multitenant: shorten schema names to stay within postgresql limits (#22494)

hobo/multitenant/middleware.py

@@ -1,6 +1,8 @@
 import os
 import glob
+import hashlib
 
+from django.utils.encoding import smart_bytes
 from django.conf import settings
 from django.db import connection
 from django.http import Http404, HttpResponseRedirect
@@ -27,7 +29,11 @@ class TenantMiddleware(object):
         '''Convert hostname to PostgreSQL schema name'''
         if hostname in getattr(settings, 'TENANT_MAPPING', {}):
             return settings.TENANT_MAPPING[hostname]
-        return hostname.replace('.', '_').replace('-', '_')
+        schema = hostname.replace('.', '_').replace('-', '_')
+        if len(schema) > 63:
+            digest = hashlib.md5(smart_bytes(schema)).hexdigest()[:4]
+            schema = '%s_%s_%s' % (schema[:29], digest, schema[-28:])
+        return schema
 
     @classmethod
     def get_tenant_by_hostname(cls, hostname):

tests_multitenant/test_middleware.py

@@ -0,0 +1,15 @@
+from hobo.multitenant.middleware import TenantMiddleware
+
+
+def test_hostname2schema():
+    assert TenantMiddleware.hostname2schema('x' * 63) == ('x' * 63)
+    shortened = TenantMiddleware.hostname2schema('x' * 64)
+    # no more than 63 characters
+    assert len(shortened) == 63
+    # it's different than just the 63 first characters
+    assert shortened != ('x' * 63)
+    # but it matches the prefix
+    assert shortened[:20] == ('x' * 20)
+    # and it matches the suffix
+    assert shortened[-20:] == ('x' * 20)
+