zero: merge pomerium/zero-sdk (#4848)

pkg/fanout/config.go

@@ -0,0 +1,116 @@
+package fanout
+
+import "time"
+
+const (
+	defaultPublishTimeout = time.Second
+	minPublishTimeout     = time.Millisecond * 100
+
+	defaultReceiverCallbackTimeout = time.Second
+	minReceiverCallbackTimeout     = time.Millisecond * 100
+
+	defaultAddSubscriberTimeout = time.Millisecond * 100
+	minAddSubscriberTimeout     = time.Millisecond * 100
+
+	defaultReceiverBufferSize   = 100
+	defaultMessageBufferSize    = 1024
+	defaultSubscriberBufferSize = 100
+)
+
+type config struct {
+	publishTimeout          time.Duration
+	receiverBufferSize      int
+	receiverCallbackTimeout time.Duration
+	publishBufferSize       int
+	subscriberBufferSize    int
+	addSubscriberTimeout    time.Duration
+}
+
+// Option configures a FanOut
+type Option func(*config)
+
+// WithPublishTimeout sets the internal timeout for publishing messages to the fanout
+func WithPublishTimeout(timeout time.Duration) Option {
+	if timeout < defaultPublishTimeout {
+		timeout = defaultPublishTimeout
+	}
+
+	return func(c *config) {
+		c.publishTimeout = timeout
+	}
+}
+
+// WithReceiverBufferSize sets the buffer size for the buffer between fanout and subscriber receiver
+func WithReceiverBufferSize(size int) Option {
+	if size < 1 {
+		size = 1
+	}
+	return func(c *config) {
+		c.receiverBufferSize = size
+	}
+}
+
+// WithReceiverCallbackTimeout sets the timeout for the callback function of the receiver
+func WithReceiverCallbackTimeout(timeout time.Duration) Option {
+	if timeout < minReceiverCallbackTimeout {
+		timeout = minReceiverCallbackTimeout
+	}
+
+	return func(c *config) {
+		c.receiverCallbackTimeout = timeout
+	}
+}
+
+// WithMessagesBufferSize sets the buffer size for the buffer that holds messages to be published
+func WithMessagesBufferSize(size int) Option {
+	if size < 1 {
+		size = 1
+	}
+	return func(c *config) {
+		c.publishBufferSize = size
+	}
+}
+
+// WithSubscriberBufferSize sets the new subscriber requsts buffer size
+func WithSubscriberBufferSize(size int) Option {
+	if size < 1 {
+		size = 1
+	}
+	return func(c *config) {
+		c.subscriberBufferSize = size
+	}
+}
+
+// WithAddSubscriberTimeout sets the timeout for adding a subscriber
+// If it is not possible to add a subscriber within the timeout,
+// it means the fanout is at capacity, and it is better to reject the subscriber,
+// that will likely be propagated to the downstream,
+// which would retry and eventually succeed with another instance
+func WithAddSubscriberTimeout(timeout time.Duration) Option {
+	if timeout < minAddSubscriberTimeout {
+		timeout = minAddSubscriberTimeout
+	}
+
+	return func(c *config) {
+		c.addSubscriberTimeout = timeout
+	}
+}
+
+func defaultFanOutConfig() config {
+	var c config
+	c.apply(
+		WithPublishTimeout(defaultPublishTimeout),
+		WithMessagesBufferSize(defaultMessageBufferSize),
+		WithReceiverCallbackTimeout(defaultReceiverCallbackTimeout),
+		WithReceiverBufferSize(defaultReceiverBufferSize),
+		WithSubscriberBufferSize(defaultSubscriberBufferSize),
+		WithAddSubscriberTimeout(defaultAddSubscriberTimeout),
+	)
+	return c
+}
+
+func (c *config) apply(opts ...Option) {
+	for _, opt := range opts {
+		opt(c)
+	}
+}