1 /**

     2  * Relational pipes

     3  * Copyright © 2020 František Kučera (Frantovo.cz, GlobalCode.info)

     4  *

     5  * This program is free software: you can redistribute it and/or modify

     6  * it under the terms of the GNU General Public License as published by

     7  * the Free Software Foundation, version 3 of the License.

     8  *

     9  * This program is distributed in the hope that it will be useful,

    10  * but WITHOUT ANY WARRANTY; without even the implied warranty of

    11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

    12  * GNU General Public License for more details.

    13  *

    14  * You should have received a copy of the GNU General Public License

    15  * along with this program. If not, see <http://www.gnu.org/licenses/>.

    16  */

    17 

    18 #include "streamlet-common.h"

    19 

    20 #include <unistd.h>

    21 

    22 /**

    23  * This streamlet is useful only for debugging or study purposes.

    24  * 

    25  * It provides two attributes:

    26  *  - pid_streamlet: getpid()

    27  *  - pid_worker: getppid()

    28  *	

    29  * Can be used for studying how the parallelism works:

    30  *  - Each instance of streamlet (each --streamlet pid) will have different pid_streamlet.

    31  *  - Each worker (their number = X in --parallelism X) will have different pid_worker.

    32  * 

    33  * So we can check how evenly the work has been distributed across processes (e.g. do some GROUP BY in SQL).

    34  */

    35 class PidStreamlet : public Streamlet {

    36 

    37 	std::vector<AttributeMetadata> getOutputAttributesMetadata() override {

    38 		std::vector<AttributeMetadata> oam;

    39 		int i = 0;

    40 		oam.push_back({getAlias(i++, L"pid_streamlet"), INTEGER});

    41 		oam.push_back({getAlias(i++, L"pid_worker"), INTEGER});

    42 		return oam;

    43 	}

    44 

    45 	std::vector<OutputAttribute> getOutputAttributes() override {

    46 		std::vector<OutputAttribute> oa;

    47 		oa.push_back({std::to_wstring(getpid()), false});

    48 		oa.push_back({std::to_wstring(getppid()), false});

    49 		return oa;

    50 	}

    51 };

    52 

    53 STREAMLET_RUN(PidStreamlet)