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Apache NiFi - Configuring MiNiFi - C++

Table of Contents

Configuring

The 'conf' directory in the root contains a template config.yml document.

This is partly compatible with the format used with the Java MiNiFi application. MiNiFi C++ is currently compatible with version 1 of the MiNiFi YAML schema. Additional information on the YAML format for the config.yml and schema versioning can be found in the MiNiFi System Administrator Guide.

MiNiFi Toolkit Converter (version 0.0.1 - schema version 1) is considered as deprecated from MiNiFi C++ 0.7.0. It was to aid in creating a flow configuration from a generated template exported from a NiFi instance. The MiNiFi Toolkit Converter tool can be downloaded from http://nifi.apache.org/minifi/download.html under the MiNiFi Toolkit Binaries section. Information on its usage is available at https://nifi.apache.org/minifi/minifi-toolkit.html. Using the toolkit is no longer supported and maintained.

It's recommended to create your configuration in YAML format or configure the agent via Command and Control protocol (see below)

Flow Controller:
    id: 471deef6-2a6e-4a7d-912a-81cc17e3a205
    name: MiNiFi Flow

Processors:
    - name: GetFile
      id: 471deef6-2a6e-4a7d-912a-81cc17e3a206
      class: org.apache.nifi.processors.standard.GetFile
      max concurrent tasks: 1
      scheduling strategy: TIMER_DRIVEN
      scheduling period: 1 sec
      penalization period: 30 sec
      yield period: 1 sec
      run duration nanos: 0
      auto-terminated relationships list:
      Properties:
          Input Directory: /tmp/getfile
          Keep Source File: true

Connections:
    - name: TransferFilesToRPG
      id: 471deef6-2a6e-4a7d-912a-81cc17e3a207
      source name: GetFile
      source id: 471deef6-2a6e-4a7d-912a-81cc17e3a206
      source relationship name: success
      destination id: 471deef6-2a6e-4a7d-912a-81cc17e3a204
      max work queue size: 0
      max work queue data size: 1 MB
      flowfile expiration: 60 sec
      drop empty: false

Remote Processing Groups:
    - name: NiFi Flow
      id: 471deef6-2a6e-4a7d-912a-81cc17e3a208
      url: http://localhost:8080/nifi
      timeout: 30 secs
      yield period: 10 sec
      Input Ports:
          - id: 471deef6-2a6e-4a7d-912a-81cc17e3a204
            name: From Node A
            max concurrent tasks: 1
            Properties:

Besides YAML configuration format, MiNiFi C++ also supports JSON configuration. To see different uses cases in both formats, please refer to the examples page for flow config examples.

NOTE: Make sure to specify id for each component (Processor, Connection, Controller, RPG etc.) to make sure that Apache MiNiFi C++ can reload the state after a process restart. The id should be unique in the flow configuration.

Parameter Contexts

Processor properties in flow configurations can be parameterized using parameters defined in parameter contexts. Flow configurations can define parameter contexts that define parameter-value pairs to be reused in the flow configuration as per the following rules:

  • Parameters within a process group can only be used if the parameter context is assigned to that process group.
  • Each process group can be assigned only one parameter context.
  • Parameter contexts can be assigned to multiple process groups.
  • The assigned parameter context has the scope of the process group, but not its child process groups.
  • The parameters can be used in the flow configuration by using the #{parameterName} syntax for processor properties.
  • Only alpha-numeric characters (a-z, A-Z, 0-9), hyphens ( - ), underscores ( _ ), periods ( . ), and spaces are allowed in parameter name.
  • # character can be used to escape the parameter syntax. E.g. if the parameterName parameter's value is xxx then #{parameterName} will be replaced with xxx, ##{parameterName} will be replaced with #{parameterName}, and #####{parameterName} will be replaced with ##xxx.
  • Sensitive parameters can only be assigned to sensitive properties and non-sensitive parameters can only be assigned to non-sensitive properties.

