mirror of https://github.com/apache/nifi.git
NIFI-259: - Moving the state management documentation to after the Clustering configuration.
Signed-off-by: Aldrin Piri <aldrin@apache.org>
This commit is contained in:
Matt Gilman
Aldrin Piri
parent
7711106d62
commit
adfa5dc0eb
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@ -368,6 +368,108 @@ cluster, s/he can grant it to the group and avoid having to grant it individuall
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[[clustering]]
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Clustering Configuration
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------------------------
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This section provides a quick overview of NiFi Clustering and instructions on how to set up a basic cluster. In the future, we hope to provide supplemental documentation that covers the NiFi Cluster Architecture in depth.
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The design of NiFi clustering is a simple master/slave model where there is a master and one or more slaves.
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While the model is that of master and slave, if the master dies, the slaves are all instructed to continue operating
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as they were to ensure the dataflow remains live. The absence of the master simply means new slaves cannot join the
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cluster and cluster flow changes cannot occur until the master is restored. In NiFi clustering, we call the master
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the NiFi Cluster Manager (NCM), and the slaves are called Nodes. See a full description of each in the Terminology section below.
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*Why Cluster?* +
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NiFi Administrators or Dataflow Managers (DFMs) may find that using one instance of NiFi on a single server is not enough to process the amount of data they have. So, one solution is to run the same dataflow on multiple NiFi servers. However, this creates a management problem, because each time DFMs want to change or update the dataflow, they must make those changes on each server and then monitor each server individually. By clustering the NiFi servers, it's possible to have that increased processing capability along with a single interface through which to make dataflow changes and monitor the dataflow. Clustering allows the DFM to make each change only once, and that change is then replicated to all the nodes of the cluster. Through the single interface, the DFM may also monitor the health and status of all the nodes.
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NiFi Clustering is unique and has its own terminology. It's important to understand the following terms before setting up a cluster.
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[template="glossary", id="terminology"]
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*Terminology* +
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*NiFi Cluster Manager*: A NiFi Cluster Manager (NCM) is an instance of NiFi that provides the sole management point for the cluster. It communicates dataflow changes to the nodes and receives health and status information from the nodes. It also ensures that a uniform dataflow is maintained across the cluster. When DFMs manage a dataflow in a cluster, they do so through the User Interface of the NCM (i.e., via the URL of the NCM's User Interface). Fundamentally, the NCM keeps the state of the cluster consistent.
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*Nodes*: Each cluster is made up of the NCM and one or more nodes. The nodes do the actual data processing. (The NCM does not process any data; all data runs through the nodes.) While nodes are connected to a cluster, the DFM may not access the User Interface for any of the individual nodes. The User Interface of a node may only be accessed if the node is manually removed from the cluster.
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*Primary Node*: Every cluster has one Primary Node. On this node, it is possible to run "Isolated Processors" (see below). By default, the NCM will elect the first node that connects to the cluster as the Primary Node; however, the DFM may select a new node as the Primary Node in the Cluster Management page of the User Interface if desired. If the cluster restarts, the NCM will "remember" which node was the Primary Node and wait for that node to re-connect before allowing the DFM to make any changes to the dataflow. The ADMIN may adjust how long the NCM waits for the Primary Node to reconnect by adjusting the property _nifi.cluster.manager.safemode.duration_ in the _nifi.properties_ file, which is discussed in the <<system_properties>> section of this document.
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*Isolated Processors*: In a NiFi cluster, the same dataflow runs on all the nodes. As a result, every component in the flow runs on every node. However, there may be cases when the DFM would not want every processor to run on every node. The most common case is when using a processor that communicates with an external service using a protocol that does not scale well. For example, the GetSFTP processor pulls from a remote directory, and if the GetSFTP on every node in the cluster tries simultaneously to pull from the same remote directory, there could be race conditions. Therefore, the DFM could configure the GetSFTP on the Primary Node to run in isolation, meaning that it only runs on that node. It could pull in data and -with the proper dataflow configuration- load-balance it across the rest of the nodes in the cluster. Note that while this feature exists, it is also very common to simply use a standalone NiFi instance to pull data and feed it to the cluster. It just depends on the resources available and how the Administrator decides to configure the cluster.
