Indexer cluster deployment

Indexer cluster deployment overview

Index replication offers benefits such as data availability, data fidelity, data recovery, disaster recovery, and search affinity. It ensures that an indexer is always available to handle data, and the indexed data is searchable. It also guarantees data consistency and fault tolerance.

An indexer cluster consists of:

  1. A single manager node to manage the cluster.

  2. Several to many peer nodes to index data and maintain multiple copies, providing redundancy and data availability.

  3. One or more search heads to coordinate searches across the set of peer nodes and provide a unified search experience

Here is a diagram of a basic, single-site indexer cluster, containing three peer nodes and supporting a replication factor of 3:

Deploy a cluster

Configure the manager node with the CLI

/opt/splunk/bin/splunk edit cluster-config -mode manager -replication_factor 4 -search_factor 3 -secret your_key -cluster_label cluster1
/opt/splunk/bin/splunk restart

Configure a peer node with the CLI

/opt/splunk/bin/splunk edit cluster-config -mode slave -master_uri https://<master-ip>:8089 -secret your_key -replication_port 9100
/opt/splunk/bin/splunk restart

Verifying the cluster configuration using the CLI

/opt/splunk/bin/splunk list cluster-config

# Manager node
/opt/splunk/bin/splunk list cluster-peers
/opt/splunk/bin/splunk show cluster-status

Configure the search head with the CLI

/opt/splunk/bin/splunk edit cluster-config -mode searchhead -master_uri https://<master-ip>:8089 -secret your_key
/opt/splunk/bin/splunk restart

All cluster configuration data is stored in server.conf

/opt/splunk/etc/system/local/server.conf
Structure of the configuration bundle

On the manager node

$SPLUNK_HOME/etc/manager-apps/
     _cluster/
          default/
          local/
     <app-name>/
     <app-name>/
     ...

On the peers

$SPLUNK_HOME/etc/peer-apps/
     _cluster/
          default/
          local/
     <app-name>/
     <app-name>/
     ...
Configure indexes on manager node

​Note: Each indexer handles retention independently

nano /opt/splunk/etc/master-apps/_cluster/local/indexes.conf

[default]
# maxHotSpanSecs sets the maximum age of data in the "hot" bucket to 90 days.
maxHotSpanSecs = 7776000

# frozenTimePeriodInSecs sets the maximum age of data in the "cold" bucket to 275 days.
frozenTimePeriodInSecs = 23760000

################################################################################
# index definitions
################################################################################

[main]
repFactor = 0

[history]
repFactor = 0

[summary]
repFactor = auto

[_internal]
repFactor = auto

[_audit]
repFactor = auto

[_thefishbucket]
repFactor = auto

[_telemetry]
homePath   = $SPLUNK_DB/_telemetry/db
coldPath   = $SPLUNK_DB/_telemetry/colddb
thawedPath = $SPLUNK_DB/_telemetry/thaweddb
repFactor = auto

[splunklogger]
repFactor = auto

[wineventlog]
homePath   = $SPLUNK_DB/wineventlog/db
coldPath   = $SPLUNK_DB/wineventlog/colddb
thawedPath = $SPLUNK_DB/wineventlog/thaweddb
maxTotalDataSizeMB = 1048576
repFactor = auto

[linux]
homePath   = $SPLUNK_DB/linux/db
coldPath   = $SPLUNK_DB/linux/colddb
thawedPath = $SPLUNK_DB/linux/thaweddb
maxTotalDataSizeMB = 512000
repFactor = auto
Enabling Phased Bundle Downloads

▶ This is recommended if a cluster master is pushing large bundles or even a smaller bundle but to a large cluster (20 or more indexers).

▶ To enable, set the following configuration within server.conf

[clustering]
mode=master
max_peers_to_download_bundle = 1
Keeping Track of Bundles

▶ The bundles folder

$SPLUNK_HOME/var/run/splunk/cluster/remote-bundle

Restarting Indexer Cluster Components:

  • Restart the master node using /opt/splunk/bin/splunk restart

  • Restart the search head using /opt/splunk/bin/splunk restart

  • Perform a rolling restart of peer nodes:

    /opt/splunk/bin/splunk edit cluster-config -percent_peers_to_restart 20
/opt/splunk/bin/splunk rolling-restart cluster-peers
/opt/splunk/bin/splunk rolling-restart cluster-peers -searchable true
Indexer Discovery

Capability of indexer clusters that enables forwarders to connect dynamically to the full set of available peer nodes.

