According to the Apache Kafka web site, “Apache Kafka is an open-source distributed event streaming platform used by thousands of companies for high-performance data pipelines, streaming analytics, data integration, and mission-critical applications.”
In recent years, Apache Kafka has seen wide adoption by the astronomy community, notably by the Vera C. Rubin Observatory. GCN operates a highly available cluster of Kafka brokers in the cloud on Amazon Web Services that distributes GCN Notices to users.
The Kafka platform itself does not care about the format of the records. However, Avro and JSON are very common formats for Kafka records because of a rich ecosystem of open-source and commercial tools for them built on Kafka (for example: Kafka Streams, ksqldb, Kafka Connect). The Vera C. Rubin Observatory's alert system uses Avro over the Confluent Wire Format. GCN is developing a unified schema for communicating Notices as JSON records (see roadmap).
See Kafka Client Setup.
Clients connecting to GCN only need to be able to make outbound (egress) TCP connections. The client connects to the following hosts and ports.
What does the warning
Subscribed topic not available: gcn.classic.text.AGILE_GRB_GROUND: Broker: Unknown topic or partition' mean?
This warning means that there have not been any recent alerts on that topic.
Some email clients in some configurations are known to add extra line breaks to emails. When you are preparing to submit a GCN Circular by email, you should always make sure that you are composing a plain text message. See the following instructions for various mail clients:
Note that it used to be common practice for Circulars submitters to add line breaks to manually wrap long paragraphs in GCN Circulars. This practice is no longer recommended in the GCN Circulars style guide.
If you had a GCN Circulars account prior to April 17, 2023, your account was migrated to the new GCN. Your receiving preferences, submitting permission, name and affiliation will be associated with your account as soon as you sign in for the first time. If you choose to sign in via email address and password, tap "Sign up" not "Forgot your password?".
Yes. During a U.S. federal government shutdown, all GCN services (GCN Circulars, GCN Notices, Kafka cluster, the web site) remain fully operational. However, there may be the following minor impacts to GCN users: