# Failed to retrieve machine-readable status via the FoundationDB Java Client API

**URL:** <https://forums.foundationdb.org/t/failed-to-retrieve-machine-readable-status-via-the-foundationdb-java-client-api/1205>\
**Category:** Using FoundationDB\
**Tags:** bindings\
**Created:** [March 7, 2019, 10:44am UTC](https://forums.foundationdb.org/t/failed-to-retrieve-machine-readable-status-via-the-foundationdb-java-client-api/1205 "2019-03-07T10:44:33Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![jltz](https://avatars.discourse-cdn.com/v4/letter/j/c0e974/32.png) [@jltz](https://forums.foundationdb.org/u/jltz)\
**Post date:** [March 7, 2019, 10:44am UTC](https://forums.foundationdb.org/t/failed-to-retrieve-machine-readable-status-via-the-foundationdb-java-client-api/1205/1 "2019-03-07T10:44:33Z")

</div>

To retrieve the machine-readable status, the following Python code works on my FDB cluster:

import fdb  
import json

fab.api\_version(600)  
db=fdb.open()  
status = json.loads(db[’\xff\xff/status/json’])  
print status

Then I have the following Java code to try to retrieve the same status:

public class FoundationDBClusterStatus {

```
private static final FDB fdb;
private static final Database db;

static {
    fdb = FDB.selectAPIVersion(600);
    db = fdb.open("/<path>/fdb.cluster");
}

public static void main(String[] args) throws InterruptedException {
    String statusInJson = db.run(tr -> {
        TransactionOptions options = tr.options();
        options.setReadSystemKeys();
        byte[] result = tr.get(Tuple.from((byte)0xff, (byte)0xff, "/status/json".getBytes()).pack()).join();
        if (result != null) {
            System.out.println("result is not null");
            return Tuple.fromBytes(result).getString(0);
        }
        else{
            System.out.println("result is null");
            return "";
        }
    });

    System.out.println("status in json is: " + statusInJson);
}

```

}

I am able to get the database object, but always get the null byte result, even though I tried to set that the key access is a system key access. Do I miss something on encoding the key?

Thanks.

---

<div class="post-metadata">

**Author:** ![gaurav](https://avatars.discourse-cdn.com/v4/letter/g/b487fb/32.png) [@gaurav](https://forums.foundationdb.org/u/gaurav)\
**Post date:** [March 7, 2019, 11:01am UTC](https://forums.foundationdb.org/t/failed-to-retrieve-machine-readable-status-via-the-foundationdb-java-client-api/1205/2 "2019-03-07T11:01:27Z")

</div>

You might have to form the key directly as a byte, without involving Tuple layer. Tuple layer encoding would create a byte array that is different from \xff\xff/status/json

---

<div class="post-metadata">

**Author:** ![jltz](https://avatars.discourse-cdn.com/v4/letter/j/c0e974/32.png) [@jltz](https://forums.foundationdb.org/u/jltz)\
**Post date:** [March 7, 2019, 9:33pm UTC](https://forums.foundationdb.org/t/failed-to-retrieve-machine-readable-status-via-the-foundationdb-java-client-api/1205/3 "2019-03-07T21:33:13Z")

</div>

Thank you for the suggestion. After I changed the code to manually construct the byte for \xff\xff/status/json, I was able to retrieve correctly the status information. The returned byte result also should not pass through the Tuple layer for String unmarshalling. The following is the code that works:

```
public static byte[] stringToBytesASCII(String str) {
    char[] buffer = str.toCharArray();
    byte[] b = new byte[buffer.length];
    for (int i = 0; i < b.length; i++) {
        b[i] = (byte) buffer[i];
    }
    return b;
}

public static void main(String[] args) throws InterruptedException {
    // we have to build the byte array and not using the Tuple layer APIs.
    String statusInJson = db.run(tr -> {
        TransactionOptions options = tr.options();
        options.setReadSystemKeys();
        byte[] stringPartOfKey= stringToBytesASCII("/status/json");
        byte[] fullKey =new byte[stringPartOfKey.length +2];

        fullKey[0] = (byte)0xff;
        fullKey[1] = (byte)0xff;

        for (int i=2; i<fullKey.length; i++) {
            fullKey[i] = stringPartOfKey[i-2];
        }

        //same to the output of the key value that we should not rely on the Tuple layer APIs.
        byte[] result = tr.get(fullKey).join();

        try {
            String str = new String(result, "UTF-8");
            return str;
        }
        catch (Exception ex) {
            System.out.println("encounter exception: " + ex.getMessage());
            return "";
        }

    });

    System.out.println("status in json is: " + statusInJson);
}
```

---

<div class="post-metadata">

**Author:** ![st96d045](https://avatars.discourse-cdn.com/v4/letter/s/e99b99/32.png) [@st96d045](https://forums.foundationdb.org/u/st96d045)\
**Post date:** [March 11, 2019, 9:03pm UTC](https://forums.foundationdb.org/t/failed-to-retrieve-machine-readable-status-via-the-foundationdb-java-client-api/1205/4 "2019-03-11T21:03:03Z")

</div>

Perhaps a simplified version of the above using ByteBuffers instead:

```
    public String getStatus() {
    return db.run(tr -> {
        TransactionOptions options = tr.options();
        options.setReadSystemKeys();

        // we have to build the byte array and not using the Tuple layer APIs.
        //same to the output of the key value that we should not rely on the Tuple layer APIs.
        ByteBuffer bb = ByteBuffer.allocate("/status/json" + 2);
        bb.put((byte)0xff);
        bb.put((byte)0xff);
        bb.put("/status/json".getBytes(Charset.defaultCharset()));
        byte[] result = tr.get(bb.array()).join();

        try {
            String str = new String(result, "UTF-8");
            return str;
        } catch (Exception ex) {
            return null;
        }
    });
}
```