Fixed input stream in mode serializing

[mslaga]

Signed-off-by: Michał Ślaga github@blinder.pl

ContentLength is optional in the HTTP header and cannot specify how much data will be copied to process. https://golang.org/src/net/http/request.go?s=12527:12599 // The value -1 indicates that the length is unknown.

and copy stderr to logs - it will be helpful for troubleshooting with function.

Description

Copy the req.InputReader stream to stdin in loop until EOF is reached.

Motivation and Context

Not works on slow machines like raspberry pi

https://github.com/openfaas/of-watchdog/issues/123

• [x ] I have raised an issue to propose this change ([required]

How Has This Been Tested?

In my case, on raspberry pi, the function always fails because of ContentLength -1

Types of changes

• [x ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [ x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x ] I've read the CONTRIBUTION guide
• [x ] I have signed-off my commits with git commit -s
• [ ] I have added tests to cover my changes.
• [x ] All new and existing tests passed.

[alexellis]

I think I understand the challenge here.

Ideally, we want a setting to configure a maximum payload size for this mode. If you are running out of resources on an RPi, you should use the streaming or HTTP modes.