GCP pub/sub, my pulled message is always empty

Question

I have two Google Cloud functions, one that publishes and another that subscribes.

This is the code

    public void publisXeroTeannt(XeroTenant xeroTenant) {
        Gson gson = new Gson();
        String xeroTenantMessage = gson.toJson(xeroTenant);
        ByteString byteString = ByteString.copyFrom(xeroTenantMessage, StandardCharsets.UTF_8);
        PubsubMessage pubsubMessage = PubsubMessage.newBuilder()
                .setData(byteString)
                .build();
        log.info("Data being published in string utf 8 is {}", pubsubMessage.getData().toStringUtf8());

        publisher.publish(pubsubMessage);
    }

When I publish, I can clearly see the log The tenant Id being published is f837ea57-feae-4965-92c5-bc1b7cd6b2a0"

I have a subscriber

@Override
    public void accept(CloudEvent event) throws Exception {
        try {
            String cloudEventData = new String(event.getData().toBytes(), StandardCharsets.UTF_8);
            Gson gson = new Gson();
            PubsubMessage pubsubMessage = gson.fromJson(cloudEventData, PubsubMessage.class);
            String encodedData = pubsubMessage.getData().toStringUtf8();
            String decodedData =
                    new String(Base64.getDecoder().decode(encodedData), StandardCharsets.UTF_8);
            log.info("Decoded message is {}", decodedData);


        } catch (Exception e) {
            log.error("Error in processing message", e);
        }
    }

But the log always says it's an empty message INFO com.demo.SubscriberFunction - The decoded message is

What's wrong here?

Did you try to log message in other part of your code? Even if it's not decoded? The decodedData sound weird for me... — guillaume blaquiere, Aug 03 '23 at 07:43
Yes, I logged them, here they are Bytestring log is and another is when I logged the PubsubMessage Data is {"message":{"@type":"type.googleapis.com/google.pubsub.v1.PubsubMessage","attributes":null,"data":"eyJ0ZW5hbnRJZCI6ImVhYmIzMDM3LTBhZGQtNGY0Ny1hYmJiLTg5OTZlNmVkOGNiMSJ9","messageId":"8085056693470552","publishTime":"2023-08-03T06:04:51.255Z"}} — Pavanraotk, Aug 03 '23 at 08:57
Can you try again after giving a higher acknowledgement deadline? Are the Subscriber and Publisher on the same project? — kiran mathew, Aug 04 '23 at 14:01
The problem was my misunderstanding of what to deserialize, fixed it, posted code that worked as an answer. I'm hoping GCP guys fix their documentation, because the above code was from documentation. — Pavanraotk, Aug 04 '23 at 23:41

score 1 · Answer 1 · answered Aug 04 '23 at 23:40

Okay, the mistake was, after deserializing into PubsubMessage, I had to get the message and from message, I had to get the data as string, which then helped me translate to my object.

Here's the code change, I just used JsonELement rather than going with PubsubMessage, this proved successful.

public void accept(CloudEvent event) throws Exception {
        try {
            String cloudEventData = new String(event.getData().toBytes(), StandardCharsets.UTF_8);
            log.info("Cloud event data is {}", cloudEventData);

            Gson gson = new Gson();

            JsonElement je = gson.fromJson(cloudEventData, JsonElement.class);
            String tenantEncoded = je.getAsJsonObject().get("message").getAsJsonObject().get("data").getAsString();
            String tenantJson = new String(Base64.getDecoder().decode(xeroTenantEncoded), StandardCharsets.UTF_8);
            log.info("Xero tenant json is {}", tenantJson);
            Tenant tenant = gson.fromJson(tenantJson, Tenant.class);

            log.info("Decoded message is {}", xeroTenant);
            if (xeroTenant != null) {
                String tenantId = tenant.getTenantId();
                if (StringUtils.isNotBlank(tenantId)) {
                    log.info("Tenant Id is {}", tenantId);
                } else {
                    log.warn("The tenant Id is empty");
                }
            } else {
                log.warn("Xero tenant from the topic is null");
            }
        } catch (Exception e) {
            log.error("Error in processing message", e);
        }
    }

GCP pub/sub, my pulled message is always empty

1 Answers1