Controlling Function Execution
Fission Concepts/Function Executors describes the major difference between executors. In this guide, we will go through how to set up/config different executors for function.
Poolmgr (Pool-based executor)
You can create a function like following to use poolmgr as backend executor.
You can use the concurrency field to control the maximum number of concurrent pod specialization(default 5) to serve requests.
The concurrency field is only supported by poolmgr.
# The default executor type for function is poolmgr
$ fission fn create --name foobar --concurrency=4 --env nodejs --code hello.js
# Or, set executor type to poolmgr explicitly
$ fission fn create --name foobar --env nodejs --code hello.js --executortype poolmgr
When an environment is created, poolmgr creates a pool of generic pods with default pool size 3.
We may want to adjust the size of pools based on our need (e.g. resource efficiency), for some historic reason fission now only supports to adjust pool size by giving --version 3 flag when creating an environment.
$ fission env create --name python --version 3 --poolsize 1 --image fission/python-env:latest
$ kubectl -n fission-function get pod -l environmentName=test
Now, you shall see only one pod for the environment we just created.
With --poolsize 0, the executor will not be able to specialize any function due to no generic pod in pool.
If you want to set resource requests/limits for all functions use the same environment, you can provide extra min/max cpu & memory flags to set them at environment-level. For example, we want to limit an environment’s min/max cpu to 100m/200m and min/max memory to 128Mi/256Mi.
$ fission env create --name python --version 3 --poolsize 1 --image fission/python-env \
--mincpu 100 --maxcpu 200 --minmemory 128 --maxmemory 256
$ fission env list
NAME UID IMAGE POOLSIZE MINCPU MAXCPU MINMEMORY MAXMEMORY EXTNET GRACETIME
python 73e4e8a3-db49-... fission/python-env 1 100m 200m 128Mi 256Mi false 360
Functions created in Pool Manager can have the following features:
- Requests Per Pod:
You can control how many requests will be served by each pod. For instance, if you want each pod to serve only 5 requests, here’s how you can do it:
$ fission fn create --name foobar --env nodejs --code hello.js --rpp 5
- OnceOnly:
This can be enabled for functions which are long running tasks, the pod will only serve one request. Each request is assured to be served by a new pod.
$ fission fn create --name foobar --env nodejs --code hello.js --yolo true
- Concurrency:
If you want to rate limit the amount of requests a function should process, you can do so by:
$ fission fn create --name foobar --env nodejs --code hello.js --con 1000
Newdeploy (New-deployment executor)
Newdeploy provides autoscaling and min/max scale setting for functions, and allow a function to handle spikes in workloads.
To create a function with newdeploy, you have to set executor type to newdeploy explicitly.
$ fission fn create --name foobar --env nodejs --code hello.js --executortype newdeploy
Unlike Poolmgr sets all configs at the environment-level. Newdeploy provides more fine grained configuration at the function-level. Here are some flags for Newdeploy:
--mincpu value Minimum CPU to be assigned to pod (In millicore, minimum 1)
--maxcpu value Maximum CPU to be assigned to pod (In millicore, minimum 1)
--minmemory value Minimum memory to be assigned to pod (In megabyte)
--maxmemory value Maximum memory to be assigned to pod (In megabyte)
--minscale value Minimum number of pods (Uses resource inputs to configure HPA)
--maxscale value Maximum number of pods (Uses resource inputs to configure HPA)
--targetcpu value Target average CPU usage percentage across pods for scaling (default: 80)
So if we want to limit a function’s min/max cpu to 100m/200m and min/max memory to 128Mi/256Mi.
$ fission fn create --name foobar --env nodejs --code hello.js --executortype newdeploy \
--minscale 1 --maxscale 3 --mincpu 100 --maxcpu 200 --minmemory 128 --maxmemory 256
$ fission fn list
NAME UID ENV EXECUTORTYPE MINSCALE MAXSCALE MINCPU MAXCPU MINMEMORY MAXMEMORY TARGETCPU
foobar afe7666a-db51-11e8... nodejs newdeploy 1 3 100m 200m 128Mi 256Mi 80
$ kubectl -n fission-function get deploy -l functionName=foobar
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
foobar-hhytbcx4 1 1 1 1 51s
With --minscale 0, a function will experience long cold-start time since it takes time for executor to create/scale deployment to 1 replica.
Eliminating cold start
If you want to eliminate the cold start for a function, you can run the function with executortype as “newdeploy” and minscale set to 1. This will ensure that at least one replica of function is always running and there is no cold start in request path.