An example for using parameters in a JSON configuration file:

{
    "parameterContexts": [
        {
            "identifier": "804e6b47-ea22-45cd-a472-545801db98e6",
            "name": "root-process-group-context",
            "description": "Root process group parameter context",
            "parameters": [
                {
                    "name": "tail_base_dir",
                    "description": "Base dir of tailed files",
                    "sensitive": false,
                    "value": "/tmp/tail/file/path"
                }
            ]
        }
    ],
    "rootGroup": {
        "name": "MiNiFi Flow",
        "processors": [
            {
                "name": "Tail test_file1.log",
                "identifier": "83b58f9f-e661-4634-96fb-0e82b92becdf",
                "type": "org.apache.nifi.minifi.processors.TailFile",
                "schedulingStrategy": "TIMER_DRIVEN",
                "schedulingPeriod": "1000 ms",
                "properties": {
                    "File to Tail": "#{tail_base_dir}/test_file1.log"
                }
            },
            {
                "name": "Tail test_file2.log",
                "identifier": "8a772a10-7c34-48e7-b152-b1a32c5db83e",
                "type": "org.apache.nifi.minifi.processors.TailFile",
                "schedulingStrategy": "TIMER_DRIVEN",
                "schedulingPeriod": "1000 ms",
                "properties": {
                    "File to Tail": "#{tail_base_dir}/test_file2.log"
                }
            }
        ],
        "parameterContextName": "root-process-group-context"
    }
}

An example for using parameters in a YAML configuration file:

    MiNiFi Config Version: 3
    Flow Controller:
      name: MiNiFi Flow
    Parameter Contexts:
      - id: 804e6b47-ea22-45cd-a472-545801db98e6
        name: root-process-group-context
        description: Root process group parameter context
        Parameters:
        - name: tail_base_dir
          description: 'Base dir of tailed files'
          sensitive: false
          value: /tmp/tail/file/path
    Processors:
    - name: Tail test_file1.log
      id: 83b58f9f-e661-4634-96fb-0e82b92becdf
      class: org.apache.nifi.minifi.processors.TailFile
      scheduling strategy: TIMER_DRIVEN
      scheduling period: 1000 ms
      Properties:
        File to Tail: "#{tail_base_dir}/test_file1.log"
    - name: Tail test_file2.log
      id: 8a772a10-7c34-48e7-b152-b1a32c5db83e
      class: org.apache.nifi.minifi.processors.TailFile
      scheduling strategy: TIMER_DRIVEN
      scheduling period: 1000 ms
      Properties:
        File to Tail: "#{tail_base_dir}/test_file2.log"
    Parameter Context Name: root-process-group-context

Configuring flow configuration format

MiNiFi supports YAML and JSON configuration formats. The desired configuration format can be set in the minifi.properties file, but it is automatically identified by default. The default value is adaptiveconfiguration, but we can force to use YAML with the yamlconfiguration value.

# in minifi.properties
nifi.flow.configuration.class.name=adaptiveconfiguration

Scheduling strategies

Currently Apache NiFi MiNiFi C++ supports TIMER_DRIVEN, EVENT_DRIVEN, and CRON_DRIVEN. TIMER_DRIVEN uses periods to execute your processor(s) at given intervals. The EVENT_DRIVEN strategy awaits for data be available or some other notification mechanism to trigger execution. EVENT_DRIVEN is the recommended strategy for non-source processors. CRON_DRIVEN executes at the desired intervals based on the CRON periods. Apache NiFi MiNiFi C++ supports standard CRON expressions ( */5 * * * * ).

Configuring encryption for flow configuration

To encrypt flow configuration set the following property to true.

# in minifi.properties
nifi.flow.configuration.encrypt=true

Configuring additional sensitive properties

It is possible to set a comma seperated list of encrypted configuration options beyond the default sensitive property list.

# in minifi.properties
nifi.sensitive.props.additional.keys=nifi.flow.configuration.file, nifi.rest.api.password

Backup previous flow configuration on flow update

It is possible to backup the previous flow configuration file with .bak extension in case of a flow update (e.g. through C2 or controller socket protocol).

# in minifi.properties
nifi.flow.configuration.backup.on.update=true

Set number of flow threads

The number of threads used by the flow scheduler can be set in the MiNiFi configuration. The default value is 5.

# in minifi.properties
nifi.flow.engine.threads=5

OnTrigger runtime alert

MiNiFi writes warning logs in case a processor has been running for too long. The period for these alerts can be set in the configuration file with the default being 5 seconds.

# in minifi.properties
nifi.flow.engine.alert.period=5 sec

Event driven processor time slice

The flow scheduler can be configured how much time it should allocate at maximum for event driven processors. The processor is triggered until it has work to do, but no more than the configured time slice. The default value is 500 milliseconds.

# in minifi.properties
nifi.flow.engine.event.driven.time.slice=500 millis

Administrative yield duration

In case an uncaught exception is thrown while running a processor, the processor will yield for the configured administrative yield time. The default yield duration is 30 seconds.

# in minifi.properties
nifi.administrative.yield.duration=30 sec

Bored yield duration

If a processor is triggered but has no work available, it will yield for the configured bored yield time. The default yield duration is 100 milliseconds.

