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Apache Phoenix(二十)因加SALT导致的HFile合并风暴
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Phoenix provides a way to transparently salt the row key with a salting byte for a particular table. You need to specify this in table creation time by specifying a table property "SALT_BUCKETS" with a value from 1 to 256. Like this: CREATE TABLE table (a_key VARCHAR PRIMARY KEY, a_col VARCHAR) SALT_BUCKETS = 20;
Apache Phoenix(二十）因加SALT导致的HFile合并风暴. 起因：在每张临时表上增加SALT_BUCKETS = 16，导致三个节点的hbase集群出现了3000多个region，出现的几种表象： 多region节点zookeeper日志：connect reset by peer; phoenix进的去，但是查询处于卡死; 多region节点HRegionServer处于CPU ...
Note: Because the Phoenix client keeps uncommitted rows in memory, be careful not to set commitSize too high. Updating data with UPSERT SELECT. When using UPSERT SELECT to write many rows in a single statement, turn on autocommit and the rows will be automatically batched according to the phoenix.mutate.batchSize.This will minimize the amount of data returned back to the client and is the most ...
When upserting a new row through Phoenix, it adds a transparent salt byte to the rowkey (eg: \x0E), the salt byte is visible from Hbase shell but not from phoenix. Problem: When we add a new row through Hbase shell, the rowkey isn't salted (no salt byte at the beginning) and the row can't be selected from phoenix using where rowkey = 'my_rowkey ...
Apache Phoenix allows to create salted tables that would distribute data accross the region servers. e.g. CREATE TABLE table (a_key VARCHAR PRIMARY KEY, a_col VARCHAR) SALT_BUCKETS = 20; In order to use this feature, a number of salt buckets must be chosen. How to choose this number of salt buckets? Should it be based in the number of region ...
This happens only for salted local indexes. If I remove the SALT_BUCKETS from the table DDL, then the test passes fine. On looking closely at the code, it seems like something is wrong with the computation of offset and subsequent parsing of the index id from the row key here (in PhoenixIndexFailurePolicy):
Since the number of salt buckets can only be set a table creation time this can be a little tricky. It takes a small amount of foresight in understanding your needs from the table AKA will the table be more read heavy or write heavy. A neutral stance would be to set the number of salt buckets to the number of Hbase RegionServers in your cluster.
Phoenix Salted Table是phoenix为了防止hbase表rowkey设计为自增序列而引发热点region读和热点region写而采取的一种表设计手段。通过在创建表的时候指定SALT_BUCKETS来实现pre-split(预分割)。如下表示创建表的时候将表预分割到20个region里面。
The second problem and the scope of this JIRA is that the function org.apache.hadoop.hbase.io.hfile.HFile.pickReaderVersion() throws exception without closing the FSDataInputStream objects even if closeIStream is set to true. This lead to orphan filesystem streams accumulating in region server and it eventually died of OOM.
phoenix 基本优化 1. SALT_BUCKETS HBASE建表之初默认一个region，当写入数据超过region分裂阈值时才会触发region分裂。我们可以通过SALT_BUCKETS方法加盐，在表构建之初就对表进行预分区。SALT_BUCKETS值的范围是1~256（2的8次方），一般将预分区的数量设置为0.5～1 倍核心数。