Status: Production

• httpstats - Standard datadog/statsd integration for HTTP services.
  • Usage
    • HTTP Service
    • HTTP Client
  • Standard Metrics
    • HTTP Service
      • Tags
    • HTTP Client
      • Tags
  • Contributing
    • License
    • Contributing Agreement

This project contains middleware for HTTP services and clients that uses xstats emit detailed runtime metrics for service operations.

The middleware exported is a func(http.Handler) http.Handler and should work with virtually any router/mux implementation that supports middleware.

var middleware = httpstats.NewMiddleware(
  httpstats.MiddlewareOptionUDPSender("statsd:8125", 1<<15, 10*time.Second, "myservice."),
)

The middleware uses xstats as the base. A stat client can be extracted using xstats.FromContext or xstats.FromRequest as needed to emit custom stats. The standard set of stats emitted automatically by the middleware are documented below.

Each service installing the middleware should emit stats to a statsd or datadog agent. The agent location and settings are configurable through the httpstats.MiddlewareOptionUDPSender or MiddlewareOptionUDPGlobalRollupSender option. The global rollup option helps prevent several forms of skew that can arise from statsd and datadog aggregation of data and is described in greater detail below.

In addition to an HTTP middleware, there is also an http.RoundTripper wrapper included that will properly manage spans for outgoing HTTP requests. To apply:

var client = &http.Client{
  Transport: httpstats.NewTransport(
    httpstats.TransportOptionTag("dependency", "some-other-service"),
  )(http.DefaultTransport),
}

Like the service middleware, the client decorator provides a set of default stats that are detailed below. No other configuration of the client decorator is needed as it will assume any options set in the middleware by nature of using the same stat client from the incoming request context.

• service_bytes_received

  A histogram of the number of bytes received in each incoming request. The name for this can be overridden with httpstats.MiddlewareOptionBytesInName.

• service_bytes_returned

  A histogram of the number of bytes sent in response to each incoming request. The name for this can be overridden with httpstats.MiddlewareOptionBytesOutName.

• service_bytes_total

  A histogram of the number of bytes sent or received as part of each incoming request. The name for this can be overridden with httpstats.MiddlewareOptionBytesTotalName.

• service_time

  A timer of the amount of time spend processing a request. The name for this can be overridden with httpstats.MiddlewareOptionRequestTimeName.

This package uses the datadog extensions to the statsd line protocol to inject metadata for metrics. All HTTP service metrics will be tagged with:

• server_method

  The HTTP method used in the incoming request.

• server_status_code

  The status code returned by the service.

• server_status

  A string representation of the exit status of the request. This will be ok for 2xx range responses, error for other responses, timeout for cases where the request context deadline was exceeded, and cancelled for cases where the request context is explicitly cancelled.

Additional tags may be injected either statically or on a per-request basis using the httpstats.MiddlewareOptionTag and httpstats.MiddlewareOptionRequestTag options respectively.

• client_request_bytes_received

  A histogram of the number of bytes read from the response body of an outgoing request. This name can be overridden using httpstats.TransportOptionBytesInName.

• client_request_bytes_sent

  A histogram of the number of bytes sent in the body of an outgoing request. This name can be overridden using httpstats.TransportOptionBytesOutName.

• client_request_bytes_total

  A histogram of the total bytes sent and read as part of an outgoing request. This name can be overridden using httpstats.TransportOptionBytesTotalName.

• client_request_time

  A timer of how long it took for the round trip to complete. This name can be overridden using stidestats.TransportOptionRequestTimeName.

  This metric will be tagged with the following:

  • method

    The HTTP method used in the outgoing request.

  • status_code

    The HTTP status code received in the response.

  • status

  A string representation of the exit status of the request. This will be ok for 2xx range responses, error for other responses, timeout for cases where the request context deadline was exceeded, and cancelled for cases where the request context is explicitly cancelled.

• client_got_connection

  A timer of how long it took for the HTTP client to acquire a TCP connection. This name may be overridden using httpstats.TransportOptionGotConnectionName.

  This metric will be tagged with the following:

  • reused

    true or false to indicate whether or not the connection was reused or created new respectively.

  • idle

    true or false to indicate whether or not the connection was pulled from the idle pool.

• client_connection_idle

  A timer of how long a cached connection spend in the idle pool before it was used again. This name may be overridden using httpstats.TransportOptionConnectionIdleName.

• client_dns

  A timer of how long it took to resolve the DNS name associated with the outgoing request. This name may be overridden using httpstats.TransportOptionDNSName.

  This metric will be tagged with the following:

  • coalesced

    true or false to indicate whether or not the resolution was shared by multiple, concurrent lookups for the same address.

  • error

    true or false to indicate whether or not there was an error in resolving DNS.

• client_tls

  A timer of how long it took to complete the TLS handshake after acquiring a TCP connection to the remote host. This name may be overridden using httpstats.TransportOptionTLSName.

  This metric will be tagged with the following:

  • error

    true or false to indicate whether or not there was an error in performing the TLS handshake.

• client_wrote_headers

  A timer of how long it took between getting a connection and writing the request headers to the stream. This measure should closely represent the total amount of time it took for a request to leave the service. This name may be overridden using httpstats.TransportOptionWroteHeadersName.

• client_first_response_byte

  A timer of how long it took between writing the headers to the stream and getting the first byte of a response. This measure should closely represent the amount of time it took the remote service to process and respond with the latency of the network included in the measure. This name may be overridden using httpstats.TransportOptionFirstResponseByteName.

• client_put_idle

  A counter emitted each time a connection is placed into the idle pool. This name may be overridden using httpstats.TransportOptionPutIdleName.

  This metric will be tagged with the following:

  • error

    true or false to indicate whether or not there was an error in performing the TLS handshake.

Unlike the service middleware, the application of tags is not universal across all stats. Instead, each client stat comes with tags that are meaningful to that specific operation. Each metric above should list the applicable tags rather than enumerating another table here.

This project is licensed under Apache 2.0. See LICENSE.txt for details.

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