Merge lp:~brian-murray/apport/zgrep-fallback into lp:apport

[Brian Murray]

The production retracers for the Error Tracker were OOM'ing regularly when trying to use zgrep to search Contents.gz for files found in the crash report. While zgrep is faster than using gzip and reading the file line by line this still seems like a good fallback option and is better than having the retrace process crash, I've implemented the proposed change in the production version of the Error Tracker and have encountered no issues with it.

As mentioned this could likely be better:

+ try:
+ line = line.decode('UTF-8').rstrip('\n')
+ # 2016-11-01 this should be better
+ except UnicodeDecodeError:
+ continue

I added because of the following lines in Contents.gz for yakkety:

 $ zgrep -a "lenska.alias" /mnt/storage/archive-mirror/dists/yakkety/Contents-amd64.gz
usr/lib/aspell/�slenska.alias universe/text/aspell-is

Thanks!

[Martin Pitt (pitti)]

I can't say that I like having two code paths for the same thing, but I accept that it's necessary. (Still, if these machines are that tight on RAM, can we increase that a bit?)

I would like this to be a bit faster and simpler though, see inline comment. Thanks!

[lp:~brian-murray/apport/zgrep-fallback]

3107. By Brian Murray on 2016-11-08

improve unicode handling after pitti's feedback

[Brian Murray (brian-murray)]

I've made the changes you've suggested, thanks!

[Martin Pitt (pitti)]

LGTM now, thanks! Please merge.

review: Approve

[Brian Murray (brian-murray)]

I don't have permission to commit to the apport project.

[Martin Pitt (pitti)]

Uh, what? Time to change that ☺ You are a member now.

=== modified file 'backends/packaging-apt-dpkg.py'
--- backends/packaging-apt-dpkg.py	2016-08-13 07:09:38 +0000
+++ backends/packaging-apt-dpkg.py	2016-11-08 19:25:48 +0000
@@ -13,6 +13,7 @@
 # the full text of the license.
 
 import subprocess, os, glob, stat, sys, tempfile, shutil, time
+import errno
 import hashlib
 import json
 
@@ -1221,9 +1222,21 @@
 
             # zgrep is magnitudes faster than a 'gzip.open/split() loop'
             package = None
-            zgrep = subprocess.Popen(['zgrep', '-m1', '^%s[[:space:]]' % file, map],
-                                     stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-            out = zgrep.communicate()[0].decode('UTF-8')
+            try:
+                zgrep = subprocess.Popen(['zgrep', '-m1', '^%s[[:space:]]' % file, map],
+                                         stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+                out = zgrep.communicate()[0].decode('UTF-8')
+            except OSError as e:
+                if e.errno != errno.ENOMEM:
+                    raise
+                file_b = file.encode()
+                import gzip
+                with gzip.open('%s' % map, 'rb') as contents:
+                    out = ''
+                    for line in contents:
+                        if line.startswith(file_b):
+                            out = line
+                            break
             # we do not check the return code, since zgrep -m1 often errors out
             # with 'stdout: broken pipe'
             if out: