Localhost#

In localhost, Lithops will use local CPUs to run functions in parallel. In this mode of execution it is not necessary to provide any kind of configuration or create a configuration file.

Configuration#

In case you have a config file, edit it and add these keys:

lithops:
    backend: localhost
    storage: localhost  # You can also set it to a public storage backend, such as aws_s3 or ibm_cos

Execution Environments#

The localhost backend can run functions both using the local python3 interpreter, or using a container image. The environment is automatically chosen depending on whether or not you provided a Docker image as a runtime.

In both cases, you can view the executions logs in your local machine using the lithops client:

lithops logs poll

Default Environment#

By default Lithops uses the local python interpreter to run the functions. That is, if for example you executed the main script with python3.12, your functions will run with python3.12. in this case, you must ensure that all the dependencies of your script are installed in your machine.

# As we use the default FunctionExecutor(), backend must be set to localhost in config
fexec = lithops.FunctionExecutor()

or alternatively, you can force the Localhost executor with:

# As we use/force the LocalhostExecutor(), backend does not need to be set to localhost in config
fexec = lithops.LocalhostExecutor()

Container Environment#

The Container environment runs the functions within a docker container. In this case you must install the Docker CE version in your machine. This environment is automatically activated when you provide a docker image as a runtime. For example, by adding the following keys in the config:

localhost:
    runtime: docker.io/lithopscloud/ibmcf-python-v312

or by using the runtime param in a function executor:

# As we use the default FunctionExecutor(), the "backend" config parameter must be set to localhost in config
fexec = lithops.FunctionExecutor(runtime='docker.io/lithopscloud/ibmcf-python-v312')

# As we use/force the LocalhostExecutor(), the "backend" config parameter does not need to be set to localhost in config
fexec = lithops.LocalhostExecutor(runtime='docker.io/lithopscloud/ibmcf-python-v312')

In this mode of execution, you can use any docker image that contains all the required dependencies. For example, the IBM Cloud Functions and Knative runtimes are compatible with it.

Summary of configuration keys for Localhost:#

Group	Key	Default	Mandatory	Additional info
localhost	runtime	python3	no	By default it uses the `python3` interpreter. It can be a container image name
localhost	version	2	no	There are 2 different localhost implementations. Use ‘1’ for using the alternative version
localhost	worker_processes	CPU_COUNT	no	Number of Lithops processes. This is used to parallelize function activations. By default it is set to the number of CPUs of your machine

Test Lithops#

Once you have your compute and storage backends configured, you can run a hello world function with:

lithops hello -b localhost -s localhost

Viewing the execution logs#

You can view the function executions logs in your local machine using the lithops client:

lithops logs poll

You can view the localhost runner logs in /tmp/lithops-*/localhost-runner.log

Localhost

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