Postprocessing Service Configuration

Introduction

The Infinite Scale postprocessing service handles the coordination of asynchronous post-processing steps.

General Prerequisites

To use the postprocessing service, an event system needs to be configured for all services. By default, Infinite Scale ships with a preconfigured nats service.

Post-Processing Functionality

The storageprovider service (storage-users) can be configured to initiate asynchronous post-processing by setting the STORAGE_USERS_OCIS_ASYNC_UPLOADS environment variable to true. If this is the case, post-processing will get initiated after uploading a file and all bytes have been received.

The postprocessing service will then coordinate configured post-processing steps like scanning the file for viruses. During post-processing, the file will be in a processing state where only a limited set of actions are available.

The processing state excludes file accessibility by users.

When all postprocessing steps have completed successfully, the file will be made accessible to users.

Additional Prerequisites for the postprocessing Service

Once post-processing has been enabled, configuring any post-processing step will require the requested services to be enabled and preconfigured. For example, to use the virusscan step, one needs to have an enabled and configured antivirus service.

Post-Processing Steps

The postprocessing service is individually configurable. This is achieved by allowing a list of post-processing steps to be performed in order of their appearance in the POSTPROCESSING_STEPS envvar. This envvar expects a comma-separated list of steps that will be executed. Currently steps known to the system are virusscan and delay. Custom steps can be added but need an existing target for processing.

Virus Scanning

To enable virus scanning as a post-processing step after uploading a file, the environment variable POSTPROCESSING_STEPS needs to contain the word virusscan at one location in the list of steps. As a result, each uploaded file gets scanned for viruses as part of the post-processing steps. Note that the antivirus service must be enabled and configured for this to work.

Delay

Though this is for development purposes only and NOT RECOMMENDED on production systems, setting the environment variable POSTPROCESSING_DELAY to a duration not equal to zero will add a delay step with the configured amount of time. Infinite Scale will continue post-processing the file after the configured delay. Use the environment variable POSTPROCESSING_STEPS and the keyword delay if you have multiple post-processing steps and want to define their order. If POSTPROCESSING_DELAY is set but the keyword delay is not contained in POSTPROCESSING_STEPS, it will be executed as the last post-processing step without being listed as the last one. In this case, a log entry will be written on service startup to notify the admin about the situation. That log entry can be avoided by adding the keyword delay to POSTPROCESSING_STEPS.

Custom Post-Processing Steps

By using the envvar POSTPROCESSING_STEPS, custom post-processing steps can be added. Any word can be used as step name but be careful not to conflict with existing keywords like virusscan and delay. In addition, if a keyword is misspelled or the corresponding service either does not exist or does not follow the necessary event communication, the postprocessing service will wait forever to get the required response to proceed and therefore does not continue with any other processing.

Prerequisites

To use custom post-processing steps, you need a custom service listening to the configured event system. For more information, see General Prerequisites.

Workflow

When defining a custom postprocessing step (eg. "customstep"), the postprocessing service will eventually send an event during postprocessing. The event will be of type StartPostprocessingStep with its field StepToStart set to "customstep". When the service defined as custom step receives this event, it can safely execute its actions. The postprocessing service will wait until it has finished its work. The event contains further information (filename, executing user, size, …​) and also requires tokens and URLs to download the file in case byte inspection is necessary.

Once the service defined as custom step has finished its work, it should send an event of type PostprocessingFinished via the configured events system back to the postprocessing service. This event needs to contain a FinishedStep field set to "customstep". It also must contain the outcome of the step, which can be one of the following:

  • delete: Abort postprocessing, delete the file.

  • abort: Abort postprocessing, keep the file.

  • retry: There was a problem that was most likely temporary and may be solved by trying again after some backoff duration. Retry runs automatically and is defined by the backoff behavior as described below.

  • continue: Continue postprocessing, this is the success case.

