4/20/2023 0 Comments Golang http client timeout![]() The biggest problem with the above example is that the number of connections to the server is not controlled. customize the maximum number of connections to a particular host However, at this time the behavior of our custom http.Client instance client is no different from that of DefaultClient, to solve the problem of the above example panic, we also need to do a progressive behavior customization of the new custom client instance. The difference is that the application of our custom http.Client instance is limited to the above specific scope and will not have any effect on other packages using the http default client. Therefore a better solution would be to define an instance of the http client for a small range of applications.Ĭlient := &http.Client // 自定义一个http客户端实例 So how do we control the behavior of the client to avoid completing client-sending tasks in resource-constrained contexts? We do this by setting the relevant properties of http.DefaultClient, but DefaultClient is a package-level variable that is shared throughout the application, and once its properties are modified, other packages that use the http default client will also be affected. Defining http client instances for small-scale applications Since the sample runtime environment allows a maximum of 256 open file descriptors per process, a “socket: too many open files” error occurs when the client establishes a connection to the server at a later stage. However, due to the context of the server’s 10s delayed reply in the above example, the client does not wait for the reply to come back by default, but tries to establish a new connection to send a new http request. We know that by default, http clients maintain connections and reuse connections to services on the same host. ![]() Let’s use a diagram to describe the situation in the above example. The value of ulimit -n in the above demo environment is 256 We see that the client above throws a panic, prompting: too many open file descriptors. Users/tonybai/Go/src//bigwhite/experiments/http-client/default-client/client.go:14 +0x78 Users/tonybai/Go/src//bigwhite/experiments/http-client/default-client/client.go:18 +0x1c7 Normally we would use this method when we only want to put a timeout for a http request only client := http.Panic: Get " dial tcp :8080: socket: too many open files You can also read about it here Specify timeout when tracing HTTP request in Go If you want to specialise your deadline/timeout to each request then use context, otherwise if you want 1 timeout for every outbound request then using client timeout is enough. Using context is request specific, while using the Client timeout might be applied to all request pass to Do method client has. Using context you can also pass any values through it describing request scope values. In this case the preferable method is using the context timeout as you have more control over it, you can use cancel without specifying timeout in case you want to cancel the request by logic decision. You have to pick one for timeout at the time creating the request as the the request will pick the smaller timeout to be applied, rendering other useless. The field timeout exist before context added to Go. Both can achieve the same thing which is to terminate the request due to timeout.īut using context is the preferred way as it's made for this task.
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