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