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*Heartbeats*: The nodes communicate their health and status to the NCM via "heartbeats", which let the NCM know they are still connected to the cluster and working properly. By default, the nodes emit heartbeats to the NCM every 5 seconds, and if the NCM does not receive a heartbeat from a node within 45 seconds, it disconnects the node due to "lack of heartbeat". (The 5-second and 45-second settings are configurable in the _nifi.properties_ file. See the <<system_properties>> section of this document for more information.) The reason that the NCM disconnects the node is because the NCM needs to ensure that every node in the cluster is in sync, and if a node is not heard from regularly, the NCM cannot be sure it is still in sync with the rest of the cluster. If, after 45 seconds, the node does send a new heartbeat, the NCM will automatically reconnect the node to the cluster. Both the disconnection due to lack of heartbeat and the reconnection once a heartbeat is received are reported to the DFM in the NCM's User Interface.
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*Communication within the Cluster* +
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As noted, the nodes communicate with the NCM via heartbeats. The communication that allows the nodes to find the NCM may be set up as multicast or unicast; this is configured in the _nifi.properties_ file (See <<system_properties>> ). By default, unicast is used. It is important to note that the nodes in a NiFi cluster are not aware of each other. They only communicate with the NCM. Therefore, if one of the nodes goes down, the other nodes in the cluster will not automatically pick up the load of the missing node. It is possible for the DFM to configure the dataflow for failover contingencies; however, this is dependent on the dataflow design and does not happen automatically.
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When the DFM makes changes to the dataflow, the NCM communicates those changes to the nodes and waits for each node to respond, indicating that it has made the change on its local flow. If the DFM wants to make another change, the NCM will only allow this to happen once all the nodes have acknowledged that they've implemented the last change. This is a safeguard to ensure that all the nodes in the cluster have the correct and up-to-date flow.
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*Dealing with Disconnected Nodes* +
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A DFM may manually disconnect a node from the cluster. But if a node becomes disconnected for any other reason (such as due to lack of heartbeat), the NCM will show a bulletin on the User Interface, and the DFM will not be able to make any changes to the dataflow until the issue of the disconnected node is resolved. The DFM or the Administrator will need to troubleshoot the issue with the node and resolve it before any new changes may be made to the dataflow. However, it is worth noting that just because a node is disconnected does not mean that it is not working; it just means that the NCM cannot communicate with the node.
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*Basic Cluster Setup* +
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This section describes the setup for a simple two-node, non-secure, unicast cluster comprised of three instances of NiFi:
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* The NCM
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* Node 1
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* Node 2
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Administrators may install each instance on a separate server; however, it is also perfectly fine to install the NCM and one of the nodes on the same server, as the NCM is very lightweight. Just keep in mind that the ports assigned to each instance must not collide if the NCM and one of the nodes share the same server.
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For each instance, certain properties in the _nifi.properties_ file will need to be updated. In particular, the Web and Clustering properties should be evaluated for your situation and adjusted accordingly. All the properties are described in the <<system_properties>> section of this guide; however, in this section, we will focus on the minimum properties that must be set for a simple cluster.
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For all three instances, the Cluster Common Properties can be left with the default settings. Note, however, that if you change these settings, they must be set the same on every instance in the cluster (NCM and nodes).
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For the NCM, the minimum properties to configure are as follows:
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* Under the Web Properties, set either the http or https port that you want the NCM to run on. If the NCM and one of the nodes are on the same server, make sure this port is different from the web port used by the node.
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* Under the Cluster Manager Properties, set the following:
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** nifi.cluster.is.manager - Set this to _true_.
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** nifi.cluster.manager.protocol.port - Set this to an open port that is higher than 1024 (anything lower requires root). Take note of this setting, as you will need to reference it when you set up the nodes.
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For Node 1, the minimum properties to configure are as follows:
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* Under the Web Properties, set either the http or https port that you want Node 1 to run on. If the NCM is running on the same server, choose a different web port for Node 1. Also, consider whether you need to set the http or https host property.
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* Under the State Management section, set the `nifi.state.management.provider.cluster` property to the identifier of the Cluster State Provider. Ensure that the Cluster State Provider has been configured in the _state-management.xml_ file. See <<state_providers>> for more information.
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* Under Cluster Node Properties, set the following:
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** nifi.cluster.is.node - Set this to _true_.
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** nifi.cluster.node.address - Set this to the fully qualified hostname of the node. If left blank, it defaults to "localhost".
