Major Description
Improve precision of stats's values
Conversion between types, such as RecInt(int64_t) to RecFloat(float),
may lead to loss of precision.
In the old code, token value was defined with StatFloat type, it would casue
unnecessary conversion when type of token is not StatFloat.
it's best to keep value with the same type of token as much as possiable.
===
For example, we have defined such expression in stats.config.xml:
<statistics>
<destination>proxy.node.http.user_agent_total_request_bytes</destination>
<destination scope="cluster">proxy.cluster.http.user_agent_total_request_bytes</destination>
<expression>
proxy.process.http.user_agent_request_document_total_size +
proxy.process.http.user_agent_request_header_total_size
</expression>
</statistics>
So:
proxy.node.http.user_agent_total_request_bytes = \
proxy.process.http.user_agent_request_document_total_size + \
proxy.process.http.user_agent_request_header_total_size
These three stats token are all RecInt types, but the code would convert them to RecFloat when evaluating the expression, like that:
proxy.node.http.user_agent_total_request_bytes = \
(RecFloat)proxy.process.http.user_agent_request_document_total_size + \
(RecFloat)proxy.process.http.user_agent_request_header_total_size
As a result, we might get the following output from stats http API:
[root@test62 trafficserver]# cat ~/bin/list-cluster.sh elinks -dump http://localhost:8080/stat/ | grep proxy_name elinks -dump http://localhost:8080/stat/ | grep nodes elinks -dump http://localhost:8080/stat/ | grep proxy.process.http.origin_server_request_document_total_size elinks -dump http://localhost:8080/stat/ | grep proxy.process.http.origin_server_request_header_total_size elinks -dump http://localhost:8080/stat/ | grep proxy.node.http.origin_server_total_request_bytes [root@test62 trafficserver]# list-cluster.sh proxy.config.proxy_name=test62.63 proxy.node.cluster.nodes=1 proxy.process.cluster.nodes=1 proxy.process.http.origin_server_request_document_total_size=0 <= #1 proxy.process.http.origin_server_request_header_total_size=359209123 <= #2 proxy.node.http.origin_server_total_request_bytes=359209120 <= #3 != (#1 + #2)
As the value increasing, the loss of precision will become more and more seriously.