Shulou(Shulou.com)05/31 Report--

This article mainly introduces how to use JournalPointer, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor take you to understand it.

The JournalPointer class description:

Class JournalPointer {

Int node_id; record MDS Rank

Int64_t pool_id; records the ID value of metadata pool

Inodeno_t front; records currently valid logs

Inodeno_t back; records the log of backup. Normally, back should be 0. If it is not 0, it means that there are outstanding log operations.

}

What the JournalPointer class writes to the cluster:

Front and back need to be written to the cluster.

Pool = metadata pool

Object_id = MDS_INO_LOG_POINTER_OFFSET+node_id+ ".0"

Methods of the JournalPointer class:

JournalPointer::load ()

| | _ _ get the object_ id value |

| _ _ Objecter::read_full (object_id, pool_id...) Read the front and backout values of JournalPointer from the cluster

| | _ _ decode (Q) parses front and backout values from the results returned by the cluster |

JournalPointer::save ()

| | _ _ encode (data) serializes front and backvalue to bufferlist |

| | _ _ get the object_ id value |

| | _ _ Objecter::write_full (object_id, pool_id,data) writes serialized front and backvalue to the cluster |

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