[IMPALA-128] DatastreamSender::Close should not do anything if Init failed

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 0.7
• Fix Version/s: Impala 0.7
• Assignee: Nong Li
• Reporter: Henry Robinson
• Created: 12/Mar/13 18:00
• Updated: 12/Mar/13 22:33
• Resolved: 12/Mar/13 22:33

Description

If DataStreamSender::Init fails because a channel could not be created, the enclosing PlanFragmentExecutor will call DataStreamSender::Close in its destructor.

DataStreamSender::Close calls DataStreamSender::Channel::Close which tries to use its client_ object, which may not be correctly initialised. Then when using it fails, ClientCache::Reopen gets called, which fails a DCHECK because the client was never handed out by the cache in the first place.

Failure to connect to a backend will be common, so this bug will get tripped a lot. We should either avoid calling Close on a bad Channel, or make sure the Channel::Close is robust to the possibility of being in a bad state.

There's a handy TODO in data-stream-sender.cc: // TODO: only close channels that didn't have any errors. It is remarkably prescient.