maxTotalConnections

maxTotalConnections is a configuration parameter used by resource connection pools to bound the total number of connections that can be open to a resource, such as a database or a remote service. It defines the ceiling for both currently active connections and idle connections that the pool may maintain at any given time. The exact naming and semantics can vary by library; some implementations call it maxTotal, maximumPoolSize, or similar.

In practice, maxTotalConnections controls the pool size. The pool may recycle and reuse connections, but once the limit is reached, new requests must wait for a connection to become available or fail with an error, depending on the pool’s settings for wait timeouts or maximum wait queue length. The value is often complemented by other pool settings such as minIdle, maxIdle, and initialSize, which influence how many connections are kept ready for use.

Choosing a value involves trade-offs. A higher limit can improve throughput under heavy load but risks exhausting the target resource, such as a database, leading to contention or saturation. A lower limit reduces resource usage but may increase latency or cause requests to fail when demand spikes. The optimal bound depends on workload characteristics, connection lifetimes, and the capacity of the underlying resource. Empirical tuning and monitoring are typically required.

Operational considerations include monitoring active and idle connections, wait times, and queue lengths. Start with a conservative value and adjust based on observed saturation and performance. If multiple pools exist, consider per-resource limits and align them with overall capacity to avoid overwhelming shared backends.

See also: maxIdle, minIdle, maxLifetime, connection pool, database connection pool.