Use cleanhttp.DefaultPooledConnection and enforce cleanup (#57)

* Use cleanhttp.DefaultPooledConnection and enforce cleanup

This allows reuse of the existing connection on retries, since they're
going to the same host, but we explicitly close idle connections to
ensure they don't stick around forever after the series of requests is
done.

Fixes #44

* Fix merge

client.go

@@ -308,7 +308,7 @@ type Client struct {
 // NewClient creates a new Client with default settings.
 func NewClient() *Client {
 	return &Client{
-		HTTPClient:   cleanhttp.DefaultClient(),
+		HTTPClient:   cleanhttp.DefaultPooledClient(),
 		RetryWaitMin: defaultRetryWaitMin,
 		RetryWaitMax: defaultRetryWaitMax,
 		RetryMax:     defaultRetryMax,
@@ -418,6 +418,10 @@ func PassthroughErrorHandler(resp *http.Response, err error, _ int) (*http.Respo
 
 // Do wraps calling an HTTP method with retries.
 func (c *Client) Do(req *Request) (*http.Response, error) {
+	if c.HTTPClient == nil {
+		c.HTTPClient = cleanhttp.DefaultPooledClient()
+	}
+
 	if c.logger() != nil {
 		switch v := c.logger().(type) {
 		case Logger:
@@ -437,6 +441,7 @@ func (c *Client) Do(req *Request) (*http.Response, error) {
 		if req.body != nil {
 			body, err := req.body()
 			if err != nil {
+				c.HTTPClient.CloseIdleConnections()
 				return resp, err
 			}
 			if c, ok := body.(io.ReadCloser); ok {
@@ -496,6 +501,7 @@ func (c *Client) Do(req *Request) (*http.Response, error) {
 			if checkErr != nil {
 				err = checkErr
 			}
+			c.HTTPClient.CloseIdleConnections()
 			return resp, err
 		}
 
@@ -526,12 +532,14 @@ func (c *Client) Do(req *Request) (*http.Response, error) {
 		}
 		select {
 		case <-req.Context().Done():
+			c.HTTPClient.CloseIdleConnections()
 			return nil, req.Context().Err()
 		case <-time.After(wait):
 		}
 	}
 
 	if c.ErrorHandler != nil {
+		c.HTTPClient.CloseIdleConnections()
 		return c.ErrorHandler(resp, err, c.RetryMax+1)
 	}
 
@@ -540,6 +548,7 @@ func (c *Client) Do(req *Request) (*http.Response, error) {
 	if resp != nil {
 		resp.Body.Close()
 	}
+	c.HTTPClient.CloseIdleConnections()
 	return nil, fmt.Errorf("%s %s giving up after %d attempts",
 		req.Method, req.URL, c.RetryMax+1)
 }

go.mod

@@ -1,6 +1,6 @@
 module github.com/hashicorp/go-retryablehttp
 
 require (
-	github.com/hashicorp/go-cleanhttp v0.5.0
+	github.com/hashicorp/go-cleanhttp v0.5.1
 	github.com/hashicorp/go-hclog v0.9.2
 )

go.sum

@@ -1,7 +1,10 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/hashicorp/go-cleanhttp v0.5.0 h1:wvCrVc9TjDls6+YGAF2hAifE1E5U1+b4tH6KdvN3Gig=
-github.com/hashicorp/go-cleanhttp v0.5.0/go.mod h1:JpRdi6/HCYpAwUzNwuwqhbovhLtngrth3wmdIIUrZ80=
+github.com/hashicorp/go-cleanhttp v0.5.1 h1:dH3aiDG9Jvb5r5+bYHsikaOUIpcM0xvgMXVoDkXMzJM=
+github.com/hashicorp/go-cleanhttp v0.5.1/go.mod h1:JpRdi6/HCYpAwUzNwuwqhbovhLtngrth3wmdIIUrZ80=
 github.com/hashicorp/go-hclog v0.9.2 h1:CG6TE5H9/JXsFWJCfoIVpKFIkFe6ysEuHirp4DxCsHI=
 github.com/hashicorp/go-hclog v0.9.2/go.mod h1:5CU+agLiy3J7N7QjHK5d05KxGsuXiQLrjA0H7acj2lQ=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=