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https://issues.apache.org/jira/browse/HBASE-12364?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14209236#comment-14209236
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ramkrishna.s.vasudevan commented on HBASE-12364:
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CPs are nothing but CoProcessors. Coprocessors are frameworks that provides
some hooks in the master, region server and regions so that the user could
control the way some of the operations are performed like flush, compaction,
scan, writes etc.
See RegionObserver, MasterObserver,RegionServerObserver etc.
The region observers are associated with the regions of a table with which the
coprocessors are associated with. Master observer's hooks are used whenever
operations related to master is happening, similar with RegionServerObservers.
The main interesting thing is that HBase gives you the opportunity to configure
these coprocessors and you could also assign priorities to them.
> API for query metrics
> ---------------------
>
> Key: HBASE-12364
> URL: https://issues.apache.org/jira/browse/HBASE-12364
> Project: HBase
> Issue Type: Improvement
> Components: metrics
> Affects Versions: 0.98.6.1
> Environment: Any Hadoop distribution.
> Reporter: Gunnar Tapper
>
> Request based on a discussion with Nick Dimiduk at Strata.
> Background: IT organizations operate on reports based on metrics. They look
> for comparative statistics such as number of queries per user per day per
> connection. Further, troubleshooting is often based on questions such as
> "what queries are each running, which user is using the most resources, and
> what query among the queries that a specific user need to be tuned?"
> Currently, the slow-query log does not provide the instrumentation needed for
> management applications to obtain and analyze this level of information. In
> itself, they slow-query doesn't contain important information that allows
> mapping of the information to user, connection, application, and so on.
> Further, the slow-query log doesn't log each get and scan, which means that
> it's not possible to see all queries that have been run against the HBase
> database.
> Preferably, a REST API is provided to obtain the required information, which
> should be extended so that each query can be mapped to environment
> information; for example:
> • Account
> • Account string
> • Client IP address
> • Query text
> • Session ID
> • Date and time
> • User name
> Start, Status, and Completion records should be provided so that it's
> possible to determine the progress and outcome of any given query. Further,
> status and completion information should contain information about resource
> usage; for example:
> • CPU time
> • Memory
> • I/Os
> • Rows read/written
> • Objects accessed
> • Wait times
> Preferably, counters are provided in both cumulative and delta (since query
> start) formats.
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