// The contents of this file are subject to the BOINC Public License
// Version 1.0 (the "License"); you may not use this file except in
// compliance with the License. You may obtain a copy of the License at
// http://boinc.berkeley.edu/license_1.0.txt
//
// Software distributed under the License is distributed on an "AS IS"
// basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
// License for the specific language governing rights and limitations
// under the License.
//
// The Original Code is the Berkeley Open Infrastructure for Network Computing.
//
// The Initial Developer of the Original Code is the SETI@home project.
// Portions created by the SETI@home project are Copyright (C) 2002
// University of California at Berkeley. All Rights Reserved.
//
// Contributor(s):
//

// -------------------------------
//
// feeder [-asynch] [-d debug_level]
// -asynch      fork and run in a separate process
//
// Creates a shared memory segment containing DB info,
// including the work array (results/workunits to send).
// This means that the scheduler CGI program doesn't have to
// access the DB to get this info.
//
// Try to keep the work array filled.
// This is a little tricky.
// We use an enumerator.
// The inner loop scans the wu_result table,
// looking for empty slots and trying to fill them in.
// When the enumerator reaches the end, it is restarted;
// hopefully there will be some new workunits.
// There are two complications:
//
//  - An enumeration may return results already in the array.
//    So, for each result, we scan the entire array to make sure
//    it's not there already.  Can this be streamlined?
//
//  - We must avoid excessive re-enumeration,
//    especially when the number of results is less than the array size.
//    Crude approach: if a "collision" (as above) occurred on
//    a pass through the array, wait a long time (5 sec)
//
// Checking for infeasible results (i.e. can't sent to any host):
//
// - the "infeasible_count" field of WU_RESULT keeps track of
//   how many times the WU_RESULT was infeasible for a host
//
// - the scheduler gives priority to results that have infeasible_count > 0
//
// - If the infeasible_count of any result exceeds MAX_INFEASIBLE_COUNT,
//   the feeder flags the result as OVER with outcome COULDNT_SEND,
//   and flags the WU for the transitioner.
//
// - the feeder tries to ensure that the number of WU_RESULTs
//   with infeasible_count  > MAX_INFEASIBLE_THRESHOLD
//   doesn't exceed MAX_INFEASIBLE (defined in sched_shmem.h)
//   If it does, then the feeder picks the WU_RESULT with
//   the largest infeasible_count, marks if COULDNT_SEND as above,
//   and repeats this until the infeasible count is low enough again

// Trigger files:
// The feeder program periodically checks for two trigger files:
//
// stop_server:  destroy shmem and exit
//               leave trigger file there (for other daemons)
// reread_db:    update DB contents in existing shmem
//               delete trigger file

// If you get an "Invalid argument" error when trying to run the feeder,
// it is likely that you aren't able to allocate enough shared memory.
// Either increase the maximum shared memory segment size in the kernel
// configuration, or decrease the MAX_PLATFORMS, MAX_APPS
// MAX_APP_VERSIONS, and MAX_WU_RESULTS in sched_shmem.h

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif

#include "boinc_db.h"
#include "shmem.h"
#include "util.h"
#include "sched_config.h"
#include "sched_shmem.h"
#include "sched_util.h"

#define MAX_INFEASIBLE_COUNT    50

#define REREAD_DB_FILENAME      "reread_db"
#define LOCKFILE                "feeder.out"
#define PIDFILE                 "feeder.pid"

SCHED_CONFIG config;

SCHED_SHMEM* ssp;

void cleanup_shmem() {
    detach_shmem((void*)ssp);
    destroy_shmem(config.shmem_key);
}

int check_reread_trigger() {
    FILE* f;
    f = fopen(REREAD_DB_FILENAME, "r");
    if (f) {
        fclose(f);
        ssp->init();
        ssp->scan_tables();
        unlink(REREAD_DB_FILENAME);
    }

    return 0;
}

static int remove_infeasible(int i) {
    int retval;
    DB_RESULT result;
    DB_WORKUNIT wu;

