No connection to firebase realtime database from cloud functions (in java)

Question

I have a function deployed in Google Cloud Functions (in Java) and while trying to access a Realtime database, there is no response at all - the only hint is that the moment I call:

query.addListenerForSingleValueEvent

I see a log entry:

Failed to find a usable hardware address from the network interfaces; using random bytes: f1:81:5a:ef:89:81:63:07

Here is my code (the function is triggered by receiving a message from the queue):

public class FetchGPWFunction implements BackgroundFunction<PubSubMessage> {
    private static final Logger logger = Logger.getLogger(FetchGPWFunction.class.getName());

    @Override
    public void accept(PubSubMessage message, Context context) {
        String data = message.data != null
                ? "Step 0.1 successful! with message: " + new String(Base64.getDecoder().decode(message.data))
                : "Step 0.1 successful!";
        logger.info(data);
        testFetchData();
    }

    private void testFetchData() {
        if (FirebaseApp.getApps().isEmpty()) {
            FirebaseApp.initializeApp();
            logger.info("Firebase application has been initialized");
        }
        DatabaseReference databaseReference = FirebaseDatabase.getInstance("https://projectid-rtdb.europe-west1.firebaseio.com").getReference();
        Query query = databaseReference.
                child("stockData").
                child("daily").
                child("pl").
                child("ALE").
                child("quotations").
                child("20201012").
                child("high");
        logger.info("launch query");
        final QueryResult queryResult = new QueryResult();
        query.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                logger.info("onDataChange >> got key=" + dataSnapshot.getKey() + " with value=" + dataSnapshot.getValue());
                queryResult.setDataSnapshot(dataSnapshot);
            }
            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
                logger.severe("onCancelled >> ERROR! " + databaseError.getMessage() + " details=" + databaseError.getDetails());
                queryResult.setError(databaseError);
            }
        });

        int loopSafeGuard = 40;
        try {
            while (!queryResult.isDone() && (loopSafeGuard > 0)) {
                Thread.sleep(500);
                loopSafeGuard--;
            }
            logger.info("Loop ended with results: dataSnapshot=" + queryResult.getDataSnapshot() + " error=" + queryResult.getError());
        } catch (InterruptedException ie) {
            logger.info("Sleeping interrupted");
        }
    }

    public static class PubSubMessage {
        String data;
        Map<String, String> attributes;
        String messageId;
        String publishTime;
    }
}

(The query result is just a wrapper:

public class QueryResult {
    private DataSnapshot dataSnapshot = null;
    private DatabaseError error = null;
    
   ...
   
    public boolean isDone() {
        return ((dataSnapshot != null) || (error != null));
    }
}

And here are logs:

Info 2021-10-21 10:25:26.377 CEST functionFetchGPWData Firebase application has been initialized
Info 2021-10-21 10:25:26.420 CEST functionFetchGPWData launch query
Warning 2021-10-21 10:25:26.829 CEST functionFetchGPWData Failed to find a usable hardware address from the network interfaces; using random bytes: f1:81:5a:ef:89:81:63:07
Info 2021-10-21 10:25:46.463 CEST functionFetchGPWData Loop ended with results: dataSnapshot=null error=null
Debug 2021-10-21 10:25:46.467 CEST Function execution took 21311 ms, finished with status: 'ok'

No errors, no exceptions! - just this weird warning:

{
  "insertId": "000000-93ea514e-7271-4fe1-8b71-672b7d028ef7",
  "jsonPayload": {
    "message": "Failed to find a usable hardware address from the network interfaces; using random bytes: f1:81:5a:ef:89:81:63:07",
    "logging.googleapis.com/sourceLocation": {
      "method": "defaultMachineId",
      "file": "io/netty/util/internal/MacAddressUtil.java"
    }
  },
  "resource": {
    "type": "cloud_function",
    "labels": {
      "function_name": "functionFetchGPWData",
      "project_id": "projectid",
      "region": "europe-central2"
    }
  },
  "timestamp": "2021-10-21T08:25:26.829Z",
  "severity": "WARNING",
  "labels": {
    "execution_id": "waz43dlcibiy"
  },
  "logName": "projects/projectid/logs/cloudfunctions.googleapis.com%2Fcloud-functions",
  "trace": "projectid/traces/b812907333b0200b82f1323a1b5f7dcd",
  "sourceLocation": {
    "file": "io/netty/util/internal/MacAddressUtil.java"
  },
  "receiveTimestamp": "2021-10-21T08:25:35.103281657Z"
}

Is this a bug in cloud functions? Am I doing something wrong (more likely ;) ). I refuse to believe that a simple Realtime database read takes more then 20 seconds.

I think you are experiencing a function cold start. Please have a look at [this thread](https://stackoverflow.com/questions/62736297/google-cloud-functions-java-11-beta-runtime-performance-issue?noredirect=1&lq=1) and let me know if it answers your question. — Farid Shumbar, Oct 22 '21 at 07:59
HI @FaridShumbar - yes, it looks like this might be the case :/ I've restructured the db structure a bit, set the timeout to a little bigger value, and it seems it is completing in ~15-20 seconds. Fortunately this is a purely background functions launched once per day, so I'll be able to live with this. But this is disturbing. Thank You VERY much! — Miłosz, Oct 23 '21 at 21:12

score 1 · Accepted Answer · answered Oct 28 '21 at 12:33

1

To wrap it up, this is another example of a Cloud Functions' cold start.

Although it's sometimes not possible to get rid of cold start completely, there are some GCP recommendations you can follow that might help reducing this effect.

answered Oct 28 '21 at 12:33

Farid Shumbar

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No connection to firebase realtime database from cloud functions (in java)

1 Answers1