mirror of
https://github.com/kata-containers/kata-containers.git
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3a1bbd0271
Add initial support for opentracing by using the `jaeger` package.
Since opentracing uses the `context` package, add a `context.Context`
as the first parameter to all the functions that we might want to
trace. Trace "spans" (trace points) are then added by extracting the
trace details from the specified context parameter.
Notes:
- Although the tracer is created in `main()`, the "root span"
(aka the first trace point) is not added until `beforeSubcommands()`.
This is by design and is a compromise: by delaying the creation of the
root span, the spans become much more readable since using the web-based
JaegerUI, you will see traces like this:
```
kata-runtime: kata-runtime create
------------ -------------------
^ ^
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Trace name First span name
(which clearly shows the CLI command that was run)
```
Creating the span earlier means it is necessary to expand 'n' spans in
the UI before you get to see the name of the CLI command that was run.
In adding support, this became very tedious, hence my design decision to
defer the creation of the root span until after signal handling has been
setup and after CLI options have been parsed, but still very early in
the code path.
- At this stage, the tracing stops at the `virtcontainers` call
boundary.
- Tracing is "always on" as there doesn't appear to be a way to toggle
it. However, its resolves to a "nop" unless the tracer can talk to a
jaeger agent.
Note that this commit required a bit of rework to `beforeSubcommands()`
to reduce the cyclomatic complexity.
Fixes #557.
Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>
79 lines
1.6 KiB
Go
79 lines
1.6 KiB
Go
// Copyright (c) 2018 Intel Corporation
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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package main
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import (
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"context"
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"io"
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opentracing "github.com/opentracing/opentracing-go"
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"github.com/uber/jaeger-client-go/config"
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)
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// Implements jaeger-client-go.Logger interface
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type traceLogger struct {
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}
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// tracerCloser contains a copy of the closer returned by createTracer() which
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// is used by stopTracing().
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var tracerCloser io.Closer
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func (t traceLogger) Error(msg string) {
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kataLog.Error(msg)
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}
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func (t traceLogger) Infof(msg string, args ...interface{}) {
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kataLog.Infof(msg, args...)
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}
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func createTracer(name string) (opentracing.Tracer, error) {
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cfg := &config.Configuration{
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ServiceName: name,
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// If tracing is disabled, use a NOP trace implementation
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Disabled: !tracing,
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// Note that span logging reporter option cannot be enabled as
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// it pollutes the output stream which causes (atleast) the
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// "state" command to fail under Docker.
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Sampler: &config.SamplerConfig{
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Type: "const",
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Param: 1,
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},
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}
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logger := traceLogger{}
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tracer, closer, err := cfg.NewTracer(config.Logger(logger))
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if err != nil {
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return nil, err
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}
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// save for stopTracing()'s exclusive use
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tracerCloser = closer
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// Seems to be essential to ensure non-root spans are logged
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opentracing.SetGlobalTracer(tracer)
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return tracer, nil
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}
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// stopTracing() ends all tracing, reporting the spans to the collector.
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func stopTracing(ctx context.Context) {
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if !tracing {
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return
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}
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span := opentracing.SpanFromContext(ctx)
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if span != nil {
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span.Finish()
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}
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// report all possible spans to the collector
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tracerCloser.Close()
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}
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