CODEWITHSUNDEEP
load-testing
DJG
DJG

Reputation: 6563

What is the difference between a concurrent connection and a concurrent request?

I am trying to do some load testing and I was told that as parameters for testing, I should include both the number of concurrent requests and the number of concurrent connections. I really don't understand how there can be multiple requests on a given connection. When a client requests a webpage from a server, it first opens a connection, sends a request and gets a reponse and then closes a connection. What am I missing here?

UPDATE: I meant to ask how it was possible for a single connection to have multiple requests concurrently (meaning simultaneously.) Otherwise, what would be the point of measuring both concurrent requests and concurrent connections? Would counting both of them be helpful in knowing how many connections are idle at a time? I realize that a single connection can handle more than one request consecutively, sorry for the confusion.

Upvotes: 1

Views: 5683

Answers (2)

CMerrill
CMerrill

Reputation: 1982

HTTP supports a feature called pipelining, which allows the browser to send multiple requests to the server over a single connection without waiting for the responses. The server must support this. IIRC, the server has to send a specific response to the request that indicates "yeah, I'll answer this request, and you can go ahead and send other requests while you're waiting". Last time I looked (many years ago), Firefox was the only browser that supported pipelining and it was turned off by default.

It is also worth noting that even without pipelining, concurrent connections is not equal to concurrent requests, because you can have open connections that are currently idle (no requests pending).

Upvotes: 2

Jeff Storey
Jeff Storey

Reputation: 57202

A server may keep a single connection open to serve multiple requests. See http://en.wikipedia.org/wiki/HTTP_persistent_connection. It describes HTTP persistent (also called keep-alive) connections. The idea is that if you make multiple requests, it removes some of the overhead of setting up and tearing down a new connection.

Upvotes: 0

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