# tangle accelerator and rabbitmq c client

tangle-accelerator/accelerator/common_core.c

mux.handle("/transaction")
api_send_transfer (accelerator/apis.c)
-> ta_send_transfer (accelerator/common_core.c)
-> -> ta_send_trytes (accelerator/common_core.c)
-> -> -> ta_attach_to_tangle (accelerator/common_core.c)
-> -> -> -> ta_pow (utils/pow.c)

const attachToTangle = async (req, callback) => {
    if (req.body.minWeightMagnitude > MWM_LIMIT) {
        callback(new Error(`Error: 'minWeightMagnitude' exceeds limit of ${MWM_LIMIT}`));
        return;
    }

    const { channel } = req.rabbit;

    let messageId;

    try {
        messageId = await job.create(JSON.stringify(req.body));
    } catch (e) {
        console.error(e);

        callback(e);

        return;
    }

    await channel.assertQueue(INCOMING_QUEUE);

    await channel.sendToQueue(INCOMING_QUEUE, asBuffer(req.body), {
        messageId,
        appId: process.env.AMQP_APP_ID
    });

    log.info({
        queue: INCOMING_QUEUE,
        name: 'job-request-ok',
        jobId: messageId
    });

    callback(null, { jobId: messageId });
};

https://github.com/iotaledger/powbox/blob/ae003df500e47f4a8f59650f7056d48277a2ec69/src/server/commands.js#L15

rabbitmq-c/examples/amqp_connect_timeout.c
https://github.com/alanxz/rabbitmq-c/blob/master/examples/amqp_connect_timeout.c

amqp_rpc_reply_t amqp_login(amqp_connection_state_t state, char const *vhost,
                            int channel_max, int frame_max, int heartbeat,
                            int sasl_method, ...) 

docker-compose run -d -p 5672:5672 rabbitmq

https://github.com/iotaledger/powbox

Work Queues
https://www.rabbitmq.com/tutorials/tutorial-two-python.html
* Message acknowledgment
* ack
* In order to make sure a message is never lost, RabbitMQ supports message acknowledgments. An ack(nowledgement) is sent back by the consumer to tell RabbitMQ that a particular message had been received, processed and that RabbitMQ is free to delete it.
* re-queue

* Message durability
* message persistence
* Marking messages as persistent doesn't fully guarantee that a message won't be lost. Although it tells RabbitMQ to save the message to disk, there is still a short time window when RabbitMQ has accepted a message and hasn't saved it yet. Also, RabbitMQ doesn't do fsync(2) for every message -- it may be just saved to cache and not really written to the disk. The persistence guarantees aren't strong,

* Fair dispatch
* prefetch_count=1
* it will dispatch it to the next worker that is not still busy.

https://github.com/apre/rabbitmq-c/blob/examples-tutorial/examples/new_task.c

https://github.com/apre/rabbitmq-c/blob/examples-tutorial/examples/worker.c

dcurl_entry
https://github.com/DLTcollab/tangle-accelerator/blob/1f45b35fcaaa5f1fb5e8d4e097c68fe78b4092e0/utils/pow.c#L11
* FPGA dcurl
* threads = 0
* transaction tryes
* mwm

rabbitmq-c/librabbitmq/amqp.h, https://github.com/alanxz/rabbitmq-c/blob/257d2918271e9fa3bf32170dc0d8a49ac323392f/librabbitmq/amqp.h

res = amqp_consume_message(conn, &envelope, NULL, 0);
* amqp_envelope_t envelope;

/**
 * Envelope object
 *
 * \since v0.4.0
 */
typedef struct amqp_envelope_t_ {
  amqp_channel_t channel; /**< channel message was delivered on */
  amqp_bytes_t
      consumer_tag;      /**< the consumer tag the message was delivered to */
  uint64_t delivery_tag; /**< the messages delivery tag */
  amqp_boolean_t redelivered; /**< flag indicating whether this message is being
                                 redelivered */
  amqp_bytes_t exchange;      /**< exchange this message was published to */
  amqp_bytes_t
      routing_key; /**< the routing key this message was published with */
  amqp_message_t message; /**< the message */
} amqp_envelope_t;

amqp_basic_publish

status = amqp_basic_publish(conn,
                                    1,
                                    amqp_cstring_bytes(exchange),
                                    amqp_cstring_bytes(queueName),
                                    0,
                                    0,
                                    &props,
                                    amqp_cstring_bytes(messagebody));

*
amqp_bytes_t
amqp_pool_alloc

Compatibility and Conformance
https://www.rabbitmq.com/specification.html