src/persistent_mode.h

// Copyright 2023 Google Inc. 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.

#ifndef NINJA_PERSISTENT_MODE_H_
#define NINJA_PERSISTENT_MODE_H_

#include <functional>
#include <string>
#include <vector>

#include "build_config.h"
#include "ipc_utils.h"
#include "persistent_service.h"

/// Implementation for Ninja's persistent mode.
///
/// This class wraps Ninja's persistent mode implementation on top of the
/// generic PersistentService class. In particular:
///
/// - Provides static methods to determine the role of the current process
///   (based on the NNINJA_PERSISTENT_MODE environment variable).
///
/// - Provides a way to check that the client and the server correspond to
///   the same build plan (see Compatibility).
///
/// - Provides client methods to check the status of the server, or stop it
///   (to implement the `-t server` tool commands).
///
/// - Provides a client method to run a query on the server, automatically
///   starting a new instance if none is available, if the available one
///   is not compatible with the current build plan, or if any of the input
///   .ninja manifest files has been updated.
///
/// - Provides a way to start the server early, and to process Ninja build
///   or tool requests on the server.
///
/// Example Usage:
///
///    // build plan configuration data used to match client/server
///    // compatibility.
///    auto compatibility = PersistentMode::Compatibility();
///    compatibility.SetBuildDir(<absolute_build_dir>);
///
///    // An object describing the current Ninja build query or tool
///    // invocation to perform.
///    PersistentMode::BuildQuery query;
///    query.config = build_config;
///    query.args = RemoteArguments(argc, argv).args();
///    ...
///
///    // A callable used to run the query, either on the server, or in the
///    // client if launching a new server was not possible.
///    auto handle_query = [](const PersistentMode::BuildQuery& query) -> int {
///       ...  // perform build or tool query.
///       return 0;
///    };
///
///    auto persistent_status = PersistentMode::GetProcessStatus();
///    is (status == PersistentMode::IsServer) {
///       PersistentMode::Server server(compatibility);
///
///       if (!server.StartLocalServer(&err))
///         Fatal("Could not start server: %s", err.c_str());
///
///       ... load build plan
///
///       // A callable used  by the server before running each
///       // query to verify if the build plan changed (e.g. an
///       // input build.ninja file was updated on the filesystem).
///       auto restart_check = []() -> bool {
///         return false;
///       };
///
///       // Run the server loop till the end.
///       server.RunServerThenExit(std::move(restart_check),
///                                std::move(handle_query));
///    }
///
///    if (persistent_status == PersistentMode::Client) {
///      PersistentMode::Client client;
///
///      // Run the query, this takes care of redirecting stdio
///      // and ensuring Ctrl-C will be handled by the server
///      // properly (i.e. to stop current query, and not abort
///      // the server).
///      int exit_code = -1;
///      if (!client.RunQuery(compatibility, query, &exit_code, &error)) {
///        Fatal("Could not run Ninja query: %s", error.c_str());
///      }
///
///      // query was run on the server.
///      exit(exit_code);
///    }
///
///    assert(persistent_status == PersistentMode::Disabled) {
///       ... load build plan
///       ... do a local build as usual.
///    }
///
struct PersistentMode {
  /// Status of persistent mode for the current process
  enum Status {
    Disabled = 0,
    IsClient,
    IsServer,
  };

  /// Return the status of the current process.
  static Status GetCurrentProcessStatus();

  /// The configuration information that each persistent server must compare
  /// with each client query to verify that they are compatible, i.e. correspond
  /// to the same Ninja build plan. Note that some flags change the way
  /// manifests are loaded, and thus introduce incompatibilities when they
  /// are different.
  struct Compatibility {
    /// Create new instance from command-line options.
    ///
    /// |input_file| is an optional pointer to the top-level Ninja manifest
    /// file name. The nullptr value defaults to "build.ninja".
    ///
    /// |build_dir| is an optional pointer to the build directory, the nullptr
    /// value defaults to the current working directory.
    ///
    /// |dupe_edges_should_err| corresponds to the `-w dupbuild=err` option,
    /// and |phony_cycle_should_err| corresponds to the `-w phonycycle=err` one,
    /// and both change the way manifest files are loaded.
    static Compatibility FromOptions(const char* input_file,
                                     const char* build_dir,
                                     bool dupe_edges_should_err,
                                     bool phony_cycle_should_err);

