lib/zodb: Teach zstor_2zurl about ZEO, NEO and Demo storages

In 6637d216 (lib/zodb: Add zstor_2zurl - way to convert a ZODB storage
into URL to access it) we added zstor_2zurl function to convert a ZODB
storage client object into an URL to access the storage. At that time
the function knew how to understand FileStorage only. Let's add support
for other storages that WCFS will need to support now.

NEO URI scheme matches the one currently used on ZODB/go side. It
semantically needs nexedi/neoppod!18
to be also applied to NEO/py side, but we do not care for now that that
patch is not merged (yet, or forever) because extracted ZURL is used
only with WCFS which uses NEO/go.

NEO support also depends on custom patch to remember SSL credentials on
NEO Client:

kirr/neo@a2f192cb

Some preliminary history:

kirr/wendelin.core@5cb39463    fixup! X wcfs/zeo started to work locally
kirr/wendelin.core@1cf3b228    X zstor_2zurl += NEO
kirr/wendelin.core@7f8fa32a    X lib/zodb: zstor_2zurl += NEO/SSL support
kirr/wendelin.core@e26524df    X wcfs, lib/zodb: DemoStorage support

lib/tests/test_zodb.py

@@ -358,8 +358,8 @@ def test_zodb_onresync():
 
 # test that zurl does not change from one open to another storage open.
 def test_zurlstable():
-    if not isinstance(testdb, testing.TestDB_FileStorage):
-        pytest.xfail(reason="zstor_2zurl is TODO for ZEO and NEO")
+    if not isinstance(testdb, (testing.TestDB_FileStorage, testing.TestDB_ZEO, testing.TestDB_NEO)):
+        pytest.xfail(reason="zstor_2zurl is TODO for %r" % testdb)
     zurl0 = None
     for i in range(10):
         zstor = testdb.getZODBStorage()

lib/zodb.py

+# -*- coding: utf-8 -*-
 # Wendelin.bigfile | common ZODB-related helpers
 # Copyright (C) 2014-2021  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
@@ -21,6 +22,7 @@
 
 import ZODB
 from ZODB.FileStorage import FileStorage
+from ZODB.DemoStorage import DemoStorage
 from ZODB import DB
 from ZODB import POSException
 from ZODB.utils import p64, u64
@@ -28,6 +30,7 @@ from persistent import Persistent
 import zodbtools.util
 from weakref import WeakSet
 import gc
+from six.moves.urllib import parse as urlparse
 
 import pkg_resources
 
@@ -290,5 +293,66 @@ def zstor_2zurl(zstor):
     if isinstance(zstor, FileStorage):
         return "file://%s" % (zstor._file_name,)
 
-    # TODO ZEO + NEO support
+    if isinstance(zstor, DemoStorage):
+        # demo:(base_zurl)/(δ_zurl)
+        return "demo:(%s)/(%s)" % (zstor_2zurl(zstor.base), zstor_2zurl(zstor.changes))
+
+    ztype = type(zstor).__module__ + "." + type(zstor).__name__
+
+    # ZEO
+    if ztype == "ZEO.ClientStorage.ClientStorage":
+        # zeo://(path|host:port)?storage=<storageID>
+        u = "zeo://"
+        _addr = zstor._addr
+        addr  = None
+        # ZEO4/3 for backward compatibility accept either a single "address" or single ("host", port) pair
+        # https://github.com/zopefoundation/ZEO/blob/4.2.0b1-49-g47d3fbe8/src/ZEO/zrpc/client.py#L179
+        if zmajor <= 4:
+            if isinstance(_addr, str):
+                addr = _addr
+            elif len(_addr) == 2 and isinstance(_addr[0], str) and isinstance(_addr[1], int):
+                addr = _addr
+        if addr is None:
+            if len(_addr) != 1:
+                raise NotImplementedError("ZEO client has multiple configured servers: %r" % (addr,))
+            addr = _addr[0]
+        # addr is either TCP (host,port) or UNIX path
+        if isinstance(addr, str):
+            u += addr
+        else:
+            host, port = addr
+            u += '%s:%d' % (host, port)
+
+        storage = zstor._storage
+        if storage != "1":
+            u += "?storage=%s" % storage
+
+        # TODO ssl
+        return u
+
+    # NEO
+    if ztype == "neo.client.Storage.Storage":
+        # neo(s)://[<credentials>@]<master>/<cluster>
+        app = zstor.app
+        if not app.ssl:
+            u = "neo://"
+        else:
+            q = urlparse.quote_plus
+            u = "neos://"
+            ca, cert, key = app.ssl_credentials # .ssl_credentials depend on kirr's patch
+            u += "ca=%s;cert=%s;key=%s@" % (q(ca), q(cert), q(key))
+
+        masterv = app.nm.getMasterList()
+        if len(masterv) == 0:
+            raise RuntimeError("%r has empty master list" % zstor)
+        if len(masterv) > 1:
+            raise NotImplementedError("NEO client has multiple configured masters: %r" % (masterv,))
+        master = masterv[0]
+        host, port = master.getAddress()
+        u += "%s:%s" % (host, port)
+
+        u += "/%s" % app.name
+
+        return u
+
     raise NotImplementedError("don't know how to extract zurl from %r" % zstor)