# in minifi.properties
nifi.bored.yield.duration=100 millis

Graceful shutdown period

It is possible to configure a graceful shutdown period, the period the flow controller will wait to unload the flow configuration and stop running processors.

# in minifi.properties
nifi.flowcontroller.graceful.shutdown.period=30 sec

FlowController drain timeout

Timeout period for finishing processing of flow files in progress when shutting down flow controller. When not set we do not wait for flow files to finish processing.

# in minifi.properties
nifi.flowcontroller.drain.timeout=500 millis

SiteToSite Security Configuration

# in minifi.properties

# enable tls
nifi.remote.input.secure=true

# if you want to enable client certificate base authorization
nifi.security.need.ClientAuth=true
# setup the client certificate and private key PEM files
nifi.security.client.certificate=./conf/client.pem
nifi.security.client.private.key=./conf/client.pem
# setup the client private key passphrase file
nifi.security.client.pass.phrase=./conf/password
# setup the client CA certificate file
nifi.security.client.ca.certificate=./conf/nifi-cert.pem

# if you do not want to enable client certificate base authorization
nifi.security.need.ClientAuth=false

It can also be configured to use the system certificate store.

# in minifi.properties
nifi.security.use.system.cert.store=true

Windows specific certificate options with the following default values:

# in minifi.properties
nifi.security.windows.cert.store.location=LocalMachine
nifi.security.windows.server.cert.store=ROOT
nifi.security.windows.client.cert.store=MY

# The CN that the client certificate is required to match; default: use the first available client certificate in the store
# nifi.security.windows.client.cert.cn=

# Comma-separated list of enhanced key usage values that the client certificate is required to have
nifi.security.windows.client.cert.key.usage=Client Authentication

You have the option of specifying an SSL Context Service definition for the RPGs instead of the properties above. This will link to a corresponding SSL Context service defined in the flow.

To do this specify the SSL Context Service Property in your RPGs and link it to a defined controller service. If you do not take this approach the options, above, will be used for TCP and secure HTTPS communications.

Remote Processing Groups:
- name: NiFi Flow
  id: 2438e3c8-015a-1000-79ca-83af40ec1998
  url: http://127.0.0.1:8080/nifi
  timeout: 30 secs
  yield period: 5 sec
  Input Ports:
      - id: 2438e3c8-015a-1000-79ca-83af40ec1999
        name: fromnifi
        max concurrent tasks: 1
        Properties:
            SSL Context Service: SSLServiceName
  Output Ports:
      - id: ac82e521-015c-1000-2b21-41279516e19a
        name: tominifi
        max concurrent tasks: 2
        Properties:
            SSL Context Service: SSLServiceName
Controller Services:
- name: SSLServiceName
  id: 2438e3c8-015a-1000-79ca-83af40ec1974
  class: SSLContextService
  Properties:
      Client Certificate: <client cert path>
      Private Key: < private key path >
      Passphrase: <passphrase path or passphrase>
      CA Certificate: <CA cert path>

If the SSL certificates are not provided with an absolute path or cannot be found on the given relative path, MiNiFi will try to find them on the default path provided in the configuration file.

# in minifi.properties

# default minifi resource path
nifi.default.directory=/path/to/cert/files/

HTTP SiteToSite Configuration

To enable HTTPSiteToSite for a remote process group. Remote Processing Groups: - name: NiFi Flow transport protocol: HTTP

HTTP SiteToSite Proxy Configuration

To enable HTTP Proxy for a remote process group.

Remote Processing Groups:
- name: NiFi Flow
  transport protocol: HTTP
  proxy host: localhost
  proxy port: 8888
  proxy user:
  proxy password:

Command and Control Configuration

Please see the C2 readme for more informatoin

State Storage

State storage is used for keeping the state of stateful processors like TailFile. This is done using RocksDB database, but can be configured to use a different state storage with custom options.

The default location of the RocksDB local state storage is the corecomponentstate directory under the MiNiFi root directory. This can be reconfigured if other directory is preferred.

# in minifi.properties
nifi.state.storage.local.path=/var/tmp/minifi-state/

To have a custom state storage one option is to configure it in the flow configuration file and set the created controller in the minifi.properties file.

# in config.yml
Controller Services:
- name: testcontroller
  id: 2438e3c8-015a-1000-79ca-83af40ec1994
  class: PersistentMapStateStorage
  Properties:
    Auto Persistence Interval:
        - value: 0 sec
    Always Persist:
        - value: true
    File:
        - value: state.txt

# in minifi.properties
nifi.state.storage.local=2438e3c8-015a-1000-79ca-83af40ec1994

Another option to define a state storage is to use the following properties in the minifi.properties file.