    Compatibility();

    /// Override the ninja_version() string. Only use this for tests.
    Compatibility& SetNinjaVersionForTest(const std::string& new_version);

    /// Change the input file, default value if "build.ninja"
    Compatibility& SetInputFile(const std::string& input_file);

    /// Change the build directory, and empty value matches the current working
    /// directory. WARNING: It is critically important for the client and server
    /// to use the same value consistenly. Outside of tests, ensure that a
    /// non-empty value is always an absolute path!
    Compatibility& SetBuildDir(const std::string& build_dir);

    /// Set the value of the `-w dupedges` flag, which changes the way build
    /// manifests are loaded. Default value is true.
    Compatibility& SetFlagDupeEdgesShouldErr(bool enabled);

    /// Set the value of the `-w phonycycle` flag, which changes the way
    /// build manifests are loaded. Default value is false.
    Compatibility& SetFlagPhonyCycleShouldErr(bool enabled);

    /// Create new instance from an encoded string.
    /// On success return new instance after clearing |*error|.
    /// On failure return empty instance after setting |*error| to non-empty
    /// string.
    static Compatibility FromEncodedString(const std::string& str,
                                           std::string* error);

    /// Convert to string for sending through IPC. Not human-readable.
    std::string ToEncodedString() const;

    /// Convert to human-readable string for debugging.
    std::string ToString() const;

    /// Return true if this instance is compatiable with |other|.
    /// On failure, return false after setting |*reason|.
    bool IsCompatibleWith(const Compatibility& other,
                          std::string* reason) const;

    /// Return working directory.
    const std::string& build_dir() const { return build_dir_; }

    /// Return a string trying to identify the Ninja version being used.
    /// Note that this may include a timestamp or content hash of the current
    /// executable as well. The default value is computed by the constructor
    /// automatically.
    const std::string& ninja_version() const { return ninja_version_; };

    /// Return a command-line used to start a server compatible with this
    /// instance.
    std::vector<std::string> ToServerArgs(
        const std::string& server_executable) const;

    /// Returns true if the build directory is absolute (or empty, in which
    /// case this will be interpreted as the absolute path of the current
    /// directory). On failure, set |*err| then return false.
    bool CheckBuildDir(std::string* err) const;

   private:
    /// Return the default Ninja version, called from constructor.
    static std::string GetDefaultNinjaVersion();

    /// Ninja version. This includes a timestamp of the Ninja executable
    /// as well. Must be the first field in this struct.
    std::string ninja_version_;

    /// Current build directory.
    std::string build_dir_;

    /// Input file name, cannot be empty, relative paths are always
    /// relative to |build_dir|.
    std::string input_file_ = "build.ninja";

    /// Options controlling how the manifest is loaded.
    bool dupe_edges_should_err_ = true;
    bool phony_cycle_should_err_ = false;
  };

  /// A callable object that returns true if any condition invalidated
  /// the content of the in-memory build graph. In practice this would be
  /// when any of the input .ninja files has changed. A return value of true
  /// indicates that the server must be stopped, and another one restarted.
  using RestartChecker = std::function<bool(void)>;

  /// Describe a query from the client to the server. This can be used to
  /// run either a build or a tool (when the |tool| field is not empty).
  struct BuildQuery {
    /// Build configuration
    BuildConfig config;

    /// Mirror the set of debug flags in "debug_flags.h" that can be set
    /// individually with `-d <flag>` on the command line that do affect
    /// each build. These are currently stored in global variables instead
    /// of BuildConfig :-/
    bool debug_explaining = false;
    bool debug_keep_depfile = false;
    bool debug_keep_rsp = false;
    bool debug_experimental_statcache = false;

    /// Set to true to dump metrics after a build.
    bool dump_metrics = false;

