A reader receives RETCODE_NO_DATA with keyed topics when the value of the key is zero [12862]

[WataruToishita]

A reader receives RETCODE_NO_DATA with keyed topics.

1. Define a data type with a key like this:
   struct sample{
   octet index;
   @key octet key_value;
   };
2. A writer write a sample with key_value = 0.
3. A reader call take_next_sample() to get the sample, but it returns RETCODE_NO_DATA.

This symptom occurs only when key_value = 0.

Expected Behavior

A reader receives RETCODE_OK regardless of key_value.

Current Behavior

A reader receives RETCODE_NO_DATA only when key_value = 0.

Steps to Reproduce

1. Edit this example and build.
   From my_sample.key_value(i + 1); to my_sample.key_value(i + 0);
2. Run example (./Keys publisher)
3. Run example (./Keys subscriber)
4. Received samples with key_value!=0 will be printed in console.

System information

• OS: Ubuntu 18.04.5
• Fast-RTPS version:
  V2.4.0: This symptom occurs.
  V2.3.0: This symptom occurs.
  V2.2.0: No Problem

[fujitatomoya]

CC: @Barry-Xu-2018 @iuhilnehc-ynos (This problem is originally come from one of our division.)

[Barry-Xu-2018]

After quickly checking, I found

While key_value is 0, an invalid InstanceHandle_t is created.

Fast-DDS/examples/C++/Keys/sample.idl

Lines 1 to 4 in 5fc0d6c

	struct sample{
	octet index;
	@Key octet key_value;
	};

While key_value is 0, the value of InstanceHandle_t is 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.

Fast-DDS/include/fastdds/rtps/common/InstanceHandle.h

Lines 34 to 37 in 5fc0d6c

	struct RTPS_DllAPI InstanceHandle_t
	{
	//!Value
	octet value[16];

If each value is 0, it is considered to be undefined.

Fast-DDS/include/fastdds/rtps/common/InstanceHandle.h

Lines 107 to 121 in 5fc0d6c

	/**
	* Know if the instance handle is defined
	* @return True if the values are not zero.
	*/
	bool isDefined() const
	{
	for (uint8_t i = 0; i < 16; ++i)
	{
	if (value[i] != 0)
	{
	return true;
	}
	}
	return false;
	}

Get warning while creating new_change.

Fast-DDS/src/cpp/rtps/writer/RTPSWriter.cpp

Lines 218 to 221 in 6b55651

	if (m_att.topicKind == WITH_KEY && !handle.isDefined())
	{
	logWarning(RTPS_WRITER, "Changes in KEYED Writers need a valid instanceHandle");
	}

InstanceHandle_t is created by the below code, which is produced by fastcdrgen tool.
So need to consider this special case while creating InstanceHandle_t

Fast-DDS/examples/C++/Keys/samplePubSubTypes.cxx

Lines 110 to 132 in 5fc0d6c

	bool samplePubSubType::getKey(void *data, InstanceHandle_t* handle, bool force_md5)
	{
	if(!m_isGetKeyDefined)
	return false;
	sample* p_type = static_cast<sample*>(data);
	eprosima::fastcdr::FastBuffer fastbuffer(reinterpret_cast<char*>(m_keyBuffer),sample::getKeyMaxCdrSerializedSize()); // Object that manages the raw buffer.
	eprosima::fastcdr::Cdr ser(fastbuffer, eprosima::fastcdr::Cdr::BIG_ENDIANNESS); // Object that serializes the data.
	p_type->serializeKey(ser);
	if(force_md5 || sample::getKeyMaxCdrSerializedSize()>16) {
	m_md5.init();
	m_md5.update(m_keyBuffer, static_cast<unsigned int>(ser.getSerializedDataLength()));
	m_md5.finalize();
	for(uint8_t i = 0;i<16;++i) {
	handle->value[i] = m_md5.digest[i];
	}
	}
	else {
	for(uint8_t i = 0;i<16;++i) {
	handle->value[i] = m_keyBuffer[i];
	}
	}
	return true;
	}

[davidhjp01]

Hello, I posted related comments previously, just in case if it can help resolving this issue:
#2215 (comment)

[MiguelCompany]

@WataruToishita @fujitatomoya @davidhjp01 Please check if #2316 solves your issues.

[fujitatomoya]

@Barry-Xu-2018 could you try that out if the problem can be solved?

[WataruToishita]

Hi @MiguelCompany,
I have verified #2316 and it solves this issue. Thank you!!

[Barry-Xu-2018]

@Barry-Xu-2018 could you try that out if the problem can be solved.

After checking, #2316 can fix this problem.

[davidhjp01]

@WataruToishita @fujitatomoya @davidhjp01 Please check if #2316 solves your issues.

Seems it works on our side as well.

[fujitatomoya]

@MiguelCompany we've done double check on this issue can be solved by #2316. please close this issue once #2316 is merged. appreciate it 👍