPC_NO_NIO_SSL"] == ni
 let packageDependencies: [Package.Dependency] = [
   .package(
     url: "https://github.com/apple/swift-nio.git",
-    from: "2.58.0"
+    from: "2.64.0"
   ),
   .package(
     url: "https://github.com/apple/swift-nio-http2.git",
@@ -132,6 +132,7 @@ extension Target.Dependency {
     package: "swift-nio-transport-services"
   )
   static let nioTestUtils: Self = .product(name: "NIOTestUtils", package: "swift-nio")
+  static let nioFileSystem: Self = .product(name: "_NIOFileSystem", package: "swift-nio")
   static let logging: Self = .product(name: "Logging", package: "swift-log")
   static let protobuf: Self = .product(name: "SwiftProtobuf", package: "swift-protobuf")
   static let protobufPluginLibrary: Self = .product(
@@ -251,7 +252,8 @@ extension Target {
     dependencies: [
       .grpcCore,
       .grpcProtobuf,
-      .nioCore
+      .nioCore,
+      .nioFileSystem
     ]
   )
     

Sources/performance-worker/ServerStats.swift

@@ -0,0 +1,130 @@
+/*
+ * Copyright 2024, gRPC Authors All rights reserved.
+ *
+ * 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.
+ */
+
+import Dispatch
+import NIOCore
+import NIOFileSystem
+
+#if canImport(Darwin)
+import Darwin
+#elseif canImport(Musl)
+import Musl
+#elseif canImport(Glibc)
+import Glibc
+#else
+let badOS = { fatalError("unsupported OS") }()
+#endif
+
+#if canImport(Darwin)
+private let OUR_RUSAGE_SELF: Int32 = RUSAGE_SELF
+#elseif canImport(Musl) || canImport(Glibc)
+private let OUR_RUSAGE_SELF: Int32 = RUSAGE_SELF.rawValue
+#endif
+
+/// Current server stats.
+@available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
+internal struct ServerStats: Sendable {
+  var time: Double
+  var userTime: Double
+  var systemTime: Double
+  var totalCPUTime: UInt64
+  var idleCPUTime: UInt64
+
+  init(
+    time: Double,
+    userTime: Double,
+    systemTime: Double,
+    totalCPUTime: UInt64,
+    idleCPUTime: UInt64
+  ) {
+    self.time = time
+    self.userTime = userTime
+    self.systemTime = systemTime
+    self.totalCPUTime = totalCPUTime
+    self.idleCPUTime = idleCPUTime
+  }
+
+  init() async throws {
+    self.time = Double(DispatchTime.now().uptimeNanoseconds) * 1e-9
+    var usage = rusage()
+    if getrusage(OUR_RUSAGE_SELF, &usage) == 0 {
+      // Adding the seconds with the microseconds transformed into seconds to get the
+      // real number of seconds as a `Double`.
+      self.userTime = Double(usage.ru_utime.tv_sec) + Double(usage.ru_utime.tv_usec) * 1e-6
+      self.systemTime = Double(usage.ru_stime.tv_sec) + Double(usage.ru_stime.tv_usec) * 1e-6
+    } else {
+      self.userTime = 0
+      self.systemTime = 0
+    }
+    let (totalCPUTime, idleCPUTime) = try await ServerStats.getTotalAndIdleCPUTime()
+    self.totalCPUTime = totalCPUTime
+    self.idleCPUTime = idleCPUTime
+  }
+
+  internal func difference(to stats: ServerStats) -> ServerStats {
+    return ServerStats(
+      time: self.time - stats.time,
+      userTime: self.userTime - stats.userTime,
+      systemTime: self.systemTime - stats.systemTime,
+      totalCPUTime: self.totalCPUTime - stats.totalCPUTime,
+      idleCPUTime: self.idleCPUTime - stats.idleCPUTime
+    )
+  }
+
+  /// Computes the total and idle CPU time after extracting stats from the first line of '/proc/stat'.
+  ///
+  /// The first line in '/proc/stat' file looks as follows:
+  /// CPU [user] [nice] [system] [idle] [iowait] [irq] [softirq]
+  /// The totalCPUTime is computed as follows:
+  /// total = user + nice + system + idle
+  private static func getTotalAndIdleCPUTime() async throws -> (
+    totalCPUTime: UInt64, idleCPUTime: UInt64
+  ) {
+    #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS) || os(Linux) || os(Android)
+    let contents: ByteBuffer
+    do {
+      contents = try await ByteBuffer(
+        contentsOf: "/proc/stat",
+        maximumSizeAllowed: .kilobytes(20)
+      )
+    } catch {
+      return (0, 0)
+    }
+
+    let view = contents.readableBytesView
+    guard let firstNewLineIndex = view.firstIndex(of: UInt8(ascii: "\n")) else {
+      return (0, 0)
+    }
+    let firstLine = String(buffer: ByteBuffer(view[0 ... firstNewLineIndex]))
+
+    let lineComponents = firstLine.components(separatedBy: " ")
+    if lineComponents.count < 5 || lineComponents[0] != "CPU" {
+      return (0, 0)
+    }
+
+    let CPUTime: [UInt64] = lineComponents[1 ... 4].compactMap { UInt64($0) }
+    if CPUTime.count < 4 {
+      return (0, 0)
+    }
+
+    let totalCPUTime = CPUTime.reduce(0, +)
+    return (totalCPUTime, CPUTime[3])
+
+    #else
+    return (0, 0)
+    #endif
+  }
+}