org.apache.hadoop.hbase.master.http

Class MetaBrowser

java.lang.Object

org.apache.hadoop.hbase.master.http.MetaBrowser

@InterfaceAudience.Private
public class MetaBrowser
extends Object

Support class for the "Meta Entries" section in resources/hbase-webapps/master/table.jsp.

Interface. This class's intended consumer is table.jsp. As such, it's primary interface is the active HttpServletRequest, from which it uses the scan_* request parameters. This class supports paging through an optionally filtered view of the contents of hbase:meta. Those filters and the pagination offset are specified via these request parameters. It provides helper methods for constructing pagination links.

• "name" - the name of the table requested. The only table of our concern here is hbase:meta; any other value is effectively ignored by the giant conditional in the jsp.
• "scan_limit" - specifies a limit on the number of region (replicas) rendered on the by the table in a single request -- a limit on page size. This corresponds to the number of RegionReplicaInfo objects produced by MetaBrowser.Results.iterator(). When a value for scan_limit is invalid or not specified, the default value of 10 is used. In order to avoid excessive resource consumption, a maximum value of 10000 is enforced.
• "scan_region_state" - an optional filter on RegionState.
• "scan_start" - specifies the rowkey at which a scan should start. For usage details, see the below section on Pagination.
• "scan_table" - specifies a filter on the values returned, limiting them to regions from a specified table. This parameter is implemented as a prefix filter on the Scan, so in effect it can be used for simple namespace and multi-table matches.

Pagination. A single page of results are made available via getResults() / an instance of MetaBrowser.Results. Callers use its Iterator consume the page of RegionReplicaInfo instances, each of which represents a region or region replica. Helper methods are provided for building page navigation controls preserving the user's selected filter set: buildFirstPageUrl(), buildNextPageUrl(byte[]). Pagination is implemented using a simple offset + limit system. Offset is provided by the "scan_start", limit via "scan_limit". Under the hood, the Scan is constructed with Scan.setMaxResultSize(long) set to ("scan_limit" +1), while the MetaBrowser.Results Iterator honors "scan_limit". The +1 allows the caller to know if a "next page" is available via MetaBrowser.Results.hasMoreResults(). Note that this pagination strategy is incomplete when it comes to region replicas and can potentially omit rendering replicas that fall between the last rowkey offset and replicaCount % page size.

Error Messages. Any time there's an error parsing user input, a message will be populated in getErrorMessages(). Any fields which produce an error will have their filter values set to the default, except for a value of "scan_limit" that exceeds 10000, in which case 10000 is used.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	MetaBrowser.Results Encapsulates the results produced by this MetaBrowser instance.

Field Summary

Fields

Modifier and Type	Field and Description
static String	NAME_PARAM
static int	SCAN_LIMIT_DEFAULT
static int	SCAN_LIMIT_MAX
static String	SCAN_LIMIT_PARAM
static String	SCAN_REGION_STATE_PARAM
static String	SCAN_START_PARAM
static String	SCAN_TABLE_PARAM

Constructor Summary

Constructors

Constructor and Description
MetaBrowser(AsyncConnection connection, javax.servlet.http.HttpServletRequest request)

Method Summary

Modifier and Type	Method and Description
String	buildFirstPageUrl()
String	buildNextPageUrl(byte[] lastRow)
List<String>	getErrorMessages()
String	getName()
MetaBrowser.Results	getResults()
Integer	getScanLimit()
RegionState.State	getScanRegionState()
byte[]	getScanStart()
TableName	getScanTable()
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

NAME_PARAM

public static final String NAME_PARAM

See Also:

Constant Field Values

SCAN_LIMIT_PARAM

public static final String SCAN_LIMIT_PARAM

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Constant Field Values

SCAN_REGION_STATE_PARAM

public static final String SCAN_REGION_STATE_PARAM

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Constant Field Values

SCAN_START_PARAM

public static final String SCAN_START_PARAM

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Constant Field Values

SCAN_TABLE_PARAM

public static final String SCAN_TABLE_PARAM

See Also:

Constant Field Values

SCAN_LIMIT_DEFAULT

public static final int SCAN_LIMIT_DEFAULT

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Constant Field Values

SCAN_LIMIT_MAX

public static final int SCAN_LIMIT_MAX

See Also:

Constant Field Values

Constructor Detail

MetaBrowser

public MetaBrowser(AsyncConnection connection,
                   javax.servlet.http.HttpServletRequest request)

Method Detail

getErrorMessages

public List<String> getErrorMessages()

getName

public String getName()

getScanLimit

public Integer getScanLimit()

getScanStart

public byte[] getScanStart()

getScanRegionState

public RegionState.State getScanRegionState()

getScanTable

public TableName getScanTable()

getResults

public MetaBrowser.Results getResults()

toString

public String toString()

Overrides:

toString in class Object

buildFirstPageUrl

public String buildFirstPageUrl()

buildNextPageUrl

public String buildNextPageUrl(byte[] lastRow)