make HTTP retry when the GoPro is overwhelmed (#128)

* switch to retryablehttp to allow downloading many files

My HERO12 did not like being asked for more than about 5-7 files
simultaneously, but dropped some of the /gp/gpMediaMetadata with a
timeout. So after the files where the call to gpMediaMetadata was
successfull were downloaded, I got presented with a bunch of errors
where it didn't work, and of cause the files were not downloaded.

Switching to a retrying approach means that we still hammer the GoPro
for the first couple seconds, but allow the requests to proceed later.

Some of this is still WIP - the config file has a timeout option, that I
dropped since I do not understand enough go to incorporate it, yet.

* use the configurable timeout sensibly

go.mod

@@ -42,6 +42,8 @@ require (
 	github.com/google/go-querystring v1.0.0 // indirect
 	github.com/google/uuid v1.1.2 // indirect
 	github.com/gookit/color v1.2.9 // indirect
+	github.com/hashicorp/go-cleanhttp v0.5.2 // indirect
+	github.com/hashicorp/go-retryablehttp v0.7.5 // indirect
 	github.com/hashicorp/hcl v1.0.0 // indirect
 	github.com/inconshreveable/mousetrap v1.0.0 // indirect
 	github.com/jbenet/go-context v0.0.0-20150711004518-d14ea06fba99 // indirect

go.sum

@@ -245,9 +245,12 @@ github.com/hashicorp/consul/sdk v0.3.0/go.mod h1:VKf9jXwCTEY1QZP2MOLRhb5i/I/ssyN
 github.com/hashicorp/errwrap v1.0.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brvKWEqk/Jc4=
 github.com/hashicorp/go-cleanhttp v0.5.0/go.mod h1:JpRdi6/HCYpAwUzNwuwqhbovhLtngrth3wmdIIUrZ80=
 github.com/hashicorp/go-cleanhttp v0.5.1/go.mod h1:JpRdi6/HCYpAwUzNwuwqhbovhLtngrth3wmdIIUrZ80=
+github.com/hashicorp/go-cleanhttp v0.5.2 h1:035FKYIWjmULyFRBKPs8TBQoi0x6d9G4xc9neXJWAZQ=
+github.com/hashicorp/go-cleanhttp v0.5.2/go.mod h1:kO/YDlP8L1346E6Sodw+PrpBSV4/SoxCXGY6BqNFT48=
 github.com/hashicorp/go-hclog v0.0.0-20180709165350-ff2cf002a8dd/go.mod h1:9bjs9uLqI8l75knNv3lV1kA55veR+WUPSiKIWcQHudI=
 github.com/hashicorp/go-hclog v0.8.0/go.mod h1:5CU+agLiy3J7N7QjHK5d05KxGsuXiQLrjA0H7acj2lQ=
 github.com/hashicorp/go-hclog v0.9.1/go.mod h1:5CU+agLiy3J7N7QjHK5d05KxGsuXiQLrjA0H7acj2lQ=
+github.com/hashicorp/go-hclog v0.9.2/go.mod h1:5CU+agLiy3J7N7QjHK5d05KxGsuXiQLrjA0H7acj2lQ=
 github.com/hashicorp/go-hclog v0.14.1/go.mod h1:whpDNt7SSdeAju8AWKIWsul05p54N/39EeqMAyrmvFQ=
 github.com/hashicorp/go-immutable-radix v1.0.0/go.mod h1:0y9vanUI8NX6FsYoO3zeMjhV/C5i9g4Q3DwcSNZ4P60=
 github.com/hashicorp/go-msgpack v0.5.3/go.mod h1:ahLV/dePpqEmjfWmKiqvPkv/twdG7iPBM1vqhUKIvfM=
@@ -257,6 +260,8 @@ github.com/hashicorp/go-multierror v1.0.0/go.mod h1:dHtQlpGsu+cZNNAkkCN/P3hoUDHh
 github.com/hashicorp/go-plugin v1.0.1/go.mod h1:++UyYGoz3o5w9ZzAdZxtQKrWWP+iqPBn3cQptSMzBuY=
 github.com/hashicorp/go-retryablehttp v0.5.3/go.mod h1:9B5zBasrRhHXnJnui7y6sL7es7NDiJgTc6Er0maI1Xs=
 github.com/hashicorp/go-retryablehttp v0.5.4/go.mod h1:9B5zBasrRhHXnJnui7y6sL7es7NDiJgTc6Er0maI1Xs=
+github.com/hashicorp/go-retryablehttp v0.7.5 h1:bJj+Pj19UZMIweq/iie+1u5YCdGrnxCT9yvm0e+Nd5M=
+github.com/hashicorp/go-retryablehttp v0.7.5/go.mod h1:Jy/gPYAdjqffZ/yFGCFV2doI5wjtH1ewM9u8iYVjtX8=
 github.com/hashicorp/go-rootcerts v1.0.0/go.mod h1:K6zTfqpRlCUIjkwsN4Z+hiSfzSTQa6eBIzfwKfwNnHU=
 github.com/hashicorp/go-rootcerts v1.0.1/go.mod h1:pqUvnprVnM5bf7AOirdbb01K4ccR319Vf4pU3K5EGc8=
 github.com/hashicorp/go-sockaddr v1.0.0/go.mod h1:7Xibr9yA9JjQq1JpNB2Vw7kxv8xerXegt+ozgdvDeDU=

pkg/utils/client.go

@@ -4,6 +4,7 @@ import (
 	"net/http"
 	"time"
 
+	"github.com/hashicorp/go-retryablehttp"
 	"github.com/spf13/viper"
 )
 
@@ -13,6 +14,14 @@ func timeoutFromConfig() int {
 	return viper.GetInt(key)
 }
 
-var Client = &http.Client{
-	Timeout: time.Duration(timeoutFromConfig()) * time.Second,
+var Client *http.Client
+
+func init() {
+	retryableClient := retryablehttp.NewClient()
+	retryableClient.Logger = nil
+	retryableClient.Backoff = retryablehttp.LinearJitterBackoff
+	timeout := time.Duration(timeoutFromConfig()) * time.Second
+	retryableClient.RetryWaitMin = timeout / 10
+	retryableClient.RetryWaitMax = timeout
+	Client = retryableClient.StandardClient()
 }