Least Connections Calculator
Model how least-connections balancing shifts new requests away from slow servers, and the arrival rate each member ends up with.
Inputs
Connections Held per Server
700
New Connections to a Healthy Server
562.5cps
New Connections to a Slow Server
187.5cps
Healthy-to-Slow Arrival Ratio
3.00×
Assessment
Least connections is correctly shedding load from the slow members
Step by step
Values used
Active connections across the pool = 4,200 connections; Servers in the pool = 6 servers; Servers responding slowly = 1 servers; How much longer a slow server holds a connection = 3 ×; New connections per second = 3,000 cps
Least Connections
least connections equalises held connections, so each server's arrival rate is inversely proportional to its hold time: rate_i = λ ÷ Σ(1 ÷ factor_j).
Connections Held per Server
= 700
New Connections to a Healthy Server
= 562.5 cps
New Connections to a Slow Server
= 187.5 cps
Healthy-to-Slow Arrival Ratio
= 3.00 ×
Assessment
= Least connections is correctly shedding load from the slow members
How it works
Because the algorithm always picks the member with the fewest live connections, connection counts converge to equal across the pool. Little's law then forces the arrival rate to be inversely proportional to hold time, so a server that takes three times as long receives a third of the new connections. Least connections is self-correcting for slow servers, which is exactly why it hides them — a member can be badly degraded and still look healthy because its connection count matches everyone else's.
Formula
Least Connections
least connections equalises held connections, so each server's arrival rate is inversely proportional to its hold time: rate_i = λ ÷ Σ(1 ÷ factor_j).
- factor
- Ratio of the slow server's hold time to a healthy one
- weight
- Sum of inverse hold times across the pool
Frequently Asked Questions
How is Least Connections calculated?
least connections equalises held connections, so each server's arrival rate is inversely proportional to its hold time: rate_i = λ ÷ Σ(1 ÷ factor_j). Because the algorithm always picks the member with the fewest live connections, connection counts converge to equal across the pool. Little's law then forces the arrival rate to be inversely proportional to hold time, so a server that takes three times as long receives a third of the new connections.
Why does Least Connections matter?
Least connections is self-correcting for slow servers, which is exactly why it hides them — a member can be badly degraded and still look healthy because its connection count matches everyone else's.
What values do I need to enter?
This calculator takes 5 inputs: Active connections across the pool, Servers in the pool, Servers responding slowly, How much longer a slow server holds a connection, New connections per second. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.
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