From 483eb2f56657e8e7f419ab1a4fab8dce9ade8609 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 27 Apr 2024 20:24:20 +0200 Subject: Adding upstream version 14.2.21. Signed-off-by: Daniel Baumann --- doc/dev/context.rst | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) create mode 100644 doc/dev/context.rst (limited to 'doc/dev/context.rst') diff --git a/doc/dev/context.rst b/doc/dev/context.rst new file mode 100644 index 00000000..1a2b2cbf --- /dev/null +++ b/doc/dev/context.rst @@ -0,0 +1,20 @@ +============= + 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. -- cgit v1.2.3