Feature: add Raft::data_metrics() and Raft::server_metrics()

[YangKian]

close #985

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This change is 

[YangKian]

@drmingdrmer Hi~ I'm done, PTAL when you have time

[drmingdrmer]

Thank you man.

The metrics producing process can be simplified:)

Reviewed 6 of 6 files at r1, all commit messages.
Reviewable status: all files reviewed, 4 unresolved discussions (waiting on @YangKian)

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openraft/src/metrics/mod.rs line 42 at r1 (raw file):

pub use metric::Metric;
pub use raft_metrics::is_data_metrics_changed;
pub use raft_metrics::is_server_metrics_changed;

I think these two functions can be removed since the spawned task I mentioned above is no necessary.

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openraft/src/metrics/raft_metrics.rs line 174 at r1 (raw file):

where NID: NodeId
{
    pub last_log_index: Option<u64>,

OpenRaft prefers the use of LogId over log-index whenever possible.
RaftMetrics::last_log_index is kept for backward compatibility.
For this newly added field, use last_log: Option<LogId> instead.

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openraft/src/metrics/raft_metrics.rs line 238 at r1 (raw file):

{
    pub id: NID,
    pub current_term: u64,

Openraft uses Vote instead of term when possible. current_term is kept in RaftMetrics for backward compatibility. In RaftServerMetrics, this field can be removed. An application can just use vote.leader_id.get_term() instead.

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openraft/src/raft/mod.rs line 210 at r1 (raw file):

                }
            }
        });

you do not have to create another task to replicate the metrics to data-metrics and server-metrics.
Just do this in report_metrics, which is the only entry in Openraft to update metrics.

[YangKian]

Reviewable status: 2 of 7 files reviewed, 4 unresolved discussions (waiting on @drmingdrmer)

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openraft/src/metrics/mod.rs line 42 at r1 (raw file):

Previously, drmingdrmer (张炎泼) wrote…

I think these two functions can be removed since the spawned task I mentioned above is no necessary.

Done.

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openraft/src/metrics/raft_metrics.rs line 174 at r1 (raw file):

Previously, drmingdrmer (张炎泼) wrote…

OpenRaft prefers the use of LogId over log-index whenever possible.
RaftMetrics::last_log_index is kept for backward compatibility.
For this newly added field, use last_log: Option<LogId> instead.

Done.

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openraft/src/metrics/raft_metrics.rs line 238 at r1 (raw file):

Previously, drmingdrmer (张炎泼) wrote…

Openraft uses Vote instead of term when possible. current_term is kept in RaftMetrics for backward compatibility. In RaftServerMetrics, this field can be removed. An application can just use vote.leader_id.get_term() instead.

Done.

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openraft/src/raft/mod.rs line 210 at r1 (raw file):

Previously, drmingdrmer (张炎泼) wrote…

you do not have to create another task to replicate the metrics to data-metrics and server-metrics.
Just do this in report_metrics, which is the only entry in Openraft to update metrics.

Done.

[drmingdrmer]

Reviewed 5 of 5 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @YangKian)