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OpenWhisk system details

The following sections provide more details about the OpenWhisk system.

OpenWhisk entities

Namespaces and packages

OpenWhisk actions, triggers, and rules belong in a namespace, and optionally a package.

Packages can contain actions and feeds. A package cannot contain another package, so package nesting is not allowed. Also, entities do not have to be contained in a package.

In IBM Cloud, an organization+space pair corresponds to a OpenWhisk namespace. For example, the organization BobsOrg and space dev would correspond to the OpenWhisk namespace /BobsOrg_dev.

You can create your own namespaces if you're entitled to do so. The /whisk.system namespace is reserved for entities that are distributed with the OpenWhisk system.

Fully qualified names

The fully qualified name of an entity is /namespaceName[/packageName]/entityName. Notice that / is used to delimit namespaces, packages, and entities.

If the fully qualified name has three parts: /namespaceName/packageName/entityName, then the namespace can be entered without a prefixed /; otherwise, namespaces must be prefixed with a /.

For convenience, the namespace can be left off if it is the user's default namespace.

For example, consider a user whose default namespace is /myOrg. Following are examples of the fully qualified names of a number of entities and their aliases.

Fully qualified name Alias Namespace Package Name
/whisk.system/cloudant/read /whisk.system cloudant read
/myOrg/video/transcode video/transcode /myOrg video transcode
/myOrg/filter filter /myOrg filter

You will be using this naming scheme when you use the OpenWhisk CLI, among other places.

Entity names

The names of all entities, including actions, triggers, rules, packages, and namespaces, are a sequence of characters that follow the following format:

  • The first character must be an alphanumeric character, or an underscore.
  • The subsequent characters can be alphanumeric, spaces, or any of the following: _, @, ., -.
  • The last character can't be a space.

More precisely, a name must match the following regular expression (expressed with Java metacharacter syntax): \A([\w]|[\w][\w@ .-]*[\[email protected]]+)\z.

System limits

Actions

OpenWhisk has a few system limits, including how much memory an action can use and how many action invocations are allowed per minute.

Note: This default limits are for the open source distribution; production deployments like IBM Cloud Functions likely have higher limits. As an operator or developer you can change some of the limits using Ansible inventory variables.

Note: On Openwhisk 2.0 with the scheduler service, concurrent in the table below really means the max containers that can be provisioned at once for a namespace. The api may be able to accept more activations than this number at once depending on a number of factors.

The following table lists the default limits for actions.

limit description configurable unit default
timeout a container is not allowed to run longer than N milliseconds per action milliseconds 60000
memory a container is not allowed to allocate more than N MB of memory per action MB 256
logs a container is not allowed to write more than N MB to stdout per action MB 10
instances an action is not allowed to have more containers than this value (new scheduler only) per action number namespace concurrency limit
concurrent no more than N activations may be submitted per namespace either executing or queued for execution per namespace number 100
minuteRate no more than N activations may be submitted per namespace per minute per namespace number 120
codeSize the maximum size of the action code configurable, limit per action MB 48
parameters the maximum size of the parameters that can be attached not configurable, limit per action/package/trigger MB 1
result the maximum size of the action result not configurable, limit per action MB 1

Per action timeout (ms) (Default: 60s)

  • The timeout limit N is in the range [100ms..300000ms] and is set per action in milliseconds.
  • A user can change the limit when creating the action.
  • A container that runs longer than N milliseconds is terminated.

Per action memory (MB) (Default: 256MB)

  • The memory limit M is in the range from [128MB..512MB] and is set per action in MB.
  • A user can change the limit when creating the action.
  • A container cannot have more memory allocated than the limit.

Per action max instance concurrency (Default: namespace limit for concurrent invocations) Only applicable using new scheduler

  • The max containers that will be created for an action before throttling in the range from [1..concurrentInvocations limit for namespace]
  • By default the max allowed containers / server instances for an action is equal to the namespace limit.
  • A user can change the limit when creating the action.
  • Defining a lower limit than the namespace limit means your max container concurrency will be the action defined limit.
  • If using actionConcurrency > 1 such that your action can handle multiple requests per instance, your true concurrency limit is actionContainerConcurrency * actionConcurrency.
  • The actions within a namespaces containerConcurrency total do not have to add up to the namespace limit though you can configure it that way to guarantee an action will get exactly the action container concurrency.
  • For example with a namespace limit of 30 with 2 actions each with a container limit of 20; if the first action is using 20, there will still be space for 10 for the other.

Per action logs (MB) (Default: 10MB)

  • The log limit N is in the range [0MB..10MB] and is set per action.
  • A user can change the limit when creating or updating the action.
  • Logs that exceed the set limit are truncated and a warning is added as the last output of the activation to indicate that the activation exceeded the set log limit.

Per action artifact (MB) (Default: 48MB)

  • The maximum code size for the action is 48MB.
  • It is recommended for a JavaScript action to use a tool to concatenate all source code including dependencies into a single bundled file.

Per activation payload size (MB) (Fixed: 1MB)

  • The maximum POST content size plus any curried parameters for an action invocation or trigger firing is 1MB.

Per activation result size (MB) (Fixed: 1MB)

  • The maximum size of a result returned from an action is 1MB.

Per namespace concurrent invocation (Default: 100)

  • The number of activations that are either executing or queued for execution for a namespace cannot exceed 100.
  • A user is currently not able to change the limits.

Invocations per minute (Fixed: 120)

  • The rate limit N is set to 120 and limits the number of action invocations in one minute windows.
  • A user cannot change this limit when creating the action.
  • A CLI or API call that exceeds this limit receives an error code corresponding to HTTP status code 429: TOO MANY REQUESTS.

Size of the parameters (Fixed: 1MB)

  • The size limit for the parameters on creating or updating of an action/package/trigger is 1MB.
  • The limit cannot be changed by the user.
  • An entity with too big parameters will be rejected on trying to create or update it.

Per Docker action open files ulimit (Fixed: 1024:1024)

  • The maximum number of open files is 1024 (for both hard and soft limits).
  • The docker run command use the argument --ulimit nofile=1024:1024.
  • For more information about the ulimit for open files see the docker run documentation.

Per Docker action processes ulimit (Fixed: 1024)

  • The maximum number of processes available to the action container is 1024.
  • The docker run command use the argument --pids-limit 1024.
  • For more information about the ulimit for maximum number of processes see the docker run documentation.

Triggers

Triggers are subject to a firing rate per minute as documented in the table below.

limit description configurable unit default
minuteRate no more than N triggers may be fired per namespace per minute per user number 60

Triggers per minute (Fixed: 60)

  • The rate limit N is set to 60 and limits the number of triggers that may be fired in one minute windows.
  • A user cannot change this limit when creating the trigger.
  • A CLI or API call that exceeds this limit receives an error code corresponding to HTTP status code 429: TOO MANY REQUESTS.