使用health api可以查看es集群的健康度。 health api的用法如下:
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curl 'http://localhost:9200/_cluster/health'
health api的返回值中有一个核心的字段status
, status
有3种取值: green, yellow, red。分别代表集群的3种状态: 主分片和副本都已经分配,主分片已经分配副本分片没有,主分片和副本都都没有分配。
也就是说, health api关注的核心在于数据的高可用。
看health api的实现:
请求会路由到master节点,然后读取clusterState中的routing_table
.
基于routing_table
, 判断索引的各个分片状态
public ClusterShardHealth(int shardId, final IndexShardRoutingTable shardRoutingTable) {
this.shardId = shardId;
for (ShardRouting shardRouting : shardRoutingTable) {
if (shardRouting.active()) {
activeShards++;
if (shardRouting.relocating()) {
// the shard is relocating, the one it is relocating to will be in initializing state, so we don't count it
relocatingShards++;
}
if (shardRouting.primary()) {
primaryActive = true;
}
} else if (shardRouting.initializing()) {
initializingShards++;
} else if (shardRouting.unassigned()) {
unassignedShards++;
}
}
if (primaryActive) {
if (activeShards == shardRoutingTable.size()) {
status = ClusterHealthStatus.GREEN;
} else {
status = ClusterHealthStatus.YELLOW;
}
} else {
status = ClusterHealthStatus.RED;
}
}
基于分片,决定索引的状态
public ClusterIndexHealth(IndexMetaData indexMetaData, IndexRoutingTable indexRoutingTable) {
this.index = indexMetaData.getIndex();
this.numberOfShards = indexMetaData.getNumberOfShards();
this.numberOfReplicas = indexMetaData.getNumberOfReplicas();
this.validationFailures = indexRoutingTable.validate(indexMetaData);
for (IndexShardRoutingTable shardRoutingTable : indexRoutingTable) {
int shardId = shardRoutingTable.shardId().id();
shards.put(shardId, new ClusterShardHealth(shardId, shardRoutingTable));
}
// update the index status
status = ClusterHealthStatus.GREEN;
for (ClusterShardHealth shardHealth : shards.values()) {
if (shardHealth.isPrimaryActive()) {
activePrimaryShards++;
}
activeShards += shardHealth.getActiveShards();
relocatingShards += shardHealth.getRelocatingShards();
initializingShards += shardHealth.getInitializingShards();
unassignedShards += shardHealth.getUnassignedShards();
if (shardHealth.getStatus() == ClusterHealthStatus.RED) {
status = ClusterHealthStatus.RED;
} else if (shardHealth.getStatus() == ClusterHealthStatus.YELLOW && status != ClusterHealthStatus.RED) {
// do not override an existing red
status = ClusterHealthStatus.YELLOW;
}
}
if (!validationFailures.isEmpty()) {
status = ClusterHealthStatus.RED;
} else if (shards.isEmpty()) { // might be since none has been created yet (two phase index creation)
status = ClusterHealthStatus.RED;
}
}
基于索引,决定集群的状态。
public ClusterStateHealth(ClusterState clusterState, String[] concreteIndices) {
RoutingTableValidation validation = clusterState.routingTable().validate(clusterState.metaData());
validationFailures = validation.failures();
numberOfNodes = clusterState.nodes().size();
numberOfDataNodes = clusterState.nodes().dataNodes().size();
for (String index : concreteIndices) {
IndexRoutingTable indexRoutingTable = clusterState.routingTable().index(index);
IndexMetaData indexMetaData = clusterState.metaData().index(index);
if (indexRoutingTable == null) {
continue;
}
ClusterIndexHealth indexHealth = new ClusterIndexHealth(indexMetaData, indexRoutingTable);
indices.put(indexHealth.getIndex(), indexHealth);
}
status = ClusterHealthStatus.GREEN;
for (ClusterIndexHealth indexHealth : indices.values()) {
activePrimaryShards += indexHealth.getActivePrimaryShards();
activeShards += indexHealth.getActiveShards();
relocatingShards += indexHealth.getRelocatingShards();
initializingShards += indexHealth.getInitializingShards();
unassignedShards += indexHealth.getUnassignedShards();
if (indexHealth.getStatus() == ClusterHealthStatus.RED) {
status = ClusterHealthStatus.RED;
} else if (indexHealth.getStatus() == ClusterHealthStatus.YELLOW && status != ClusterHealthStatus.RED) {
status = ClusterHealthStatus.YELLOW;
}
}
if (!validationFailures.isEmpty()) {
status = ClusterHealthStatus.RED;
} else if (clusterState.blocks().hasGlobalBlock(RestStatus.SERVICE_UNAVAILABLE)) {
status = ClusterHealthStatus.RED;
}
// shortcut on green
if (status.equals(ClusterHealthStatus.GREEN)) {
this.activeShardsPercent = 100;
} else {
List shardRoutings = clusterState.getRoutingTable().allShards();
int activeShardCount = 0;
int totalShardCount = 0;
for (ShardRouting shardRouting : shardRoutings) {
if (shardRouting.active()) activeShardCount++;
totalShardCount++;
}
this.activeShardsPercent = (((double) activeShardCount) / totalShardCount) * 100;
}
}
理解health api, 需要理解clusterState。 好在这些都是只读的信息,不难理解。