revisionbranchcache: fall back to slow path if starting readonly (issue4531)
Transitioning to Mercurial versions with revision branch cache could be slow as
long as all operations were readonly (revset queries) and the cache would be
populated but not written back.
Instead, fall back to using the consistently slow path when readonly and the
cache doesn't exist yet. That avoids the overhead of populating the cache
without writing it back.
If not readonly, it will still populate all missing entries initially. That
avoids repeated writing of the cache file with small updates, and it also makes
sure a fully populated cache available for the readonly operations.
#!/usr/bin/env python
#
# Dumps output generated by Mercurial's command server in a formatted style to a
# given file or stderr if '-' is specified. Output is also written in its raw
# format to stdout.
#
# $ ./hg serve --cmds pipe | ./contrib/debugcmdserver.py -
# o, 52 -> 'capabilities: getencoding runcommand\nencoding: UTF-8'
import sys, struct
if len(sys.argv) != 2:
print 'usage: debugcmdserver.py FILE'
sys.exit(1)
outputfmt = '>cI'
outputfmtsize = struct.calcsize(outputfmt)
if sys.argv[1] == '-':
log = sys.stderr
else:
log = open(sys.argv[1], 'a')
def read(size):
data = sys.stdin.read(size)
if not data:
raise EOFError
sys.stdout.write(data)
sys.stdout.flush()
return data
try:
while True:
header = read(outputfmtsize)
channel, length = struct.unpack(outputfmt, header)
log.write('%s, %-4d' % (channel, length))
if channel in 'IL':
log.write(' -> waiting for input\n')
else:
data = read(length)
log.write(' -> %r\n' % data)
log.flush()
except EOFError:
pass
finally:
if log != sys.stderr:
log.close()