Client Configuration

pip install gcn-kafka

conda install -c conda-forge gcn-kafka

from gcn_kafka import Consumer

# Connect as a consumer.
# Warning: don't share the client secret with others.
consumer = Consumer(client_id='fill me in',
                    client_secret='fill me in')

# List all topics
print(consumer.list_topics().topics)

# Subscribe to topics and receive alerts
consumer.subscribe(['gcn.classic.text.FERMI_GBM_FIN_POS',
                    'gcn.classic.text.LVC_INITIAL'])
while True:
    for message in consumer.consume():
        value = message.value()
        print(value)

python example.py

npm install gcn-kafka

import { Kafka } from 'gcn-kafka'

// Create a client.
// Warning: don't share the client secret with others.
const kafka = new Kafka({
  client_id: 'fill me in',
  client_secret: 'fill me in',
})

// List topics
const admin = kafka.admin()
const topics = await admin.listTopics()
console.log(topics)

// Subscribe to topics and receive alerts
const consumer = kafka.consumer()
try {
  await consumer.subscribe({
    topics: [
        'gcn.classic.text.FERMI_GBM_FIN_POS',
        'gcn.classic.text.LVC_INITIAL',
    ],
  })
} catch (error) {
  if (error.type === 'TOPIC_AUTHORIZATION_FAILED')
  {
    console.warn('Not all subscribed topics are available')
  } else {
    throw error
  }
}

await consumer.run({
  eachMessage: async (payload) => {
    const value = payload.message.value
    console.log(value?.toString())
  },
})

node example.mjs

npm install gcn-kafka

const { Kafka } = require('gcn-kafka');

(async () => {
  // Create a client.
  // Warning: don't share the client secret with others.
  const kafka = new Kafka({
    client_id: 'fill me in',
    client_secret: 'fill me in',
  })

  // List topics
  const admin = kafka.admin()
  const topics = await admin.listTopics()
  console.log(topics)
  
  // Subscribe to topics and receive alerts
  const consumer = kafka.consumer()
  try {
    await consumer.subscribe({
      topics: [
          'gcn.classic.text.FERMI_GBM_FIN_POS',
          'gcn.classic.text.LVC_INITIAL',
      ],
    })
  } catch (error) {
    if (error.type === 'TOPIC_AUTHORIZATION_FAILED')
    {
      console.warn('Not all subscribed topics are available')
    } else {
      throw error
    }
  }

  await consumer.run({
    eachMessage: async (payload) => {
      const value = payload.message.value
      console.log(value?.toString())
    },
  })
})()

node example.cjs

#include <openssl/bio.h>
#include <openssl/evp.h>
#include <openssl/rand.h>
#include <librdkafka/rdkafka.h>
#include <stdio.h>


int main(int argc, char **argv)
{
  char errstr[512];
  int err;

  // Generate random group ID
  char rand_bytes[256], group_id[2 * sizeof(rand_bytes)] = {'\0'};
  RAND_bytes(rand_bytes, sizeof(rand_bytes));
  BIO *b64 = BIO_new(BIO_f_base64());
  BIO *mem = BIO_new(BIO_s_mem());
  BIO_set_flags(b64, BIO_FLAGS_BASE64_NO_NL);
  BIO_push(b64, mem);
  BIO_write(b64, rand_bytes, sizeof(rand_bytes) - 1);
  BIO_flush(b64);
  BIO_read(mem, group_id, sizeof(group_id) - 1);
  BIO_free_all(b64);

  char *conf_kv[][2] = {
    {"bootstrap.servers", "kafka.gcn.nasa.gov"},
    {"group.id", group_id},
    {"sasl.mechanisms", "OAUTHBEARER"},
    // Warning: don't share the client secret with others.
    {"sasl.oauthbearer.client.id", "fill me in"},
    {"sasl.oauthbearer.client.secret", "fill me in"},
    {"sasl.oauthbearer.method", "oidc"},
    {"sasl.oauthbearer.token.endpoint.url", "https://auth.gcn.nasa.gov/oauth2/token"},
    {"security.protocol", "sasl_ssl"}
  };

  static const char *topics[] = {
    "gcn.classic.text.FERMI_GBM_FIN_POS",
    "gcn.classic.text.LVC_INITIAL"
  };

  static const int num_conf_kv = sizeof(conf_kv) / sizeof(*conf_kv);
  static const int num_topics = sizeof(topics) / sizeof(*topics);

