HTTP Client: Increase max conns and reqs

With Redfish Aggregation there is a need for a large amount of
requests to be sent to a satellite BMC.  Our current throughput of
4 connections with a 50 request buffer can be easily overwhelmed due
to the use of $expand.  Also, BMCWeb itself can support 100 active
connections so multiple clients could be attempting to query a
satellite BMC that is being aggregated.

Increase the maximum number of connections to a destination to 20 and
increase the buffer request size to 500.  These figures should be fine
since the requests themselves have a very small memory footprint and
the number of active connections is only a fifth of what the BMCWeb
in the satellite BMC should be able to support.

Note that these figures are an improvement over the current values.
They allowed making multi-level $expand requests without dropping any
subrequests due to the buffer becoming full.  Further tuning will be
done in a future patch if it is determined that optimal performance can
be obtained by choosing different values.

Tested:
Debug logs after sending a multi-level $expand query showed the entire
connection pool being filled as well as well over 100 Requests being
queued.  The additional connections provided enough throughput to
handle repeated simultaneous requests.

Signed-off-by: Carson Labrado <clabrado@google.com>
Change-Id: I96f165b5fbc76086e55b65faaaa49eb2753f8ef6

1 files changed, 4 insertions, 3 deletions

diff --git a/http/http_client.hpp b/http/http_client.hpp
index a2cd62eb8d..c902e1a66b 100644
--- a/http/http_client.hpp
+++ b/http/http_client.hpp
@@ -50,9 +50,10 @@
 namespace crow
 {
 
-// It is assumed that the BMC should be able to handle 4 parallel connections
-constexpr uint8_t maxPoolSize = 4;
-constexpr uint8_t maxRequestQueueSize = 50;
+// With Redfish Aggregation it is assumed we will connect to another instance
+// of BMCWeb which can handle 100 simultaneous connections.
+constexpr size_t maxPoolSize = 20;
+constexpr size_t maxRequestQueueSize = 500;
 constexpr unsigned int httpReadBodyLimit = 131072;
 constexpr unsigned int httpReadBufferSize = 4096;