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modules/client/sync: Add linear buffer size conf item; add help texts to some confs.

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This commit is contained in:
Jason Volk 2019-03-17 13:24:24 -07:00
parent 9ab3549660
commit 22fe24f54f
2 changed files with 56 additions and 4 deletions
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55
modules/client/sync.cc
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@ -35,6 +35,38 @@ on the server, and then continue to call this API to get incremental deltas
to the state, and to receive new messages.
)"};
const auto linear_delta_max_help
{R"(
Maximum number of events to scan sequentially for a /sync. This determines
whether linear-sync or polylog-sync mode is used to satisfy the request. If
the difference between the since token (lower-bound) and the upper-bound of
the sync is within this value, the linear-sync mode is used. If it is more
than this value a polylog-sync mode is used. The latter is used because at
some threshold it becomes too expensive to scan a huge number of events to
grab only those that the client requires; it is cheaper to conduct a series
of random-access queries with polylog-sync instead. Note the exclusive
upper-bound of a sync is determined either by a non-spec query parameter
'next_batch' or the vm::current_sequence+1.
)"};
const auto linear_buffer_size_help
{R"(
The size of the coalescing buffer used when conducting a linear-sync. During
the sequential scan of events, when an event is marked as required for the
client's sync it is stringified and appended to this buffer. The buffer has
the format of a json::vector of individual events. At the end of the linear
sync, the objects in this buffer are merged into a single spec /sync response.
When this buffer is full the linear sync must finish and respond to the client
with whatever it has. The event::idx of the last event that fit into the buffer
forms the basis for the next_batch so the client can continue with another linear
/sync to complete the range.
)"};
decltype(ircd::m::sync::flush_hiwat)
ircd::m::sync::flush_hiwat
{
@ -47,6 +79,15 @@ ircd::m::sync::buffer_size
{
{ "name", "ircd.client.sync.buffer_size" },
{ "default", long(128_KiB) },
{ "help", "Response chunk buffer size" },
};
decltype(ircd::m::sync::linear_buffer_size)
ircd::m::sync::linear_buffer_size
{
{ "name", "ircd.client.sync.linear.buffer_size" },
{ "default", long(96_KiB) },
{ "help", linear_buffer_size_help },
};
decltype(ircd::m::sync::linear_delta_max)
@ -54,6 +95,7 @@ ircd::m::sync::linear_delta_max
{
{ "name", "ircd.client.sync.linear.delta.max" },
{ "default", 1024 },
{ "help", linear_delta_max_help },
};
decltype(ircd::m::sync::polylog_only)
@ -361,7 +403,8 @@ try
const unique_buffer<mutable_buffer> buf
{
96_KiB //TODO: XXX
// must be at least worst-case size of m::event plus some.
std::max(size_t(linear_buffer_size), size_t(96_KiB))
};
window_buffer wb{buf};
@ -457,7 +500,15 @@ ircd::m::sync::linear_proffer(data &data,
return consumed;
});
return wb.remaining() >= 65_KiB; //TODO: XXX
const bool enough_space_for_more
{
// The buffer must have at least this much more space
// to continue with the iteration. Otherwise if the next
// worst-case event does not fit, bad things.
wb.remaining() >= 68_KiB
};
return enough_space_for_more;
}};
const auto completed

1
modules/client/sync.h
View file

@ -21,6 +21,7 @@ namespace ircd::m::sync
extern conf::item<size_t> flush_hiwat;
extern conf::item<size_t> buffer_size;
extern conf::item<size_t> linear_buffer_size;
extern conf::item<size_t> linear_delta_max;
extern conf::item<bool> longpoll_enable;
extern conf::item<bool> polylog_only;