You cancel the request when the function finishes using defer. The context is independent of the request and it will reach it's deadline unless, cancelled previously. The deadline applies to all future 339 // and pending I/O, not just the immediately following call to 340 // Read or Write. 336 // 337 // A deadline is an absolute time after which I/O operations 338 // fail instead of blocking. It is equivalent to calling both 335 // SetReadDeadline and SetWriteDeadline. This means the goroutine won't hang around forever if the ch receive happens before the timeout is reached. The goroutine doesn't know (or care) whether the value is received. The timeout channel is buffered with space for 1 value, allowing the timeout goroutine to send to the channel and then exit. We could go on streaming like this forever without risk of getting stuck. In the example above, we put a timeout of 5 seconds on the Do phases of the request, but then we spend at least 8 seconds reading the body in 8 rounds, each time with a timeout of 2 seconds. On files that support SetDeadline, any pending I/O operations will be canceled and return immediately with an error. Close closes the File, rendering it unusable for I/O. Instead of setting a timeout directly on the read, you can close the os.File after a timeout. It's critical for an HTTP server exposed to the Internet to enforce timeouts on client connections. The "So you want to expose Go on the Internet" post has more information on server timeouts, in particular about HTTP/2 and Go 1.7 bugs. Rather than closing a socket connection after an HTTP request, it will add it to an idle connection pool, and if you try to make another HTTP request before the idle connection timeout (90 seconds by default), then it will re-use that existing connection rather than creating a new one. type Context interface defer () From the http.Client documentation: If the returned error is nil, the Response will contain a non-nil Body which the user is expected to close.Įven though the server may have decided to close its end of the connection, the connection is still open on our client side and it will stay that way until an attempt to read from it is made (at which point the client will detect that the other end is closed).īy default, the Golang HTTP client will do connection pooling. Context's methods may be called by multiple goroutines simultaneously. net/http offers two ways to cancel a client request: Request.Cancel and, new in 1.7, Context.Ī Context carries a deadline, a cancellation signal, and other values across API boundaries. includes all time spent following redirects, while the granular timeouts are specific for each request, since http.Transport is a lower level system that has no concept of redirects. You then do a select and either wait 10 seconds or wait for the context to finish. Let's say that request returns in 2 seconds. You pass it to the request and make that request. If you have one or more functions called frequently that all create temporary http.Clients, they could all leave connections open and consume too much memory or too many file descriptors and won’t be able to open any more files or connections.ĬloseIdleConnections should resolve that scenario, but I’d recommend keeping the same http.Client around so that you don’t need to make a new one every time.You create a context with 5 seconds timeout. Garbage collection will eventually clean up the memory and idle connections, but it’s not deterministic. Also, exiting the function, is not the garbage collector supposed to clear any memory used by the clinet, and thus any iddle connections ?
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