$ fission fn create --name hello --env node --code hello.js --minscale 1 --executortype newdeploy
Autoscaling
Let’s create a function to demonstrate the autoscaling behavior in Fission. We create a simple function which outputs “Hello World” in using NodeJS. We have kept the CPU request and limit purposefully low to simulate the load and also kept the target CPU percent to 50%.
$ fission fn create --name hello --env node --code hello.js --executortype newdeploy \
--minmemory 64 --maxmemory 128 --minscale 1 --maxscale 6 --targetcpu 50
function 'hello' created
Now let’s use hey to generate the load with 250 concurrent and a total of 10000 requests:
$ hey -c 250 -n 10000 http://${FISSION_ROUTER}/hello
Summary:
Total: 67.3535 secs
Slowest: 4.6192 secs
Fastest: 0.0177 secs
Average: 1.6464 secs
Requests/sec: 148.4704
Total data: 160000 bytes
Size/request: 16 bytes
Response time histogram:
0.018 [1] |
0.478 [486] |∎∎∎∎∎∎∎
0.938 [971] |∎∎∎∎∎∎∎∎∎∎∎∎∎∎
1.398 [2686] |∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎
1.858 [2326] |∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎
2.318 [1641] |∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎
2.779 [1157] |∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎∎
3.239 [574] |∎∎∎∎∎∎∎∎∎
3.699 [120] |∎∎
4.159 [0] |
4.619 [38] |∎
Latency distribution:
10% in 0.7037 secs
25% in 1.1979 secs
50% in 1.5038 secs
75% in 2.1959 secs
90% in 2.6670 secs
95% in 2.8855 secs
99% in 3.4102 secs
Details (average, fastest, slowest):
DNS+dialup: 0.0058 secs, 0.0000 secs, 1.0853 secs
DNS-lookup: 0.0000 secs, 0.0000 secs, 0.0000 secs
req write: 0.0000 secs, 0.0000 secs, 0.0026 secs
resp wait: 1.6405 secs, 0.0176 secs, 3.6144 secs
resp read: 0.0001 secs, 0.0000 secs, 0.0056 secs
Status code distribution:
[200] 10000 responses
While the load is being generated, we will watch the HorizontalPodAutoscaler and how it scales over a period of time. As you can notice, the number of pods is scaled from 1 to 3 after the load rises from 8 - 103%. After the load generator stops, it takes a few iterations to scale down from 3 to 1 pod.
When testing the scaling behavior, do keep in mind that the scaling event has an initial delay of up to a minute and waits for the average CPU to reach 110% above the threshold before scaling up. It is best to maintain a minimum number of pods which can handle initial load and scale as needed.
You will notice that the scaling up and down has different behavior in terms of response time. This behavior is governed by the frequency at which the controller watches (which defaults to 30s) and parameters set on controller-manager for upscale/downscale delay. More details can be found here
$ kubectl -n fission-function get hpa -w
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
hello-qoxmothj Deployment/hello-qoxmothj 5% / 50% 1 6 1 3m
hello-qoxmothj Deployment/hello-qoxmothj 8% / 50% 1 6 1 3m
hello-qoxmothj Deployment/hello-qoxmothj 103% / 50% 1 6 1 4m
hello-qoxmothj Deployment/hello-qoxmothj 103% / 50% 1 6 3 5m
hello-qoxmothj Deployment/hello-qoxmothj 25% / 50% 1 6 3 5m
hello-qoxmothj Deployment/hello-qoxmothj 25% / 50% 1 6 3 6m
hello-qoxmothj Deployment/hello-qoxmothj 5% / 50% 1 6 3 6m
hello-qoxmothj Deployment/hello-qoxmothj 5% / 50% 1 6 3 7m
hello-qoxmothj Deployment/hello-qoxmothj 5% / 50% 1 6 3 7m
hello-qoxmothj Deployment/hello-qoxmothj 5% / 50% 1 6 3 8m
hello-qoxmothj Deployment/hello-qoxmothj 5% / 50% 1 6 3 8m
hello-qoxmothj Deployment/hello-qoxmothj 5% / 50% 1 6 3 9m
hello-qoxmothj Deployment/hello-qoxmothj 5% / 50% 1 6 3 9m
hello-qoxmothj Deployment/hello-qoxmothj 5% / 50% 1 6 3 10m
hello-qoxmothj Deployment/hello-qoxmothj 5% / 50% 1 6 3 10m
hello-qoxmothj Deployment/hello-qoxmothj 7% / 50% 1 6 1 11m
hello-qoxmothj Deployment/hello-qoxmothj 6% / 50% 1 6 1 11m
hello-qoxmothj Deployment/hello-qoxmothj 6% / 50% 1 6 1 12m
hello-qoxmothj Deployment/hello-qoxmothj 6% / 50% 1 6 1 12m