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** nifi.cluster.node.protocol.port - Set this to an open port that is higher than 1024 (anything lower requires root). If Node 1 and the NCM are on the same server, make sure this port is different from the nifi.cluster.manager.protocol.port.
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** nifi.cluster.node.unicast.manager.address - Set this to the NCM's fully qualified hostname.
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** nifi.cluster.node.unicast.manager.protocol.port - Set this to exactly the same port that was set on the NCM for the property nifi.cluster.manager.protocol.port.
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For Node 2, the minimum properties to configure are as follows:
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* Under the Web Properties, set either the http or https port that you want Node 2 to run on. Also, consider whether you need to set the http or https host property.
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* Under the State Management section, set the `nifi.state.management.provider.cluster` property to the identifier of the Cluster State Provider. Ensure that the Cluster State Provider has been configured in the _state-management.xml_ file. See <<state_providers>> for more information.
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* Under the Cluster Node Properties, set the following:
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** nifi.cluster.is.node - Set this to _true_.
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** nifi.cluster.node.address - Set this to the fully qualified hostname of the node. If left blank, it defaults to "localhost".
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** nifi.cluster.node.protocol.port - Set this to an open port that is higher than 1024 (anything lower requires root).
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** nifi.cluster.node.unicast.manager.address - Set this to the NCM's fully qualified hostname.
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** nifi.cluster.node.unicast.manager.protocol.port - Set this to exactly the same port that was set on the NCM for the property nifi.cluster.manager.protocol.port.
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Now, it is possible to start up the cluster. Technically, it does not matter which instance starts up first. However, you could start the NCM first, then Node 1 and then Node 2. Since the first node that connects is automatically elected as the Primary Node, this sequence should create a cluster where Node 1 is the Primary Node. Navigate to the URL for the NCM in your web browser, and the User Interface should look similar to the following:
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image:ncm.png["NCM User Interface", width=940]
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*Troubleshooting*
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If you encounter issues and your cluster does not work as described, investigate the nifi.app log and nifi.user log on both the NCM and the nodes. If needed, you can change the logging level to DEBUG by editing the conf/logback.xml file. Specifically, set the level="DEBUG" in the following line (instead of "INFO"):
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----
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<logger name="org.apache.nifi.web.api.config" level="INFO"
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additivity="false">
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<appender-ref ref="USER_FILE"/>
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</logger>
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----
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[[state_management]]
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State Management
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----------------
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@ -667,108 +769,6 @@ This output can be rather verbose but provides extremely valuable information fo
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[[clustering]]
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Clustering Configuration
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------------------------
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This section provides a quick overview of NiFi Clustering and instructions on how to set up a basic cluster. In the future, we hope to provide supplemental documentation that covers the NiFi Cluster Architecture in depth.
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The design of NiFi clustering is a simple master/slave model where there is a master and one or more slaves.
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While the model is that of master and slave, if the master dies, the slaves are all instructed to continue operating
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as they were to ensure the dataflow remains live. The absence of the master simply means new slaves cannot join the
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cluster and cluster flow changes cannot occur until the master is restored. In NiFi clustering, we call the master
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the NiFi Cluster Manager (NCM), and the slaves are called Nodes. See a full description of each in the Terminology section below.
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*Why Cluster?* +
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NiFi Administrators or Dataflow Managers (DFMs) may find that using one instance of NiFi on a single server is not enough to process the amount of data they have. So, one solution is to run the same dataflow on multiple NiFi servers. However, this creates a management problem, because each time DFMs want to change or update the dataflow, they must make those changes on each server and then monitor each server individually. By clustering the NiFi servers, it's possible to have that increased processing capability along with a single interface through which to make dataflow changes and monitor the dataflow. Clustering allows the DFM to make each change only once, and that change is then replicated to all the nodes of the cluster. Through the single interface, the DFM may also monitor the health and status of all the nodes.
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NiFi Clustering is unique and has its own terminology. It's important to understand the following terms before setting up a cluster.
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[template="glossary", id="terminology"]
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*Terminology* +
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*NiFi Cluster Manager*: A NiFi Cluster Manager (NCM) is an instance of NiFi that provides the sole management point for the cluster. It communicates dataflow changes to the nodes and receives health and status information from the nodes. It also ensures that a uniform dataflow is maintained across the cluster. When DFMs manage a dataflow in a cluster, they do so through the User Interface of the NCM (i.e., via the URL of the NCM's User Interface). Fundamentally, the NCM keeps the state of the cluster consistent.
