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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include <vespa/vespalib/stllike/string.h>
namespace vespalib {
/**
* An Issue is an error encountered during program execution that will
* not affect the program flow. It is like an exception that is not
* (re-)thrown, but rather logged as a warning, or like an error that
* augments the computation result instead of replacing it. Issues are
* reported by the code identifying that something is wrong; similar
* to logging a warning. Issues are handled by an Issue::Handler that
* is bound to the current thread; similar to try/catch used by
* exceptions, but rather than disrupting the program flow we only
* capture any issues encountered along the way. Thread-local data
* structures are used to match the reporting of an issue with its
* appropriate handler, making it possible to handle issues across
* arbitrary synchronous API boundaries without changing the APIs to
* explicitly wire all issues through them.
*
* An Issue object represents a single issue. The static 'report'
* functions are used to report an issue. The static 'listen' function
* is used to bind an Issue::Handler to the current thread using a
* special object that should reside on the stack and unbinds the
* handler when destructed. Handler bindings can be nested. Issue
* reports will be routed to the last handler bound to the thread.
*
* Note that the objects binding handlers to threads must not be
* destructed out of order; just let them go out of scope.
**/
class Issue
{
private:
vespalib::string _message;
public:
Issue(vespalib::string message);
const vespalib::string &message() const { return _message; }
struct Handler {
virtual void handle(const Issue &issue) = 0;
virtual ~Handler() = default;
};
class Binding
{
public:
struct Link {
Handler &handler;
Link *next;
};
private:
Link _link;
public:
Binding(Handler &handler);
Binding(Binding &&) = delete;
Binding(const Binding &) = delete;
Binding &operator=(Binding &&) = delete;
Binding &operator=(const Binding &) = delete;
~Binding();
};
static void report(const Issue &issue);
static Binding listen(Handler &handler);
static void report(vespalib::string msg);
static void report(const std::exception &e);
static void report(const char *format, ...) __attribute__ ((format (printf,1,2)));
};
}
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