Shulou(Shulou.com)06/01 Report--

Segment detection and failover mechanism

GP Master will first detect the Primary status. If the Primary is not reachable, it will detect the Mirror status. There are a total of 4 Primary/Mirror states:

Primary is alive, Mirror is alive. After the GP Master probe Primary is successful, it returns directly for the next Segment test; Primary is alive, Mirror is dead. After GP Master successfully detects Primary, it learns from the status returned by Primary that Mirror is dead (after Mirror is dead, Primary will detect and change itself into ChangeTracking mode). At this time, update the Master meta-information and proceed to the next Segment test; Primary is dead and Mirror is alive. After GP Master fails to detect Primary, it detects Mirror and finds that Mirror is alive. At this time, update the meta-information on Master and make Mirror take over Primary (failover) for the next Segment detection; Primary is dead, Mirror is dead. After GP Master failed to detect Primary, the probe Mirror,Mirror also failed until the maximum value was retried, the detection of this Segment was finished, the Master meta information was not updated, and the next Segment detection was carried out.

The 2-4 above requires gprecoverseg for segment recovery.

For failed segment nodes; it will be skipped and ignored at startup.

[gpadmin@mdw ~] $gpstart== ≥ gpstart:mdw:gpadmin- [INFO]:-Starting gpstart with args: = = ≥ gpstart:mdw:gpadmin- [INFO]:-Gathering information and validating the environment...== ≥ gpstart:mdw:gpadmin- [INFO]:-Greenplum Binary Version: 'postgres (Greenplum Database) 5.0.0 build 1 requests = ≥. = = ≥ gpstart:mdw:gpadmin- [INFO]:-Master Started...== ≥ gpstart:mdw:gpadmin- [INFO]:-Shutting down master== ≥ gpstart:mdw:gpadmin- [WARNING]:-Skipping startup of segment marked down in configuration: on sdw2 directory / data/gpdata/gpdatam/gpseg0

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