countertest.go

     1  // Copyright 2023 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // countertest provides testing utilities for counters.
     6  // This package cannot be used except for testing.
     7  package countertest
     8  
     9  import (
    10  	"sync"
    11  	"testing"
    12  
    13  	"golang.org/x/telemetry/counter"
    14  	ic "golang.org/x/telemetry/internal/counter"
    15  	"golang.org/x/telemetry/internal/telemetry"
    16  )
    17  
    18  var (
    19  	openedMu sync.Mutex
    20  	opened   bool
    21  )
    22  
    23  // SupportedPlatform reports if this platform supports Open()
    24  const SupportedPlatform = !telemetry.DisabledOnPlatform
    25  
    26  func isOpen() bool {
    27  	openedMu.Lock()
    28  	defer openedMu.Unlock()
    29  	return opened
    30  }
    31  
    32  // Open enables telemetry data writing to disk.
    33  // This is supposed to be called once during the program execution
    34  // (i.e. typically in TestMain), and must not be used with
    35  // golang.org/x/telemetry/counter.Open.
    36  func Open(telemetryDir string) {
    37  	openedMu.Lock()
    38  	defer openedMu.Unlock()
    39  	if opened {
    40  		panic("Open was called more than once")
    41  	}
    42  	telemetry.Default = telemetry.NewDir(telemetryDir)
    43  
    44  	// TODO(rfindley): reinstate test coverage with counter rotation enabled.
    45  	// Before the [counter.Open] and [counter.OpenAndRotate] APIs were split,
    46  	// this called counter.Open (which rotated!).
    47  	counter.Open()
    48  	opened = true
    49  }
    50  
    51  // ReadCounter reads the given counter.
    52  func ReadCounter(c *counter.Counter) (count uint64, _ error) {
    53  	return ic.Read(c)
    54  }
    55  
    56  // ReadStackCounter reads the given StackCounter.
    57  func ReadStackCounter(c *counter.StackCounter) (stackCounts map[string]uint64, _ error) {
    58  	return ic.ReadStack(c)
    59  }
    60  
    61  // ReadFile reads the counters and stack counters from the given file.
    62  func ReadFile(name string) (counters, stackCounters map[string]uint64, _ error) {
    63  	return ic.ReadFile(name)
    64  }
    65  
    66  func init() {
    67  	// Extra safety check.
    68  	if !testing.Testing() {
    69  		panic("use of this package is disallowed in non-testing code")
    70  	}
    71  }
    72
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