Recognize certain Junos AS Path regexes and convert them to VI construct

[samarthdhingra]

Performance optimization for some of Junos AS path regex patterns by converting them to existing VI construct AsSetsMatchingRanges . This bypasses converting these junos specific regular expression to java regular expression.

Following Junos AS Path regex patterns are included :

• ".* N .*" : "AS Path contains N"
• ".* N" or ".* N$" : "AS Path ends with N"
• "N .*" or "^N .*" : "AS Path starts with N".
• ".* [start-end] .*" OR ".* start-end .*" : "AS Path contains an ASN in range between start and end included"
• "[start-end]" or "start-end" : "AS Path matches single ASN number in range between start and end included
• "N": "AS Path matches single ASN number"

If one of the above patterns don't match, then fallback to the existing solution of converting to java regex using AsPathRegex

As part of testing using bf_session.init_snapshot_from_text(..) for a single device config with multiple range pattern regexes, snapshot initialization time decreased from ~155s to ~3s.

[batfish-bot]

This change is 

[anothermattbrown]

Reviewable status: 0 of 4 files reviewed, 1 unresolved discussion (waiting on @samarthdhingra)

---

projects/batfish/src/test/java/org/batfish/representation/juniper/AsPathMatchExprParserTest.java line 97 at r1 (raw file):

    @Test
    public void testAsPathMatchRegexFallback() {
        for (String regex : new String[]{"1234", "1234?", "1234{0,1}", "12{1,4} 34", "[123-125]", "123 (56 | 78)?", "()"}) {

this pattern would be good to optimize

Code quote:

"[123-125]",

[samarthdhingra]

Reviewable status: 0 of 4 files reviewed, 1 unresolved discussion (waiting on @samarthdhingra)

projects/batfish/src/test/java/org/batfish/representation/juniper/AsPathMatchExprParserTest.java line 97 at r1 (raw file):

    @Test
    public void testAsPathMatchRegexFallback() {
        for (String regex : new String[]{"1234", "1234?", "1234{0,1}", "12{1,4} 34", "[123-125]", "123 (56 | 78)?", "()"}) {

this pattern would be good to optimize

Code quote:

"[123-125]",

Done.
Added following new patterns :

"N": "AS Path matches single ASN number"
"[start-end]" or "start-end" : "AS Path matches single ASN number in range between start and end included
".* start-end .*" : "AS Path contain ASN number in range between start and end included

[anothermattbrown]

Reviewed 2 of 4 files at r1, 2 of 2 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @samarthdhingra)

[anothermattbrown]

Have you measured how much this speeds up parsing configs with these patterns, and how much its slow down parsing configs without them?

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @samarthdhingra)

[samarthdhingra]

Have you measured how much this speeds up parsing configs with these patterns, and how much its slow down parsing configs without them?

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @samarthdhingra)

Depending on the as-path regex pattern, I observe most execution time improvement if the junos regex contains range pattern .* start-end .* or .* [start-end] .* (depending on the different between the ranges).

For the sample config tested using bf_session.init_snapshot_from_text(..) the speed up was from ~155s to ~3s

[anothermattbrown]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @samarthdhingra)

[anothermattbrown]

Reviewed 4 of 4 files at r3, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @samarthdhingra)

[codecov]

Codecov Report

Merging #8770 (6b49010) into master (15abe44) will increase coverage by 0.00%.
The diff coverage is 98.43%.

❗ Current head 6b49010 differs from pull request most recent head 6584618. Consider uploading reports for the commit 6584618 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #8770   +/-   ##
=======================================
  Coverage   72.32%   72.32%           
=======================================
  Files        3288     3289    +1     
  Lines      168552   168612   +60     
  Branches    19755    19764    +9     
=======================================
+ Hits       121907   121956   +49     
- Misses      37552    37561    +9     
- Partials     9093     9095    +2     

Files Changed	Coverage Δ
.../representation/juniper/AsPathMatchExprParser.java	98.27% <98.27%> (ø)
...g/batfish/representation/juniper/PsFromAsPath.java	66.66% <100.00%> (+2.38%)	⬆️
...fish/representation/juniper/PsFromAsPathGroup.java	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

[dhalperi]

Reviewed 2 of 2 files at r4, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @samarthdhingra)