The backoff behavior as mentioned in the retry outcome can be configured using the POSTPROCESSING_RETRY_BACKOFF_DURATION and POSTPROCESSING_MAX_RETRIES environment variables. The backoff duration is calculated using the following formula after each failure: backoff_duration = POSTPROCESSING_RETRY_BACKOFF_DURATION * 2^(number of failures - 1). This means that the time between the next round grows exponentially limited by the number of retries. Steps that still don’t succeed after the maximum number of retries will be automatically moved to the abort state.

CLI Commands

Resume Post-Processing

If post-processing fails in one step due to an unforeseen error, current uploads will not be retried automatically. A system administrator can instead run CLI commands to retry the failed upload which is a two step process. For details on the storage-users command see the Manage Unfinished Uploads documentation.

  • First list ongoing upload sessions:

    ocis storage-users uploads sessions
  • If you want to restart all uploads, just rerun the command with the --restart flag:

    ocis storage-users uploads sessions --restart
  • If you want to restart only one upload, use the postprocessing restart command with the ID selected:

    ocis postprocessing restart -u <uploadID>

Alternatively, instead of starting one specific upload, a system admin can also restart all uploads that are currently in a specific step.

Examples:

ocis postprocessing restart                # Restarts all uploads where postprocessing is finished, but upload is not finished.
ocis postprocessing restart -s "finished"  # Equivalent to the above.
ocis postprocessing restart -s "virusscan" # Restart all uploads currently in virusscan step.

Event Bus Configuration

The Infinite Scale event bus can be configured by a set of environment variables.

  • If you are using a binary installation as described in Binary Setup or Bare Metal with systemd, the address of the event bus OCIS_EVENTS_ENDPOINT is predefined as localhost address without the need for further configuration, but changable on demand.

  • In case of an orchestrated installation like with Docker or Kubernetes, the event bus must be an external service for scalability like a Redis Sentinel cluster or a key-value-store NATS JetStream. Both named stores are supported and also used in Caching and Persistence. The store used is not part of the Infinite Scale installation and must be separately provided and configured.

  • Note that from a configuration point of view, caching and persistence are independent of the event bus configuration.

Note that for each global environment variable, a service-based one might be available additionally. For precedences see Environment Variable Notes. Check the configuration section below.

Without the aim of completeness, see the list of environment variables to configure the event bus:

Envvar Description

OCIS_EVENTS_ENDPOINT

The address of the event system.

OCIS_EVENTS_CLUSTER

The clusterID of the event system. Mandatory when using NATS as event system.

OCIS_EVENTS_ENABLE_TLS

Enable TLS for the connection to the events broker.

OCIS_INSECURE

Whether to verify the server TLS certificates.

OCIS_EVENTS_AUTH_USERNAME

The username to authenticate with the events broker.

OCIS_EVENTS_AUTH_PASSWORD

The password to authenticate with the events broker.

Storing

The postprocessing service needs to store some metadata about uploads to be able to orchestrate post-processing. When running in single binary mode, the default in-memory implementation will be just fine. In distributed deployments it is recommended to use a persistent store, see below for more details.

The postprocessing service can use a configured store via the global OCIS_PERSISTENT_STORE environment variable.

Note that for each global environment variable, a service-based one might be available additionally. For precedences see Environment Variable Notes. Check the configuration section below. Supported stores are:

Store Type Description

memory

Basic in-memory store and the default.

redis-sentinel

Stores data in a configured Redis Sentinel cluster.

nats-js-kv

Stores data using key-value-store feature of NATS JetStream.

noop

Stores nothing. Useful for testing. Not recommended in production environments.

ocmem

(deprecated) Advanced in-memory store allowing max size.

redis

(deprecated) Stores data in a configured Redis cluster.

etcd

(deprecated) Stores data in a configured etcd cluster.

nats-js

(deprecated) Stores data using the key-value-store feature of NATS JetStream.

Other store types may work but are currently not supported.

