Add data.py DEFAULT_SR setting

In some cases, we may prefer to favour a local SR to store test VM disks,
to avoid latency or unstabilities related to network or shared file servers.
However it's not good practice to make a local SR the default SR for a pool of several hosts.
Hence this configuration value that you can set to `local` so that our tests use this SR by default.
Possible values:
- 'default': keep using the pool's default SR
- 'local': use the first local SR found instead

Signed-off-by: Samuel Verschelde <[email protected]>

conftest.py

@@ -6,7 +6,7 @@
 
 import lib.config as global_config
 
-from lib.common import wait_for, vm_image, is_uuid
+from lib.common import safe_split, wait_for, vm_image, is_uuid
 from lib.common import setup_formatted_and_mounted_disk, teardown_formatted_and_mounted_disk
 from lib.netutil import is_ipv6
 from lib.pool import Pool
@@ -283,7 +283,24 @@ def imported_vm(host, vm_ref):
         name = vm.name()
         logging.info(">> Reuse VM %s (%s) on host %s" % (vm_ref, name, host))
     else:
-        vm = host.import_vm(vm_ref)
+        # where to import to: default SR, or first local SR
+        try:
+            from data import DEFAULT_SR
+        except ImportError:
+            DEFAULT_SR = 'default'
+        assert DEFAULT_SR in ['default', 'local']
+
+        if DEFAULT_SR == 'default':
+            vm = host.import_vm(vm_ref)
+        elif DEFAULT_SR == 'local':
+            local_sr_uuids = safe_split(
+                # xe sr-list doesn't support filtering by host UUID!
+                host.ssh(['xe sr-list host=$HOSTNAME content-type=user minimal=true']),
+                ','
+            )
+            assert local_sr_uuids, "The first pool master (host A1) MUST have a local SR since DEFAULT_SR=='local'"
+            vm = host.import_vm(vm_ref, local_sr_uuids[0])
+
     yield vm
     # teardown
     if not is_uuid(vm_ref):

data.py-dist

@@ -32,6 +32,16 @@ VM_IMAGES = {
     'mini-linux-x86_64-uefi': 'alpine-uefi-minimal-3.12.0.xva'
 }
 
+# In some cases, we may prefer to favour a local SR to store test VM disks,
+# to avoid latency or unstabilities related to network or shared file servers.
+# However it's not good practice to make a local SR the default SR for a pool of several hosts.
+# Hence this configuration value that you can set to `local` so that our tests use this SR by default.
+# This setting affects VMs managed by the `imported_vm` fixture.
+# Possible values:
+# - 'default': keep using the pool's default SR
+# - 'local': use the first local SR found instead
+DEFAULT_SR = 'default'
+
 # Default NFS device config:
 DEFAULT_NFS_DEVICE_CONFIG = {
 #    'server': '10.0.0.2', # URL/Hostname of NFS server