GitHub user vanzin opened a pull request:
https://github.com/apache/spark/pull/20952
[SPARK-6951][core] Speed up parsing of event logs during listing.
This change introduces two optimizations to help speed up generation
of listing data when parsing events logs.
The first one allows the parser to be stopped when enough data to
create the listing entry has been read. This is currently the start
event plus environment info, to capture UI ACLs. If the end event is
needed, the code will skip to the end of the log to try to find that
information, instead of parsing the whole log file.
Unfortunately this works better with uncompressed logs. Skipping bytes
on compressed logs only saves the work of parsing lines and some events,
so not a lot of gains are observed.
The second optimization deals with in-progress logs. It works in two
ways: first, it completely avoids parsing the rest of the log for
these apps when enough listing data is read. This, unlike the above,
also speeds things up for compressed logs, since only the very beginning
of the log has to be read.
On top of data, the code that decides whether to re-parse logs to get
updated listing data will ignore in-progress applications until they've
completed.
Both optimizations can be disabled but are enabled by default.
I tested this on some fake event logs to see the effect. I created
500 logs of about 60M each (so ~30G uncompressed; each log was 1.7M
when compressed with zstd). Below, C = completed, IP = in-progress,
the size means the amount of data re-parsed at the end of logs
when necessary.
```
none/C none/IP zstd/C zstd/IP
On / 16k 2s 2s 22s 2s
On / 1m 3s 2s 24s 2s
Off 1.1m 1.1m 26s 24s
```
This was with 4 threads on a single local SSD. As expected from the
previous explanations, there are considerable gains for in-progress
logs, and for uncompressed logs, but not so much when looking at the
full compressed log.
As a side note, I removed the custom code to get the scan time by
creating a file on HDFS; since file mod times are not used to detect
changed logs anymore, local time is enough for the current use of
the SHS.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/vanzin/spark SPARK-6951
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/20952.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #20952
commit 5d3e0f40a3861374cf934887dec231a83a31ac4e
Author: Marcelo Vanzin
Date: 2018-03-09T20:00:04Z
[SPARK-6951][core] Speed up parsing of event logs during listing.
This change introduces two optimizations to help speed up generation
of listing data when parsing events logs.
The first one allows the parser to be stopped when enough data to
create the listing entry has been read. This is currently the start
event plus environment info, to capture UI ACLs. If the end event is
needed, the code will skip to the end of the log to try to find that
information, instead of parsing the whole log file.
Unfortunately this works better with uncompressed logs. Skipping bytes
on compressed logs only saves the work of parsing lines and some events,
so not a lot of gains are observed.
The second optimization deals with in-progress logs. It works in two
ways: first, it completely avoids parsing the rest of the log for
these apps when enough listing data is read. This, unlike the above,
also speeds things up for compressed logs, since only the very beginning
of the log has to be read.
On top of data, the code that decides whether to re-parse logs to get
updated listing data will ignore in-progress applications until they've
completed.
Both optimizations can be disabled but are enabled by default.
I tested this on some fake event logs to see the effect. I created
500 logs of about 60M each (so ~30G uncompressed; each log was 1.7M
when compressed with zstd). Below, C = completed, IP = in-progress,
the size means the amount of data re-parsed at the end of logs
when necessary.
```
none/C none/IP zstd/C zstd/IP
On / 16k 2s 2s 22s 2s
On / 1m 3s 2s 24s 2s
Off 1.1m 1.1m 26s 24s
```
This was with 4 threads on a single local SSD. As expected from the
previous explanations, there are considerable gains for in-progress
logs, and for uncompressed logs, but not so much when looking at the
full compressed log.
