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Cat Client for Go

中文文档

gocat supports Go 1.8+

gocat is highly dependent on ccat. (through CGO)

Since we are using the thread local to storage the transaction stack in ccat, which is necessary to build a message tree. It's hard for us to let it work appropriately with goroutines. (Because a goroutine can be run in different threads, due to the MPG model)

We don't support message tree in this version, but don't worry, we are still working on it and having some great ideas at the moment.

Installation

via go get

$ go get github.com/dianping/cat/lib/go/...

Initialization

Some preparations needs to be done before initializing gocat.

Then you can initialize gocat with the following codes:

import (
    "gocat"
)

func init() {
    gocat.Init("appkey")
}

Only English characters (a-z, A-Z), numbers (0-9), underscore (_) and dash (-) are allowed in appkey.

Documentation

Transaction

t := cat.NewTransaction(TTYPE, "test")
defer t.Complete()

We strongly recommend defer keyword to make sure that the transaction completed, or it may cause problems.

Transaction apis

We offered a series of APIs to modify the transaction.

  • AddData
  • SetStatus
  • SetDuration
  • SetDurationStart
  • SetTimestamp
  • Complete

These APIs can be easily used with the following codes.

t := cat.NewTransaction(TTYPE, "test")
defer t.Complete()
t.AddData("testcase")
t.AddData("foo", "bar")
t.SetStatus(gocat.FAIL)
t.SetDurationStart(time.Now().UnixNano() - time.Second.Nanoseconds() * 5)
t.SetTimestamp(time.Now().UnixNano() - time.Second.Nanoseconds())
t.SetDuration(time.Millisecond.Nanoseconds() * 1000)

There is something you have to know about the transaction APIs:

  1. You can call AddData several times, the added data will be connected by &.
  2. It's meaningless to specify duration and durationStart in the same transaction, although we did so in the example :)
  3. Never forget to complete the transaction! Or you will get corrupted message trees and memory leaks!

NewCompletedTransactionWithDuration

Log a transaction with a specified duration in nanoseconds and complete it immediately.

Due to the transaction has been auto-completed, the timestamp will be turned back. (Like it had been created in the past)

Note that the specified duration should be less than 60 seconds, or we won't turn back the timestamp.

cat.NewCompletedTransactionWithDuration(TTYPE, "completed", time.Second.Nanoseconds() * 24)
// The following code is illegal
cat.NewCompletedTransactionWithDuration(TTYPE, "completed-over-60s", time.Second.Nanoseconds() * 65)

Event

LogEvent

// Log a event with success status and empty data.
cat.LogEvent("Event", "E1")

// The 3rd parameter (status) is optional, default is "0".
// It can be any of string value.
// The event will be treated as "problem" unless the given status == gocat.SUCCESS ("0")
// which will be recorded in our problem report.
cat.LogEvent("Event", "E2", gocat.FAIL)
cat.LogEvent("Event", "E3", "failed")

// The 4th parameter (data) is optional, default is "".
// It can be any of string value.
cat.LogEvent("Event", "E4", "failed", "some debug info")

LogError

Log an error with error stack traces.

Error is a special event, type = Exception and name = error by default.

name can be overwritten by the 2nd parameter.

error stack traces will be collected and added to data.

err := errors.New("error")
// With default name 'error'
cat.LogError(err)
// Or you can specify the name through the 2nd parameter.
cat.LogError(err, 'error-name')

Metric

We do aggregation metrics every second.

For example, if you have called count 3 times in the same second (with the same name), we will just summarize the value of them and report once to the server.

In the case of duration, we use averaged value instead of summarized value.

LogMetricForCount

cat.LogMetricForCount("metric-1")
cat.LogMetricForCount("metric-2", 3)

LogMetricForDuration

cat.LogMetricForDuration("metric-3", 150 * time.Millisecond.Nanoseconds())