# in minifi.properties
nifi.state.storage.local.class.name=PersistentMapStateStorage
nifi.state.storage.local.always.persist=true
nifi.state.storage.local.auto.persistence.interval=0 sec

Configuring Repositories

Apache MiNiFi C++ uses three repositories similarly to Apache NiFi:

  • The Flow File Repository holds the metadata (like flow file attributes) of the flow files.
  • The Content Repository holds the content of the flow files.
  • The Provenance Repository holds the history of the flow files.

The underlying implementation to use for these repositories can be configured in the minifi.properties file.

The Flow File Repository can be configured with the nifi.flowfile.repository.class.name property. If not specified, it uses the FlowFileRepository class by default, which stores the flow file metadata in a RocksDB database. Alternatively it can be configured to use a VolatileFlowFileRepository that keeps the state in memory (so the state gets lost upon restart), or the NoOpRepository for not keeping any state.

# in minifi.properties
nifi.flowfile.repository.class.name=VolatileFlowFileRepository

The Content Repository can be configured with the nifi.content.repository.class.name property. If not specified, it uses the DatabaseContentRepository class by default, which persists the content in a RocksDB database. DatabaseContentRepository is also the default value specified in the minifi.properties file. Alternatively it can be configured to use a VolatileContentRepository that keeps the state in memory (so the state gets lost upon restart), or the FileSystemRepository to keep the state in regular files.

NOTE: RocksDB database has a limit of 4GB for the size of a database object. Due to this if you expect to process larger flow files than 4GB you should use the FileSystemRepository. The downside of using FileSystemRepository is that it does not have the transactional guarantees of the RocksDB repository implementation.

# in minifi.properties
nifi.content.repository.class.name=FileSystemRepository

During startup, MiNiFi checks if the flowfiles and their respective content are in good health (corruption can rarely occur due to ungraceful shutdowns) and filters out these corrupt flowfiles. This can slow down startup if there is a significant number of flowfiles. This health check can be disabled by setting nifi.flowfile.repository.check.health to false

The Provenance Repository can be configured with the nifi.provenance.repository.class.name property. If not specified, it uses the ProvenanceRepository class by default, which persists the provenance events in a RocksDB database. Alternatively it can be configured to use a VolatileProvenanceRepository that keeps the state in memory (so the state gets lost upon restart), or the NoOpRepository to not keep track of the provenance events. By default we do not keep track of the provenance data, so NoOpRepository is the value specified in the default minifi.properties file.

# in minifi.properties
nifi.flowfile.repository.class.name=NoOpRepository

Configuring Volatile Repositories

As stated before each of the repositories can be configured to be volatile (state kept in memory and flushed upon restart) or persistent. Volatile repositories have some additional options, that can be specified in the following ways:

# in minifi.properties
# For Volatile Repositories:
nifi.flowfile.repository.class.name=VolatileFlowFileRepository
nifi.provenance.repository.class.name=VolatileProvenanceRepository
nifi.content.repository.class.name=VolatileContentRepository

# configuration options
# maximum number of entries to keep in memory
nifi.volatile.repository.options.flowfile.max.count=15000
# maximum number of bytes to keep in memory, also limited by option above
nifi.volatile.repository.options.flowfile.max.bytes=7680 KB

# maximum number of entries to keep in memory
nifi.volatile.repository.options.provenance.max.count=15000
# maximum number of bytes to keep in memory, also limited by option above
nifi.volatile.repository.options.provenance.max.bytes=7680 KB

# maximum number of entries to keep in memory
nifi.volatile.repository.options.content.max.count=15000
# maximum number of bytes to keep in memory, also limited by option above
nifi.volatile.repository.options.content.max.bytes=7680 KB
# limits locking for the content repository
nifi.volatile.repository.options.content.minimal.locking=true

NOTE: If the volatile repository reaches the maximum number of entries, it will start to drop the oldest entries, and replace them with the new entries in round robin manner. Make sure to set the maximum number of entries to a reasonable value, so that the repository does not run out of memory.

Configuring Repository storage locations

Persistent repositories, such as the Flow File repository, use a configurable path to store data. The repository locations and their defaults are defined below. By default the MINIFI_HOME env variable is used. If this is not specified we extrapolate the path and use the root installation folder. You may specify your own path in place of these defaults.