    /// Optional tool name, empty means a build is requested, instead of a
    /// tool run.
    std::string tool;

    /// List of command-line arguments. If |tool| is empty, this is a list
    /// of targets and should not contain any option. If |tool| is not empty
    /// then this is a list of arguments for the tool.
    std::vector<std::string> args;

    std::string ToEncodedString() const;
    std::string ToString() const;

    void WriteGlobalVariables() const;

    static BuildQuery FromEncodedString(const std::string& str,
                                        std::string* error);
  };

  /// A special value that can be returned by a BuildQueryHandler to
  /// indicate that the server should exit immediately after
  /// serving the query.
  static constexpr int kServerExit = -2;

  /// A callable object that implements a query. The result value can
  /// be the special kServerExit value to indicate that the server
  /// should stop immediately. Otherwise, it must be a process exit
  /// code that is >= 0, corresponding to the result of the query.
  using BuildQueryHandler = std::function<int(const BuildQuery&)>;

  class Client {
   public:
    /// Create new instance.
    Client();

    /// Set the path to the server executable. By default, this is the value
    /// returned by GetCurrentExecutable(), but this method allows one to
    /// override it for testing.
    void SetServerExecutable(const std::string& server_path);

    /// Return server executable path. Used for testing.
    const std::string server_executable() const { return server_executable_; }

    /// Return true if a server is already running, serving a given build
    /// directory. An empty |build_dir| string means the current working
    /// directory.
    bool IsServerRunning(const std::string& build_dir);

    /// Retrieve process ID of server, if it exists, for |build_dir|,
    /// or -1 otherwise. NOTE: DOES NOT WORK ON WINDOWS YET.
    int GetServerPidFor(const std::string& build_dir);

    /// Stop the server if it exists, return true if a server was running
    /// before the call for a given build directory. An empty |build_dir|
    /// string means the current working directory.
    bool StopServer(const std::string& build_dir, std::string* err);

    /// Ask the server to run a query for us.
    ///
    /// |compatibility| is used to connect either launch a new server instance,
    /// or verify that the existing one serving |compatibility.build_dir()| is
    /// compatible (if not, that instance is shut down, and a new one is
    /// launched).
    ///
    /// On success return true and set |*exit_code_ptr| to the result of the
    /// query, on failure to connect to the server, set |*error| and return
    /// false.
    bool RunQuery(const Compatibility& compatibility, const BuildQuery& query,
                  int* exit_code_ptr, std::string* error);

   private:
    static PersistentService::Client GetService(const std::string& build_dir);

    std::string server_executable_;
  };

  class Server {
   public:
    /// Create new instance. This does not do anything except recording
    /// the value of |compatibility|.
    explicit Server(const Compatibility& compatibility);

    /// Set the timeout, in milliseconds, used by server instances waiting
    /// for new client connections. On expiration, the server will shutdown
    /// gracefully. A negative value (the default) means no timeout.
    /// This must be called before StartLocalServer() or RunServerThenExit().
    void SetConnectionTimeoutMs(int64_t connection_timeout_ms) {
      server_.SetConnectionTimeoutMs(connection_timeout_ms);
    }

    /// Start the server in the current process. This can be called before
    /// RunServerThenExit() to quickly acquire the service named pipe and fail
    /// if not possible, before performing expensive operations like loading
    /// the build plan. Called by RunServerThenExit() implicitly otherwise.
    bool StartLocalServer(std::string* error);

    /// Run the server main loop, which will handle incoming
    /// build requests by first calling |restart_checker| to verify whether
    /// a restart is needed (e.g. if the build plan changed), then serve
    /// the request with |query_handler|. This function never returns.
    void RunServerThenExit(RestartChecker restart_checker,
                           BuildQueryHandler query_handler);

   private:
    bool RunQueryOnServer(IpcHandle connection,
                          const BuildQueryHandler& query_handler);

    Compatibility compatibility_;
    int64_t connection_timeout_ms_ = -1;
    PersistentService::Server server_;
  };
};

#endif  // NINJA_PERSISTENT_MODE_H_