mysql + Azkaban: Reading "LongBlob"

Question

I am trying to build a query layer on 'azkaban' Database. (Language used: Java) I am running into, what I thought would be a simple problem (but turning out to be irritating).

This is the query I am running:

select exec_id, CONVERT(log USING latin1)from execution_logs

"log" is a Column of type 'longblob'

This is my Java code for reading "log"s:

try {
    Connection conn = AzkabanClient.getPhoenixConnection(conf);
    String s = " select exec_id,  log from execution_logs ";
    PreparedStatement pstmt = conn.prepareStatement(s);
    ResultSet rs = pstmt.executeQuery();
    String logString="";
    while(rs.next()){
        int i = rs.getInt("exec_id");
        InputStream inputStream = rs.getBinaryStream("log");
        java.io.BufferedReader in = new BufferedReader(new java.io.InputStreamReader(inputStream));
        String str;
        while ((str = in.readLine()) != null) {
            logString += str;
        }
        inputStream.close();
    }
    conn.close();
}catch(Exception e){
    LOGGER.error("Error =>" + e);
}

The problem here is: By the end of while loop, I am able to read the 'log' for a row in the table, but the String is unreadable (encoded?)

eg:

logString = "‹Å\]Ç•}^ÿ>°]ÕÕÝUzY‰”Uà8Žììbg¦¥..."

I have tried to modify the query like this:

"select exec_id, CONVERT(log using latin1) from execution_logs"

But still the same issue.

I tried "utf8", but when I do that, I get NULL in column "log" of the ResultSet.

Please help if somebody has experience this or know how to go about solving this?

In the meanwhile, I will keep trying things.

Thanks

---

Still trying: I am using xampp now (just to do quick prototyping).

In phpmyadmin UI, when I click on the blob, it downloads a '.bin' file. On mac, I can open this file and see proper "English" words (or logs in english), as expected.

But how to do this programatically?

Answer 1

So after a lot of digging into azkaban, I found that this is how one should query for LongBlobs in azkaban-Database:

public String getErrorLog(){
    String returnString = "";
            try {
                Connection conn = AzkabanClient.getPhoenixConnection(conf);
                String s = " select exec_id, enc_type,  log from execution_logs where exec_id = 3964 and name = 'http-time-series-hourly' ";
                PreparedStatement pstmt = conn.prepareStatement(s);
                ResultSet rs = pstmt.executeQuery();
                while (rs.next()) {
                    int i = rs.getInt("exec_id");
                    ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
                    EncodingType encType = EncodingType.fromInteger(rs.getInt("enc_type"));
                    int debug = 0;
                    byte[] data = rs.getBytes("log");
                    try {
                        byte[] buffer = data;
                        ByteArrayOutputStream byteArrayOutputStream = null;
                        if (encType == EncodingType.GZIP) {
                            byteArrayOutputStream = GZIPUtils.unGzipBytesOutputStream(data);
                        }

                        returnString = new String(byteArrayOutputStream.toByteArray(), "UTF-8");
                    } catch (IOException e) {
                        throw new SQLException(e);
                    }
                }
                conn.close();
            } catch (Exception e) {
                LOGGER.error("Error =>" + e);
            }

            return returnString;
}

where :

GZIPUtils is:

public class GZIPUtils {

    public static ByteArrayOutputStream unGzipBytesOutputStream(byte[] bytes) throws IOException {
        ByteArrayInputStream byteInputStream = new ByteArrayInputStream(bytes);
        GZIPInputStream gzipInputStream = new GZIPInputStream(byteInputStream);

        ByteArrayOutputStream byteOutputStream = new ByteArrayOutputStream();
        IOUtils.copy(gzipInputStream, byteOutputStream);

        return byteOutputStream;
}
}

and EncodingType:

public static enum EncodingType {
    PLAIN(1), GZIP(2);

    private int numVal;

    EncodingType(int numVal) {
        this.numVal = numVal;
    }

    public int getNumVal() {
        return numVal;
    }

    public static EncodingType fromInteger(int x) {
        switch (x) {
            case 1:
                return PLAIN;
            case 2:
                return GZIP;
            default:
                return PLAIN;
        }
    }
}