feat(bridge): allow random provider selection

app/portal/bridgeconf.py

@@ -10,7 +10,7 @@ from wtforms.validators import DataRequired, NumberRange
 
 from app.extensions import db
 from app.models.base import Pool
-from app.models.bridges import BridgeConf
+from app.models.bridges import BridgeConf, ProviderAllocation
 from app.portal.util import response_404, view_lifecycle
 
 bp = Blueprint("bridgeconf", __name__)
@@ -36,6 +36,12 @@ class NewBridgeConfForm(FlaskForm):  # type: ignore
     expiry_hours = IntegerField('Expiry Timer (hours)',
                                 description=("The number of hours to wait after a bridge is deprecated before its "
                                              "destruction."))
+    provider_allocation = SelectField('Provider Allocation Method',
+                                      description="How to allocate new bridges to providers.",
+                                      choices=[
+                                          ("COST", "Use cheapest provider first"),
+                                          ("RANDOM", "Use providers randomly"),
+                                      ])
     submit = SubmitField('Save Changes')
 
 
@@ -51,6 +57,12 @@ class EditBridgeConfForm(FlaskForm):  # type: ignore
     expiry_hours = IntegerField('Expiry Timer (hours)',
                                 description=("The number of hours to wait after a bridge is deprecated before its "
                                              "destruction."))
+    provider_allocation = SelectField('Provider Allocation Method',
+                                      description="How to allocate new bridges to providers.",
+                                      choices=[
+                                          ("COST", "Use cheapest provider first"),
+                                          ("RANDOM", "Use providers randomly"),
+                                      ])
     submit = SubmitField('Save Changes')
 
 
@@ -85,6 +97,7 @@ def bridgeconf_new(group_id: Optional[int] = None) -> ResponseReturnValue:
         bridgeconf.target_number = form.target_number.data
         bridgeconf.max_number = form.max_number.data
         bridgeconf.expiry_hours = form.expiry_hours.data
+        bridgeconf.provider_allocation = ProviderAllocation[form.provider_allocation.data]
         bridgeconf.created = datetime.utcnow()
         bridgeconf.updated = datetime.utcnow()
         try:
@@ -115,12 +128,14 @@ def bridgeconf_edit(bridgeconf_id: int) -> ResponseReturnValue:
                               target_number=bridgeconf.target_number,
                               max_number=bridgeconf.max_number,
                               expiry_hours=bridgeconf.expiry_hours,
+                              provider_allocation=bridgeconf.provider_allocation.name,
                               )
     if form.validate_on_submit():
         bridgeconf.description = form.description.data
         bridgeconf.target_number = form.target_number.data
         bridgeconf.max_number = form.max_number.data
         bridgeconf.expiry_hours = form.expiry_hours.data
+        bridgeconf.provider_allocation = ProviderAllocation[form.provider_allocation.data]
         bridgeconf.updated = datetime.utcnow()
         try:
             db.session.commit()

app/terraform/block/bridge.py

@@ -25,7 +25,7 @@ class BlockBridgeAutomation(BaseAutomation):
         super().__init__(*args, **kwargs)
 
     def perform_deprecations(self, ids: List[str], bridge_select_func: Callable[[str], Optional[Bridge]]
-                             ) -> List[Tuple[str, str]]:
+                             ) -> List[Tuple[str, str, str]]:
         rotated = []
         for id_ in ids:
             bridge = bridge_select_func(id_)

app/terraform/bridge/meta.py

@@ -1,9 +1,10 @@
 import datetime
 import logging
+import random
 from typing import Tuple, List
 
 from app import db
-from app.models.bridges import BridgeConf, Bridge
+from app.models.bridges import BridgeConf, Bridge, ProviderAllocation
 from app.models.cloud import CloudProvider, CloudAccount
 from app.terraform import BaseAutomation
 
@@ -40,11 +41,11 @@ def create_bridges_in_account(bridgeconf: BridgeConf, account: CloudAccount, cou
     return created
 
 
-def create_bridges(bridgeconf: BridgeConf, count: int) -> int:
+def create_bridges_by_cost(bridgeconf: BridgeConf, count: int) -> int:
     """
-    Creates a bridge resource for the given bridge configuration.
+    Creates bridge resources for the given bridge configuration using the cheapest available provider.
     """
-    logging.debug("Creating %s bridges for configuration %s", count, bridgeconf.id)
+    logging.debug("Creating %s bridges by cost for configuration %s", count, bridgeconf.id)
     created = 0
     for provider in BRIDGE_PROVIDERS:
         if created >= count:
@@ -54,13 +55,48 @@ def create_bridges(bridgeconf: BridgeConf, count: int) -> int:
                 CloudAccount.destroyed.is_(None),
                 CloudAccount.enabled.is_(True),
                 CloudAccount.provider == provider,
-        ):
+        ).all():
             logging.info("Creating bridges in %s", account)
             created += create_bridges_in_account(bridgeconf, account, count - created)
     logging.debug("Created %s bridges", created)
     return created
 
 
+def _accounts_with_room() -> List[CloudAccount]:
+    accounts = CloudAccount.query.filter(
+        CloudAccount.destroyed.is_(None),
+        CloudAccount.enabled.is_(True),
+    ).all()
+    accounts_with_room: List[CloudAccount] = []
+    for account in accounts:
+        if len(active_bridges_in_account(account)) < account.max_instances:
+            accounts_with_room.append(account)
+    return accounts_with_room
+
+
+def create_bridges_by_random(bridgeconf: BridgeConf, count: int) -> int:
+    """
+    Creates bridge resources for the given bridge configuration using random providers.
+    """
+    logging.debug("Creating %s bridges by random for configuration %s", count, bridgeconf.id)
+    created = 0
+    while candidate_accounts := _accounts_with_room():
+        #  Not security-critical random number generation
+        account = random.choice(candidate_accounts)  # nosec: B311
+        create_bridges_in_account(bridgeconf, account, 1)
+        created += 1
+        if created == count:
+            return count
+    return created  # No account with room
+
+
+def create_bridges(bridgeconf: BridgeConf, count: int) -> int:
+    if bridgeconf.provider_allocation == ProviderAllocation.COST:
+        return create_bridges_by_cost(bridgeconf, count)
+    else:
+        return create_bridges_by_random(bridgeconf, count)
+
+
 def deprecate_bridges(bridgeconf: BridgeConf, count: int, reason: str = "redundant") -> int:
     logging.debug("Deprecating %s bridges (%s) for configuration %s", count, reason, bridgeconf.id)
     deprecated = 0