Azure / Azure/azure-functions-java-worker

OutputBinding not compatible with com.azure.core.models.CloudEvent

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area:java-functions Enhancement Needs: Triage (Functions) New Feature reviewed
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Mô tả

#### Investigative information

Please provide the following:

- Timestamp:
- Function App name:
- Function name(s) (as appropriate):
- Invocation ID:
- Region:

I'm not sure what the format of a CosmosDBTrigger is, and I am unable to provide this information for my current setup at the time.

#### Repro steps

As a function:

Trigger a function with com.azure.core.models.CloudEvent as the type of the OutputBinding in combination with @EventGridOutput.

```java
final @EventGridOutput(
name = "OutputEvent",
topicEndpointUri = "EventGridTopicEndpoint",
topicKeySetting = "EventGridTopicKey")
OutputBinding eventGridOutput
```

As a standalone issue:

```java
package org.example.functions;

import com.azure.core.models.CloudEvent;
import com.azure.core.models.CloudEventDataFormat;
import com.azure.core.util.BinaryData;
import com.google.gson.Gson;

public class Foo {

public static void main(String[] args) {
CloudEvent cloudEvent = new CloudEvent("mySource", "myType", BinaryData.fromObject(new Object()), CloudEventDataFormat.JSON, "application/json");
Gson gson = new Gson();
gson.toJson(cloudEvent);
}

}
```
More specific, it's the serialization of com.azure.core.implementation.util.SerializableContent, used by com.azure.core.util.BinaryData#fromObject(java.lang.Object) that causes the issue

```java
package org.example.functions;

import com.azure.core.implementation.serializer.DefaultJsonSerializer;
import com.google.gson.Gson;

public class Bar {

public static void main(String[] args) {
Gson gson = new Gson();
gson.toJson(new SerializableContent(new Object(), new DefaultJsonSerializer()));
}
}
```

#### Expected behavior

The CloudEvent is serialized and sent to the desired output binding.

#### Actual behavior

The runtime is unusable after one trigger due a (swallowed?) StackOverflowError and nothing is sent to the output as a result.

#### Known workarounds

- Create a custom class that implements the CloudEvent spec.

#### Related information

Provide any related information

Basically it all boils down to Jackson vs Gson. The [CloudEvent](https://github.com/Azure/azure-sdk-for-java/blob/21d71f77f0b489db1667b6bd5a989208b1372d7c/sdk/eventgrid/azure-messaging-eventgrid/src/main/java/com/azure/messaging/eventgrid/implementation/models/CloudEvent.java#L19) uses Jackson annotations to imply serialization rules while the azure-functions-java-worker uses [Gson](https://github.com/Azure/azure-functions-java-worker/blob/31e0a81e8522327c201bacbfc82665fcded6953e/src/main/java/com/microsoft/azure/functions/worker/binding/RpcUnspecifiedDataTarget.java#L6) for serialization. Ironically, the last change on RpcUnspecifiedDataTarget.java, was switching from Jackson to Gson.

Note that com.azure.core.models.CloudEvent#binaryData is annotated with @JsonIgnore. This property is what causes the StackOverflowError when serializing with Gson.

I'm using java 8 to dodge the issues caused by reflection due modularization in java 9.
@CosmosDBTrigger as trigger
@EventGridOutput as output binding

Ideally, there is a consensus in using Jackson vs Gson throughout the azure java projects to prevent such issues in the future.

Furthermore, the CloudEvent implementation doesn't even work with Jackson due to com.azure.core.models.CloudEvent#getData not returning the actual data. Instead it serializes to SerializableContent.

```java
@JsonProperty("data")
private JsonNode data;

public BinaryData getData() {
if (this.binaryData == null) {
if (this.data != null) {
this.binaryData = BinaryData.fromObject(this.data, SERIALIZER);
} else if (this.dataBase64 != null) {
this.binaryData = BinaryData.fromBytes(Base64.getDecoder().decode(this.dataBase64));
}
}

return this.binaryData;
}
```

Serializing CloudEvent with Jackson:

```java
package org.example.functions;

import com.azure.core.models.CloudEvent;
import com.azure.core.models.CloudEventDataFormat;
import com.azure.core.util.BinaryData;
import com.fasterxml.jackson.databind.ObjectMapper;

public class Jackson {

public static void main(String[] args) throws Exception {
CloudEvent cloudEvent = new CloudEvent("mySource", "myType", BinaryData.fromObject(new Object()), CloudEventDataFormat.JSON, "application/json");
ObjectMapper objectMapper = new ObjectMapper();
System.out.println(objectMapper.writeValueAsString(cloudEvent));
}
}
```
Output:

```json
{"id":"19b834e0-803b-4c12-9d21-4e6efea3f3b9","source":"mySource","data":{"replayable":true,"length":2},"data_base64":null,"type":"myType","time":null,"specversion":"1.0","dataschema":null,"datacontenttype":"application/json","subject":null}
```
Note that the data property is the serialized representation of SerializableContent through 'replayable' and 'length'.

The CloudEvent implementation for Event Grid is unusable at this point without changes to the azure-sdk-for-java.
https://github.com/Azure/azure-sdk-for-java/issues/36000

Please let me know if you require addition info.

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Hướng nghiên cứu

Bắt đầu với src/main/java/com/microsoft/azure/functions/worker/binding/RpcUnspecifiedDataTarget.java và tái hiện lỗi bằng các ví dụ Gson độc lập trong issue. So sánh hành vi tuần tự hóa của nó với triển khai Azure CloudEvent được tham chiếu và xác minh rằng một CloudEvent có thể được tuần tự hóa mà không xảy ra StackOverflowError và được gửi qua EventGrid output binding.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.

Đánh giá

Công nghệ
azure, java
Lĩnh vực
backend, cloud
Loại issue
Lỗi
Độ khó
4/5
Thời gian dự kiến
3-5 ngày
Mức độ hoạt động
Đình trệ
Độ rõ ràng
Khá rõ ràng
Mức phù hợp với người mới
35/100

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