Getting Started with Avro [closed]

Question

I want to get started with using Avro with Map Reduce. Can Someone suggest a good tutorial / example to get started with. I couldnt find much through the internet search.

Panoptic

Answer 1

I recently did a project that was heavily based on Avro data and not having used this data format before, I had to start from scratch. You are right in that it is rather hard to get much help from online sources when getting started with Avro. The material that I would recommend to you is:

• By far, the most helpful source that I found was the Avro section (p103-p116) in Tom White's Hadoop: The Definitive Guide book as well as his Github page for the code he uses in the book.
• For additional code examples I looked at Ron Bodkin's Github page avro-mr-sample.
• In my case I used Python for reading and writing Avro files and for that I used this tutorial.
• Even though it is obvious, I will add the link to the Avro Users mailing list. There is a ton of information to be found there and after I had read the above material and implemented a bunch of code, I found myself spending hours looking through the archives.

Finally, my last suggestion to you is to use Avro 1.4.1 with Hadoop 0.20.2 and ONLY that combination. I had some major issues getting my code to run using Hadoop 0.21 and more recent Avro versions.

Catadromous

I would add that the section on Avro is in Hadoop: The Definitive Guide Second Edition. My 1st Ed is woefully inadequate. – Denys

@RichardClayton As of now, the latest 4th edition is fairly decent. It goes into much more detail and than the (near-useless) "Hadoop MapReduce Guide" in the Avro documentation. Note that there's no need to buy the book itself - one can subscribe to Safari Books or even use a trial. – Speculative

Answer 2

Other links:

• JavaDocs are sometimes needed.
• This InfoQ article may be of some use
• Avro Serialization

The main problem I see with documentation (little that does exist) is that it focuses on very laborious "generic" approach; which seems odd because it combines worst of both world -- you must still provide full schema for data, but get no benefit from static types or such. The automatic code-generation is more convenient, but less well covered.

Staples

Answer 3

https://github.com/apache/avro/blob/trunk/lang/java/mapred avro source code do have examples. e.g. TestReflectJob help me to write map-reduce job using my pre-defined domain objects

Ruhl

Answer 4

Javascript + jQuery : https://codepen.io/GentjanLikaj/pen/dyPXLXX

$( "#btn1" ).click(function() {
    $( "table" ).remove();
    var text1 = document.getElementById('text').value;
    var text1=text1.replace(/(\r\n|\n|\r)/gm,"");
    var sep = document.getElementById('sep').value;
    var aray = text1.split(sep);
    var formato = '<select class="form"><option value="string">string</option><option value="int">int</option><option value="date">date</option><option value="datetime">datetime</option><option value="float">float</option><option value="varchar(50)">varchar</option></select>';
    var univoco = '<input id="checkbox" type="checkbox" name="univoco" value="true" > <br>';
    var null1 = '<input id="null" class="null11" type="checkbox" name="univoco" value="null" checked> <br>';
    var html = '<table id="tbl" class="table table-sm  table-striped table-centered .thead-dark "><thead class="thead-dark"><tr class="table-primary"><th scope="col">ColumnName</th><th scope="col">Format</th>  <th scope="col">Null</th>   </tr>  </thead> <tbody>';
    $.each(aray, function(i, val) {
        html += '<tr><td id = "val">' + val + '</td><td id = "form">' + formato + '</td><td id = "nul">' + null1 + '</td></tr>';
    });
    html += '</tbody></table>'; 
    $("#table").append(html);
});

$( "#btn2").click(function() {
    $( "#avro" ).empty();
    var myRows = {myRows:[]};
    var $th = $('#tbl th');
    $('#tbl tbody tr').each(function(i, tr){
        var obj = {}, 
        $tds = $(tr).find('td');
        $td1 = $(tr).find('select.form').children("option:selected");
        $tds2 = $(tr).find('#checkbox');
        $tds3 = $(tr).find('#null');
        $th.each(function(){
            obj['name'] = $tds.eq(0).text();
            var type=$td1.eq(0).val();
            var nullv=$tds3.eq(0).is(':checked');
            if (type=='date') {
                type={type:"int", logicalType:"date"};
            }else if (nullv == true) {
                type = [type ,'null' ];
            }
            else{
                type;
            }
            obj['type'] = type;
            // obj['univoco'] = $tds2.eq(0).is(':checked');
            // obj['null'] = $tds3.eq(0).is(':checked');
        });
        myRows.myRows.push(obj);        
    }); 
    console.log(JSON.stringify(myRows));
    var header = '{ <br> &nbsp &nbsp "type": "record"  ,  <br>   &nbsp &nbsp "namespace": "Mezzora" ,  <br>  &nbsp &nbsp "name": "ReportDSL" ,  <br>   &nbsp &nbsp  "fields": [ <br>';
    $('#avro').append(header);
    text ='&nbsp &nbsp &nbsp &nbsp &nbsp '+JSON.stringify(myRows.myRows[0])  +"<br>";
    $('#avro').append(text);
    var i;
    for (i = 1; i < myRows.myRows.length; i++) {
        text ='&nbsp &nbsp &nbsp &nbsp &nbsp  ,'+ JSON.stringify(myRows.myRows[i])  +"<br>";
        $('#avro').append(text);
    }
    var footer = '&nbsp &nbsp &nbsp &nbsp  ] <br> }';
    $('#avro').append(footer);  
});

