See comments added in this commit at A40.
So far, I've been doing CP mode testing with a handful of (very useful)
network partition combinations using:
machi_chain_manager1_converge_demo:t(3, [{private_write_verbose,true}, {consistency_mode, cp_mode}, {witnesses, [a]}]).
Next steps:
* Expand number & types of partitions
* Expand to chain lengths of 5 and beyond
So, I'm 50% sure this is a good idea for CP mode: if there's
a later public projection than P_current, then who knows what
we might have missed. So, call make_zerf() to find out the
absolute latest. Problem: flapping state appears to be lost,
booo.
If we use verbose output from:
machi_chain_manager1_converge_demo:t(3, [{private_write_verbose,true}, {consistency_mode, cp_mode}, {witnesses, [a]}]).
And use:
tail -f typescript_file | egrep --line-buffered 'SET|attempted|CONFIRM'
... then we can clearly see a chain safety violation when moving from
epoch 81 -> 83. I need to add more smarts to the safety checking,
both at the individual transition sanity check and at the converge_demo
overall rolling sanity check.
Key to output: CONFIRM by epoch {num} {csum} at {UPI} {Repairing}
SET # of FLUs = 3 members [a,b,c]).
CONFIRM by epoch 1 <<96,161,96,...>> at [a,b] [c]
CONFIRM by epoch 5 <<134,243,175,...>> at [b,c] []
CONFIRM by epoch 7 <<207,93,225,...>> at [b,c] []
CONFIRM by epoch 47 <<60,142,248,...>> at [b,c] []
SET partitions = [{c,b},{c,a}] (1 of 2) at {22,3,34}
CONFIRM by epoch 81 <<223,58,184,...>> at [a,b] []
SET partitions = [{b,c},{b,a}] (2 of 2) at {22,3,38}
CONFIRM by epoch 83 <<33,208,224,...>> at [a,c] []
SET partitions = []
CONFIRM by epoch 85 <<173,179,149,...>> at [a,c] [b]
So, the problem is that the chain manager isn't finishing repair
because UPI=[a], and a is a witness, and a can't do the list files etc etc
repair stuff that repairer FLUs need to do.
The best (?) way forward is to add some advance smarts to the
chain manager so that it doesn't propose a UPI of 100% witnesses?
PULSE managed to create a situation where machi_proxy_flu_client1
would appear to fail a remote attempt to write_projection. The
client would retry, but the 1st attempt really did get through to
the server. So, if we hit this case, we try to read the projection,
and if it's exactly equal to what we tried to write, we consider the
op a success.
Ditto for write_chunk.
Fix up eunit test to accomodate the change of semantics.
Due to changes by slf/chain-manager/cp-mode branch, there are
no longer extraneous epoch changes by "larger" authors that
re-suggest the same UPI+Repairing just because their author rank
is very slightly higher than the current epoch. Thus the
partial_stop_restart2() test only needs to deal with one epoch
change instead of the original two.
