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Editor to share with you the Ceph Jewel version of the third copy of the reading operation of the example analysis, I believe that most people do not know much about it, so share this article for your reference, I hope you will learn a lot after reading this article, let's go to know it!

1. Main OSD read processing flow

OSD::ms_fast_dispatch ()

| | _ OSD::dispatch_session_waiting () |

| | _ OSD::dispatch_op_fast () |

| | _ OSD::handle_op () |

| | _ _ OSD::get_pg_or_queue_for_pg () finds the corresponding PG and Pool information in OpRequest |

| | _ OSD::enqueue_op () |

| | _ PG::queue_op () |

| | _ _ OSD::ShardedThreadPool::ShardedWQ::queue () put PG and Op in the queue together |

OSD::ShardedOpWQ::_process () is responsible for handling Op in the OSD::ShardedThreadPool::ShardedWQ queue

| | _ _ PGQueueable::RunVis::operator () (const OpRequestRef & op) |

| | _ OSD::dequeue_op () |

| | _ ReplicatedPG::do_request () |

| | _ _ check whether the current PG is in flush or peering status. If so, put op in the waiting_for_peered queue and wait for PG to become available |

| | _ _ check whether the current PG is in Active state, and if not, put the op in the waiting_for_active queue |

| | _ _ check whether the current PG is in REPLAY status, and if so, put the op in the waiting_for_active queue |

| | _ ReplicatedPG::do_op () |

| | _ _ RepliatedPG::do_pg_op () CEPH_OSD_RMW_FLAG_PGOP the operation on PG that is included in the request |

| | _ _ create hobject_t class object (head) based on op request |

| | _ _ check whether object name length / object locator key length / object locator namespace length is greater than osd_max_object_name_len |

| | _ _ check whether the head of object is valid through FileStore |

| | _ _ check whether the op request address is in the blacklist of OSDMap |

| | _ _ for write requests, check whether the data size of the write request is greater than the osd_max_write_ size value |

| | _ _ if the head of the op request is currently unreadable, put the op in the waiting_for_unreadable_object queue and call the maybe_kick_recovery () function to try to start recovery |

| | _ _ ReplicatedPG::is_degraded_or_backfilling_object () checks whether the head requested by the current op is in recovery or backfill status |

| | _ _ ReplicatedPG::wait_for_degraded_object () puts the head of the current op request into the waiting_for_degraded_object queue |

| | _ _ check whether head is in the objects_blocked_on_degraded_snap queue, and if so, put the head of the current op request into the waiting_for_degraded_object queue |

| | _ _ check whether head is in the objects_blocked_on_snap_promotion queue, and if so, put the head of the current op request into the waiting_for_blocked_object queue |

| | _ _ check whether head is in the objects_blocked_on_cache_full queue, and if so, put the head of the current op request into the waiting_for_cache_not_full queue |

| | _ _ check whether the snapdir of head is unreadable. If so, put the snapdir of head into the waiting_for_unreadable_object queue and call the maybe_kick_recovery () function to try to start recovery. |

| | _ _ check whether the snapdir of head is in recovery or backfill status, and if so, put the snapdir of head into the waiting_for_degraded_object queue |

| | _ _ for op write request is already in PGLog, if the write operation has been completed, the MOSDOpReply message is returned directly to the client and CEPH_OSD_FLAG_ACK is set, otherwise the op is placed in the waiting_for_ack or waiting_for_ondisk queue |

| | _ _ ReplicatedPG::find_object_context () gets object context information |

| | _ _ check whether the object context is in io blocked state, and if so, put the op request into the waiting_for_blocked_object or waiting_for_degraded_object queue |

| | _ ReplicatedPG::execute_ctx () |

| | _ ReplicatedPG::prepare_transaction () |

| | _ _ create MOSDOpReply message instance |

| | _ _ call ReplicatePG::complete_read_ctx () to return the result of the read operation to the client |

The above is all the contents of the article "sample Analysis of three copies of the Ceph Jewel version". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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