    WU_RESULT& wu_result = ssp->wu_results[i];
    wu_result.present = false;      // mark as absent
    result = wu_result.result;
    wu = wu_result.workunit;

    log_messages.printf(
        SchedMessages::NORMAL,
        "[%s] declaring result as unsendable; infeasible count %d\n",
        result.name, wu_result.infeasible_count
    );

    result.server_state = RESULT_SERVER_STATE_OVER;
    result.outcome = RESULT_OUTCOME_COULDNT_SEND;
    retval = result.update();
    if (retval) {
        log_messages.printf(
            SchedMessages::CRITICAL,
            "[%s]: can't update: %d\n",
            result.name, retval
        );
        return retval;
    }
    wu.transition_time = time(0);
    retval = wu.update();
    if (retval) {
        log_messages.printf(
            SchedMessages::CRITICAL,
            "[%s]: can't update: %d\n",
            wu.name, retval
        );
        return retval;
    }

    return 0;
}

static void scan_work_array(
    DB_RESULT& result, char* clause,
    int& nadditions, int& ncollisions, int& ninfeasible,
    bool& no_wus
) {
    int i, j, retval;
    DB_WORKUNIT wu;
    bool collision, restarted_enum = false;

    for (i=0; i<ssp->nwu_results; i++) {
        WU_RESULT& wu_result = ssp->wu_results[i];
        if (wu_result.present) {
            if (wu_result.infeasible_count > MAX_INFEASIBLE_COUNT) {
                remove_infeasible(i);
            } else if (wu_result.infeasible_count > MAX_INFEASIBLE_THRESHOLD) {
                ninfeasible++;
            }
        } else {
try_again:
            retval = result.enumerate(clause);
            if (retval) {

                // if we already restarted the enum on this array scan,
                // there's no point in doing it again.
                //
                if (restarted_enum) {
                    log_messages.printf(SchedMessages::DEBUG,
                        "already restarted enum on this array scan\n"
                    );
                    break;
                }

                // restart the enumeration
                //
                restarted_enum = true;
                retval = result.enumerate(clause);
                log_messages.printf(SchedMessages::DEBUG,
                    "restarting enumeration\n"
                );
                if (retval) {
                    log_messages.printf(SchedMessages::DEBUG,
                        "enumeration restart returned nothing\n"
                    );
                    no_wus = true;
                    break;
                }
            }

            // there's a chance this result was sent out
            // after the enumeration started.
            // So read it from the DB again
            //
            retval = result.lookup_id(result.id);
            if (retval) {
                log_messages.printf(SchedMessages::NORMAL,
                    "[%s] can't reread result: %d\n", result.name, retval
                );
                goto try_again;
            }
            if (result.server_state != RESULT_SERVER_STATE_UNSENT) {
                log_messages.printf(
                    SchedMessages::NORMAL,
                    "[%s] RESULT STATE CHANGED\n",
                    result.name
                );
                goto try_again;
            }
            collision = false;
            for (j=0; j<ssp->nwu_results; j++) {
                if (ssp->wu_results[j].present
                    && ssp->wu_results[j].result.id == result.id
                ) {
                    ncollisions++;
                    collision = true;
                    break;
                }
            }
            if (!collision) {
                log_messages.printf(
                    SchedMessages::NORMAL,
                    "[%s] adding result in slot %d\n",
                    result.name, i
                );
                retval = wu.lookup_id(result.workunitid);
                if (retval) {
                    log_messages.printf(
                        SchedMessages::CRITICAL,
                        "[%s] can't read workunit #%d: %d\n",
                        result.name, result.workunitid, retval
                    );
                    continue;
                }
                wu_result.result = result;
                wu_result.workunit = wu;
                wu_result.present = true;
                wu_result.infeasible_count = 0;
                nadditions++;
            }
        }
    }
}

static int remove_most_infeasible() {
    int i, max, imax=-1;

