A Client Library for HBase using asynchbase

There is another client library clojure-hbase. It uses hbase java library. I opted for asynchbase because it promises better performance

Currently Basenji is under development and is not production ready.

Leiningen users include following line in your project.clj

[net.kirankulkarni/basenji "0.1.1"]

All the operations are available in basenji.core namespace. Just require every function in it to start with

(require '[basenji.core :refer :all])

You need to get a hbase-client and use hbase-wrap macro before you call any operation. To get client you can use get-hbase-client It takes two parameters quorum-spec and base-path.

(get-hbase-client "host1,host2,host3", "/hbase")
;;; Since /hbase is common base-path we can skip it
(get-hbase-client "host1,host2,host3")
;;; If you are doing development you can skip quorum, it will connect to localhost
(get-hbase-client)

For executing every operation you must use hbase-wrap macro

(hbase-wrap hbase-client
            forms)

forms can be any clojure s-expressions.

It supports HBase operation put, get, scan and delete.

Atomically inserts a row in HBase. Actually with this you can insert multiple qualifiers-values of single family. If your row has more than one column-family you need to call put for each one of them.

(hbase-wrap hbase-client
            (put "test" "r1" "cf1" {:q1 "val1", :q2 "val2"}))

Get a whole row from HBase.

(hbase-wrap hbase-client
            (get-row "test" "r2"))

Output is a sorted-map of row-qualifiers-timestmp and

{row-bytes
 {qual1-bytes {timestamp1 val1
               timestamp2 val2}
  qual2-bytes {timestamp1 val1
               timestamp2 val2}}

e.g.

(hbase-wrap hbase-client
            (get-row "test" "r2"))

{#<byte[] [B@1e4877ec> {#<byte[] [B@27b9367c> {1378563922180 #<byte[] [B@70a81b43>}, #<byte[] [B@2c96057d> {1378563922180 #<byte[] [B@2d426869>}}}

You can also provide row-fn, qual-fn and val-fn which will be run on respective byte-arrays

(hbase-wrap hbase-client
            (get-row "test" "r2"
                     :row-fn #(String. %)
                     :qual-fn #(String. %)
                     :val-fn #(String. %)))

{"r2" {"q1" {1378563922180 "val1"}, "q3" {1378563922180 "val3"}}}

HBase provides excellent range-queries. You can use scan API to perform a range-query. It take a table-name argument which will scan whole table. You can provide optional arguments to narrow it down:

start-row - Start Row for the scan (Inclusive) stop-row - Stop Row for the scan (Exclusive) family - Column Family to scan qualifiers - List of qualifiers to scan and return min-timestamp - All values equal to and above this will be returned (Inclusive) max-timestamp - All values below this will be returned (Exclusive)

It also accepts functions to process result like get: row-fn - Function that will be applied to row-key bytes qual-fn - Function that will be applied to qualifier bytes val-fn - Function that will be applied to value bytes

A table scan can return many results and there is a probabily that your JVM memory will be overwhelmed with all these result. Hence this function is lazy and will fetch one row at a time from HBase. You can turn this behavior by passing keyword argument :lazy? false to the scan function

(hbase-wrap hbase-client
            (scan "test"
                  :start-row "r1"
                  :end-row "r3"
                  :family "d"
                  :qualifiers [:q1 :q3]
                  :row-fn #(String. %)
                  :qual-fn #(String. %)
                  :val-fn #(String. %)))

({"r1" {"q1" {1378287632328 "q1"}}} {"r2" {"q1" {1378563922180 "val1"}, "q3" {1378563922180 "val3"}}})

Using this operation you can delete a row or a column-family of a row or a column in a row or a value of row

(hbase-wrap hbase-client
            (delete "test" "r5" ))

Apart from these operations it also provides some more utilities:

table-exists? - It checks whether given table exists in HBase column-family-exists? - It checks whether given column-family exists in given HBase table. flush - Flushes to Hbase any buffered client-side operation get-stats - Return client stats

Copyright © 2013 Kiran Kulkarni

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.