userver: Handling OS signals
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Handling OS signals

Table of Contents

Default behavior

  • SIGINT - return trace
  • SIGTERM, SIGQUIT - shutdown service
  • SIGUSR1 - reopen file descriptors for log (logrotate)

User behavior

The component os_signals::ProcessorComponent stores os_signals::Processor and listens to SIGUSR1 and SIGUSR2 signals. You can use AddListener function to subscribe to these signals.

For example, we use signal SIGUSR1 in components::Logging for reopening files after executing logrotate.

Example

  1. Add in private field class
    os_signals::Subscriber signal_subscribe_
  2. In in the component's constructor, register a signal listener. For example, components::Logging uses the following code:
    Logging::Logging(const ComponentConfig& config, const ComponentContext& context)
    : signal_subscriber_(context.FindComponent<os_signals::ProcessorComponent>()
    .Get()
    .AddListener(this, kName, os_signals::kSigUsr1,
    &Logging::OnLogRotate))
  3. In the component's destructor, unsubscribe from the signal
    signal_subscriber_.Unsubscribe();