[llvm] [llvm]Add a simple Telemetry framework (PR #102323)

[Jonas Devlieghere via llvm-commits]

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+//===- llvm/Telemetry/Telemetry.h - Telemetry -------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file provides the basic framework for Telemetry
+///
+/// It comprises of three important structs/classes:
+///
+/// - Telemeter: The class responsible for collecting and forwarding
+///              telemery data.
+/// - TelemetryInfo: data courier
+/// - TelemetryConfig: this stores configurations on Telemeter.
+///
+/// Refer to its documentation at llvm/docs/Telemetry.rst for more details.
+//===---------------------------------------------------------------------===//
+
+#ifndef LLVM_TELEMETRY_TELEMETRY_H
+#define LLVM_TELEMETRY_TELEMETRY_H
+
+#include <chrono>
+#include <ctime>
+#include <memory>
+#include <optional>
+#include <string>
+
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/JSON.h"
+
+namespace llvm {
+namespace telemetry {
+
+/// Configuration for the Telemeter class.
+/// This stores configurations from both users and vendors and is passed
+/// to the Telemeter upon contruction. (Any changes to the config after
+/// the Telemeter's construction will not have effect on it).
+///
+/// This struct can be extended as needed to add additional configuration
+/// points specific to a vendor's implementation.
+struct Config {
+  // If true, telemetry will be enabled.
+  bool EnableTelemetry;
+
+  // Implementation-defined names of additional destinations to send
+  // telemetry data (Could be stdout, stderr, or some local paths, etc).
+  //
+  // These strings will be interpreted by the vendor's code.
+  // So the users must pick the  from their vendor's pre-defined
+  // set of Destinations.
+  std::vector<std::string> AdditionalDestinations;
+};
+
+/// Defines a convenient type for timestamp of various events.
+/// This is used by the EventStats below.
+using SteadyTimePoint = std::chrono::time_point<std::chrono::steady_clock>;
+
+/// Various time (and possibly memory) statistics of an event.
+struct EventStats {
+  // REQUIRED: Start time of an event
+  SteadyTimePoint Start;
+  // OPTIONAL: End time of an event - may be empty if not meaningful.
+  std::optional<SteadyTimePoint> End;
+  // TBD: could add some memory stats here too?
+
+  EventStats() = default;
+  EventStats(SteadyTimePoint Start) : Start(Start) {}
+  EventStats(SteadyTimePoint Start, SteadyTimePoint End)
+      : Start(Start), End(End) {}
+};
+
+/// Describes the exit signal of an event.
+/// This is used by TelemetryInfo below.
+struct ExitDescription {
+  int ExitCode;
+  std::string Description;
+};
+
+/// For isa, dyn_cast, etc operations on TelemetryInfo.
+typedef unsigned KindType;
+/// This struct is used by TelemetryInfo to support isa<>, dyn_cast<>
+/// operations.
+/// It is defined as a struct (rather than an enum) because it is
+/// expectend to be extended by subclasses which may have
+/// additional TelemetryInfo types defined to describe different events.
+struct EntryKind {
+  static const KindType Base = 0;
+};
+
+/// TelemetryInfo is the data courier, used to move instrumented data
+/// from the tool being monitored to the Telemery framework.
+///
+/// This base class contains only the basic set of telemetry data.
+/// Downstream implementations can add more fields as needed to describe
+/// additional events.
+///
+/// For example, The LLDB debugger can define a DebugCommandInfo subclass
+/// which has additional fields about the debug-command being instrumented,
+/// such as `CommandArguments` or `CommandName`.
+struct TelemetryInfo {
+  // This represents a unique-id, conventionally corresponding to
+  // a tool's session - i.e., every time the tool starts until it exits.
+  //
+  // Note: a tool could have multiple sessions running at once, in which
+  // case, these shall be multiple sets of TelemetryInfo with multiple unique
+  // ids.
+  //
+  // Different usages can assign different types of IDs to this field.
+  std::string SessionId;
+
+  // Time/memory statistics of this event.
+  EventStats Stats;
+
+  std::optional<ExitDescription> ExitDesc;
+
+  // Counting number of entries.
+  // (For each set of entries with the same SessionId, this value should
+  // be unique for each entry)
+  size_t Counter;
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JDevlieghere wrote:

I think these members are already too specific. For the Telemetry framework I'm planning to hook the up with, none of these are relevant except possibly the session id, which really should just be a unique identifier. 

https://github.com/llvm/llvm-project/pull/102323