PEL: Add ability to create event logs

There are cases where the PEL code wants to be able to create OpenBMC
event logs (and thus PELs) for problems it encounters when trying to
create or import other PELs.  For example, if the host were to send down
a malformed PEL, this code would like to create a new event log and
capture part of that bad PEL in the new PEL for debug purposes, as the
malformed PEL cannot be reported anywhere since it is malformed.

To handle this, create the EventLogger class that provides a log()
function that allows the PEL extension code to create OpenBMC event logs
(and thus PELs) from within.

The underlying function to do the event log creating is passed in via
the constructor so that it can be changed for testing.

The sd_event_add_defer function (wrapped by sdeventplus) is used to
dispatch the creation of a single event, so that the entry point is from
the event loop.  If there are still events left on the queue after that,
then they will be also be scheduled with sd_event_add_defer so that the
events are always created from event loop calls.

EventLogger does not allow events to be added to the queue if it is
being done from within the creation function so that the code can't
get stuck in a loop of creating a new event every time an event is
created.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I6a9062074dc62cfb6043139ff0a9f3dfcd06c708

1 files changed, 187 insertions, 0 deletions

diff --git a/extensions/openpower-pels/event_logger.hpp b/extensions/openpower-pels/event_logger.hpp
new file mode 100644
index 0000000..b4df0d4
--- /dev/null
+++ b/extensions/openpower-pels/event_logger.hpp
@@ -0,0 +1,187 @@
+#pragma once
+
+#include "additional_data.hpp"
+#include "elog_entry.hpp"
+
+#include <phosphor-logging/log.hpp>
+#include <queue>
+#include <sdeventplus/event.hpp>
+#include <sdeventplus/source/event.hpp>
+#include <tuple>
+
+namespace openpower::pels
+{
+
+/**
+ * @class EventLogger
+ *
+ * This class handles creating OpenBMC event logs (and thus PELs) from
+ * within the PEL extension code.
+ *
+ * The function to actually create the event log is passed in via the
+ * constructor so that different functions can be used when testing.
+ *
+ * To create the event log, call log() with the appropriate arguments
+ * and the log will be created as soon as the flow gets back to the event
+ * loop.  If the queue isn't empty after a log is created, the next
+ * one will be scheduled to be created from the event loop again.
+ *
+ * This class does not allow new events to be added while inside the
+ * creation function, because if the code added an event log every time
+ * it tried to create one, it would do so infinitely.
+ */
+class EventLogger
+{
+  public:
+    using ADMap = std::map<std::string, std::string>;
+    using LogFunction = std::function<void(
+        const std::string&, phosphor::logging::Entry::Level, const ADMap&)>;
+
+    static constexpr size_t msgPos = 0;
+    static constexpr size_t levelPos = 1;
+    static constexpr size_t adPos = 2;
+    using EventEntry = std::tuple<std::string, phosphor::logging::Entry::Level,
+                                  AdditionalData>;
+
+    EventLogger() = delete;
+    ~EventLogger() = default;
+    EventLogger(const EventLogger&) = delete;
+    EventLogger& operator=(const EventLogger&) = delete;
+    EventLogger(EventLogger&&) = delete;
+    EventLogger& operator=(EventLogger&&) = delete;
+
+    /**
+     * @brief Constructor
+     *
+     * @param[in] event - The sd_event object
+     * @param[in] creator - The function to use to create the event log
+     */
+    EventLogger(sd_event* event, LogFunction creator) :
+        _event(event), _creator(creator)
+    {
+    }
+
+    /**
+     * @brief Adds an event to the queue so that it will be created
+     *        as soon as the code makes it back to the event loop.
+     *
+     * Won't add it to the queue if already inside the create()
+     * callback.
+     *
+     * @param[in] message - The message property of the event log
+     * @param[in] severity - The severity level of the event log
+     * @param[in] ad - The additional data property of the event log
+     */
+    void log(const std::string& message,
+             phosphor::logging::Entry::Level severity, const AdditionalData& ad)
+    {
+        if (!_inEventCreation)
+        {
+            _eventsToCreate.emplace(message, severity, ad);
+
+            if (!_eventSource)
+            {
+                scheduleCreate();
+            }
+        }
+        else
+        {
+            phosphor::logging::log<phosphor::logging::level::INFO>(
+                "Already in event create callback, skipping new create",
+                phosphor::logging::entry("ERROR_NAME=%s", message.c_str()));
+        }
+    }
+
+    /**
+     * @brief Returns the event log queue size.
+     *
+     * @return size_t - The queue size
+     */
+    size_t queueSize() const
+    {
+        return _eventsToCreate.size();
+    }
+
+    /**
+     * @brief Schedules the create() function to run using the
+     *        'defer' sd_event source.
+     */
+    void scheduleCreate()
+    {
+        _eventSource = std::make_unique<sdeventplus::source::Defer>(
+            _event, std::bind(std::mem_fn(&EventLogger::create), this,
+                              std::placeholders::_1));
+    }
+
+  private:
+    /**
+     * @brief Creates an event log and schedules the next one if
+     *        there is one.
+     *
+     * This gets called from the event loop by the sd_event code.
+     *
+     * @param[in] source - The event source object used
+     */
+    void create(sdeventplus::source::EventBase& source)
+    {
+        _eventSource.reset();
+
+        if (_eventsToCreate.empty())
+        {
+            return;
+        }
+
+        auto event = _eventsToCreate.front();
+        _eventsToCreate.pop();
+
+        _inEventCreation = true;
+
+        try
+        {
+            _creator(std::get<msgPos>(event), std::get<levelPos>(event),
+                     std::get<adPos>(event).getData());
+        }
+        catch (std::exception& e)
+        {
+            phosphor::logging::log<phosphor::logging::level::ERR>(
+                "EventLogger's create function threw an exception",
+                phosphor::logging::entry("ERROR=%s", e.what()));
+        }
+
+        _inEventCreation = false;
+
+        if (!_eventsToCreate.empty())
+        {
+            scheduleCreate();
+        }
+    }
+
+    /**
+     * @brief The sd_event object.
+     */
+    sdeventplus::Event _event;
+
+    /**
+     * @brief The user supplied function to create the event log.
+     */
+    LogFunction _creator;
+
+    /**
+     * @brief Keeps track of if an event is currently being created.
+     *
+     * Guards against creating new events while creating events.
+     */
+    bool _inEventCreation = false;
+
+    /**
+     * @brief The event source object used for scheduling.
+     */
+    std::unique_ptr<sdeventplus::source::Defer> _eventSource;
+
+    /**
+     * @brief The queue of event logs to create.
+     */
+    std::queue<EventEntry> _eventsToCreate;
+};
+
+} // namespace openpower::pels