Skip to content

Configuring an engine host

An Engine Host is configured by creating a configuration document. Below is the outline structure of the server's configuration document.

Configuration for an engine host

The configuration document is built up using a series of administration calls:

Configuring the basic properties

Configure the basic properties

The basic properties are used in logging and events originating from the server. They help to document the purpose of the server (which helps with problem determination) and enable performance improvements by allowing the server to ignore activity or metadata that is not relevant to its operation.

The basic properties include two unique identifiers that are set up when you first create the configuration document:

Property Description
localServerId Unique identifier for this server. By default, this is initialized to a randomly generated Universal Unique identifier (UUID).
localServerName Meaningful name for the server for use in messages and UIs. Ideally this value is unique to aid administrators in understanding the source of messages and events from the server. This value is set to the server name assigned when the configuration is created.

The other basic properties have values that can be changed through the admin services API:

Property Description
localServerType Descriptive type name for the server. Again this is useful information for the administrator to understand the role of the server. The default value is Open Metadata and Governance Server.
organizationName Descriptive name for the organization that owns the local server/repository. This is useful when the open metadata repository cluster consists of metadata servers from different organizations, or different departments of an enterprise. The default value is null.
localServerUserId UserId to use for server-initiated REST calls. The default is OMAGServer.
localServerPassword Password to use for server-initiated REST calls. The default is null. This means that only the userId is sent in the HTTP header.
maxPageSize The maximum page size that can be set on requests to the server. The default value is 1000. A value of zero means unlimited page size. Although supported, the zero value is not recommended because it provides no protection from a large request denial of service attack.

The sections that follow cover how to set up these values.

Set server type name

The server type name should be set to something that describes the OMAG Server's role. It may be the name of a specific product that it is enabling, or a role in the metadata and governance landscape. The default value is Open Metadata and Governance Server.

If you have no specific value to set the server type name to, we recommend that you set the server type name to null. This will cause the server start up process will derive a standard server type name based on the rest of the configuration for the server.

POST - set server type


Set organization name

The organization name may be the owning organization or department or team supported by the server.

POST - set organization name


Set the server's userId and optional password

The server's userId is used when processing requests that do not have an end user, such as receiving an event from a topic. The default value is OMAGServer. Ideally each server should have its own userId, so it is possible to restrict the resources that each server has access to and identify the origin of updates to the metadata elements.

If the password is specified as well, the userId and password combination are used to provide authentication information on each REST call made by the server.

POST - set server's userId


POST - set server's password


Set the maximum page size for REST API requests

The maximum page size value sets an upper limit on the number of results that a caller can request on any paging REST API to this server. Setting maximum page size helps to prevent a denial of service attack that uses very large requests to overwhelm the server. A value of 0 means no limit, and leaves the server open to such attacks.

POST - set maximum page size

Configuring the audit log

Configure the audit log

Egeria's audit log provides a configurable set of destinations for audit records and other diagnostic logging for an OMAG Server. Some destinations also support a query interface to allow an administrator to understand how the server is running.

Each audit log record has a severity that can be used to route it to one or more specific destinations. Therefore, when an audit log destination is configured, it is optionally supplied with a list of severities to filter audit log records it should receive.

The audit log severities are as follows:

Severity Description
Information The server is providing information about its normal operation.
Event An event was received from another member of the open metadata repository cohort.
Decision A decision has been made related to the interaction of the local metadata repository and the rest of the cohort.
Action An Action is required by the administrator. At a minimum, the situation needs to be investigated and if necessary, corrective action taken.
Error An error occurred, possibly caused by an incompatibility between the local metadata repository and one of the remote repositories. The local repository may restrict some of the metadata interchange functions as a result.
Exception An unexpected exception occurred. This means that the server needs some administration attention to correct configuration or fix a logic error because it is not operating as a proper peer in the open metadata repository cohort.
Security Unauthorized access to a service or metadata instance has been attempted.
Startup A new component is starting up.
Shutdown An existing component is shutting down.
Asset An auditable action relating to an asset has been taken.
Types Activity is occurring that relates to the open metadata types in use by this server.
Cohort The server is exchanging registration information about an open metadata repository cohort that it is connecting to.
Trace This is additional information on the operation of the server that may be of assistance in debugging a problem. It is not normally logged to any destination, but can be added when needed.
PerfMon This log record contains performance monitoring timing information for specific types of processing. It is not normally logged to any destination, but can be added when needed.
<Unknown> Uninitialized Severity

The default audit log destination is the console audit log destination. This writes selected parts of each audit log record to "standard out" (stdout). It is configured to receive log records of all severities except Trace and PerfMon.

The default audit log destination is added automatically to Cohort Member servers when a repository, or cohort connection is configured.

For View Servers and Governance Servers, it is only added when other audit log destinations are configured. Therefore, is it necessary to issue at least one of the following configuration commands for the audit log for these types of servers.

