Manticore Search Manual: Creating a cluster > Setting up replication

Load balancing is turned on by default for any distributed table that uses mirroring. By default, queries are distributed randomly among the mirrors. You can change this behavior by using the ha_strategy.

ha_strategy = {random|nodeads|noerrors|roundrobin}

The mirror selection strategy for load balancing is optional and is set to random by default.

The strategy used for mirror selection, or in other words, choosing a specific agent mirror in a distributed table, is controlled by this directive. Essentially, this directive controls how master performs the load balancing between the configured mirror agent nodes. The following strategies are implemented:

The default balancing mode is simple linear random distribution among the mirrors. This means that equal selection probabilities are assigned to each mirror. This is similar to round-robin (RR), but does not impose a strict selection order.

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Example

Example

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ha_strategy = random

The default simple random strategy does not take into account the status of mirrors, error rates, and most importantly, actual response latencies. To address heterogeneous clusters and temporary spikes in agent node load, there are a group of balancing strategies that dynamically adjust the probabilities based on the actual query latencies observed by the master.

The adaptive strategies based on latency-weighted probabilities work as follows:

Latency stats are accumulated in blocks of ha_period_karma seconds.
Latency-weighted probabilities are recomputed once per karma period.
The "dead or alive" flag is adjusted once per request, including ping requests.

Initially, the probabilities are equal. On every step, they are scaled by the inverse of the latencies observed during the last karma period, and then renormalized. For example, if during the first 60 seconds after the master startup, 4 mirrors had latencies of 10 ms, 5 ms, 30 ms, and 3 ms respectively, the first adjustment step would go as follows:

Initial percentages: 0.25, 0.25, 0.25, 0.25.
Observed latencies: 10 ms, 5 ms, 30 ms, 3 ms.
Inverse latencies: 0.1, 0.2, 0.0333, 0.333.
Scaled percentages: 0.025, 0.05, 0.008333, 0.0833.
Renormalized percentages: 0.15, 0.30, 0.05, 0.50.

This means that the first mirror would have a 15% chance of being chosen during the next karma period, the second one a 30% chance, the third one (slowest at 30 ms) only a 5% chance, and the fourth and fastest one (at 3 ms) a 50% chance. After that period, the second adjustment step would update those chances again, and so on.

The idea is that once the observed latencies stabilize, the latency weighted probabilities will stabilize as well. All these adjustment iterations are meant to converge at a point where the average latencies are roughly equal across all mirrors.

Latency-weighted probabilities, but dead mirrors are excluded from the selection. A "dead" mirror is defined as a mirror that has resulted in multiple hard errors (e.g. network failure, or no answer, etc) in a row.

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Example

Example

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ha_strategy = nodeads

Latency-weighted probabilities, but mirrors with a worse error/success ratio are excluded from selection.

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Example

Example

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ha_strategy = noerrors

Simple round-robin selection, that is, selecting the first mirror in the list, then the second one, then the third one, etc, and then repeating the process once the last mirror in the list is reached. Unlike with the randomized strategies, RR imposes a strict querying order (1, 2, 3, ..., N-1, N, 1, 2, 3, ..., and so on) and guarantees that no two consecutive queries will be sent to the same mirror.

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Example

Example

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ha_strategy = roundrobin

ha_period_karma = 2m

ha_period_karma defines the size of the agent mirror statistics window, in seconds (or a time suffix). Optional, the default is 60.

For a distributed table with agent mirrors, the server tracks several different per-mirror counters. These counters are then used for failover and balancing. (The server picks the best mirror to use based on the counters.) Counters are accumulated in blocks of ha_period_karma seconds.

After beginning a new block, the master may still use the accumulated values from the previous one until the new one is half full. Thus, any previous history stops affecting the mirror choice after at most 1.5 times ha_period_karma seconds.

Although at most 2 blocks are used for mirror selection, up to 15 last blocks are actually stored for instrumentation purposes. They can be inspected using the SHOW AGENT STATUS statement.

ha_ping_interval = 3s

ha_ping_interval directive defines the interval between pings sent to the agent mirrors, in milliseconds (or with a time suffix). This option is optional and its default value is 1000.

For a distributed table with agent mirrors, the server sends all mirrors a ping command during idle periods to track their current status (whether they are alive or dead, network roundtrip time, etc.). The interval between pings is determined by the ha_ping_interval setting.

If you want to disable pings, set ha_ping_interval to 0.

With Manticore, write transactions (such as INSERT, REPLACE, DELETE, TRUNCATE, UPDATE, COMMIT) can be replicated to other cluster nodes before the transaction is fully applied on the current node. Currently, replication is supported for percolate, rt and distributed tables in Linux and macOS.

Native Windows binaries for Manticore do not support replication. We recommend installing Manticore via WSL (Windows Subsystem for Linux).

