connectionpool: add configurable reuse lifetime for connections

Summary:
Re-using long-running connections can cause problems, as the `hg serve` process
on the server may be using large amounts of resources.  Add a new configuration
option `connectionpool.lifetime`.  Connections that are older than that time
will be closed and not re-used.

Reviewed By: DurhamG

Differential Revision: D8204415

fbshipit-source-id: ac937778e3dc79e77e367017db2141066bd17263

mercurial/configitems.py

@@ -157,6 +157,7 @@ coreconfigitem(
 )
 coreconfigitem("commands", "update.requiredest", default=False)
 coreconfigitem("committemplate", ".*", default=None, generic=True)
+coreconfigitem("connectionpool", "lifetime", default=None)
 coreconfigitem("convert", "cvsps.cache", default=True)
 coreconfigitem("convert", "cvsps.fuzz", default=60)
 coreconfigitem("convert", "cvsps.logencoding", default=None)

mercurial/connectionpool.py

@@ -7,6 +7,8 @@
 
 from __future__ import absolute_import
 
+import time
+
 from . import extensions, sshpeer, util
 
 
@@ -46,6 +48,13 @@ class connectionpool(object):
                     proc = peer._subprocess
                     if proc.poll() is not None:
                         conn = None
+                # If the connection has expired, close it
+                if conn is not None and conn.expired():
+                    self.repo._ui.debug(
+                        "not reusing expired connection to %s\n" % conn.path
+                    )
+                    conn.close()
+                    conn = None
             except IndexError:
                 pass
 
@@ -63,7 +72,7 @@ class connectionpool(object):
             if util.safehasattr(peer, "cleanup"):
                 extensions.wrapfunction(peer, "cleanup", _cleanup)
 
-            conn = connection(pathpool, peer)
+            conn = connection(self._repo.ui, pathpool, peer, path)
 
         return conn
 
@@ -90,9 +99,15 @@ class standaloneconnection(object):
 
 
 class connection(object):
-    def __init__(self, pool, peer):
+    def __init__(self, ui, pool, peer, path):
+        self._ui = ui
         self._pool = pool
         self.peer = peer
+        self.path = path
+        self.expiry = None
+        lifetime = ui.configint("connectionpool", "lifetime")
+        if lifetime is not None:
+            self.expiry = time.time() + lifetime
 
     def __enter__(self):
         return self
@@ -101,10 +116,16 @@ class connection(object):
         # Only add the connection back to the pool if there was no exception,
         # since an exception could mean the connection is not in a reusable
         # state.
-        if type is None:
-            self._pool.append(self)
-        else:
+        if type is not None:
             self.close()
+        elif self.expired():
+            self._ui.debug("closing expired connection to %s\n" % self.path)
+            self.close()
+        else:
+            self._pool.append(self)
+
+    def expired(self):
+        return self.expiry is not None and time.time() > self.expiry
 
     def close(self):
         if util.safehasattr(self.peer, "cleanup"):

mercurial/help/config.txt

@@ -593,6 +593,13 @@ below can be referred as ``{listupfiles}``::
        "HG: removed {file}\n"   }{if(files, "",
        "HG: no files changed\n")}
 
+``connectionpool``
+------------------
+
+``lifetime``
+    Number of seconds for which connections in the connection pool can be kept
+    and reused.  Connections that are older than this won't be reused.
+
 ``decode/encode``
 -----------------
 

tests/test-fb-hgext-remotefilelog-prefetch.t

@@ -262,3 +262,12 @@
   3 files fetched over 1 fetches - (0 misses, 100.00% hit ratio) over * (glob)
   abort: z2@109c3a557a73: not found in manifest! (?)
 
+# Test connection pool lifetime
+  $ clearcache
+  $ hg prefetch -r 0::1 --debug --config connectionpool.lifetime=0 | grep 'closing expired connection'
+  4 files fetched over 1 fetches - (0 misses, 100.00% hit ratio) over * (glob)
+  closing expired connection to ssh://user@dummy/master
+  $ clearcache
+  $ hg prefetch -r 0::1 --debug --config connectionpool.lifetime=300 | grep 'closing expired connection'
+  4 files fetched over 1 fetches - (0 misses, 100.00% hit ratio) over * (glob)
+  [1]