If you have any questions, or want to get attention for a PR or issue please reach out on the #logging-and-metrics channel in the cloudfoundry slack
Go library to collect and emit metric and logging data from CF components. https://godoc.org/github.com/cloudfoundry/dropsonde
See dropsonde-protocol for the full specification of the dropsonde Protocol Buffer format.
Use this script to generate Go handlers for the various protobuf messages.
import (
"github.com/cloudfoundry/dropsonde"
)
func main() {
dropsonde.Initialize("localhost:3457", "router", "z1", "0")
}
This initializes dropsonde, along with the logs and metrics packages. It also instruments the default HTTP handler for outgoing requests, instrument itself (to count messages sent, etc.), and provides basic runtime stats.
The first argument is the destination for messages (typically metron). The host and port is required. The remaining arguments form the origin. This list is used by downstream portions of the dropsonde system to track the source of metrics.
Alternatively, import github.com/cloudfoundry/dropsonde/metrics
to include the
ability to send custom metrics, via metrics.SendValue
and metrics.IncrementCounter
.
After calling dropsonde.Initialize
(as above), the subpackages logs
and metrics
are also initialized. (They can be separately initialized, though this requires more setup of emitters, etc.)
Currently, dropsonde only supports sending logs for platform-hosted applications (i.e. not the emitting component itself).
Use logs.SendAppLog
and logs.SendAppErrorLog
to send single logs, e.g.
logs.SendAppLog("b7ba6142-6e6a-4e0b-81c1-d7025888cce4", "An event happened!", "APP", "0")
To process a stream of app logs (from, say, a socket of an application's STDOUT output), use logs.ScanLogStream
and logs.ScanErrorLogStream
:
logs.ScanLogStream("b7ba6142-6e6a-4e0b-81c1-d7025888cce4", "APP", "0", appLogSocketConnection)
See the Cloud Foundry DEA Logging Agent (currently deprecated) for an example code that scans log streams using these methods.
As mentioned earlier, initializing Dropsonde automatically instruments the default HTTP server and client objects in the net/http
package, and will automatically send HttpStart
and HttpStop
events for every request served or made.
For instrumentation of other metrics, use the metrics
package.
metrics.SendValue(name, value, unit)
sends an event that records the value of a measurement at an instant in time. (These are often called "gauge" metrics by other libraries.) The value is of type float64
, and the unit
is mandatory. We recommend following this guide for unit names, and highly encourage SI units and prefixes where appropriate.metrics.IncrementCounter(name)
and metrics.AddToCounter(name, delta)
send events that increment the named counter (by one or the specified non-negative delta
, respectively). Note that the cumulative total is not included in the event message, only the increment.There are some metric functions/methods which return Chainer
types, which can be used to apply tags before sending. In the simplest case, the call will cascade until Send()
:
err := metrics.Value(name, value, unit).
SetTag("foo", "bar").
SetTag("bacon", 12).
Send()
In more complicated code, the chainer can be passed around, adding tags until the metric is ready to be sent. For example, pre-marshal, you may want to add tags about the type:
chainer := metrics.Value(name, value, unit).
SetTag("req-mimetype", "json").
SetTag("name", v.Name)
Later, it could tags about the chosen response type:
chainer = chainer.SetTag("resp-mimetype", respType)
And finally, add tags about the final state:
err := chainer.SetTag("resp-state", "error").
SetTag("resp-code", http.StatusBadRequest).
Send()
Note: It is important to note that for counter metrics are summed individually and not in total. If you have historically emitted a counter without tags it is best practice to continue to emit that total metric without tags, and add additional metrics for the individual tagged metrics you'd like to track.
For details on manual usage of dropsonde, please refer to the
Godocs. Pay particular
attenion to the ByteEmitter
, InstrumentedHandler
, and InstrumentedRoundTripper
types.
Programs wishing to emit events and metrics should use the package as described
above. For programs that wish to process events, we provide the dropsonde/unmarshaller
and dropsonde/marshaller
packages for decoding/reencoding raw Protocol Buffer
messages. Use dropsonde/signature
to sign
and validate messages.