Limit memory mode at 100 buckets and return error appropriately

~~~
mc: <ERROR> Failed to create bucket for URL [http://localhost:9000/newbucket-101]. Reason: [You have attempted to create more buckets than allowed.].
~~~

Response from server

pkg/api/api_bucket_handlers.go

@@ -171,6 +171,10 @@ func (server *minioAPI) putBucketHandler(w http.ResponseWriter, req *http.Reques
 			w.Header().Set("Connection", "close")
 			w.WriteHeader(http.StatusOK)
 		}
+	case drivers.TooManyBuckets:
+		{
+			writeErrorResponse(w, req, TooManyBuckets, acceptsContentType, req.URL.Path)
+		}
 	case drivers.BucketNameInvalid:
 		{
 			writeErrorResponse(w, req, InvalidBucketName, acceptsContentType, req.URL.Path)

pkg/api/api_object_handlers.go

@@ -163,6 +163,10 @@ func (server *minioAPI) putObjectHandler(w http.ResponseWriter, req *http.Reques
 		w.WriteHeader(http.StatusOK)
 	case drivers.ObjectExists:
 		{
+			// we need to debate about this, if this is the right message to send back
+			// https://github.com/minio-io/minio/issues/505
+
+			// Ideally we can use 405 Method No Allowed
 			writeErrorResponse(w, req, NotImplemented, acceptsContentType, req.URL.Path)
 		}
 	case drivers.BadDigest:

pkg/api/api_router.go

@@ -20,12 +20,13 @@ import (
 	"log"
 	"net/http"
 
+	"time"
+
 	router "github.com/gorilla/mux"
 	"github.com/minio-io/minio/pkg/api/config"
 	"github.com/minio-io/minio/pkg/api/quota"
 	"github.com/minio-io/minio/pkg/iodine"
 	"github.com/minio-io/minio/pkg/storage/drivers"
-	"time"
 )
 
 // private use

pkg/storage/drivers/errors.go

@@ -78,6 +78,9 @@ type BucketExists GenericBucketError
 // BucketNotFound - requested bucket not found
 type BucketNotFound GenericBucketError
 
+// TooManyBuckets - total buckets exceeded
+type TooManyBuckets GenericBucketError
+
 /// Object related errors
 
 // ObjectNotFound - requested object not found
@@ -149,6 +152,11 @@ func (e BucketExists) Error() string {
 	return "Bucket exists: " + e.Bucket
 }
 
+// Return string an error formatted as the given text
+func (e TooManyBuckets) Error() string {
+	return "Bucket limit exceeded beyond 100, cannot create bucket: " + e.Bucket
+}
+
 // Return string an error formatted as the given text
 func (e BucketNotFound) Error() string {
 	return "Bucket not Found: " + e.Bucket

pkg/storage/drivers/memory/memory.go

@@ -60,6 +60,10 @@ type storedObject struct {
 	metadata drivers.ObjectMetadata
 }
 
+const (
+	totalBuckets = 100
+)
+
 // Start memory object server
 func Start(maxSize uint64) (chan<- string, <-chan error, drivers.Driver) {
 	ctrlChannel := make(chan string)
@@ -263,6 +267,10 @@ func (memory *memoryDriver) CreateObject(bucket, key, contentType, expectedMD5Su
 // CreateBucket - create bucket in memory
 func (memory *memoryDriver) CreateBucket(bucketName, acl string) error {
 	memory.lock.RLock()
+	if len(memory.bucketMetadata) == totalBuckets {
+		memory.lock.RLock()
+		return iodine.New(drivers.TooManyBuckets{Bucket: bucketName}, nil)
+	}
 	if !drivers.IsValidBucket(bucketName) {
 		memory.lock.RUnlock()
 		return iodine.New(drivers.BucketNameInvalid{Bucket: bucketName}, nil)