HDFS-17878. Reduce frequency of getDatanodeListForReport calls for metrics#8220
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kokonguyen191 wants to merge 1 commit intoapache:trunkfrom
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HDFS-17878. Reduce frequency of getDatanodeListForReport calls for metrics#8220kokonguyen191 wants to merge 1 commit intoapache:trunkfrom
kokonguyen191 wants to merge 1 commit intoapache:trunkfrom
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ZanderXu
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Apr 1, 2026
| public boolean isSufficientlyReplicated(BlockInfo b) { | ||
| // Compare against the lesser of the minReplication and number of live DNs. | ||
| final int liveReplicas = countNodes(b).liveReplicas(); | ||
| if (liveReplicas == 0) { |
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Perhaps we can make this PR more focused, simply providing a cache machine for a list of DataNodes, without making any other modifications.
| private final boolean randomNodeOrderEnabled; | ||
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| /** Cached map of DatanodeReportType -> list of DatanodeDescriptor for metrics purposes. */ | ||
| private volatile Cache<DatanodeReportType, List<DatanodeDescriptor>> datanodeListSnapshots = null; |
| synchronized(this) { | ||
| host2DatanodeMap.remove(datanodeMap.put(node.getDatanodeUuid(), node)); | ||
| } | ||
| Cache<DatanodeReportType, List<DatanodeDescriptor>> tmpDatanodeListSnapshots = |
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how about remove this invalidateAll.
If you want to remove the dead datanode from the cache in time, we also need to update the decommission status, right? So we can make it more simple, just updated the cache with a fixed interval.
| return dnId; | ||
| } | ||
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| public void refreshDatanodeListSnapshot(long newExpirationMs) { |
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It's better to support this hot-reload operations in a new PR if you think it's necessary.
| * Low impact version of {@link #getDatanodeListForReport} with possible stale | ||
| * data for low impact usage (metrics). | ||
| */ | ||
| public List<DatanodeDescriptor> getDatanodeListSnapshotForReport( |
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getDatanodeListForReportWithCache
| /** Fetch live and dead datanodes. */ | ||
| public void fetchDatanodes(final List<DatanodeDescriptor> live, | ||
| final List<DatanodeDescriptor> dead, final boolean removeDecommissionNode) { | ||
| final List<DatanodeDescriptor> dead, final boolean removeDecommissionNode, boolean useCache) { |
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please add a method without many changes.
fetchDatanodes(final List<DatanodeDescriptor> live,
final List<DatanodeDescriptor> dead, final boolean removeDecommissionNode) {
fetchDatanodes(live, dead, removeDecommisionNode, false);
}
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Description of PR
getDatanodeListForReportis called by a lot of metrics method while holding synchronized lock, interfering with more critical ops like datanodeReport while not having critical data (metrics). Best to reduce the frequency of calls to this method. This patch added a configurable cache that is force-wiped when there is a change in DNs, else expires using the configured expiration period.How was this patch tested?
Product cluster + local UT benchmark