| ClientMetrics<M,Req,Resp> | 
 The client metrics SPI that Vert.x will use to call when client events occur. 
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| DatagramSocketMetrics | 
 The datagram/udp metrics SPI which Vert.x will use to call when each event occurs pertaining to datagram sockets. 
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| EventBusMetrics<H> | 
 The event bus metrics SPI which Vert.x will use to call when each event occurs. 
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| HttpClientMetrics<R,W,S> | 
 The http client metrics SPI that Vert.x will use to call when http client events occur. 
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| HttpServerMetrics<R,W,S> | 
 The http server metrics SPI that Vert.x will use to call when each http server event occurs. 
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| Metrics | 
 The metrics interface is implemented by metrics providers that wants to provide monitoring of
 Vert.x core. 
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| MetricsProvider | 
Metrics provider is the base SPI used by metrics implementations to retrieve a  Metrics
 object.  
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| NetworkMetrics<S> | 
 An SPI used internally by Vert.x to gather metrics on a net socket which serves
 as a base class for TCP or UDP. 
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| PoolMetrics<Q,T> | 
 Worker pool metrics 
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| TCPMetrics<S> | 
 An SPI used internally by Vert.x to gather metrics on a net socket which serves
 as a base class for things like HttpServer and HttpClient, all of which serve TCP connections. 
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| VertxMetrics | 
 The main Vert.x metrics SPI which Vert.x will use internally. 
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