2828
2929
3030class VmPool :
31- """Pool of VMs already started and used to decrease response time.
31+ """Pool of existing VMs
32+
33+ For function VM we keep the VM a while after they have run, so we can reuse them and thus decrease response time.
3234 After running, a VM is saved for future reuse from the same function during a
3335 configurable duration.
34-
35- The counter is used by the VMs to set their tap interface name and the corresponding
36- IPv4 subnet.
3736 """
3837
39- counter : int # Used to provide distinct ids to network interfaces
4038 executions : dict [ItemHash , VmExecution ]
4139 message_cache : dict [str , ExecutableMessage ]
4240 network : Network | None
@@ -45,7 +43,6 @@ class VmPool:
4543 creation_lock : asyncio .Lock
4644
4745 def __init__ (self , loop : asyncio .AbstractEventLoop ):
48- self .counter = settings .START_ID_INDEX
4946 self .executions = {}
5047 self .message_cache = {}
5148
@@ -150,25 +147,13 @@ def get_unique_vm_id(self) -> int:
150147 This identifier is used to name the network interface and in the IPv4 range
151148 dedicated to the VM.
152149 """
153- _ , network_range = settings .IPV4_ADDRESS_POOL .split ("/" )
154- available_bits = int (network_range ) - settings .IPV4_NETWORK_PREFIX_LENGTH
155- self .counter += 1
156- if self .counter < 2 ** available_bits :
157- # In common cases, use the counter itself as the vm_id. This makes it
158- # easier to debug.
159- return self .counter
160- else :
161- # The value of the counter is too high and some functions such as the
162- # IPv4 range dedicated to the VM do not support such high values.
163- #
164- # We therefore recycle vm_id values from executions that are not running
165- # anymore.
166- currently_used_vm_ids = {execution .vm_id for execution in self .executions .values ()}
167- for i in range (settings .START_ID_INDEX , 255 ** 2 ):
168- if i not in currently_used_vm_ids :
169- return i
170- msg = "No available value for vm_id."
171- raise ValueError (msg )
150+ # Take the first id that is not already taken
151+ currently_used_vm_ids = {execution .vm_id for execution in self .executions .values ()}
152+ for i in range (settings .START_ID_INDEX , 255 ** 2 ):
153+ if i not in currently_used_vm_ids :
154+ return i
155+ msg = "No available value for vm_id."
156+ raise ValueError (msg )
172157
173158 def get_running_vm (self , vm_hash : ItemHash ) -> VmExecution | None :
174159 """Return a running VM or None. Disables the VM expiration task."""
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