script.ipp

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#include <adc/builder/builder.hpp>
#include <adc/publisher/publisher.hpp>
#include <cstdlib>
#include <iostream>
#include <fstream>
#include <filesystem>
#include <unistd.h>
 
namespace adc {
 
using std::cout;
 
typedef std::string string;
typedef std::string_view string_view;
 
 
/*! \brief User script publisher plugin. The program specified
  by environment variable is used to asynchronously deliver
  published messages. It is invoked in a shell as:
     ($prog $messagefile > /dev/null 2>&1 || /bin/rm $messagefile) &
 */
class script_plugin : public publisher_api {
    enum state {
        ok,
        err
    };
    enum mode {
        /* the next mode needed for correct operation */
        pi_config,
        pi_init,
        pi_pub_or_final
    };
 
public:
    /// \brief The default scratch directory for user script messages.
    /// This directory must be globally writable and should be fast.
    /// Overridden with env("ADC_SCRIPT_PLUGIN_DIRECTORY").
    static const inline char *adc_script_plugin_dir_default = "/dev/shm/adc";
 
    /// \brief The default path to a user script or program.
    /// This program should be user accessible.
    /// Overridden with env("ADC_SCRIPT_PLUGIN_PROG").
    /// The default : is a non-operation.
    static const inline char *adc_script_plugin_prog_default = ":";
 
    /// \brief ADC script plugin enable debug messages; (default "0": none)
    /// "2" provides message send debugging
    /// "1" provides lighter debugging
    /// Overridden with env("ADC_SCRIPT_PLUGIN_DEBUG").
    inline static const char *adc_script_plugin_debug_default = "0";
 
private:
    const std::map< const string, const string > plugin_script_config_defaults =
    {   {"DIRECTORY", adc_script_plugin_dir_default},
        {"DEBUG", adc_script_plugin_debug_default},
        {"PROG", adc_script_plugin_prog_default}
    };
    inline static const char *plugin_prefix = "ADC_SCRIPT_PLUGIN_";
    const string vers;
    const std::vector<string> tags;
    string fdir;
    string prog;
    int debug;
    enum state state;
    bool paused;
    enum mode mode;
 
    int config(const string& dir, string_view sprog, const string &sdebug) {
        if (mode != pi_config)
            return 2;
        uid_t ui = geteuid();
        fdir = dir + string("/") + std::to_string(ui);
        prog = sprog;
        mode = pi_init;
        std::stringstream ss(sdebug);
        ss >> debug;
        if (debug < 0) {
            debug = 0;
        }
        if (debug > 0) {
            std::cout<< "script plugin configured" <<std::endl;
        }
        return 0;
    }
 
    // find field in m, then with prefix in env, then the default.
    const string get(const std::map< string, string >& m,
            string field, string_view env_prefix) {
        // fields not defined in config_defaults raise an exception.
        auto it = m.find(field);
        if (it != m.end()) {
            return it->second;
        }
        string en = string(env_prefix) += field;
        char *ec = getenv(en.c_str());
        if (!ec) {
            return plugin_script_config_defaults.at(field);
        } else {
            return string(ec);
        }
    }
    
    string get_temp_file_name() {
        string tplt = fdir + "/json-sh-msg-XXXXXX";
        char * cstr = new char [tplt.length()+1];
        std::strcpy (cstr, tplt.c_str());
        int fd = mkstemp(cstr);
        if (fd >= 0) {
            string f(cstr);
            delete[] cstr;
            close(fd);
            // current user now owns tempfile.
            return f;
        }
        std::cout<< "'script' plugin: mkstemp failed" <<std::endl;
        delete[] cstr;
        return "";
    }
 
    // invoke script with json in f as arg 1, then delete f.
    // wrap this in a thread to make it non-blocking eventually.
    int script_send(string& f)
    {
        string qcmd = "(" + prog + " " + f +
            "> /dev/null 2>&1 || /bin/rm " + f + ") &";
        int err2 = std::system(qcmd.c_str());
        if (debug > 1) {
            std::cout << "script plugin file: " << f << std::endl;
            std::cout << "script plugin err: " << err2 << std::endl;
        }
        return 0;
    }
 
public:
    script_plugin() : vers("1.0.0") , tags({"none"}), debug(0), state(ok), paused(false), mode(pi_config) { }
 
        int publish(std::shared_ptr<builder_api> b) {
        if (paused)
            return 0;
        if (state != ok)
            return 1;
        if (mode != pi_pub_or_final)
            return 2;
        // write to tmpfile, run script and then delete tmpfile
        // this could be made fancy with a work queue in a later reimplementation.
        // try for /dev/shm/adc for performance and fall back to tmpdir
        string fname = get_temp_file_name();
        if (debug) {
            std::cout << "script plugin temp name: " << fname <<std::endl;
        }
        // open dump file
        std::ofstream out(fname);
        if (out.good()) {
            out << b->serialize() << std::endl;
            if (out.good()) {
                if (debug) {
                    std::cout << "plugin 'script' wrote" << std::endl;
                }
                out.close();
                script_send(fname); // send also removes file
                return 0;
            } else {
                std::cout << "script plugin failed write" << std::endl;
                return 1;
            }
        }
        std::filesystem::remove(fname);
        std::cout << "script plugin failed open " <<fname<< std::endl;
        return 1;
    }
 
        int config(const std::map< std::string, std::string >& m) {
        return config(m, plugin_prefix );
    }
 
        int config(const std::map< std::string, std::string >& m, std::string_view env_prefix) {
        string d = get(m, "DIRECTORY", env_prefix);
        string prog = get(m, "PROG", env_prefix);
        string sdebug = get(m, "DEBUG", env_prefix);
        return config(d, prog, sdebug);
    }
 
    const std::map< const std::string, const std::string> & get_option_defaults() {
        return plugin_script_config_defaults;
    }
        
    int initialize() {
        std::map <string, string >m;
        // config if never config'd
        if (!fdir.size())
            config(m);
        if (mode != pi_init) {
            return 2;
        }
        if ( state == err ) {
            std::cout << "script plugin initialize found pre-existing error" << std::endl;
            return 3;
        }
        std::error_code ec;
        std::filesystem::create_directories(fdir, ec);
        if (ec.value() != 0 && ec.value() != EEXIST ) {
            state = err;
            std::cout << "unable to create scratch directory for plugin 'script'; "
                    << fdir << " : " << ec.message() << std::endl;
            return ec.value();
        } else {
            if (debug) {
                std::cout << "created " << fdir <<std::endl;
            }
            mode = pi_pub_or_final;
        }
        return 0;
    }
 
        void finalize() {
        if (mode == pi_pub_or_final) {
            state = ok;
            paused = false;
            mode = pi_config;
        } else {
            if (debug) {
                std::cout << "script plugin finalize on non-running plugin" << std::endl;
            }
        }
    }
 
    void pause() {
        paused = true;
    }
 
        void resume() {
        paused = false;
    }
 
    string_view name() const {
        return "script";
    }
 
    string_view version() const {
        return vers;
    }
 
    ~script_plugin() {
        if (debug) {
            std::cout << "Destructing script_plugin" << std::endl;
        }
    }
};
 
} // adc