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GO2Sky is an instrument SDK library, written in Go, by following Apache SkyWalking tracing and metrics formats.
$ go get -u github.com/SkyAPM/go2sky
The API of this project is still evolving. The use of vendoring tool is recommended.
By completing this quickstart, you will learn how to trace local methods. For more details, please view the example.
GO2Sky can export traces to Apache SkyWalking OAP server or local logger. In the following example, we configure GO2Sky to export to OAP server,
which is listening on oap-skywalking port 11800, and all the spans from this program will be associated with a service name example.
reporter.GRPCReporter can also adjust the behavior through reporter.GRPCReporterOption, view all.
r, err := reporter.NewGRPCReporter("oap-skywalking:11800")
if err != nil {
log.Fatalf("new reporter error %v \n", err)
}
defer r.Close()
tracer, err := go2sky.NewTracer("example", go2sky.WithReporter(r))
You can also create tracer with sampling rate. It supports decimals between 0-1 (two decimal places), representing the sampling percentage of trace.
tracer, err := go2sky.NewTracer("example", go2sky.WithReporter(r), go2sky.WithSampler(0.5))
Also could customize correlation context config.
tracer, err := go2sky.NewTracer("example", go2sky.WithReporter(r), go2sky.WithSampler(0.5), go2sky.WithCorrelation(3, 128))
To create a span in a trace, we used the Tracer to start a new span. We indicate this as the root span because of
passing context.Background(). We must also be sure to end this span, which will be show in End span.
span, ctx, err := tracer.CreateLocalSpan(context.Background())
A sub span created as the children of root span links to its parent with Context.
subSpan, newCtx, err := tracer.CreateLocalSpan(ctx)
Get custom data from tracing context.
value := go2sky.GetCorrelation(ctx, key)
Put custom data to tracing context.
success := go2sky.PutCorrelation(ctx, key, value)
We must end the spans so they becomes available for sending to the backend by a reporter.
subSpan.End()
span.End()
Set and get global Tracer
// new tracer
tr, err := go2sky.NewTracer("example")
// registers `tracer` as the global Tracer
go2sky.SetGlobalTracer(tr)
// returns the registered global Tracer
// if none is registered then an instance of `nil` is returned
tracer := go2sky.GetGlobalTracer()
Get the activeSpan in the Context.
go2sky.ActiveSpan(ctx)
Save the activeSpan to Context
go2sky.WithSpan(ctx, activeSpan)
Get the ServiceName of the activeSpan in the Context.
go2sky.ServiceName(ctx)
Get the ServiceInstanceName of the activeSpan in the Context.
go2sky.ServiceInstanceName(ctx)
Get the TraceID of the activeSpan in the Context.
go2sky.TraceID(ctx)
Get the TraceSegmentID of the activeSpan in the Context.
go2sky.TraceSegmentID(ctx)
Get the SpanID of the activeSpan in the Context.
go2sky.SpanID(ctx)
Go2sky agent reports the segments periodically. It would not wait for all finished segments reported when the service exits.
We cover some advanced topics about GO2Sky.
Trace links spans belong to it by using context propagation which varies between different scenario.
We use context package to link spans. The root span usually pick context.Background(), and sub spans
will inject the context generated by its parent.
//Create a new context
entrySpan, entryCtx, err := tracer.CreateEntrySpan(context.Background(), ...)
// Some operation
...
// Link two spans by injecting entrySpan context into exitSpan
exitSpan, err := tracer.CreateExitSpan(entryCtx, ...)
We use Entry span to extract context from downstream service, and use Exit span to inject context to
upstream service.
Entry and Exit spans make sense to OAP analysis which generates topology map and service metrics.
//Extract context from HTTP request header `sw8`
span, ctx, err := tracer.CreateEntrySpan(r.Context(), "/api/login", func(key string) (string, error) {
return r.Header.Get(key), nil
})
// Some operation
...
// Inject context into HTTP request header `sw8`
span, err := tracer.CreateExitSpan(req.Context(), "/service/validate", "tomcat-service:8080", func(key, value string) error {
req.Header.Set(key, value)
return nil
})
We set tags into a span which is stored in the backend, but some tags have special purpose. OAP server may use them to aggregate metrics, generate topology map and etc.
They are defined as constant in root package with prefix Tag.
Inject trace context into the log text. SkyWalking LAL(log analysis language) engine could extract the context from the text and correlate trace and logs.
// Get trace context data
import go2skylog "github.com/SkyAPM/go2sky/log"
logContext = go2skylog.FromContext(ctx)
// Build context data string
// Inject context string into log
// Context format string: [$serviceName,$instanceName,$traceId,$traceSegmentId,$spanId]
contextString := logContext.String()
Go to go2sky-plugins repo to see all the plugins, click here.
Below is the full list of supported environment variables you can set to customize the agent behavior, please read the descriptions for what they can achieve.
| Environment Variable | Description | Default |
|---|---|---|
SW_AGENT_NAME |
The name of the Go service | unset |
SW_AGENT_LAYER |
Instance belong layer name which define in the backend | unset |
SW_AGENT_INSTANCE_NAME |
The name of the Go service instance | Randomly generated |
SW_AGENT_SAMPLE |
Sample rate, 1 setting it to 1 means full sampling | 1 |
SW_AGENT_COLLECTOR_BACKEND_SERVICES |
The backend OAP server address | unset |
SW_AGENT_AUTHENTICATION |
The authentication token to verify that the agent is trusted by the backend OAP, as for how to configure the backend, refer to the yaml. | unset |
SW_AGENT_COLLECTOR_HEARTBEAT_PERIOD |
Agent heartbeat report period. Unit, second | 20 |
SW_AGENT_COLLECTOR_GET_AGENT_DYNAMIC_CONFIG_INTERVAL |
Sniffer get agent dynamic config interval. Unit, second | 20 |
SW_AGENT_COLLECTOR_MAX_SEND_QUEUE_SIZE |
Send span queue buffer length | 30000 |
SW_AGENT_PROCESS_STATUS_HOOK_ENABLE |
Enable the Process Status Hook feature | false |
SW_AGENT_PROCESS_LABELS |
The labels of the process, multiple labels split by "," | unset |
Configuration Discovery Service provides the dynamic configuration for the agent, defined in gRPC and stored in the backend.
Golang agent supports the following dynamic configurations.
| Config Key | Value Description | Value Format Example |
|---|---|---|
| agent.sample_rate | The percentage of trace when sampling. It's [0, 1], Same with WithSampler parameter. |
0.1 |
This feature is used in cooperation with the skywalking-rover project.
When go2sky keeps alive with the backend, it would write a metadata file to the local (temporary directory) at the same time, which describes the information of the current process. The rover side scans all processes, find out which process contains this metadata file. Finally, the rover could collect, profiling, with this process.
The metadata file use to save metadata with current process, it save in: {TMPDIR}/apache_skywalking/process/{pid}/metadata.properties.
Also, when the go2sky keep alive with backend, modify and open time of the metadata file would be updated.
| Key | Type | Description |
|---|---|---|
| layer | string | this process layer. |
| service_name | string | this process service name. |
| instance_name | string | this process instance name. |
| process_name | string | this process process name, it's same with the instance name. |
| properties | json | the properties in instance, the process labels also in the properties value. |
| labels | string | the process labels, multiple labels split by ",". |
| language | string | current process language, which is golang. |
Please read the official documentation of rover to get more information.
Apache License 2.0. See LICENSE file for details.
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