Add audit log destinations

If the server is a development or test server, then the default audit log configuration is probably sufficient, and you should use the following command:

POST - set default audit log destination


Note: Using this command overrides all previous audit log destinations configured for the server.

If this server is a production server then you will probably want to set up the audit log destinations explicitly. You can add multiple destinations and each one can be set up to receive different severities of audit log records.

There are various destinations that can be configured for the audit log:

Since the default audit log destination is also a console audit log destination, only use this option to add the Trace and PerfMon severities.

POST - add console audit log destination


The body of the request should be a list of severities

If an empty list is passed as the request body then all severities are supported by the destination.

This destination writes JSON files in a shared directory. One file for each audit log record.

POST - add JSON file-based audit log destination


The body of the request should be a list of severities

If an empty list is passed as the request body then all severities are supported by the destination.

This destination writes each log record as an event on the supplied event topic. It assumes that the event bus is set up first.

POST - add event-based audit log destination


The body of the request should be a list of severities

If an empty list is passed as the request body then all severities are supported by the destination.

This writes full log records to the slf4j ecosystem. When configuring slf4j as destination you also need to specify audit log logger category via the application properties of the OMAG Server Platform. This is described in Connecting the OMAG Audit Log Framework section of the developer logging guide.

The configuration of the slf4j ecosystem determines it ultimate destination(s).

POST - add slf4j audit log destination


The body of the request should be a list of severities

If an empty list is passed as the request body then all severities are supported by the destination.

This sets up an audit log destination that is described though a connection. In this case, the connection is passed in the request body and the supported severities are supplied in the connection's configuration properties.

POST - add connection-based audit log destination


It is also possible to set up all the audit log destinations in one command as a list of connections. Using this option overrides all previous audit log destinations and so can be used as the update command. The list of connections is passed in the request body and the supported severities are supplied in each connection's configuration properties.

POST - add a list of connection-based audit log destinations


Retrieving audit log destinations

The configured list of audit log destinations can be retrieved using this command:

GET - the list of configured audit log destinations


Updating audit log destinations

Audit log destinations can be updated individually, by qualified name using the following command:

POST - update connection-based audit log destination


If you are not sure what the audit log connection is called, retrieve the list of configured audit log connections and the resulting list of audit log connections will include the qualified names.

Remove audit log destinations

The following will remove all audit log destinations, enabling you to add a new set of audit log destinations.

DELETE - clear all audit log destinations


It is also possible to remove a single audit log destination using its connection's qualified name.

DELETE - clear then named audit log destination

Configuring the server security connector

Configure the server security connector

Metadata that is being aggregated from different sources is likely to need comprehensive access controls.

Egeria provides fine-grained security control for metadata access. It is implemented in a server metadata security connector that is called whenever requests are made for to the server.

Security is configured for a specific OMAG Server by adding a connection for this connector to the server's configuration documentusing the following command.

POST - configure security connector


This passes in a connection used to create the server security connector in the request body.

    "class": "Connection",
    "connectorType": {
        "class": "ConnectorType",
        "connectorProviderClassName": "{fullyQualifiedJavaClassName}"
Example: set up the sample server security connector

For example, this is the connection that would set up the sample server security connector provided for the Coco Pharmaceuticals case study:

    "class": "Connection",
    "connectorType": {
        "class": "ConnectorType",
        "connectorProviderClassName": "org.odpi.openmetadata.metadatasecurity.samples.OpenMetadataServerSecurityProvider"

Determine configured security

GET - query the server security connector setting

Response indicating no security
    "class": "ConnectionResponse",
    "relatedHTTPCode": 200
Response indicating a specific security connector

If the response looks more like the JSON below, a connector is configured. The connectorProviderClassName tells you which connector is being used.

    "class": "ConnectionResponse",
    "relatedHTTPCode": 200,
    "connection": {
        "class": "Connection",
        "connectorType": {
            "class": "ConnectorType",
            "connectorProviderClassName": "{fullyQualifiedJavaClassName}"

Remove configured security

DELETE - remove configured security connector


This removes all authorization checking from the server.

Configuring the engine host services

Configure the engine host services

The engine host services provide the base implementation of the engine host OMAG Server.

There are two parts to configuring the engine host services:

Specify location of governance engine definitions

The location of the metadata access server running the Governance Engine OMAS that will supply the definitions of the governance engines, is configured using two properties:

POST - specify location of governance engine definitions


With a request body like the following:

    "class": "OMAGServerClientConfig",
    "omagserverPlatformRootURL": {{MDServerURLRoot}},
    "omagserverName" : "{{MDServerName}}"

Configure the engines services

The engine services (or Open Metadata Engine Services (OMES) to give them their full name) also run in the engine host. Each engine service provides support for a particular type of governance engine which is in turn, a collection of governance services. The governance engine is described in a Governance Engine Definition

List engine services

It is possible to get a description of each of the registered engine services using the following command:

GET - list engine services


Note the engineServiceURLMarker for the engine service that you want to configure.

