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Showing content from https://www.alibabacloud.com/help/en/functioncompute/fc-2-0/user-guide/http-handlers-2 below:

HTTP handlers - Function Compute

This topic describes the structural features, invocation descriptions, and limits of HTTP handlers in a custom runtime. This topic also provides examples on how to use an HTTP handler and links to some frequently asked questions.

Function Compute transparently passes your requests, including methods, paths, queries, request headers, request bodies, and common headers generated by Function Compute to HTTP servers. You can smoothly migrate existing HTTP web applications.

The method that you can use to invoke an HTTP handler is similar to that of a web API operation. You can send a request to invoke an HTTP handler by using cURL, Postman, or a browser. When you use a browser to access an HTTP trigger, a function may be downloaded in a forceful manner. For more information about how to resolve this issue, see When I use a web browser to access a function with an HTTP trigger, why do I need to download the response?

Header

Description

(Optional) x-fc-base-path

If you do not specify a custom domain name, /2016-08-15/proxy/${servicename}/${functionname}/ is used as the value of x-fc-base-path.

(Optional) x-fc-status

This header behaves in a similar manner to a header in an event function. This is applicable to HTTP functions that are not migrated to Function Compute but created by calling a web API operation.

You can include the

field in response headers to report to

whether the local function is successfully invoked.

• If you do not specify a value for the x-fc-status field, Function Compute considers the invocation successful. If an error occurs during function execution, the system does not report the error to Function Compute. In this case, the business logic may not be affected, but the observability of Function Compute is affected. The following figure provides an example.
• If you specify a value for the x-fc-status field, the system reports function invocation failures to Function Compute by using the x-fc-status field. If an error occurs during function invocation, the system records the error stack information in logs. The following figure provides an example.

Note We recommend that you specify the StatusCode and x-fc-status fields in the HTTP response.

• Only one HTTP trigger can be created for an HTTP function in each version or alias of a service. For more information, see Manage versions and Manage aliases.

• Limits on HTTP requests

  • Request headers do not support custom fields that start with x-fc- or the following fields:

    • connection

    • keep-alive

  • The system returns the 400 status code and InvalidArgument error code if a request exceeds one of the following limits:

    • Headers size: The total size of all keys and values in headers cannot exceed 8 KB.

    • Path size: The total size of the path, including all query parameters, cannot exceed 4 KB.

    • Body size: The total size of the body of a synchronous invocation request cannot exceed 32 MB. The total size of the body of an asynchronous invocation request cannot exceed 128 KB.

• HTTP response limits

  • Response headers do not support custom fields that start with x-fc- or the following fields:

    • connection

    • content-length

    • date

    • keep-alive

    • server

    • content-disposition:attachment

      Note

      For security reasons, if you use the default domain name aliyuncs.com of Function Compute, the server forcibly adds the content-disposition: attachment field to response headers. This field makes the returned results to be downloaded as an attachment in a browser. To remove this limit, you must specify a custom domain name. For more information, see Configure a custom domain name.

  • If a response exceeds one of the following limits, the system returns status code 502 and error BadResponse.

    • Headers size: The total size of all keys and values in headers cannot exceed 8 KB.

• Others

  You can bind custom domain names to map different HTTP paths for HTTP functions. For more information, see Configure a custom domain name. You can also use API Gateway to implement similar features by setting the backend service type to HTTP and specifying the HTTP function path as the backend service address. For more information, see Use Function Compute as the backend service of an API operation.

You can use Serverless Devs to migrate your applications to Function Compute with a few clicks. The following example shows how to use Serverless Devs to deploy and invoke a function in an efficient manner. You can modify the sample code based on your business requirements.

• Python

• C++

• Spring Boot

• F#

• Must the listening port of a custom runtime be the same as that of the HTTP server of the custom runtime?

• What do I do if the FunctionNotStarted error occurs when I invoke a third-party service in a service started in a custom runtime?

• What do I do if a function exits unexpectedly and the "Process exited unexpectedly before completing request" message is reported?

• What do I do if a 404 error occurs when I use a browser or the cURL tool to access a function?

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