| # Copyright 2015 The Chromium Authors. All rights reserved. |
| # Use of this source code is governed by a BSD-style license that can be |
| # found in the LICENSE file. |
| |
| """Helper classes that make it easier to instrument code for monitoring.""" |
| |
| |
| class ScopedIncrementCounter(object): |
| """Increment a counter when the wrapped code exits. |
| |
| The counter will be given a 'status' = 'success' or 'failure' label whose |
| value will be set to depending on whether the wrapped code threw an exception. |
| |
| Example: |
| |
| mycounter = Counter('foo/stuff_done') |
| with ScopedIncrementCounter(mycounter): |
| DoStuff() |
| |
| To set a custom status label and status value: |
| |
| mycounter = Counter('foo/http_requests') |
| with ScopedIncrementCounter(mycounter, 'response_code') as sc: |
| status = MakeHttpRequest() |
| sc.set_status(status) # This custom status now won't be overwritten if |
| # the code later raises an exception. |
| """ |
| |
| def __init__(self, counter, label='status', success_value='success', |
| failure_value='failure'): |
| self.counter = counter |
| self.label = label |
| self.success_value = success_value |
| self.failure_value = failure_value |
| self.status = None |
| |
| def set_failure(self): |
| self.set_status(self.failure_value) |
| |
| def set_status(self, status): |
| self.status = status |
| |
| def __enter__(self): |
| self.status = None |
| return self |
| |
| def __exit__(self, exc_type, exc_value, traceback): |
| if self.status is None: |
| if exc_type is None: |
| self.status = self.success_value |
| else: |
| self.status = self.failure_value |
| self.counter.increment({self.label: self.status}) |
