gistfile1.txt

                      application                exception context            phosphor-loggingd           journald

                       +-----+                       +-----+                      +-----+                 +-----+
         log event detected  |                       |     |                      |     |                 |     |
            "producer" |     |                       |     |                      |     |                 |     |
                       |  +  |                       |     |                      |     |                 |     |
+------->              |  |  |                       |     |                      |     |                 |     |
|                      |  |  |                       |     |                      |     |                 |     |
|                     elog() |                       |     |                      |     |                 |     |
|                      |  |  |                       |     |                      |     |                 |     |
|                      |  |  |                       |     |                      |     |                 |     |
|                      |  |  |                       |     |                      |     |                 |     |
|                      |  +----------------------------------------------------------------------------------+  |
|                      |     |                       |     |                      |     |                 |  |  |
|                      |     |                  ->  key value pairs, transaction ID  -> |                 |  |  |
|                      |     |                       |     |                      |     |                 |  |  |
|                      |     |                       |     |                      |     |                 |  |  |
|                      |     |                       |     |                      |     |                 |  |  |
|                      |  <----------------------------------------------------------------------------------<  |
|                      |  |  |                       |     |                      |     |                 |     |
|                      |  |  |                       |     |                      |     |                 |     |
|                      |  |  |                       |     |                      |     |                 |     |
|                      |  |  |                       |     |                      |     |                 |     |
| phosphor logging     |  |  |                       |     |                      |     |                 |     |
| library              |  |  |      throw(T)         |     |                      |     |                 |     |
|                      |  >-----------------------------+  |                      |     |                 |     |
|                      |     |                       |  |  |                      |     |                 |     |
|                      |     |                       |  |  |                      |     |                 |     |
|                      |     |                  +--------------+                  |     |                 |     |
|                      |     |                       |  |  |                      |     |                 |     |
|                      |     |                       |  |  |                      |     |                 |     |
|                      |  +-----------------------------<  |                      |     |                 |     |
|                      |  |  |      catch(T)         |     |                      |     |                 |     |
|                      |  |  |                       |     |                      |     |                 |     |
|                     commit()                       |     |                      |     |                 |     |
|                      |  |  |                       |     |                      |     |                 |     |
|                      |  |  |                       |     |                      |     |                 |     |
|                      |  |  |                       |     |                      |     |                 |     |
|                      |  >--------------------------+-----+-------------------------+  |                 |     |
|                      |     |         private dbus api (commit(transaction id))  |  |  |                 |     |
|                      |     |                       |     |                      |  |  |                 |     |
+------>               |     |                       |     |                      |  |  |                 |     |
                       |     |                       |     |                      |  |  |                 |     |
                       |     |                       |     |                      |  |  |                 |     |
                       |     |                       |     |                      |  |  |                 |     |
                       |     |                       |     |                      |  |  |                 |     |
                       |     |                       |     |                      |  +-----------------------+  |
                       |     |                       |     |                      |  |  |                 |  +  |
                       |     |                       |     |                      |  |  |        find key value pairs(transaction ID)
                       |     |                       |     |                      |  |  |                 |  |  |
                       |     |                       |     |                      |  <-----------------------+  |
                       |     |                       |     |                      |  |  |                 |     |
                       |     |                       |     |                      |  +-------------+      |     |
                       |     |                       |     |                      |  |  |          |      |     |
                       |     |                       |     |                      |  |  |     instantiate Logging.Entry
                       |     |                       |     |                      |  |  |          |      |     |
                       |     |                       |     |                      |  <-------------+      |     |
                       |     |                       |     |                      |  |  |                 |     |
                       |     |                       |     |                      |  v  |                 |     |
                       |     |                       |     |                      |     |                 |     |
                       |     |                       |     |                      |     |                 |     |
                       |     |                       |     |                      |     |                 |     |
                       +-----+                       +-----+                      +-----+                 +-----+


Glossary:

message id:        an enumeration for a location in the codebase
message arguments: source of truth for event metadata, known only to the event producer
event metadata:    the content of the logging format (pel, sel, etc)


phosphor-logging +1:
message arguments are compile-time checked


phosphor-logging -1:
dbus api is private ("internal")
leads developers to conflating logging with error handling