Reroute Unassigned Shards——遇到主shard 出现的解决方法就是重新路由
Red Cluster! 摘自：http://blog.kiyanpro.com/2016/03/06/elasticsearch/reroute-unassigned-shards/ There are 3 cluster states: green: All primary and replica shards are active yellow: All primary shards are active, but not all replica shards are active red: Not all primary shards are active When cluster health is red, it means cluster is dead. And that means you can do nothing until it’s recovered, which is very bad indeed. I will share with you how to deal with one common situation:when cluster is red due to unassigned shards. Steps The general idea is pretty simple: find those shards which are unassigned, manually assign them to a node with reroute API. Let’s see how we can do that step by step. Then we can combine them into a configurable simple script. Step 1: Check Unassigned Shards To get cluster information, we usually use cat APIs. There is aGET /_cat/shardsendpoint to show a detailed view of what nodes contain which shards[1]. Cat shards 1 2 3 4 5 6 7 8 9 # cat shards verbose curl "http://your.elasticsearch.host.com:9200/_cat/shards?v" # cat shards index curl "http://your.elasticsearch.host.com:9200/_cat/shards/wiki2" # example return # wiki2 0 p STARTED 197 3.2mb 192.168.56.10 Stiletto # wiki2 1 p STARTED 205 5.9mb 192.168.56.30 Frankie Raye # wiki2 2 p STARTED 275 7.8mb 192.168.56.20 Commander Kraken By piping cat shards to fgrep, we can get all unassigned shards. Get unassigned shards 1 2 3 4 5 6 # cat shards with fgrep curl "http://your.elasticsearch.host.com:9200/_cat/shards" | fgrep UNASSIGNED # example return # wiki1 0 r UNASSIGNED ALLOCATION_FAILED # wiki1 1 r UNASSIGNED ALLOCATION_FAILED # wiki1 2 r UNASSIGNED ALLOCATION_FAILED If you don’t want to deal with shell script, you can also find these unassigned shards using another endpointPOST /_flush/synced[2]. This endpoint is actually not just some information. It allows an administrator to initiate a synced flush manually. This can be particularly useful for a planned (rolling) cluster restart where you can stop indexing and don’t want to wait the default 5 minutes for idle indices to be sync-flushed automatically. It returns with a json response. _flush/synced 1 curl -XPOST "http://your.elasticsearch.host.com:9200/twitter/_flush/synced" If there are failed shards in the response, we can iterate through a failures array to get all unassigned ones. Example response with failed shards 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 { "_shards": { "total":4, "successful":1, "failed":1 }, "twitter": { "total":4, "successful":3, "failed":1, "failures": [ { "shard":1, "reason":"unexpected error", "routing": { "state":"STARTED", "primary":false, "node":"SZNr2J_ORxKTLUCydGX4zA", "relocating_node":null, "shard":1, "index":"twitter" } } ] } } Step 2: Reroute The reroute command allows to explicitly execute a cluster reroute allocation command including specific commands[3]. An unassigned shard can be explicitly allocated on a specific node. Reroute example 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 curl -XPOST 'localhost:9200/_cluster/reroute' -d'{ "commands" : [ { "move" : { "index" : "test", "shard" : 0, "from_node" : "node1", "to_node" : "node2" } }, { "allocate" : { "index" : "test", "shard" : 1, "node" : "node3" } } ] }' There are 3 kinds of commands you can use: move: Move a started shard from one node to another node. Accepts index and shard for index name and shard number, from_node for the node to move the shard from, and to_node for the node to move the shard to. cancel: Cancel allocation of a shard (or recovery). Accepts index and shard for index name and shard number, and node for the node to cancel the shard allocation on. It also accepts allow_primary flag to explicitly specify that it is allowed to cancel allocation for a primary shard. This can be used to force resynchronization of existing replicas from the primary shard by cancelling them and allowing them to be reinitialized through the standard reallocation process. allocate: Allocate an unassigned shard to a node. Accepts the index and shard for index name and shard number, and node to allocate the shard to. It also accepts allow_primary flag to explicitly specify that it is allowed to explicitly allocate a primary shard (might result in data loss). Combining step 2 with the unassigned shards from Step 1, we can reroute all unassigned shards 1 by 1, thus getting faster cluster recovery from red state. Example Solutions Python Below is a python script I wrote usingPOST /_flush/syncedandPOST /reroute Shell Script Below is a shell script I found elsewhere in a blog post[4] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 for shardin $(curl -XGET http://localhost:9200/_cat/shards | grep UNASSIGNED | awk'{print $2}');do curl -XPOST 'localhost:9200/_cluster/reroute' -d'{ "commands" : [ { "allocate" : { "index" : "t37", # index name "shard" : $shard, "node" : "datanode15", # node name "allow_primary" : true } } ] }' sleep 5 done EDIT: Based on Vincent’s comment I updated the shell script: Possible Unassigned Shard Reasons FYI, these are the possible reasons for a shard be in a unassigned state[1]: Name Comment INDEX_CREATED Unassigned as a result of an API creation of an index CLUSTER_RECOVERED Unassigned as a result of a full cluster recovery INDEX_REOPENED Unassigned as a result of opening a closed index DANGLING_INDEX_IMPORTED Unassigned as a result of importing a dangling index NEW_INDEX_RESTORED Unassigned as a result of restoring into a new index EXISTING_INDEX_RESTORED Unassigned as a result of restoring into a closed index REPLICA_ADDED Unassigned as a result of explicit addition of a replica ALLOCATION_FAILED Unassigned as a result of a failed allocation of the shard NODE_LEFT Unassigned as a result of the node hosting it leaving the cluster REROUTE_CANCELLED Unassigned as a result of explicit cancel reroute command REINITIALIZED When a shard moves from started back to initializing, for example, with shadow replicas REALLOCATED_REPLICA A better replica location is identified and causes the existing replica allocation to be cancelled References ElasticSearch Document Cat Shards ElasticSearch Document Synced Flush ElasticSearch Document Cluster Reroute How to fix your elasticsearch cluster stuck in initializing shards mode? 本文转自张昺华-sky博客园博客，原文链接：http://www.cnblogs.com/bonelee/p/7459408.html，如需转载请自行联系原作者