# in minifi.properties
nifi.provenance.repository.directory.default=${MINIFI_HOME}/provenance_repository
nifi.flowfile.repository.directory.default=${MINIFI_HOME}/flowfile_repository
nifi.database.content.repository.directory.default=${MINIFI_HOME}/content_repository

Configuring compression for rocksdb database

Rocksdb has an option to set compression type for its database to use less disk space. If content repository or flow file repository is set to use the rocksdb database as their storage, then we have the option to compress those repositories. On Unix operating systems zlib, bzip2, zstd, lz4 and lz4hc compression types and on Windows xpress compression type is supported by MiNiFi C++. If the property is set to auto then xpress will be used on Windows, zstd on Unix operating systems. These options can be set in the minifi.properies file with the following properties:

 # in minifi.properties
 nifi.flowfile.repository.rocksdb.compression=zlib
 nifi.content.repository.rocksdb.compression=auto

Configuring compaction for rocksdb database

Rocksdb has an option to run compaction at specific intervals not just when needed.

 # in minifi.properties
 nifi.flowfile.repository.rocksdb.compaction.period=2 min
 nifi.database.content.repository.rocksdb.compaction.period=2 min

Configuring synchronous or asynchronous writes for RocksDB content repository

RocksDB has an option to set synchronous writes for its database, ensuring that the write operation does not return until the data being written has been pushed all the way to persistent storage. In MiNiFi C++, this is set to true by default to avoid any data loss, as according to the RocksDB documentation using non-sync writes can result in data loss in the event of a host machine crash. You can read more information about this option on the RocksDB wiki page. If you prefer to use non-sync writes in your content repository for better write performance and can accept the possibility of the mentioned data loss, you can set this option to false.

# in minifi.properties
nifi.content.repository.rocksdb.use.synchronous.writes=true

Configuring checksum verification for RocksDB reads

RocksDB has an option to verify checksums for its database reads. This option is set to false by default for better performance. If you prefer to enable checksum verification you can set this option to true.

# in minifi.properties
nifi.content.repository.rocksdb.read.verify.checksums=false
nifi.flowfile.repository.rocksdb.read.verify.checksums=false
nifi.provenance.repository.rocksdb.read.verify.checksums=false
nifi.rocksdb.state.storage.read.verify.checksums=false

Global RocksDB options

There are a few options for RocksDB that are set for all used RocksDB databases in MiNiFi: create_if_missing is set to true use_direct_io_for_flush_and_compaction is set to true use_direct_reads is set to true keep_log_file_num is set to 5

Any RocksDB option can be set or overriden using the nifi.global.rocksdb.options. prefix in the minifi.properties file.

# in minifi.properties
nifi.global.rocksdb.options.keep_log_file_num=7
nifi.global.rocksdb.options.atomic_flush=true

RocksDB options can also be overridden for a specific repository using the nifi.<repository>.rocksdb.options. prefix in the minifi.properties file.

# in minifi.properties
nifi.flowfile.repository.rocksdb.options.keep_log_file_num=3
nifi.content.repository.rocksdb.options.atomic_flush=true
nifi.provenance.repository.rocksdb.options.use_direct_reads=false
nifi.state.storage.rocksdb.options.use_direct_io_for_flush_and_compaction=false

Shared database

It is also possible to use a single database to store multiple repositories with the minifidb:// scheme. This could help with migration and centralize agent state persistence. In the scheme the final path segment designates the column family in the repository, while the preceding path indicates the directory the rocksdb database is created into. E.g. in minifidb:///home/user/minifi/agent_state/flowfile a directory will be created at /home/user/minifi/agent_state populated with rocksdb-specific content, and in that repository a logically separate "subdatabase" is created under the name "flowfile".

# in minifi.properties
nifi.flowfile.repository.directory.default=minifidb://${MINIFI_HOME}/agent_state/flowfile
nifi.database.content.repository.directory.default=minifidb://${MINIFI_HOME}/agent_state/content
nifi.state.storage.local.path=minifidb://${MINIFI_HOME}/agent_state/processor_states

We should not simultaneously use the same directory with and without the minifidb:// scheme. Moreover the "default" name is restricted and should not be used.

