pvxs/documentation/details.rst

Reporting a Bug

Before reporting a bug, please check to see if this issue has already been reported.

When composing a new report, please run the included automatic tests "make runtests" and mention the results. It is enough to mention "All tests successful." if this is so. (see runtests)

Bug reports should always include:

• EPICS Base version or VCS commit
• PVXS module version or VCS commit
• libevent version or VCS commit (running "pvxget -V" shows these)
• EPICS host and target archs. (eg. "linux-x86_64")
• Host OS name and version (eg. run "cat /etc/issue")
• Compiler name and version (eg. run "gcc --version")
• The values of any $EPICS_PVA* environment variables which are set.
• Any local/site modifications to PVXS or libevent
• Concise instructions for reproducing the issue.

Additional information which may be relevant:

• Number of network interfaces if more than one.
• Whether clients and/or servers are on the same host or diffrent hosts.
• Whether clients and/or servers are in the same subnet or different subnets
• Whether network traffic crosses between virtual machine(s) and physical host(s).
• Firewall rules on UDP traffic to/from port 5075 or TCP connections to port 5074
• Any local/site modifications to EPICS Base

Contributing

The recommended path for including changes is through [Pull Request](https://github.com/mdavidsaver/pvxs/pulls).

When changing c++ code please do:

• Indent with 4 spaces. No hard tabs. UNIX style EoL.
• Try to maintain the style of surrounding code.
• Include meaningful code comments where reasonable.

but do not:

• Add any c++ global constructors or destructors in the pvxs library. (Ok in tools, examples, or tests)

When committing changes please do:

• Include a commit message
• Break up changes into multiple commits where reasonable
• Include whitespace only changes as seperate commits

Notes

Misc. notes on design and Implementation.

• All Server and client Context instances listening on the same UDP port# within a process will share a single UDP socket.
• The UDP local multicast fanout aspect of the PVA protocol is not implemented.
• Client UDP search retry follows a linear backoff starting from 1 second and stepping to 30 seconds. cf. bucketInterval and nBuckets in client.cpp.
• To level UDP search traffic, search retry may delay a PV for an extra bucket if the difference in the number of PVs in the desired and subsequent buckets is too large.
• Client Context::hurryUp() expires the search bucket timer immediately, saving up to bucketInterval seconds.
• Each Value refers points to a pair of FieldDesc and FieldStorage in arrays of the same. Value::operator[] steps around in these arrays.
• There is a hidden StructTop which holds the FieldStorage array and holds a shared_ptr to the FieldDesc array to join ownership of the two.
• TCP connection buffering will read up to tcp_readahead (cf. conn.h) bytes while waiting for a complete header. After a header is received, the larger of tcp_readahead or the message body length is buffered.