man package:http-client

Number of connections to a single host to keep alive. Default: 10. Since 0.1.0
Total number of idle connection to keep open at a given time. This limit helps deal with the case where you are making a large number of connections to different hosts. Without this limit, you could run out of file descriptors. Additionally, it can be set to zero to prevent reuse of any connections. Doing this is useful when the server your application is talking to sits behind a load balancer. Default: 512 Since 0.3.7
Perform the given modification to a Request before performing it. This function may be called more than once during request processing. see https://github.com/snoyberg/http-client/issues/350 Default: no modification Since 0.4.4
Perform the given modification to a Response after receiving it. Default: no modification
Create an insecure connection. Since 0.1.0
Default timeout to be applied to requests which do not provide a timeout value. Default is 30 seconds
Exceptions for which we should retry our request if we were reusing an already open connection. In the case of IOExceptions, for example, we assume that the connection was closed on the server and therefore open a new one. Since 0.1.0
Set the proxy override value, only for HTTP (insecure) connections. Since 0.4.7
Set the proxy override value, for both HTTP (insecure) and HTTPS (insecure) connections. Since 0.4.7
Set the proxy override value, only for HTTPS (secure) connections. Since 0.4.7
Create a TLS connection. Default behavior: throw an exception that TLS is not supported. Since 0.1.0
Action wrapped around all attempted Requests, usually used to wrap up exceptions in library-specific types. Default: wrap all IOExceptions in the InternalException constructor.
Configure the maximum size, in bytes, of an HTTP header field. Default: 4096
Configure the maximum number of HTTP header fields. Default: 100
How HTTP proxy server settings should be discovered. Default: respect the proxy value on the Request itself. Since 0.4.7
How HTTPS proxy server settings should be discovered. Default: respect the proxy value on the Request itself. Since 0.4.7
Create a TLS proxy connection. Default behavior: throw an exception that TLS is not supported. Since 0.2.2
Keeps track of open connections for keep-alive. If possible, you should share a single Manager between multiple threads and requests. Since 0.1.0
Settings for a Manager. Please use the defaultManagerSettings function and then modify individual settings. For more information, see http://www.yesodweb.com/book/settings-types. Since 0.1.0