Manticore's replication is powered by the Galera library and boasts several impressive features:

True multi-master: read and write to any node at any time.
Virtually synchronous replication no slave lag and no data loss after a node crash.
Hot standby: no downtime during failover (since there is no failover).
Tightly coupled: all nodes hold the same state and no diverged data between nodes is allowed.
Automatic node provisioning: no need to manually backup the database and restore it on a new node.
Easy to use and deploy.
Detection and automatic eviction of unreliable nodes.
Certification-based replication.

To set up replication in Manticore Search:

The data_dir option must be set in the "searchd" section of the configuration file. Replication is not supported in plain mode.
A listen directive must be specified, containing an IP address accessible by other nodes, or a node_address with an accessible IP address.
Optionally, you can set unique values for server_id on each cluster node. If no value is set, the node will attempt to use the MAC address or a random number to generate the server_id.

If there is no replication listen directive set, Manticore will use the first two free ports in the range of 200 ports after the default protocol listening port for each created cluster. To set replication ports manually, the listen directive (of replication type) port range must be defined and the address/port range pairs must not intersect between different nodes on the same server. As a rule of thumb, the port range should specify at least two ports per cluster.

A replication cluster is a group of nodes in which a write transaction is replicated. Replication is set up on a per-table basis, meaning that one table can only belong to one cluster. There is no limit on the number of tables that a cluster can have. All transactions such as INSERT, REPLACE, DELETE, TRUNCATE on any percolate or real-time table that belongs to a cluster are replicated to all the other nodes in that cluster. Distributed tables can also be part of the replication process. Replication is multi-master, so writes to any node or multiple nodes simultaneously will work just as well.

To create a cluster, you can typically use the command create cluster with CREATE CLUSTER <cluster name>, and to join a cluster, you can use join cluster with JOIN CLUSTER <cluster name> at 'host:port'. However, in some rare cases, you may want to fine-tune the behavior of CREATE/JOIN CLUSTER. The available options are:

This option specifies the name of the cluster. It should be unique among all the clusters in the system.

Note: The maximum allowable hostname length for the JOIN command is 253 characters. If you exceed this limit, searchd will generate an error.

The path option specifies the data directory for write-set cache replication and incoming tables from other nodes. This value should be unique among all the clusters in the system and should be specified as a relative path to the data_dir. directory. By default, it is set to the value of data_dir.

The nodes option is a list of address:port pairs for all the nodes in the cluster, separated by commas. This list should be obtained using the node's API interface and can include the address of the current node as well. It is used to join the node to the cluster and to rejoin it after a restart.

The options option allows you to pass additional options directly to the Galera replication plugin, as described in the Galera Documentation Parameters

When working with a replication cluster, all write statements such as INSERT, REPLACE, DELETE, TRUNCATE, UPDATE that modify the content of a cluster's table must use thecluster_name:index_name expression instead of the table name. This ensures that the changes are propagated to all replicas in the cluster. If the correct expression is not used, an error will be triggered.

In the JSON interface, the cluster property must be set along with the table name for all write statements to a cluster's table. Failure to set the cluster property will result in an error.

The Auto ID for a table in a cluster should be valid as long as the server_id is correctly configured.

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INSERT INTO posts:weekly_index VALUES ( 'iphone case' )
TRUNCATE RTINDEX click_query:weekly_index
UPDATE INTO posts:rt_tags SET tags=(101, 302, 304) WHERE MATCH ('use') AND id IN (1,101,201)
DELETE FROM clicks:rt WHERE MATCH ('dumy') AND gid>206

POST /insert -d '
{
  "cluster":"posts",
  "index":"weekly_index",
  "doc":
  {
    "title" : "iphone case",
    "price" : 19.85
  }
}'
POST /delete -d '
{
  "cluster":"posts",
  "index": "weekly_index",
  "id":1
}'

$index->addDocuments([
        1, ['title' => 'iphone case', 'price' => 19.85]
]);
$index->deleteDocument(1);

indexApi.insert({"cluster":"posts","index":"weekly_index","doc":{"title":"iphone case","price":19.85}})
indexApi.delete({"cluster":"posts","index":"weekly_index","id":1})

res = await indexApi.insert({"cluster":"posts","index":"weekly_index","doc":{"title":"iphone case","price":19.85}});
 res = await indexApi.delete({"cluster":"posts","index":"weekly_index","id":1});

InsertDocumentRequest newdoc = new InsertDocumentRequest();
HashMap<String,Object> doc = new HashMap<String,Object>(){{
    put("title","Crossbody Bag with Tassel");
    put("price",19.85);
}};
newdoc.index("weekly_index").cluster("posts").id(1L).setDoc(doc);
sqlresult = indexApi.insert(newdoc);

DeleteDocumentRequest deleteRequest = new DeleteDocumentRequest();
deleteRequest.index("weekly_index").cluster("posts").setId(1L);
indexApi.delete(deleteRequest);

