Was a service previously. Now contains both merklet
and the naive implementations. Put construction
timing stuff into the test.
Tests are not truly meaningful yet.
* maybe_gc/2 is triggered at machi_file_proxy, when chunk is deleted
and the file is larger than `max_file_size`
* A file is deleted if all chunks except 1024 bytes header are trimmed
* If a file is going to be deleted, file_proxy notifies metadata_mgr
to remember the filename persistently, whose filename is
`known_files_<FluName>`
* Such trimmed filenames are stored in a machi_plist file per flu
* machi_file_proxy could not be started if the filename is in the
manager's list. Consequently, any write, read and trim operations
cannot happen against deleted file.
* After the file was trimmed, any read request to the file returns
`{error, trimmed}`
* Disclaimer: no tests written yet and machi_plist does not support
any recovery from partial writes.
* Add some thoughts as comments for repairing trims.
* State diagram of every byte is as follows:
```
state\action| write/append | read_chunk | trim_chunk
------------+----------------+------------------+---------------
unwritten | -> written | fail (+repair) | -> trimmed
written | noop or repair | return content | -> trimmed
trimmed | fail | fail | noop
```
* When repairing multiple chunks at once and any of its repair
failed, the whole read request and repair work will fail
* Rename read_repair3 and read_repair4 to do_repair_chunks and
do_repair chunk in machi_file_proxy
* This pull request changes return semantics of read_chunk(), that
returns any chunk included in requested range
* First and last chunk may be cut to fit the requested range
* In machi_file_proxy, unwritten_bytes are removed and replaced by
machi_csum_table
This is simply a change of read_chunk() protocol, where a response of
read_chunk() becomes list of written bytes along with checksum. All
related code including repair is changed as such. This is to pass all
tests and not actually supporting partial chunks.
For debuging from shell, some functions in machi_cinfo are exported:
- public_projection/1
- private_projection/1
- fitness/1
- chain_manager/1
- flu1/1
The FLU psup starts the chain manager in active mode by default
(as it should for normal run-time operation.) By adding the
{active_mode, false} tuple to the options list, we can
tell the chain manager that it should be explicitly manipulated
during tests.
I am treating the original write-once branch as a prototype
which I am now throwing away. I had too much work interleved
in there, so I felt like the best thing to do would be to cut
a new clean branch and pull the files over and start over
against a recent-ish master.
We will have to refactor the other things in FLU in a more
piecemeal fashion.
Last night we hit a rare case of failed convergence.
f was out of sync with the rest of the world.
f: upi=[b,g,f] repairing=[a,c]
The "rest of the world" used a larger chain at:
*: upi=[c,b,g,a], repairing=[f]
And f refused to join the larger chain because of the way that
IsRelevantToMe_p was being calculated before this commit.
Hrrrm, though, I'm not convinced that this particular problem
is fixed 100% by this patch. What if the chain lengths were
the same but also UPI incompatible? e.g. if I remove 'a' from
the "real world (in the partition simulator)" example above:
f: upi=[b,g,f] repairing=[c]
*: upi=[c,b,g], repairing=[f]
Hrmmmmm, I may need to reintroduce the my-recent-adopted-projection-
flapping-like-counter thingie to try to break this kind of
incompatible deadlock.
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]
