Database

Problem: The client operates a 6-node multi-DC replication setup for Cassandra, consisting of 3 nodes in the PROD datacenter and 3 nodes in the DR datacenter. They are planning to perform DDL changes, including altering tables to adjust the default_time_to_live parameter and dropping and recreating a table with a new definition. However, they are unsure […]

Problem: The client encountered a critical issue while starting one of their production pods during a Cassandra migration. Although the PostgreSQL migration completed successfully, the Cassandra migration failed with a com.datastax.oss.driver.api.core.AllNodesFailedException, indicating that the driver could not connect to any Cassandra nodes. This blocked the production deployment. Process: Step 1: Initial Analysis The logs revealed […]

Problem: A client managing a multi-datacenter Apache Cassandra setup observed an inconsistency in rack configuration between two datacenters. In the primary datacenter (`dc1`), all three nodes were configured with the same rack identifier (`rack1`), whereas in the secondary datacenter (`drdc`), each node was correctly configured with unique rack values (`rack1`, `rack2`, `rack3`). This raised concerns […]

Problem: The client encountered a critical issue in their Apache Cassandra setup: the Disaster Recovery (DR) cluster was consuming significantly more filesystem (FS) space than the primary cluster, despite having the same data replication strategy. As a result, one of the DR nodes hit 100% disk usage, causing the replica to go down. The client […]

Problem: The client wanted to integrate Apache Cassandra metrics into Prometheus for monitoring and alerting. While using JMX Exporter with Node Exporter, they noticed that too many unwanted metrics were being fetched. This resulted in performance issues such as delayed response times from the curl command and unnecessary load on Prometheus. Additionally, key metrics like […]

Problem: A client from the telecommunications sector encountered critical issues while attempting to deploy a new Apache Cassandra cluster on AWS. After unpacking the Cassandra tarball and attempting to start the service manually, the Cassandra process failed to initialize due to a Java memory allocation error. The error indicated that the Java Virtual Machine (JVM) […]

Problem: The client reported that they had deployed a billing system for one of their customers, which uses PostgreSQL 15 within a high availability cluster managed by Patroni. As the system entered production, the customer requested that sensitive data within the database tables (such as names, addresses, phone numbers, and card information) be encrypted or […]

Problem: The client experienced a failover event in their PostgreSQL cluster managed by Patroni, between 01:00 and 02:00 AM. Process: Step 1: Initial Investigation Initial logs from PostgreSQL (postgresql-Fri-00.log and postgresql-Fri-01.log) revealed regular query activity. This included frequent queries from monitoring tools (pg_stat_all_tables, pg_locks, etc.), checkpoint logging, and client connection messages. There were no immediate […]

Problem: The client encountered a persistent issue related to file descriptor exhaustion on their PostgreSQL version 15 database, running on a Patroni High Availability cluster with RHEL 8.10. The PostgreSQL logs frequently reported the error: “out of file descriptors: Too many open files; release and retry” during database operations. Although the client had significantly increased […]