Fix[BMQ]: unsafe schemalearner use #618
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dorjesinpo
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src/groups/bmq/bmqa/bmqa_message.h
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| @@ -60,6 +60,7 @@ | |||
| // BMQ | |||
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| #include <bmqa_queueid.h> | |||
| #include <bmqp_messageproperties.h> | |||
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The only change in this header is this new field:
bmqp::MessageProperties::SchemaPtr d_schema_sp
It is a pointer type, so we don't need to know the class sizeof in advance. We can replace include to a heavy header with a forward declaration to this type. At some point in the future we might want to optimize includes to achieve a better compilation time.
If you think it's helpful, you can make this change now.
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We can. No nested MessageProperties::Schema though, now it has to be MessageProperties_Schema
src/groups/bmq/bmqimp/bmqimp_event.h
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| @@ -811,8 +803,11 @@ inline void Event::addCorrelationId(const bmqt::CorrelationId& correlationId, | |||
| // BSLS_ASSERT_SAFE(messageEventMode() == MessageEventMode::e_READ); | |||
| // BSLS_ASSERT_SAFE(d_rawEvent.isAckEvent()); | |||
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| d_correlationIds.push_back( | |||
| bsl::make_pair(correlationId, subscriptionHandleId)); | |||
| d_contexts.resize(d_contexts.size() + 1); | |||
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Here, we construct MessageContext with a default constructor, then reassign all fields one by one. Might be better to emplace_back:
https://github.com/bloomberg/bde/blob/65f2de5338d10f6a947357af66b100b1490616bb/groups/bsl/bslstl/bslstl_vector.h#L3681
src/groups/bmq/bmqimp/bmqimp_event.h
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| void addContext(const bmqt::CorrelationId& correlationId, | ||
| unsigned int subscriptionHandleId = | ||
| bmqt::SubscriptionHandle::k_INVALID_HANDLE_ID, | ||
| bmqp::MessageProperties::SchemaPtr schema = |
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New arg schema not mentioned in docs
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| const SchemaPtr& result = contextHandle->d_schema_sp; | ||
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| if (!result) { |
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Can we assume that it's an unlikely scenario? Or is it better to evaluate the expression without such assumptions?
| MessageProperties mps(d_allocator_p); | ||
| int rc = mps.streamIn(blob, input, result); | ||
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| if (rc == 0) { |
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If rc != 0 we will silently return an empty SchemaPtr. Should we log something or skip the message?
| @@ -99,6 +99,8 @@ class MessageProperties_Schema { | |||
| bslma::Allocator* basicAllocator); | |||
| MessageProperties_Schema(const MessageProperties_Schema& other); | |||
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| ~MessageProperties_Schema(); | |||
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Let's also add BSLS_KEYWORD_FINAL to the class head, since we declared a non-virtual destructor?
class MessageProperties_Schema BSLS_KEYWORD_FINAL {
| @@ -45,6 +45,8 @@ struct SchemaLearner::SchemaHandle { | |||
| // If 'false', needs new translation. | |||
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| SchemaHandle(SchemaIdType id); | |||
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| ~SchemaHandle(); | |||
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Let's also add BSLS_KEYWORD_FINAL to the class head, since we declared a non-virtual destructor?
struct SchemaLearner::SchemaHandle BSLS_KEYWORD_FINAL {
| bmqp::MessageProperties::SchemaPtr schema = schemaLearner().learn( | ||
| schemaLearner().createContext(queueId), | ||
| bmqp::MessagePropertiesInfo(info.d_header), | ||
| bdlbb::Blob()); |
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Looking at learn implementation:
SchemaLearner::SchemaPtr
SchemaLearner::learn(Context& context,
const MessagePropertiesInfo& input,
const bdlbb::Blob& blob)
{
const SchemaIdType inputId = input.schemaId();
if (!isPresentAndValid(inputId)) {
// Nothing to do
return SchemaPtr(); // RETURN
}
We have an early return if schemaId is not present or valid. Does it happen for all messages that don't have message properties? If it can happen that frequently, we do a lot of unnecessary work here:
- Pass args and call
schemaLearner().createContext(queueId) - Within
schemaLearner().createContext(queueId)make lookup in a map (we don't use its result) - Construct
bdlbb::Blob()that we don't use - Pass args and call
SchemaLearner::learnjust to return early
Do you think it's worth to avoid these extra operations if we don't have schemaId?
Signed-off-by: dorjesinpo <[email protected]>
Signed-off-by: dorjesinpo <[email protected]>
Signed-off-by: dorjesinpo <[email protected]>
Signed-off-by: dorjesinpo <[email protected]>
dorjesinpo
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Cannot use
bmqp::SchemaLearnerin both FSM and event threads.Instead, call the leaner in FSM and cache the result (schema) in the generated event.