Configure engine service

Configuration document contents for an integration service

The descriptive information and operational status are filled out automatically by the administration services based on the engineServiceURLMarker value that you supply. The other values are supplied on the configuration call.

Each engine service is configured with the network location of the Metadata Access Server running the appropriate partner service. There are a set of options that the engine service supports along with the list of configuration properties for the governance engines that will be run in the engine service. The governance engine's configuration properties identify which governance engine to run. The governance engine's definition, including the services it supports are retrieved from the metadata access server when the engine service starts up.

POST - configure engine service


With a request body like the following:

    "class": "EngineServiceRequestBody",
    "omagserverPlatformRootURL": {{MDServerURLRoot}},
    "omagserverName" : "{{MDServerName}}",
    [ {
         "class": "EngineConfig",
         "engineQualifiedName" : " ... "             
         "engineUserId" : " ... "
    } ]


  • engineQualifiedName - set up the qualified name of the GovernanceEngine entity stored in the metadata servers.
  • engineUserId - set up the user id for the engine: if this is null, the engine host's userId is used on requests to the Open Metadata Access Service (OMAS).

Remove engine host services

The following command removes the configuration for the engine host services from an OMAG Server's configuration document. This may be used if the engine host services have been added in error.

DELETE - remove engine host services

Example configuration of an engine host

This is an example of the configuration for an engine host. It has a single engine service (Asset Analysis OMES) and the default audit log. Both the Governance Engine OMAS used by the engine host services and the Discovery Engine OMAS used by the Asset Analysis OMES are running on the metadata access server called myserver.

    "class": "OMAGServerConfigResponse",
    "relatedHTTPCode": 200,
    "omagserverConfig": {
        "class": "OMAGServerConfig",
        "versionId": "V2.0",
        "localServerId": "8b745d03-5ffc-4978-81ab-bd3d5156eebe",
        "localServerName": "myserver",
        "localServerType": "Open Metadata and Governance Server",
        "localServerURL": "https://localhost:9443",
        "localServerUserId": "OMAGServer",
        "maxPageSize": 1000,
        "engineHostServicesConfig": {
            "omagserverPlatformRootURL": "https://localhost:9443",
            "omagserverName": "myMetadataServer",
            "engineServices": [
                    "class": "EngineServiceConfig",
                    "engineId": 6000,
                    "engineQualifiedName": "Asset Analysis",
                    "engineServiceFullName": "Asset Analysis OMES",
                    "engineServiceURLMarker": "asset-analysis",
                    "engineServiceDescription": "Analyses the content of an asset's real world counterpart, generates annotations in an open discovery report that is attached to the asset in the open metadata repositories .",
                    "engineServiceWiki": "",
                    "engines" : [ {"engineId" : "daff1dca-984b-4b8a-8a8f-febaf72b82a8",
                                   "engineName" : "engine1", 
                                   "engineUserId" : "engine1UserId"},
                                  {"engineId" : "a80aa0f8-2ea0-4f84-b613-d68becba2693",
                                   "engineName" : "engine2", 
                                   "engineUserId" : "engine2UserId"} ],
                    "engineServiceOperationalStatus": "ENABLED",
                    "engineServiceAdminClass": "org.odpi.openmetadata.engineservices.assetanalysis.admin.AssetAnalysisAdmin",
                    "omagserverPlatformRootURL": "https://localhost:9443",
                    "omagserverName": "myMetadataServer"
        "repositoryServicesConfig": {
            "class": "RepositoryServicesConfig",
            "auditLogConnections": [
                    "class": "Connection",
                    "headerVersion": 0,
                    "displayName": "Console",
                    "connectorType": {
                        "class": "ConnectorType",
                        "headerVersion": 0,
                        "type": {
                            "class": "ElementType",
                            "headerVersion": 0,
                            "elementOrigin": "LOCAL_COHORT",
                            "elementVersion": 0,
                            "elementTypeId": "954421eb-33a6-462d-a8ca-b5709a1bd0d4",
                            "elementTypeName": "ConnectorType",
                            "elementTypeVersion": 1,
                            "elementTypeDescription": "A set of properties describing a type of connector."
                        "guid": "4afac741-3dcc-4c60-a4ca-a6dede994e3f",
                        "qualifiedName": "Console Audit Log Store Connector",
                        "displayName": "Console Audit Log Store Connector",
                        "description": "Connector supports logging of audit log messages to stdout.",
                        "connectorProviderClassName": "org.odpi.openmetadata.adapters.repositoryservices.auditlogstore.console.ConsoleAuditLogStoreProvider"
                    "configurationProperties": {
                        "supportedSeverities": [
        "auditTrail": [
            "Tue Dec 08 18:38:32 GMT 2020 me updated configuration for engine service asset-analysis.",
            "Tue Dec 08 18:43:47 GMT 2020 me set up default audit log destinations."

Raise an issue or comment below