Dictionary<string, Object> doc = new Dictionary<string, Object>();
doc.Add("title", "Crossbody Bag with Tassel");
doc.Add("price", 19.85);
InsertDocumentRequest newdoc = new InsertDocumentRequest(index: "weekly_index", cluster:posts, id: 1, doc: doc);
var sqlresult = indexApi.Insert(newdoc);

DeleteDocumentRequest deleteDocumentRequest = new DeleteDocumentRequest(index: "weekly_index", cluster: "posts", id: 1);
indexApi.Delete(deleteDocumentRequest);

Read statements such as SELECT, CALL PQ, DESCRIBE can either use regular table names that are not prepended with a cluster name, or they can use the cluster_name:index_nameformat. If the latter is used, the cluster_name component is ignored.

When using the HTTP endpoint json/search, the cluster property can be specified if desired, but it can also be omitted.

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SQL
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SELECT * FROM weekly_index
CALL PQ('posts:weekly_index', 'document is here')

Replication plugin options can be adjusted using the SET statement.

A list of available options can be found in the Galera Documentation Parameters .

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SQL
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SET CLUSTER click_query GLOBAL 'pc.bootstrap' = 1

It's possible for replicated nodes to diverge from one another, leading to a state where all nodes are labeled as non-primary. This can occur as a result of a network split between nodes, a cluster crash, or if the replication plugin experiences an exception when determining the primary component. In such a scenario, it's necessary to select a node and promote it to the role of primary component.

To identify the node that needs to be promoted, you should compare the last_committed cluster status variable value on all nodes. If all the servers are currently running, there's no need to restart the cluster. Instead, you can simply promote the node with the highest last_committed value to the primary component using the SET statement (as demonstrated in the example).

The other nodes will then reconnect to the primary component and resynchronize their data based on this node.

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SQL
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SET CLUSTER posts GLOBAL 'pc.bootstrap' = 1

To use replication, you need to define one listen port for SphinxAPI protocol and one listen for replication address and port range in the configuration file. Also, specify the data_dir folder to receive incoming tables.

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ini

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searchd {
  listen   = 9312
  listen   = 192.168.1.101:9360-9370:replication
  data_dir = /var/lib/manticore/
  ...
 }

To replicate tables, you must create a cluster on the server that has the local tables to be replicated.

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CREATE CLUSTER posts

POST /cli -d "
CREATE CLUSTER posts
"

$params = [
    'cluster' => 'posts'
    ]
];
$response = $client->cluster()->create($params);

utilsApi.sql('CREATE CLUSTER posts')

res = await utilsApi.sql('CREATE CLUSTER posts');

utilsApi.sql("CREATE CLUSTER posts");

utilsApi.Sql("CREATE CLUSTER posts");

Add these local tables to the cluster

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ALTER CLUSTER posts ADD pq_title
ALTER CLUSTER posts ADD pq_clicks

POST /cli -d "
ALTER CLUSTER posts ADD pq_title
"
POST /cli -d "
ALTER CLUSTER posts ADD pq_clicks
"

$params = [
  'cluster' => 'posts',
  'body' => [
     'operation' => 'add',
     'index' => 'pq_title'

  ]
];
$response = $client->cluster()->alter($params);
$params = [
  'cluster' => 'posts',
  'body' => [
     'operation' => 'add',
     'index' => 'pq_clicks'

  ]
];
$response = $client->cluster()->alter($params);

utilsApi.sql('ALTER CLUSTER posts ADD pq_title')
utilsApi.sql('ALTER CLUSTER posts ADD pq_clicks')

res = await utilsApi.sql('ALTER CLUSTER posts ADD pq_title');
res = await utilsApi.sql('ALTER CLUSTER posts ADD pq_clicks');

utilsApi.sql("ALTER CLUSTER posts ADD pq_title");
utilsApi.sql("ALTER CLUSTER posts ADD pq_clicks");

utilsApi.Sql("ALTER CLUSTER posts ADD pq_title");
utilsApi.Sql("ALTER CLUSTER posts ADD pq_clicks");

All other nodes that wish to receive a replica of the cluster's tables should join the cluster as follows:

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JOIN CLUSTER posts AT '192.168.1.101:9312'

POST /cli -d "
JOIN CLUSTER posts AT '192.168.1.101:9312'
"

$params = [
  'cluster' => 'posts',
  'body' => [
      '192.168.1.101:9312'
  ]
];
$response = $client->cluster->join($params);

utilsApi.sql('JOIN CLUSTER posts AT \'192.168.1.101:9312\'')

res = await utilsApi.sql('JOIN CLUSTER posts AT \'192.168.1.101:9312\'');

utilsApi.sql("JOIN CLUSTER posts AT '192.168.1.101:9312'");

utilsApi.Sql("JOIN CLUSTER posts AT '192.168.1.101:9312'");

When running queries, prepend the table name with the cluster name posts: or use the cluster property for HTTP request object.