# in minifi.properties
nifi.flowfile.repository.directory.default=minifidb://${MINIFI_HOME}/agent_state/flowfile
nifi.database.content.repository.directory.default=${MINIFI_HOME}/agent_state
^ error: using the same database directory without the "minifidb://" scheme
nifi.state.storage.local.path=minifidb://${MINIFI_HOME}/agent_state/default
^ error: "default" is restricted

Configuring Repository encryption

It is possible to provide rocksdb-backed repositories a key to request their encryption.

in conf/bootstrap.conf
nifi.flowfile.repository.encryption.key=805D7B95EF44DC27C87FFBC4DFDE376DAE604D55DB2C5496DEEF5236362DE62E
nifi.database.content.repository.encryption.key=
# nifi.state.management.provider.local.encryption.key=

In the above configuration the first line will cause FlowFileRepository to use the specified 256 bit key. The second line will trigger the generation of a random (256 bit) key persisted back into conf/bootstrap.conf, which DatabaseContentRepository will then use for encryption. (This way one can request encryption while not bothering with what key to use.) Finally, as the last line is commented out, it will make the state manager use plaintext storage, and not trigger encryption.

Mixing encryption with shared backend

When multiple repositories use the same directory (as with minifidb:// scheme) they should either be all plaintext or all encrypted with the same key.

Configuring Repository Cleanup

When a flow file content is no longer needed we can specify the deletion strategy.

# any value other than 0 enables garbage collection with the specified frequency
# while a value of 0 sec triggers an immediate deletion as soon as the resource
# is not needed
# (the default value is 1 sec)
nifi.database.content.repository.purge.period = 1 sec

Caveats

Systems that have limited memory must be cognizant of the options above. Limiting the max count for the number of entries limits memory consumption but also limits the number of events that can be stored. If you are limiting the amount of volatile content you are configuring, you may have excessive session rollback due to invalid stream errors that occur when a claim cannot be found.

The content repository has a default option for "minimal.locking" set to true. This will attempt to use lock free structures. This may or may not be optimal as this requires additional additional searching of the underlying vector. This may be optimal for cases where max.count is not excessively high. In cases where object permanence is low within the repositories, minimal locking will result in better performance. If there are many processors and/or timing is such that the content repository fills up quickly, performance may be reduced. In all cases a locking cache is used to avoid the worst case complexity of O(n) for the content repository; however, this caching is more heavily used when "minimal.locking" is set to false.

Configuring provenance repository storage

Provenance repository size buffer size and TTL can be configured when used with RocksDB. If not set it uses the available maximum RocksDB values.

#in minifi.properties
nifi.provenance.repository.max.storage.size=16 MB
nifi.provenance.repository.max.storage.time=30 days

Provenance Reporter

Add Provenance Reporting to config.yml
Provenance Reporting:
  scheduling strategy: TIMER_DRIVEN
  scheduling period: 1 sec
  url: http://localhost:8080/nifi
  port uuid: 471deef6-2a6e-4a7d-912a-81cc17e3a204
  batch size: 100

REST API access

Configure REST API user name and password
nifi.rest.api.user.name=admin
nifi.rest.api.password=password

if you want to enable client certificate
nifi.https.need.ClientAuth=true
nifi.https.client.certificate=./conf/client.pem
nifi.https.client.private.key=./conf/client.key
nifi.https.client.pass.phrase=./conf/password
nifi.https.client.ca.certificate=./conf/nifi-cert.pem

UID generation

MiNiFi needs to generate many unique identifiers in the course of operations. There are a few different uid implementations available that can be configured in minifi-uid.properties.

Implementation for uid generation can be selected using the uid.implementation property values:

  1. time - use uuid_generate_time (default option if the file or property value is missing or invalid)
  2. random - use uuid_generate_random
  3. uuid_default - use uuid_generate (will attempt to use uuid_generate_random and fall back to uuid_generate_time if no high quality randomness is available)
  4. minifi_uid - use custom uid algorthim

If minifi_uuid is selected MiNiFi will use a custom uid algorthim consisting of first N bits device identifier, second M bits as bottom portion of a timestamp where N + M = 64, the last 64 bits is an atomic incrementor.

This is faster than the random uuid generator and encodes the device id and a timestamp into every value, making tracing of flowfiles, etc easier.

It does require more configuration. uid.minifi.device.segment.bits is used to specify how many bits at the beginning to reserve for the device identifier. It also puts a limit on how many distinct devices can be used. With the default of 16 bits, there are a maximum of 65,535 unique device identifiers that can be used. The 48 bit timestamp won't repeat for almost 9,000 years. With 24 bits for the device identifier, there are a maximum of 16,777,215 unique device identifiers and the 40 bit timestamp won't repeat for about 35 years.

Additionally, a unique hexadecimal uid.minifi.device.segment should be assigned to each MiNiFi instance.