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*Nodes*: Each cluster is made up of the NCM and one or more nodes. The nodes do the actual data processing. (The NCM does not process any data; all data runs through the nodes.) While nodes are connected to a cluster, the DFM may not access the User Interface for any of the individual nodes. The User Interface of a node may only be accessed if the node is manually removed from the cluster.
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*Primary Node*: Every cluster has one Primary Node. On this node, it is possible to run "Isolated Processors" (see below). By default, the NCM will elect the first node that connects to the cluster as the Primary Node; however, the DFM may select a new node as the Primary Node in the Cluster Management page of the User Interface if desired. If the cluster restarts, the NCM will "remember" which node was the Primary Node and wait for that node to re-connect before allowing the DFM to make any changes to the dataflow. The ADMIN may adjust how long the NCM waits for the Primary Node to reconnect by adjusting the property _nifi.cluster.manager.safemode.duration_ in the _nifi.properties_ file, which is discussed in the <<system_properties>> section of this document.
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*Isolated Processors*: In a NiFi cluster, the same dataflow runs on all the nodes. As a result, every component in the flow runs on every node. However, there may be cases when the DFM would not want every processor to run on every node. The most common case is when using a processor that communicates with an external service using a protocol that does not scale well. For example, the GetSFTP processor pulls from a remote directory, and if the GetSFTP on every node in the cluster tries simultaneously to pull from the same remote directory, there could be race conditions. Therefore, the DFM could configure the GetSFTP on the Primary Node to run in isolation, meaning that it only runs on that node. It could pull in data and -with the proper dataflow configuration- load-balance it across the rest of the nodes in the cluster. Note that while this feature exists, it is also very common to simply use a standalone NiFi instance to pull data and feed it to the cluster. It just depends on the resources available and how the Administrator decides to configure the cluster.
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*Heartbeats*: The nodes communicate their health and status to the NCM via "heartbeats", which let the NCM know they are still connected to the cluster and working properly. By default, the nodes emit heartbeats to the NCM every 5 seconds, and if the NCM does not receive a heartbeat from a node within 45 seconds, it disconnects the node due to "lack of heartbeat". (The 5-second and 45-second settings are configurable in the _nifi.properties_ file. See the <<system_properties>> section of this document for more information.) The reason that the NCM disconnects the node is because the NCM needs to ensure that every node in the cluster is in sync, and if a node is not heard from regularly, the NCM cannot be sure it is still in sync with the rest of the cluster. If, after 45 seconds, the node does send a new heartbeat, the NCM will automatically reconnect the node to the cluster. Both the disconnection due to lack of heartbeat and the reconnection once a heartbeat is received are reported to the DFM in the NCM's User Interface.
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*Communication within the Cluster* +
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As noted, the nodes communicate with the NCM via heartbeats. The communication that allows the nodes to find the NCM may be set up as multicast or unicast; this is configured in the _nifi.properties_ file (See <<system_properties>> ). By default, unicast is used. It is important to note that the nodes in a NiFi cluster are not aware of each other. They only communicate with the NCM. Therefore, if one of the nodes goes down, the other nodes in the cluster will not automatically pick up the load of the missing node. It is possible for the DFM to configure the dataflow for failover contingencies; however, this is dependent on the dataflow design and does not happen automatically.
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When the DFM makes changes to the dataflow, the NCM communicates those changes to the nodes and waits for each node to respond, indicating that it has made the change on its local flow. If the DFM wants to make another change, the NCM will only allow this to happen once all the nodes have acknowledged that they've implemented the last change. This is a safeguard to ensure that all the nodes in the cluster have the correct and up-to-date flow.
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*Dealing with Disconnected Nodes* +
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A DFM may manually disconnect a node from the cluster. But if a node becomes disconnected for any other reason (such as due to lack of heartbeat), the NCM will show a bulletin on the User Interface, and the DFM will not be able to make any changes to the dataflow until the issue of the disconnected node is resolved. The DFM or the Administrator will need to troubleshoot the issue with the node and resolve it before any new changes may be made to the dataflow. However, it is worth noting that just because a node is disconnected does not mean that it is not working; it just means that the NCM cannot communicate with the node.
