Rewind the request body for retries

[srikanthccv]

Fixes #193

prepareRequest in HTTP Sender returns a http.Request

opamp-go/client/internal/httpsender.go

Line 201 in deb3388

func (h *HTTPSender) prepareRequest(ctx context.Context) (*http.Request, error) {

We have the backoff retry strategy for failed requests; however, underlying transport would close the request body and should be rewound for any subsequent attempt. This creates a thin wrapper around the http.Request that helps to rewind the body before making a request. We hijack and close the underlying connection to simulate the connection error case.

[codecov]

Codecov Report

Patch coverage is 89.33% of modified lines.

Files Changed	Coverage
client/types/callbacks.go	ø
server/httpconnection.go	0.00%
server/wsconnection.go	ø
client/internal/mockserver.go	85.71%
client/internal/httpsender.go	88.00%
client/httpclient.go	100.00%
client/internal/clientcommon.go	100.00%
client/internal/receivedprocessor.go	100.00%
server/callbacks.go	100.00%
server/serverimpl.go	100.00%

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[tigrannajaryan]

Since the code has changed, do you mind squashing into one commit and updating the PR description to reflect what the code does? I will then do another review pass.

[srikanthccv]

Updated, PTAL.

[evan-bradley]

I'm concerned this won't be completely reliable. My understanding is that this is intended to wait for the request to fail before starting a server, is there a way we can wait for the OnConnectFailed callback to fire before starting it?

[tigrannajaryan]

+1

[srikanthccv]

I added this when trying to create a failed test based on this discussion #194 (comment). This is no longer needed because the connection refused error doesn't reproduce the original issue so I updated the test to create a connection reset issue. Hope this is clear.

[phanidevavarapu]

@tigrannajaryan @srikanthccv are we good to merge this? I also started facing the similar issue.