How?

  1. Peer nodes provide their receiving ports to the master.

  2. Forwarders poll the master for the list of available peer nodes.

  3. Master transmits the peer nodes list to the forwarders.

  4. The forwarders send data to the peer nodes using load balancing.

Indexer Discovery Configuration Master Node (Edit server.conf)

[indexer_discovery]
pass4SymmKey = <IDSecret>
indexerWeightByDiskCapacity = true

Forwarders (Edit outputs.conf)

[indexer_discovery:manager1]
manager_uri = https://<ip>:8089
pass4SymmKey = <IDSecret>

[tcpout:group1]
indexerDiscovery = manager1
autoLBFrequency = 30
forceTimebasedAutoLB = true
useACK = true

[tcpout]
defaultGroup = group1
Indexer Cluster Upgrade

Indexer Cluster Upgrade Considerations:

  1. Peer nodes must have the same OS family.

  2. Peer nodes must run exactly the same Splunk version.

  3. Master node must run the highest Splunk version.

  4. Search head must run higher Splunk version than the peer nodes.

Indexer Cluster Upgrade High-level Overview:

  1. Upgrade the master node.

  2. Upgrade the search heads.

  3. Enable maintenance mode.

  4. Upgrade the peer nodes.

  5. Disable maintenance mode.

Maintenance mode enabled/disabled on master node.

/opt/splunk/bin/splunk enable maintenance-mode
/opt/splunk/bin/splunk show maintenance-mode
/opt/splunk/bin/splunk disable maintenance-mode

Remove Excess Buckets

  • Using the master dashboard (GUI)

  • Using the CLI:

    /opt/splunk/bin/splunk list excess-buckets [index-name]
/opt/splunk/bin/splunk remoev excess-buckets [index-name]

List of commands and parameters related to clustering

/opt/splunk/bin/splunk help clustering

Configuration Bundle Deployment

  1. Deployed from master node using Splunk Web or CLI

  2. Initiates rolling restart of all peer nodes if needed

/opt/splunk/bin/splunk validate cluster-bundle --check-restart
/opt/splunk/bin/splunk apply cluster-bundle
/opt/splunk/bin/splunk show cluster-bundle-status
/opt/splunk/bin/splunk rollback cluster-bundle

Make data rebalance search-safe

Master Node (Edit server.conf)

searchable_rebalance = true
rebalance_search_completion_timeout = 360

Best practice: Forward manager node data to the indexer layer

Ensure necessary indexes exist on the indexers:

  • Check if indexes like _audit and _internal are present on both the manager node and the indexers.

  • If custom indexes exist only on the manager node, make sure to create the same indexes on the indexers to hold the corresponding manager data.

Configure the manager node as a forwarder:

  • Create an outputs.conf file on the manager node.

  • Configure load-balanced forwarding across the set of peer nodes.

  • Turn off indexing on the manager node to prevent it from retaining data locally and forwarding it to the peers.

Note: Ensure that the manager node is also set up as a search head in the indexer cluster. This allows it to perform searches and access the data it forwards to the peers.

Here is an example outputs.conf file:

# Turn off indexing
[indexAndForward]
index = false
 
[tcpout]
defaultGroup = my_peers_nodes 
forwardedindex.filter.disable = true  
indexAndForward = false 
 
[tcpout:my_peers_nodes]
server=10.10.10.1:9997,10.10.10.2:9997,10.10.10.3:9997

This example assumes that each peer node's receiving port is set to 9997.

Configure the peers for index replication:

  • Ensure that all necessary indexes are available on the peers.

  • If you need to install apps or change configurations, apply the changes to all peers in a consistent manner, ensuring that they use a common set of indexes.

  • If you need to add indexes (including indexes defined by an app), configure the peers to use the same set of indexes.

Note: After configuring the peers, you can start replicating data between the manager node and the peers.

Forwarder Outputs Example

[tcpout]
defaultGroup = my_peers_nodes

[tcpout:my_peers_nodes]
useACK = true
server=10.10.10.1:9997,10.10.10.2:9997,10.10.10.3:9997
autoLBFrequency = 60
autoLBVolume = 1048576

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