$( "#btn3").click(function() {
    $( "#sql" ).empty();
    var myRows = {myRows:[]};
    var $th = $('#tbl th');
    $('#tbl tbody tr').each(function(i, tr){
        var obj = {}, 
        $tds = $(tr).find('td');
        $td1 = $(tr).find('select.form').children("option:selected");
        $tds2 = $(tr).find('#checkbox');
        $tds3 = $(tr).find('#null');
        $th.each(function(){
            obj['name'] = $tds.eq(0).text();
            var type=$td1.eq(0).val();
            var nullv=$tds3.eq(0).is(':checked');
            if (nullv == false) {
                type= type +' not null';
            }else if (nullv == true) {
                type = type +' null' ;
            }else{
                if (type == 'string') {
                    type = 'varchar(50)';
                }else{
                    type;
                }
            }           
            obj['type'] = type;
            // obj['univoco'] = $tds2.eq(0).is(':checked');
            // obj['null'] = $tds3.eq(0).is(':checked');
        });
        myRows.myRows.push(obj);        
    }); 
    console.log(JSON.stringify(myRows));
    var header = 'CREATE TABLE [schema].[tblName] &nbsp ( <br>';
    $('#sql').append(header);
    var i;
    for (i = 0; i < myRows.myRows.length; i++) {
        text ='&nbsp &nbsp &nbsp &nbsp &nbsp '+ JSON.stringify(myRows.myRows[i].name).replace('\"',' ').replace('\"',' ') +JSON.stringify(myRows.myRows[i].type).replace('\"',' ').replace('\"',' ')   +", <br>";
        $('#sql').append(text);
    }
    var footer = ');';
    $('#sql').append(footer);   
});

.parent {
    display: grid;
    grid-template-columns: repeat(10, 1fr);
    grid-template-rows: repeat(12, 1fr);
    grid-column-gap: 20px;
    grid-row-gap: 0px;
    }
    
    .div1 { grid-area: 1 / 2 / 2 / 11; }
    .div2 { grid-area: 5 / 6 / 6 / 7; }
    .div3 { grid-area: 3 / 1 / 5 / 12; }
    .div4 { grid-area: 2 / 1 / 3 / 2; }
    .div5 { grid-area: 6 / 1 / 13 / 4; }
    .div6 { grid-area: 6 / 4 / 13 / 8; }
    .div7 { grid-area: 6 / 8 / 13 / 12; }
    
    .div6 , .div7{

        border: 1px solid black;
        margin-right: 10px;
    }

    #btn1{
        margin-bottom: 30px;
    }

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title></title>
  <script  src="https://code.jquery.com/jquery-3.4.1.js"  integrity="sha256-WpOohJOqMqqyKL9FccASB9O0KwACQJpFTUBLTYOVvVU="   crossorigin="anonymous"> </script>
  <link href="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-Vkoo8x4CGsO3+Hhxv8T/Q5PaXtkKtu6ug5TOeNV6gBiFeWPGFN9MuhOf23Q9Ifjh" crossorigin="anonymous">
</head>
<body>
    <h2>Insert the text and the separator and press the button: </h2>
    <div class="parent">
        <div class="div1"></div>
        <div class="div2 btn btn-alert"></div>
        <div class="div3">
      <textarea name="text" id="text" cols="120" rows="4" placeholder="ColumnName1,ColumName2,ColumName3,ColumName4,............"></textarea>
      <input type="button"  value="Convert to Table" id="btn1" class="btn btn-primary"> 
    </div>
        <div class="div4">Separatetor<input type="text" name="sep" id="sep" value=","> </div>
        <div class="div5">
            <input type="button" value="Convert to Avro" class="btn btn-success" id="btn2">
            <input type="button" value="Convert to SQL Create" class="btn btn-info" id="btn3">
            <div id="table"></div>
        </div>
        <div class="div6 card">
            <div class="card-header font-weight-bolder">Avro Format</div>
            <div class="card-body" id='avro'>
            </div>
        </div>
        <div class="div7 card">
            <div class="card-header font-weight-bolder">SQL Create</div>
            <div class="card-body" id='sql'>
            </div>
        </div>
    </div>
</body>
</html>

Acarpous