The postprocessing service can only be scaled if not using the memory store and the stores are configured identically over all instances!
If you have used one of the deprecated stores of a former version, you should reconfigure to use one of the supported ones as the deprecated stores will be removed in a later version.
Store specific notes
  • When using redis-sentinel:
    The Redis master to use is configured via e.g. OCIS_PERSISTENT_STORE_NODES in the form of <sentinel-host>:<sentinel-port>/<redis-master> like 10.10.0.200:26379/mymaster.

  • When using nats-js-kv:

    • It is recommended to set OCIS_PERSISTENT_STORE_NODES to the same value as OCIS_EVENTS_ENDPOINT. That way the cache uses the same nats instance as the event bus.

    • Authentication can be added, if configured, via OCIS_CACHE_AUTH_USERNAME and OCIS_CACHE_AUTH_PASSWORD.

    • It is possible to set OCIS_CACHE_DISABLE_PERSISTENCE to instruct nats to not persist cache data on disc.

Configuration

Environment Variables

The postprocessing service is configured via the following environment variables. Read the Environment Variable Types documentation for important details.

  • 5.0.2

Environment variables for the postprocessing service
Name Type Default Value Description

OCIS_TRACING_ENABLED
POSTPROCESSING_TRACING_ENABLED

bool

false

Activates tracing.

OCIS_TRACING_TYPE
POSTPROCESSING_TRACING_TYPE

string

The type of tracing. Defaults to '', which is the same as 'jaeger'. Allowed tracing types are 'jaeger' and '' as of now.

OCIS_TRACING_ENDPOINT
POSTPROCESSING_TRACING_ENDPOINT

string

The endpoint of the tracing agent.

OCIS_TRACING_COLLECTOR
POSTPROCESSING_TRACING_COLLECTOR

string

The HTTP endpoint for sending spans directly to a collector, i.e. http://jaeger-collector:14268/api/traces. Only used if the tracing endpoint is unset.

OCIS_LOG_LEVEL
POSTPROCESSING_LOG_LEVEL

string

The log level. Valid values are: 'panic', 'fatal', 'error', 'warn', 'info', 'debug', 'trace'.

OCIS_LOG_PRETTY
POSTPROCESSING_LOG_PRETTY

bool

false

Activates pretty log output.

OCIS_LOG_COLOR
POSTPROCESSING_LOG_COLOR

bool

false

Activates colorized log output.

OCIS_LOG_FILE
POSTPROCESSING_LOG_FILE

string

The path to the log file. Activates logging to this file if set.

POSTPROCESSING_DEBUG_ADDR

string

127.0.0.1:9255

Bind address of the debug server, where metrics, health, config and debug endpoints will be exposed.

POSTPROCESSING_DEBUG_TOKEN

string

Token to secure the metrics endpoint.

POSTPROCESSING_DEBUG_PPROF

bool

false

Enables pprof, which can be used for profiling.

POSTPROCESSING_DEBUG_ZPAGES

bool

false

Enables zpages, which can be used for collecting and viewing in-memory traces.

OCIS_PERSISTENT_STORE
POSTPROCESSING_STORE

string

nats-js-kv

The type of the store. Supported values are: 'memory', 'ocmem', 'etcd', 'redis', 'redis-sentinel', 'nats-js', 'noop'. See the text description for details.

OCIS_PERSISTENT_STORE_NODES
POSTPROCESSING_STORE_NODES

[]string

[127.0.0.1:9233]

A list of nodes to access the configured store. This has no effect when 'memory' or 'ocmem' stores are configured. Note that the behaviour how nodes are used is dependent on the library of the configured store. See the Environment Variable Types description for more details.

POSTPROCESSING_STORE_DATABASE

string

postprocessing

The database name the configured store should use.

POSTPROCESSING_STORE_TABLE

string

The database table the store should use.

OCIS_PERSISTENT_STORE_TTL
POSTPROCESSING_STORE_TTL

Duration

0s

Time to live for events in the store. See the Environment Variable Types description for more details.

OCIS_PERSISTENT_STORE_SIZE
POSTPROCESSING_STORE_SIZE

int

0

The maximum quantity of items in the store. Only applies when store type 'ocmem' is configured. Defaults to 512 which is derived from the ocmem package though not exclicitely set as default.

