[IMPALA-5795] BackendConfig::LookUpBackendDescriptor() may fail to look up non-executor coordinator

• Type: Sub-task
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Fix Version/s: Impala 2.10.0
• Component/s: Distributed Exec
• Labels: crash
• Target Version: Impala 2.11.0
• Epic Color: ghx-label-3
• Assignee: Michael Ho
• Reporter: Sailesh Mukil
• Created: 14/Aug/17 01:41
• Updated: 03/Oct/17 00:37
• Resolved: 03/Oct/17 00:37

Description

When we call LookUpBackendDescriptor() with a specific address, we always expect that we've stored the backend list for that host in the backend_map_:

/// Return the list of backends on a particular host. The caller must make sure that the
/// host is actually contained in backend_map_.
const BackendList& GetBackendListForHost(const IpAddr& ip) const;

However, for configuration with dedicated coordinator, a coordinator can be non-executor so it will not be found in backend_map_

If that is the case, on debug binaries, this would trip up this DCHECK in GetBackendListForHost():
https://github.com/michaelhkw/incubator-impala/blob/krpc/be/src/scheduling/backend-config.cc#L25

On release binaries, it would hit a SEGFAULT here:
https://github.com/michaelhkw/incubator-impala/blob/krpc/be/src/scheduling/backend-config.cc#L79

This bug only exists on KRPC branch.