Asset directory

There is an asset directory specified using the nifi.asset.directory agent property, which defaults to ${MINIFI_HOME}/asset. The files referenced in the .state file in this directory are managed by the agent. They are deleted, updated, downloaded using the asset sync c2 command. For the asset sync command to work, the c2 server must be made aware of the current state of the managed assets by adding the AssetInformation entry to the nifi.c2.root.classes property.

Files and directories not referenced in the .state file are not directly controlled by the agent, although it is possible to download an asset (triggered through the c2 protocol) into the asset directory instead.

Controller Services

If you need to reference a controller service in your config.yml file, use the following template. In the example, below, ControllerServiceClass is the name of the class defining the controller Service. ControllerService1 is linked to ControllerService2, and requires the latter to be started for ControllerService1 to start.

Controller Services:
  - name: ControllerService1
    id: 2438e3c8-015a-1000-79ca-83af40ec1974
    class: ControllerServiceClass
    Properties:
      Property one: value
      Linked Services:
      - value: ControllerService2
  - name: ControllerService2
    id: 2438e3c8-015a-1000-79ca-83af40ec1992
    class: ControllerServiceClass
    Properties:

Linux Power Manager Controller Service

The linux power manager controller service can be configured to monitor the battery level and status ( discharging or charging ) via the following configuration. Simply provide the capacity path and status path along with your threshold for the trigger and low battery alarm and you can monitor your battery and throttle the threadpools within MiNiFi C++. Note that the name is identified must be ThreadPoolManager.

Controller Services:
- name: ThreadPoolManager
  id: 2438e3c8-015a-1000-79ca-83af40ec1888
  class: LinuxPowerManagerService
  Properties:
      Battery Capacity Path: /path/to/battery/capacity
      Battery Status Path: /path/to/battery/status
      Trigger Threshold: 90
      Low Battery Threshold: 50
      Wait Period: 500 ms

MQTT Controller service

The MQTTController Service can be configured for MQTT connectivity and provide that capability to your processors when MQTT is built.

Controller Services:
- name: mqttservice
  id: 294491a38-015a-1000-0000-000000000001
  class: MQTTContextService
  Properties:
      Broker URI: localhost:1883
      Client ID: client ID
      Quality of Service: 2

Network Prioritizer Controller Service

The network prioritizer controller service can be configured to manage prioritizing and binding to specific network interfaces. Linked Services, can be used as a prioritized list to create a disjunction among multiple networking prioritizers. This allows you to create classes with different configurations that create multiple prioritizations. Max Throughput is the maximum throughput in bytes per second. Max Payload is the maximum number of bytes supported by that prioritizer. If a prioritizer is configured with the option "Default Prioritizer: true," then all socket communications will use that default prioritizer.

In the configuration below there are two classes defined under "NetworkPrioritizerService", one class "NetworkPrioritizerService2" defines en0, and en1. If en0 is down at any point, then en1 will be given priority before resorting to en2 and en3 of "NetworkPrioritizerService3". If the throughput for "NetworkPrioritizerService2" exceeds the defined throughput or the max payload of 1024, then "NetworkPrioritizerService3" will be used. If Max Payload and Max Throughput are not defined, then they will not be limiting factors.

Since connection queues can't be re-prioritized, this can create a starvation problem if no connection is available.  The configuration is required to account for this.

Controller Services:

  • name: NetworkPrioritizerService id: 2438e3c8-015a-1000-79ca-83af40ec1883 class: NetworkPrioritizerService Properties: Linked Services: NetworkPrioritizerService2,NetworkPrioritizerService3
  • name: NetworkPrioritizerService2 id: 2438e3c8-015a-1000-79ca-83af40ec1884 class: NetworkPrioritizerService Properties: Network Controllers: en0,en1 Max Throughput: 1,024,1024 Max Payload: 1024
  • name: NetworkPrioritizerService3 id: 2438e3c8-015a-1000-79ca-83af40ec1884 class: NetworkPrioritizerService Properties: Network Controllers: en2,en3 Max Throughput: 1,024,1024 Max Payload: 1,024,1024

Disk space watchdog

Stops MiNiFi FlowController activity (excluding C2), when the available disk space on either of the repository volumes go below stop.threshold, checked every interval, then restarts when the available space on all repository volumes reach at least restart.threshold.

# in minifi.properties
minifi.disk.space.watchdog.enable=true
minifi.disk.space.watchdog.interval=15 sec
minifi.disk.space.watchdog.stop.threshold=100 MB
minifi.disk.space.watchdog.restart.threshold=150 MB

Extension configuration

To notify the agent which extensions it should load see [Loading extensions](Extensions.md#Loading extensions).

