Re: master: t5800-remote-helpers.sh hangs on test "pulling from remote remote"

From: Clemens Buchacher <drizzd@aon.at>
Date: Apr 21, 2012, 23:35 UTC
Message-ID: <20120421233521.GB20473@ecki>
In-Reply-To: <20120421201524.GA18419@padd.com>

Hi Pete,

Thanks for solving the mystery.

On Sat, Apr 21, 2012 at 04:15:24PM -0400, Pete Wyckoff wrote:

Show 12 quoted lines

> 
> Not sure yet what is the right way to fix this.  And I don't know
> if it's just git-remote-testgit that has the problem because it
> forks an importer, or if other remote helpers would be similarly
> affected.
> 
> The easiest fix is to invoke "python -u" in
> git-remote-testgit.py, or do
> 
>     sys.stdin = os.fdopen(sys.stdin.fileno(), 'r', 0)
> 
> But I'm not sure if this works on all systems.

Which part are you worried about? Maybe the patch below is more portable?

> We could also consider adding a handshake after "export", to give the
> helper time to get ready.

Not sure I understand. The helper is throwing away some input. It seems to me there is nothing one can do to prevent such brokeness.

It would be nice if the deadlock could be detected and if git would time out in such a case, instead of hanging forever. But rather long delays can also be the result of the remote helper legimitately waiting for data from a slow network.

Clemens ---

diff --git a/git-remote-testgit.py b/git-remote-testgit.py
index 616e772..bdd1116 100644
--- a/git-remote-testgit.py
+++ b/git-remote-testgit.py
@@ -135,6 +135,22 @@ def update_local_repo(repo):
     return repo
 
 
+def read_line_fd(fd):
+    """Read from fd until end of line or EOF, and no further.
+    """
+
+    line = ''
+
+    while True:
+        c = os.read(fd, 1)
+        if c == '':
+            break
+        line += c
+        if c == '\n':
+            break
+
+    return line
+
 def do_import(repo, args):
     """Exports a fast-import stream from testgit for git to import.
     """
@@ -149,7 +165,7 @@ def do_import(repo, args):
     refs = [ref]
 
     while True:
-        line = sys.stdin.readline()
+        line = read_line_fd(sys.stdin.fileno())
         if line == '\n':
             break
         if not line.startswith('import '):
@@ -211,9 +227,7 @@ def read_one_line(repo):
         time.sleep(int(sleepy))
         debug("Awake, to readline")
 
-    line = sys.stdin.readline()
-
-    cmdline = line
+    cmdline = read_line_fd(sys.stdin.fileno())
 
     if not cmdline:
         warn("Unexpected EOF")

-- 
1.7.10