    max = 0;
    for (i=0; i<ssp->nwu_results; i++) {
        WU_RESULT& wu_result = ssp->wu_results[i];
        if (wu_result.present && wu_result.infeasible_count > max) {
            imax = i;
            max = wu_result.infeasible_count;
        }
    }
    if (max == 0) return -1;        // nothing is infeasible

    return remove_infeasible(imax);
}

void feeder_loop() {
    int i, n, retval, nadditions, ncollisions, ninfeasible;
    DB_RESULT result;
    bool no_wus;
    char clause[256];

    sprintf(clause, "where server_state=%d order by random",
        RESULT_SERVER_STATE_UNSENT
    );

    while (1) {
        nadditions = 0;
        ncollisions = 0;
        ninfeasible = 0;
        no_wus = false;

        scan_work_array(
            result, clause, nadditions, ncollisions, ninfeasible, no_wus
        );

        ssp->ready = true;

        if (ninfeasible > MAX_INFEASIBLE) {
            n = ninfeasible - MAX_INFEASIBLE;
            for (i=0; i<n; i++ ) {
                retval = remove_most_infeasible();
                if (retval) break;
            }
        }
        if (nadditions == 0) {
            log_messages.printf(SchedMessages::DEBUG, "No results added; sleeping 1 sec\n");
            sleep(1);
        } else {
            log_messages.printf(SchedMessages::DEBUG, "Added %d results to array\n", nadditions);
        }
        if (no_wus) {
            log_messages.printf(SchedMessages::DEBUG, "No results available; sleeping 5 sec\n");
            sleep(5);
        }
        if (ncollisions) {
            log_messages.printf(SchedMessages::DEBUG, "Some results already in array - sleeping 5 sec\n");
            sleep(5);
        }
        fflush(stdout);
        check_stop_trigger();
        check_reread_trigger();
    }
}

int main(int argc, char** argv) {
    int i, retval;
    bool asynch = false;
    void* p;

    unlink(REREAD_DB_FILENAME);

    retval = config.parse_file("..");
    if (retval) {
        log_messages.printf(SchedMessages::CRITICAL, "can't parse config file\n");
        exit(1);
    }

    for (i=1; i<argc; i++) {
        if (!strcmp(argv[i], "-asynch")) {
            asynch = true;
        } else if (!strcmp(argv[i], "-d")) {
            log_messages.set_debug_level(atoi(argv[++i]));
        }
    }

    if (asynch) {
        if (fork()!=0) {
            exit(0);
        }
    }

#if 0
    // Call lock_file after fork(), because file locks are not always inherited
    //
    if (lock_file(LOCKFILE)) {
        log_messages.printf(SchedMessages::NORMAL, "Another copy of feeder is already running\n");
        exit(1);
    }
    write_pid_file(PIDFILE);
#endif

    log_messages.printf(SchedMessages::NORMAL, "Starting\n");

    retval = destroy_shmem(config.shmem_key);
    if (retval) {
        log_messages.printf(SchedMessages::CRITICAL, "can't destroy shmem\n");
        exit(1);
    }
    retval = create_shmem(config.shmem_key, sizeof(SCHED_SHMEM), &p);
    if (retval) {
        log_messages.printf(SchedMessages::CRITICAL, "can't create shmem\n");
        exit(1);
    }
    ssp = (SCHED_SHMEM*)p;
    ssp->init();

    atexit(cleanup_shmem);
    install_stop_signal_handler();

    retval = boinc_db.open(config.db_name, config.db_host, config.db_user, config.db_passwd);
    if (retval) {
        log_messages.printf(SchedMessages::CRITICAL, "boinc_db.open: %d; %s\n", retval, boinc_db.error_string());
        exit(1);
    }
    ssp->scan_tables();

    log_messages.printf(
        SchedMessages::NORMAL,
        "feeder: read "
        "%d platforms, "
        "%d apps, "
        "%d app_versions\n",
        ssp->nplatforms,
        ssp->napps,
        ssp->napp_versions
    );

    feeder_loop();
}