objstore.s3: add trace functionality

docs/storage.md

@@ -51,6 +51,8 @@ config:
   http_config:
     idle_conn_timeout: 0s
     insecure_skip_verify: false
+  trace:
+    enable: false
 ```
 
 AWS region to endpoint mapping can be found in this [link](https://docs.aws.amazon.com/general/latest/gr/rande.html#s3_region)
@@ -62,6 +64,7 @@ For debug and testing purposes you can set
 
 * `insecure: true` to switch to plain insecure HTTP instead of HTTPS
 * `http_config.insecure_skip_verify: true` to disable TLS certificate verification (if your S3 based storage is using a self-signed certificate, for example)
+* `trace.enable: true` to enable the minio client's verbose logging. Each request and response will be logged into the debug logger, so debug level logging must be enabled for this functionality.
 
 ### Credentials
 By default Thanos will try to retrieve credentials from the following sources:

pkg/objstore/s3/s3.go

@@ -44,6 +44,11 @@ type Config struct {
 	SecretKey       string            `yaml:"secret_key"`
 	PutUserMetadata map[string]string `yaml:"put_user_metadata"`
 	HTTPConfig      HTTPConfig        `yaml:"http_config"`
+	TraceConfig     TraceConfig       `yaml:"trace"`
+}
+
+type TraceConfig struct {
+	Enable bool `yaml:"enable"`
 }
 
 // HTTPConfig stores the http.Transport configuration for the s3 minio client.
@@ -152,6 +157,11 @@ func NewBucketWithConfig(logger log.Logger, config Config, component string) (*B
 		sse = encrypt.NewSSE()
 	}
 
+	if config.TraceConfig.Enable {
+		logWriter := log.NewStdlibAdapter(level.Debug(logger), log.MessageKey("s3TraceMsg"))
+		client.TraceOn(logWriter)
+	}
+
 	bkt := &Bucket{
 		logger:          logger,
 		name:            config.Bucket,