mirror of
https://github.com/ceph/ceph
synced 2024-12-16 00:15:35 +00:00
21 lines
997 B
ReStructuredText
21 lines
997 B
ReStructuredText
|
=============
|
||
|
|
CephContext
|
||
|
|
=============
|
||
|
|
|
||
|
|
A CephContext represents a single view of the Ceph cluster. It comes complete
|
||
|
|
with a configuration, a set of performance counters (PerfCounters), and a
|
||
|
|
heartbeat map. You can find more information about CephContext in
|
||
|
|
src/common/ceph_context.h.
|
||
|
|
|
||
|
|
Generally, you will have only one CephContext in your application, called
|
||
|
|
g_ceph_context. However, in library code, it is possible that the library user
|
||
|
|
will initialize multiple CephContexts. For example, this would happen if he
|
||
|
|
called rados_create more than once.
|
||
|
|
|
||
|
|
A ceph context is required to issue log messages. Why is this? Well, without
|
||
|
|
the CephContext, we would not know which log messages were disabled and which
|
||
|
|
were enabled. The dout() macro implicitly references g_ceph_context, so it
|
||
|
|
can't be used in library code. It is fine to use dout and derr in daemons, but
|
||
|
|
in library code, you must use ldout and lderr, and pass in your own CephContext
|
||
|
|
object. The compiler will enforce this restriction.
|