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INSERT INTO posts:pq_title VALUES ( 3, 'test me' )

POST /insert -d '
{
  "cluster":"posts",
  "index":"pq_title",
  "id": 3
  "doc":
  {
    "title" : "test me"
  }
}'

$index->addDocuments([
        3, ['title' => 'test me']
]);

indexApi.insert({"cluster":"posts","index":"pq_title","id":3"doc":{"title":"test me"}})

res = await indexApi.insert({"cluster":"posts","index":"pq_title","id":3"doc":{"title":"test me"}});

InsertDocumentRequest newdoc = new InsertDocumentRequest();
HashMap<String,Object> doc = new HashMap<String,Object>(){{
    put("title","test me");
}};
newdoc.index("pq_title").cluster("posts").id(3L).setDoc(doc);
sqlresult = indexApi.insert(newdoc);

Dictionary<string, Object> doc = new Dictionary<string, Object>();
doc.Add("title", "test me");
InsertDocumentRequest newdoc = new InsertDocumentRequest(index: "pq_title", cluster: "posts", id: 3, doc: doc);
var sqlresult = indexApi.Insert(newdoc);

All queries that modify tables in the cluster are now replicated to all nodes in the cluster.

To create a replication cluster, you must set its name at a minimum.

If you are creating a single cluster or the first cluster, you may omit the path option. In this case, the data_dir option will be used as the cluster path. However, for all subsequent clusters, you must specify the path and the path must be available. The nodes option may also be set to list all nodes in the cluster.

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CREATE CLUSTER posts
CREATE CLUSTER click_query '/var/data/click_query/' as path
CREATE CLUSTER click_query '/var/data/click_query/' as path, 'clicks_mirror1:9312,clicks_mirror2:9312,clicks_mirror3:9312' as nodes

POST /cli -d "
CREATE CLUSTER posts
"
POST /cli -d "
CREATE CLUSTER click_query '/var/data/click_query/' as path
"
POST /cli -d "
CREATE CLUSTER click_query '/var/data/click_query/' as path, 'clicks_mirror1:9312,clicks_mirror2:9312,clicks_mirror3:9312' as nodes
"

$params = [
    'cluster' => 'posts',
    ]
];
$response = $client->cluster()->create($params);
$params = [
    'cluster' => 'click_query',
    'body' => [
        'path' => '/var/data/click_query/'
    ]    
    ]
];
$response = $client->cluster()->create($params);
$params = [
    'cluster' => 'click_query',
    'body' => [
        'path' => '/var/data/click_query/',
        'nodes' => 'clicks_mirror1:9312,clicks_mirror2:9312,clicks_mirror3:9312'
    ]    
    ]
];
$response = $client->cluster()->create($params);

utilsApi.sql('CREATE CLUSTER posts')
utilsApi.sql('CREATE CLUSTER click_query \'/var/data/click_query/\' as path')
utilsApi.sql('CREATE CLUSTER click_query \'/var/data/click_query/\' as path, \'clicks_mirror1:9312,clicks_mirror2:9312,clicks_mirror3:9312\' as nodes')

res = await utilsApi.sql('CREATE CLUSTER posts');
res = await utilsApi.sql('CREATE CLUSTER click_query \'/var/data/click_query/\' as path');
res = await utilsApi.sql('CREATE CLUSTER click_query \'/var/data/click_query/\' as path, \'clicks_mirror1:9312,clicks_mirror2:9312,clicks_mirror3:9312\' as nodes');

utilsApi.sql("CREATE CLUSTER posts");
utilsApi.sql("CREATE CLUSTER click_query '/var/data/click_query/' as path");
utilsApi.sql("CREATE CLUSTER click_query '/var/data/click_query/' as path, 'clicks_mirror1:9312,clicks_mirror2:9312,clicks_mirror3:9312' as nodes");

utilsApi.Sql("CREATE CLUSTER posts");
utilsApi.Sql("CREATE CLUSTER click_query '/var/data/click_query/' as path");
utilsApi.Sql("CREATE CLUSTER click_query '/var/data/click_query/' as path, 'clicks_mirror1:9312,clicks_mirror2:9312,clicks_mirror3:9312' as nodes");

If the nodes option is not specified when creating a cluster, the first node that joins the cluster will be saved as the nodes option.

Load balancing

ha_strategy

Simple random balancing

Adaptive randomized balancing

nodeads

noerrors

Round-robin balancing

Instance-wide options

ha_period_karma

ha_ping_interval

Setting up replication

Replication cluster

name

path

nodes

options

Write statements

Read statements

Cluster parameters

Cluster with diverged nodes

Replication and cluster

Creating a replication cluster