doc: add session WG meeting

[belochub]

Sessions WG meeting

Date: 2017-02-21

Invited:

• Alexey Orlenko <eaglexrlnk@gmail.com> (@aqrln) from server team
• Mykola Bilochub <nbelochub@gmail.com> (@belochub) from server team
• Denys Otrishko <shishugi@gmail.com> (@lundibundi) from Android team
• Andrew Vysotskyi <firemaaaan@gmail.com> (@Gagnant) from iOS team

Present:

• Alexey Orlenko <eaglexrlnk@gmail.com> (@aqrln) from server team
• Mykola Bilochub <nbelochub@gmail.com> (@belochub) from server team
• Denys Otrishko <shishugi@gmail.com> (@lundibundi) from Android team

Agenda:

• General way of reconnection to existing sessions;
• Session restoration mechanisms architecture;
• The problems with reconnection mobile developers encountered in our last
  project and proper ways to solve them;
• Handshake packet formats (for request and response) that will be used to
  implement reconnection to existing sessions.

Conclusions:

• To make packet numbers unique for every session, not connection like it was before;

• To send total count of packets sent and received by each side during the session
  in handshake packet, like this:

  { handshake: [0, 'appName'], session: ['sessionId', sent_count, received_count] }

  and answer

  { handshake: [0], ok: [sent_count, received_count] }

[aqrln]

/cc @lundibundi @Gagnant

[aqrln]

@belochub I've edited your post so that it includes the file contents.

[aqrln]

I'd like to make a few additions to this. We omitted these questions somehow.

1. Even though packet IDs are incremented throughout the session, not the connection, handshake packets are always 0 since we don't know which packet IDs to use until a handshake has been performed. After that, the order continues as it should have been if there hadn't been reconnection, with an extra handshake being transparent.

2. The standard ERR_AUTH_FAILED error will be used for any handshake authentication strategy, regardless of it being login, session or anything we may probably add later. What it means for session restoration handshakes is that if session ID is invalid, the server responds with { handshake: [0], error: [11] }.

@belochub, @lundibundi, @Gagnant, do you agree with these additions or there are any objections to them?

[aqrln]

@GYFK thanks for your approval, it is actually a good idea for all mobile developers that deal with JSTP to be familiar with this information. I'll /cc @lidaamber too.

[aqrln]

Still waiting for all Session WG members and meeting participants to approve or decline #81 (comment).

@lundibundi @Gagnant

[aqrln]

@belochub now that all the meeting participants have shown their approval for #81 (comment) and taking into account that it is not only a direct follow-up to the things we discussed but actually a part of these things that wasn't stated explicitly during the meeting, though crucial for the implementation we approved, can you please add it to the file under some appropriate heading?

[aqrln]

LGTM

[aqrln]

Landed in 6781669.

[aqrln]

Warning to anyone reading this, especially those coming from the markdown file via the PR-URL link: there are changes to these specs, the discussion is continued in #85.

[aqrln]

Refs: #35