Scale Machine CPU and RAM
All new apps on the Fly Platform are V2 Apps, running on Fly Machines. Our docs apply to V2 Apps, but we still include legacy V1 Apps info where appropriate.
We’re migrating all V1 Apps to V2 in phases. Learn more about how and why we’re getting off Nomad.
You can also migrate your V1 app yourself using our migration and migration troubleshooting tools, or migrate your V1 app manually.
fly scale commands apply VM memory and CPU settings to entire process groups in a Fly App. There are two subcommands for scaling these per-VM resources: fly scale vm applies a preset CPU/RAM combination; fly scale memory adjusts RAM relative to the preset’s base RAM.
You can scale an app even if it has crashed. Its VMs are restarted with the new specification.
For existing Nomad/V1 Fly Apps: There’s a whole doc on scaling V1 (Nomad) apps.
Check the VM resources on an app
Here’s a simple web app with two Machines running in different regions: two in Toronto and one in Tokyo. All the app’s Machines belong to the default process group, app, since I didn’t explicitly configure any processes.
fly status
App
Name = testrun
Owner = personal
Hostname = testrun.fly.dev
Image = testrun:deployment-01GWZY7ZVJ2HNED4B0KZBPS3AQ
Platform = machines
Machines
ID PROCESS VERSION REGION STATE HEALTH CHECKS LAST UPDATED
148ed599c14189 app 3 yyz started 1 total, 1 passing 2023-04-04T19:30:57Z
32874400f35285 app 3 yyz started 1 total, 1 passing 2023-04-04T19:33:44Z
9080e6e1f94987 app 3 nrt started 1 total, 1 passing 2023-04-04T19:31:22Z
fly scale show shows the CPU and RAM settings for all the Machines deployed using fly deploy under this app.
fly scale show
VM Resources for app: testrun
Groups
NAME COUNT KIND CPUS MEMORY REGIONS
app 3 shared 1 256 MB nrt,yyz(2)
These Machines are running at the shared-cpu-1x preset scale, with a single shared vCPU and 256MB RAM.
Select a preset CPU/RAM combination
There are a number of VM size presets available. See the list of valid named presets with fly platform vm-sizes.
Scale to a different preset using fly scale vm. In general, you should choose a named VM “size” based on your desired CPU type and scale; RAM can be increased separately.
fly scale vm shared-cpu-2x
Updating machine 148ed599c14189
Waiting for 148ed599c14189 to become healthy (started, 1/1)
Machine 148ed599c14189 updated successfully!
Updating machine 32874400f35285
Waiting for 32874400f35285 to become healthy (started, 1/1)
Machine 32874400f35285 updated successfully!
Updating machine 9080e6e1f94987
Waiting for 9080e6e1f94987 to become healthy (started, 1/1)
Machine 9080e6e1f94987 updated successfully!
Scaled VM Type to 'shared-cpu-2x'
CPU Cores: 2
Memory: 512 MB
Check that the app process group has had this scale applied:
fly scale show
VM Resources for app: testrun
Groups
NAME COUNT KIND CPUS MEMORY REGIONS
app 3 shared 2 512 MB nrt,yyz(2)
(V2 only) You can also confirm that an individual Machine’s config matches this, using fly machine status:
fly machine status 148ed599c14189
Machine ID: 148ed599c14189
Instance ID: 01GX6Q2WE04M85XTHGPYGJK4X6
State: started
VM
...
Process Group = app
CPU Kind = shared
vCPUs = 2
Memory = 512
...
Looks good!
Add RAM
If you are happy with the provisioned CPU resources, but want more memory, then use fly scale memory to top up the RAM.
If your app crashes with an out-of-memory error, then scale up its RAM. Flyctl restarts the Machines to use the new setting.
fly scale memory 4096
Updating machine 32874400f35285
Waiting for 32874400f35285 to become healthy (started, 1/1)
Machine 32874400f35285 updated successfully!
Updating machine 148ed599c14189
Waiting for 148ed599c14189 to become healthy (started, 1/1)
Machine 148ed599c14189 updated successfully!
Updating machine 9080e6e1f94987
Waiting for 9080e6e1f94987 to become healthy (started, 1/1)
Machine 9080e6e1f94987 updated successfully!
Scaled VM Type to 'shared-cpu-2x'
CPU Cores: 2
Memory: 4096 MB
fly scale show
VM Resources for app: testrun
Groups
NAME COUNT KIND CPUS MEMORY REGIONS
app 3 shared 2 4096 MB nrt,yyz(2)
If you try to set an incompatible CPU/RAM combination through fly scale memory, flyctl will let you know. There’s a list of allowed CPU/RAM combinations and their prices on our Pricing page.
Scale by process group
Use the --group option to specify the process group to scale, with either fly scale vm or fly scale memory.
Here’s an app with two process groups defined:
fly scale show
VM Resources for app: mr18-2
Groups
NAME COUNT KIND CPUS MEMORY REGIONS
worker 2 shared 1 512 MB ams,yyz
web 1 shared 1 512 MB yyz
Say the workers are constantly crunching data and need to be bigger. You can scale a single process group using the --group option:
fly scale vm performance-2x --group worker
Updating machine 0e286561f35586
No health checks found
Machine 0e286561f35586 updated successfully!
Updating machine 32873d9b012048
No health checks found
Machine 32873d9b012048 updated successfully!
Scaled VM Type for 'worker' to 'performance-2x'
CPU Cores: 2
Memory: 4096 MB
Check the result:
fly scale show
VM Resources for app: mr18-2
Groups
NAME COUNT KIND CPUS MEMORY REGIONS
worker 2 performance 2 4096 MB ams,yyz
web 1 shared 1 512 MB yyz
Machines not belonging to Fly Launch
If an app has Machines not belonging to Fly Launch—that is, created using fly machine run or the Machines API, or fly machine cloned from such a Machine, and not assimilated during a migration to a V2 App—fly status will warn you of their existence.
The app-wide fly scale commands do not apply to these Machines, but you can scale any Machine individually with fly machine update:
fly machine update --size shared-cpu-2x 21781973f03e89
fly machine update --memory 1024 21781973f03e89
fly machine update --cpus 2 21781973f03e89
Again, if you try to set an incompatible CPU/RAM combination through fly machine update --memory or fly machine update --cpus, flyctl will let you know.