start to deal with xmlrpclib errors

add an offline mode for metadata as well

diff --git a/manifold/manifoldapi.py b/manifold/manifoldapi.py
index 18c555c..6a0e1d2 100644 (file)
--- a/manifold/manifoldapi.py
+++ b/manifold/manifoldapi.py
@@ -5,39 +5,56 @@ from myslice.config import Config
 
 debug=True
 
-class ManifoldAPI:
+class SessionExpired (Exception):
+    def __init__ (self,message):
+        self.message=message
+    def __repr__ (self): 
+        return "<SessionExpired: %s>"%self.message
 
-  def __init__(self, auth=None, cainfo=None):
+class ManifoldAPI:
 
-    config = Config()
-    self.auth = auth
-    self.cainfo = cainfo
-    self.errors = []
-    self.trace = []
-    self.calls = {}
-    self.multicall = False
-    self.url = config.manifold_url
-    self.server = xmlrpclib.Server(self.url, verbose=False, allow_none=True)
+    def __init__(self, auth=None, cainfo=None):
+        
+        config = Config()
+        self.auth = auth
+        self.cainfo = cainfo
+        self.errors = []
+        self.trace = []
+        self.calls = {}
+        self.multicall = False
+        self.url = config.manifold_url
+        self.server = xmlrpclib.Server(self.url, verbose=False, allow_none=True)
 
-  def __getattr__(self, methodName):
-      def func(*args, **kwds):
-        result=getattr(self.server, methodName)(self.auth, *args, **kwds)
-        ### debug
-        if debug:
-          print '===> backend call',methodName, self.auth, self.url,'->',
-          if not result:                        print "no/empty result"
-          elif isinstance (result,str):         print "result is '%s'"%result
-          elif isinstance (result,list):        print "result is a %d-elts list"%len(result)
-          else:                                 print "dont know how to display result"
-        ###
-        return result
-      return func
+    def __getattr__(self, methodName):
+        def func(*args, **kwds):
+            try:
+                result=getattr(self.server, methodName)(self.auth, *args, **kwds)
+                if debug:
+                    print '===> backend call',methodName, self.auth, self.url,'->',
+                    if not result:                        print "no/empty result"
+                    elif isinstance (result,str):         print "result is '%s'"%result
+                    elif isinstance (result,list):        print "result is a %d-elts list"%len(result)
+                    else:                                 print "dont know how to display result"
+                return result
+            except xmlrpclib.Fault, error:
+                ### xxx this is very rough for now
+                # until we have some agreement about how the API calls should return error conditions
+                # in some less unpolite way than this anoanymous exception, we assume it's a problem with the session
+                # that needs to be refreshed
+                if error.faultCode == 8002:
+                    reason="most likely your session has expired"
+                    reason += " (the manifold API has no unambiguous error reporting mechanism yet)"
+                    raise SessionExpired(reason)
+            except Exception,error:
+                print "ManifoldAPI: unexpected exception",error
+                raise
+        return func
 
-  def send_manifold_query (self, manifold_query):
-    (action,subject)= (manifold_query.action,manifold_query.subject)
-    if action=='get':
-      return self.server.Get(self.auth, subject, manifold_query.filters, {}, manifold_query.fields)
-    # xxx...
-    else:
-      print "WARNING: ManifoldAPI.send_manifold_query: only 'get' implemented for now"
-    
+    def send_manifold_query (self, manifold_query):
+        (action,subject)= (manifold_query.action,manifold_query.subject)
+        if action=='get':
+            # use self.Get rather than self.server.Get so we catch exceptions as per __getattr__
+            return self.Get(self.auth, subject, manifold_query.filters, {}, manifold_query.fields)
+        # xxx...
+        else:
+            print "WARNING: ManifoldAPI.send_manifold_query: only 'get' implemented for now"

diff --git a/manifold/manifoldproxy.py b/manifold/manifoldproxy.py
index 733f209..c444a37 100644 (file)
--- a/manifold/manifoldproxy.py
+++ b/manifold/manifoldproxy.py
@@ -4,7 +4,7 @@ import json
 from django.http import HttpResponse, HttpResponseForbidden
 
 from manifold.manifoldquery import ManifoldQuery
-from manifold.manifoldapi import ManifoldAPI
+from manifold.manifoldapi import ManifoldAPI, SessionExpired
 
 debug=False
 debug=True
@@ -63,10 +63,14 @@ with the query passed using POST"""
         # actually forward
         manifold_api= ManifoldAPI(auth=manifold_api_session_auth)
         if debug: print 'manifoldproxy.proxy: sending to backend', manifold_query
-        answer=manifold_api.send_manifold_query (manifold_query)
-        if debug: 
-            try:        print "received answer from backend with %d rows"%len(answer)
-            except:     print "received answer from backend - can't say len"
+        # xxx we should embed the values inside a geni-like wrapper
+        try:
+            answer=manifold_api.send_manifold_query (manifold_query)
+            if debug: 
+                try:        print "received answer from backend with %d rows"%len(answer)
+                except:     print "received answer from backend - can't say len"
+        except SessionExpired,error:
+            answer=[ error.message ] 
         json_answer=json.dumps(answer)
         if (debug):
             with (file(offline_filename,"w")) as f:
@@ -74,8 +78,8 @@ with the query passed using POST"""
         if debug_spin:
             import time
             time.sleep(debug_spin)
-        # return json-encoded answer
         return HttpResponse (json_answer, mimetype="application/json")
+
     except:
         import traceback
         traceback.print_exc()

diff --git a/manifold/metadata.py b/manifold/metadata.py
index 8aed126..3475139 100644 (file)
--- a/manifold/metadata.py
+++ b/manifold/metadata.py
@@ -2,6 +2,10 @@ import json
 
 from manifold.manifoldapi import ManifoldAPI
 
+# turn this on if you want to work offline
+work_offline=False
+#work_offline=True
+
 class MetaData:
 
     def __init__ (self, auth):
@@ -9,6 +13,14 @@ class MetaData:
         self.hash_by_subject={}
 
     def fetch (self):
+        offline_filename="offline_metadata.json"
+        if work_offline:
+            try:
+                with file(offline_metadata) as f:
+                    self.hash_by_subject=json.loads(f.read())
+                return
+            except:
+                print "metadata.work_offline: failed to decode %s"%offline_filename
         manifold_api = ManifoldAPI(self.auth)
         fields = ['table', 'column.column',
                   'column.description','column.header', 'column.title',
@@ -18,6 +30,9 @@ class MetaData:
                   'column.platforms.platform_url']
         results = manifold_api.Get('metadata:table', [], [], fields)
         self.hash_by_subject = dict ( [ (result['table'], result) for result in results ] )
+        # save for next time we use offline mode
+        with file(offline_filename,'w') as f:
+            f.write(json.dumps(self.hash_by_subject))
 
     def to_json(self):
         return json.dumps(self.hash_by_subject)