code structure for append needs refactoring #59

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opened 2016-03-29 09:51:08 +00:00 by slfritchie · 0 comments

slfritchie commented

2016-03-29 09:51:08 +00:00

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Hrm. With the introduction of eleveldb for max offset & checksum storage, the overall flow for append operations is now messy IMHO and needs refactoring.

For example, given a max file size rollover, there's an icky race between machi_flu_filename_mgr and machi_flu_append_server and machi_file_proxy. It's the file proxy proc that decides that it's time to rollover, but there are already append filename assignments by machi_flu_append_server (in collusion with the filename server) but not yet file offsets (which are assigned by file proxy).

For example, try a stress test using basho_bench, large'ish appends (e.g. 256KB or 1MB), and a small max_file_size value in app.config (e.g. 10MB). It works, but max latencies are absurdly high while a rollover is in progress. Also, the logs show that it's likely for a file to be closed for rollover twice. The second time is caused by racing straggler operations that are forwarded to a new file proxy proc.

Hrm. With the introduction of eleveldb for max offset & checksum storage, the overall flow for `append` operations is now messy IMHO and needs refactoring. For example, given a max file size rollover, there's an icky race between machi_flu_filename_mgr and machi_flu_append_server and machi_file_proxy. It's the file proxy proc that decides that it's time to rollover, but there are already append filename assignments by machi_flu_append_server (in collusion with the filename server) but not yet file offsets (which are assigned by file proxy). For example, try a stress test using basho_bench, large'ish appends (e.g. 256KB or 1MB), and a small `max_file_size` value in `app.config` (e.g. 10MB). It works, but max latencies are absurdly high while a rollover is in progress. Also, the logs show that it's likely for a file to be closed for rollover _twice_. The second time is caused by racing straggler operations that are forwarded to a new file proxy proc.