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*Basic Cluster Setup* +
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This section describes the setup for a simple two-node, non-secure, unicast cluster comprised of three instances of NiFi:
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* The NCM
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* Node 1
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* Node 2
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Administrators may install each instance on a separate server; however, it is also perfectly fine to install the NCM and one of the nodes on the same server, as the NCM is very lightweight. Just keep in mind that the ports assigned to each instance must not collide if the NCM and one of the nodes share the same server.
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|
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For each instance, certain properties in the _nifi.properties_ file will need to be updated. In particular, the Web and Clustering properties should be evaluated for your situation and adjusted accordingly. All the properties are described in the <<system_properties>> section of this guide; however, in this section, we will focus on the minimum properties that must be set for a simple cluster.
|
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For all three instances, the Cluster Common Properties can be left with the default settings. Note, however, that if you change these settings, they must be set the same on every instance in the cluster (NCM and nodes).
|
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|
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For the NCM, the minimum properties to configure are as follows:
|
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|
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* Under the Web Properties, set either the http or https port that you want the NCM to run on. If the NCM and one of the nodes are on the same server, make sure this port is different from the web port used by the node.
|
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* Under the Cluster Manager Properties, set the following:
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** nifi.cluster.is.manager - Set this to _true_.
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** nifi.cluster.manager.protocol.port - Set this to an open port that is higher than 1024 (anything lower requires root). Take note of this setting, as you will need to reference it when you set up the nodes.
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For Node 1, the minimum properties to configure are as follows:
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* Under the Web Properties, set either the http or https port that you want Node 1 to run on. If the NCM is running on the same server, choose a different web port for Node 1. Also, consider whether you need to set the http or https host property.
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* Under the State Management section, set the `nifi.state.management.provider.cluster` property to the identifier of the Cluster State Provider. Ensure that the Cluster State Provider has been configured in the _state-management.xml_ file. See <<state_providers>> for more information.
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* Under Cluster Node Properties, set the following:
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** nifi.cluster.is.node - Set this to _true_.
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** nifi.cluster.node.address - Set this to the fully qualified hostname of the node. If left blank, it defaults to "localhost".
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** nifi.cluster.node.protocol.port - Set this to an open port that is higher than 1024 (anything lower requires root). If Node 1 and the NCM are on the same server, make sure this port is different from the nifi.cluster.manager.protocol.port.
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** nifi.cluster.node.unicast.manager.address - Set this to the NCM's fully qualified hostname.
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** nifi.cluster.node.unicast.manager.protocol.port - Set this to exactly the same port that was set on the NCM for the property nifi.cluster.manager.protocol.port.
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For Node 2, the minimum properties to configure are as follows:
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* Under the Web Properties, set either the http or https port that you want Node 2 to run on. Also, consider whether you need to set the http or https host property.
|
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* Under the State Management section, set the `nifi.state.management.provider.cluster` property to the identifier of the Cluster State Provider. Ensure that the Cluster State Provider has been configured in the _state-management.xml_ file. See <<state_providers>> for more information.
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* Under the Cluster Node Properties, set the following:
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** nifi.cluster.is.node - Set this to _true_.
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** nifi.cluster.node.address - Set this to the fully qualified hostname of the node. If left blank, it defaults to "localhost".
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** nifi.cluster.node.protocol.port - Set this to an open port that is higher than 1024 (anything lower requires root).
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** nifi.cluster.node.unicast.manager.address - Set this to the NCM's fully qualified hostname.
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** nifi.cluster.node.unicast.manager.protocol.port - Set this to exactly the same port that was set on the NCM for the property nifi.cluster.manager.protocol.port.
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Now, it is possible to start up the cluster. Technically, it does not matter which instance starts up first. However, you could start the NCM first, then Node 1 and then Node 2. Since the first node that connects is automatically elected as the Primary Node, this sequence should create a cluster where Node 1 is the Primary Node. Navigate to the URL for the NCM in your web browser, and the User Interface should look similar to the following:
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image:ncm.png["NCM User Interface", width=940]
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*Troubleshooting*
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If you encounter issues and your cluster does not work as described, investigate the nifi.app log and nifi.user log on both the NCM and the nodes. If needed, you can change the logging level to DEBUG by editing the conf/logback.xml file. Specifically, set the level="DEBUG" in the following line (instead of "INFO"):
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----
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<logger name="org.apache.nifi.web.api.config" level="INFO"
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additivity="false">
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<appender-ref ref="USER_FILE"/>
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</logger>
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----
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[[bootstrap_properties]]
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Bootstrap Properties
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--------------------
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