  // Assemble configuration
  rd_kafka_conf_t *conf = rd_kafka_conf_new();
  for (int i = 0; i < num_conf_kv; i ++)
  {
    if (rd_kafka_conf_set(conf, conf_kv[i][0], conf_kv[i][1],
                          errstr, sizeof(errstr)))
    {
      fprintf(stderr, "%s\n", errstr);
      rd_kafka_conf_destroy(conf);
      return 1;
    }
  }

  // Create consumer
  rd_kafka_t *rk = rd_kafka_new(RD_KAFKA_CONSUMER, conf, errstr, sizeof(errstr));
  if (!rk) {
    fprintf(stderr, "%s\n", errstr);
    return 1;
  }
  
  // List topics
  const rd_kafka_metadata_t *metadata;
  err = rd_kafka_metadata(rk, 0, NULL, &metadata, -1);
  if (err) {
    fprintf(stderr, "%s\n", rd_kafka_err2str(err));
    rd_kafka_destroy(rk);
    return 1;
  }
  for (int i = 0; i < metadata->topic_cnt; i ++)
  {
    printf("%s\n", metadata->topics[i].topic);
  }
  rd_kafka_metadata_destroy(metadata);
  
  // Subscribe to topics
  rd_kafka_topic_partition_list_t *topics_partitions =
    rd_kafka_topic_partition_list_new(num_topics);
  for (int i = 0; i < num_topics; i ++)
    rd_kafka_topic_partition_list_add(topics_partitions, topics[i],
                                      RD_KAFKA_PARTITION_UA);
  err = rd_kafka_subscribe(rk, topics_partitions);
  rd_kafka_topic_partition_list_destroy(topics_partitions);
  if (err)
  {
    rd_kafka_destroy(rk);
    fprintf(stderr, "%s\n", rd_kafka_err2str(err));
    return 1;
  }

  // Consume messages
  while (1)
  {
    rd_kafka_message_t *message = rd_kafka_consumer_poll(rk, -1);

    if (!message)
    {
      continue;
    } else if (message->err == RD_KAFKA_RESP_ERR__PARTITION_EOF) {
      // Ignore this error; it just means that we are at the end of the stream
      // and need to wait for more data.
    } else if (message->err == RD_KAFKA_RESP_ERR_UNKNOWN_TOPIC_OR_PART) {
      // Unknown topic or partition; print warning and continue.
      fprintf(stderr, "%s\n", rd_kafka_message_errstr(message));
    } else if (message->err) {
      fprintf(stderr, "%s\n", message->err, rd_kafka_message_errstr(message));
      rd_kafka_consumer_close(rk);
      rd_kafka_destroy(rk);
      return 1;
    } else {
      printf("%.*s\n", message->len, message->payload);
    }

    rd_kafka_message_destroy(message);
  }

  rd_kafka_consumer_close(rk);
  rd_kafka_destroy(rk);

  return 0;
}

gcc $(pkg-config --cflags libcrypto) example.c $(pkg-config --libs libcrypto) -lrdkafka

./a.out

  using Confluent.Kafka;


  var config = new ConsumerConfig
  {
    SecurityProtocol = SecurityProtocol.SaslSsl,
    BootstrapServers = "kafka.gcn.nasa.gov",
    GroupId = Guid.NewGuid().ToString(),
    SaslMechanism = SaslMechanism.OAuthBearer,
    SaslOauthbearerMethod = SaslOauthbearerMethod.Oidc,
    SaslOauthbearerTokenEndpointUrl = "https://auth.gcn.nasa.gov/oauth2/token",
    // Warning: don't share the client secret with others
    SaslOauthbearerClientId = "fill me in",
    SaslOauthbearerClientSecret = "fill me in"
  };

  // Create a client.
  using (var consumer = new ConsumerBuilder<Ignore, string>(config).Build())
  {
    // Subscribe to topics
    consumer.Subscribe(new List<string> {
      "gcn.classic.text.FERMI_GBM_FIN_POS",
      "gcn.classic.text.LVC_INITIAL"
    });

    // List all topics
    consumer.Subscription.ForEach(topic => Console.WriteLine(topic));    
    
    // Consume messages
    while (true)
    {
      try
      {
        var consumeResult = consumer.Consume();
        Console.WriteLine(consumeResult.Message.Value);
      }
      catch (Exception ex)
      {
        if (!ex.Message.Contains("Subscribed topic not available"))
        {
          throw;
        }
      }
    }
  }