it helps if the code actually does what the comment above it claims.
clarify it a bit, so i don't get stupid ideas again.
This reverts commit cf6a7b4d18.
propagating many messages from a fast store (typically maildir or a
local IMAP server) to a slow asynchronous store could cause gigabytes of
data being buffered. avoid this by throttling fetches if the target
context reports memory usage above a configurable limit.
REFMAIL: 9737edb14457c71af4ed156c1be0ae59@mpcjanssen.nl
some servers actually bother to close down the SSL connection before
closing the socket.
this fixes the spurious "unhandled SSL error 6" messages.
REFMAIL: 20150120114805.GA17586@leeloo.kyriasis.com
the server can actually close the zlib stream before closing the socket,
so we need to accept it.
we don't do anything beyond that - the actual EOF will be signaled by
the socket, and if the server (erroneously) sends more data, zlib will
tell us about it.
REFMAIL: 1423048708-975-1-git-send-email-alex.bennee@linaro.org
zlib reports Z_BUF_ERROR when a flush is attempted without any activity
since the previous flush (if any). while this is harmless as such,
discerning the condition from genuine errors would be much harder than
avoiding the pointless flush in the first place.
REFMAIL: eb5681612f17be777bc8d138d31dd6d6@mpcjanssen.nl
don't retry dead Stores for every Channel.
this also introduces a state for transient errors (specifically, connect
failures), but this is currently unused.
a directory is no mailbox unless it contains a cur/ subdir.
but if that one is present, create new/ and tmp/ if they are missing.
this makes it possible to resume interrupted maildir creations.
don't try to lock it until we actually read or write it.
the idea is to not fail with SyncState * if we tried to load the state
before selecting a non-existing mailbox. this is ok, because if the
mailbox is missing, we obviously have no sync state pertaining to it,
either.
as a side effect, this allows simplifying an error path.
when LITERAL+ is used, the server has no chance for early rejection of
messages. this means that the client can upload megabytes for nothing.
so simply don't use LITERAL+ for big messages. of course this adds
server roundtrips, but that's tough luck.
the limit could be arguably higher than 100k (or even configurable).
i set it to ~2 sec with my fairly average DSL line.
the primary objective is reducing the number of small SSL packets (which
are always padded), but fewer syscalls in the non-SSL case should be
good as well.
instead of keeping the structures in an opaque array (which was a shadow
of the struct pollfd array if poll() was supported), make them directly
addressable.
this has the advantage that notifier-altering operations (mostly
en-/disabling) don't need to look up the structure by file handle each
time.
on the downside, data locality in the main loop is worse.
neither of these have any real effect on performance.
note that the structures are not allocated separately, but embedded into
the the parent structure (like sockets already were).