Python processors

Please see the Python Processors Readme.

Log configuration

By default the application logs for Apache MiNiFi C++ can be found in the ${MINIFI_HOME}/logs/minifi-app.log file with default INFO level logging. The logger can be reconfigured in the ${MINIFI_HOME}/conf/minifi-log.properties file to use different output streams, log level, and output format.

Log appenders

In the configuration file it is possible to define different output streams by defining what type of appenders (log sinks) should be used for logging. The following appenders are supported:

  • rollingappender - logs written to this log sink are written to a file with a rolling policy
  • stdout - logs written to this log sink are written to the standard output
  • stderr - logs written to this log sink are written to the standard error
  • syslog - logs written to this log sink are written to the syslog
  • alert - logs written to this log sink are critical logs forwarded through HTTP as alerts
  • nullappender - logs written to this log sink are discarded

Defining a new appender can be done in the format appender.<appender name>=<appender type> followed by defining its properties. For example here is how to define a rolling file appender:

# in minifi-log.properties
appender.rolling=rollingappender
appender.rolling.directory=${MINIFI_HOME}/logs
appender.rolling.file_name=minifi-app.log
appender.rolling.max_files=3
appender.rolling.max_file_size=5 MB

Here's an example of an alert appender with its available properties:

# in minifi-log.properties
appender.alert1=alert
appender.alert1.url=<URL>
appender.alert1.filter=<regex pattern to match logs against>
appender.alert1.rate.limit=10 min
appender.alert1.flush.period=5 s
appender.alert1.batch.size=100 KB
appender.alert1.buffer.limit=1 MB
appender.alert1.level=TRACE
appender.alert1.ssl.context.service=<Name of the SSLContextService>

Log levels

After the appenders are defined you can set the log level and logging target for each of them. Appenders can be set to log everything on a specific log level, but you can also define some appenders to only write logs from specific namespaces or classes with different log levels. The log level can be set to one of the following values: OFF, TRACE, DEBUG, INFO, WARN, ERROR, CRITICAL. The log levels can be set in the following way:

# in minifi-log.properties
# Set the rolling appender to log everything with INFO level
logger.root=INFO,rolling
# But only write logs from the org::apache::nifi::minifi::FlowController class with ERROR level
logger.org::apache::nifi::minifi::core::logging::FlowController=ERROR,rolling

# Write all error logs in the minifi namespace to the alert1 appender
logger.org::apache::nifi::minifi=ERROR,alert1

# Logs from the FlowController class should be written to the stderr and rolling appenders with DEBUG level
logger.org::apache::nifi::minifi::FlowController=DEBUG,stderr,rolling

# Log warnings and errors from the LoggerConfiguration class to all appenders
logger.org::apache::nifi::minifi::core::logging::LoggerConfiguration=WARN

Log pattern

The log pattern can be changed if needed using the spdlog.pattern property. The documentation of the pattern flags can be found on the spdlog's custom formatting wiki page. The default log pattern is the following, but there are additional examples in the default minifi-log.properties file:

# in minifi-log.properties
spdlog.pattern=[%Y-%m-%d %H:%M:%S.%e] [%n] [%l] %v

Log compression

Logs can be retrieved with the C2 Debug command through the C2 protocol. For this functionality some logs are kept in memory in compressed form. The following properties can be used to configure the limits for this compression:

# in minifi-log.properties
compression.cached.log.max.size=8 MB
compression.compressed.log.max.size=8 MB

Shortening log messages

There are some additional properties that can be used to shorten log messages:

# in minifi-log.properties
# The spdlog.shorten_names can be set to prune package names from logs
spdlog.shorten_names=true

# Use the following if you do not want to include the UUID of the component at the end of log lines
logger.include.uuid=false

# You can set the maximum length of the log entries
max.log.entry.length=4096

NOTE: All log configuration properties can be changed through C2 protocol with the property update command, using the nifi.log. prefix. For example to change the root log level with the logger.root property through C2, the C2 property update command should change the nifi.log.logger.root property.

Recommended Antivirus Exclusions

Antivirus software can take a long time to scan large directories and the numerous files within them. Additionally, if the antivirus software locks files or directories during a scan, those resources are unavailable to the MiNiFi C++ process. To prevent these performance and reliability issues from occurring, it is highly recommended to configure your antivirus software to skip scans on the following MiNiFi C++ directories (or the specified alternatives defined in the minifi.properties file):

  • content_repository
  • flowfile_repository
  • logs
  • provenance_repository
  • corecomponentstate