OCIS_PERSISTENT_STORE_AUTH_USERNAME
POSTPROCESSING_STORE_AUTH_USERNAME

string

The username to authenticate with the store. Only applies when store type 'nats-js-kv' is configured.

OCIS_PERSISTENT_STORE_AUTH_PASSWORD
POSTPROCESSING_STORE_AUTH_PASSWORD

string

The password to authenticate with the store. Only applies when store type 'nats-js-kv' is configured.

OCIS_EVENTS_ENDPOINT
POSTPROCESSING_EVENTS_ENDPOINT

string

127.0.0.1:9233

The address of the event system. The event system is the message queuing service. It is used as message broker for the microservice architecture.

OCIS_EVENTS_CLUSTER
POSTPROCESSING_EVENTS_CLUSTER

string

ocis-cluster

The clusterID of the event system. The event system is the message queuing service. It is used as message broker for the microservice architecture. Mandatory when using NATS as event system.

OCIS_INSECURE
POSTPROCESSING_EVENTS_TLS_INSECURE

bool

false

Whether the ocis server should skip the client certificate verification during the TLS handshake.

OCIS_EVENTS_TLS_ROOT_CA_CERTIFICATE
POSTPROCESSING_EVENTS_TLS_ROOT_CA_CERTIFICATE

string

The root CA certificate used to validate the server’s TLS certificate. If provided POSTPROCESSING_EVENTS_TLS_INSECURE will be seen as false.

OCIS_EVENTS_ENABLE_TLS
POSTPROCESSING_EVENTS_ENABLE_TLS

bool

false

Enable TLS for the connection to the events broker. The events broker is the ocis service which receives and delivers events between the services.

OCIS_EVENTS_AUTH_USERNAME
POSTPROCESSING_EVENTS_AUTH_USERNAME

string

The username to authenticate with the events broker. The events broker is the ocis service which receives and delivers events between the services.

OCIS_EVENTS_AUTH_PASSWORD
POSTPROCESSING_EVENTS_AUTH_PASSWORD

string

The password to authenticate with the events broker. The events broker is the ocis service which receives and delivers events between the services.

POSTPROCESSING_STEPS

[]string

[]

A list of postprocessing steps processed in order of their appearance. Currently supported values by the system are: 'virusscan', 'policies' and 'delay'. Custom steps are allowed. See the documentation for instructions. See the Environment Variable Types description for more details.

POSTPROCESSING_DELAY

Duration

0s

After uploading a file but before making it available for download, a delay step can be added. Intended for developing purposes only. If a duration is set but the keyword 'delay' is not explicitely added to 'POSTPROCESSING_STEPS', the delay step will be processed as last step. In such a case, a log entry will be written on service startup to remind the admin about that situation. See the Environment Variable Types description for more details.

POSTPROCESSING_RETRY_BACKOFF_DURATION

Duration

5s

The base for the exponential backoff duration before retrying a failed postprocessing step. See the Environment Variable Types description for more details.

POSTPROCESSING_MAX_RETRIES

int

14

The maximum number of retries for a failed postprocessing step.

YAML Example

  • 5.0.2

# Autogenerated
# Filename: postprocessing-config-example.yaml

tracing:
  enabled: false
  type: ""
  endpoint: ""
  collector: ""
log:
  level: ""
  pretty: false
  color: false
  file: ""
debug:
  addr: 127.0.0.1:9255
  token: ""
  pprof: false
  zpages: false
store:
  store: nats-js-kv
  nodes:
  - 127.0.0.1:9233
  database: postprocessing
  table: ""
  ttl: 0s
  size: 0
  username: ""
  password: ""
postprocessing:
  events:
    endpoint: 127.0.0.1:9233
    cluster: ocis-cluster
    tls_insecure: false
    tls_root_ca_certificate: ""
    enable_tls: false
    username: ""
    password: ""
  steps: []
  delayprocessing: 0s
  retry_backoff_duration: 5s
  max_retries: 14