HttpComponents PoolingHttpClientConnectionManager maxPerRoute and maxTotal?

Question

Can someone explain to me what setMaxPerRoute(max) and setMaxTotal(max) do with respect to the HttpComponents PoolingHttpClientConnectionManager?

Answer 1

These options control the size of the connection pool.

• setMaxTotal(max) defines the connection limit for the connection pool.
• setMaxPerRoute(max) defines the connection restriction on one HTTP route. In simple cases, you can understand this as a limitation on the end host. Under the hood, everything looks a little more interesting: HttpClient supports a couple of HttpRoute objects that represent each host chain, for example proxy1 -> proxy2 -> targetHost . Connections are united according to the route principle. In simple cases, when you use the default route-building mechanism and do not support a proxy server, your routes will most likely include only the target host, so limiting the connection pool by route effectively becomes the limit for each node.

Example:

Suppose you have setMaxPerRoute(5) and setMaxTotal(20) . This means that you can use up to 5 connections for each target host at the same time: 5 connections to google.com, 5 more connections to oracle.com, etc. The total amount of open connections cannot exceed 20, regardless of the number of hosts with which you communicate.