Emit datadog metric when Elasticsearch index is set to read only/allow delete - #27
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Emit datadog metric when Elasticsearch index is set to read only/allow delete#27gherceg wants to merge 1 commit into
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gherceg
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July 20, 2026 01:05
Emits elasticsearch.index.read_only_allow_delete=1 per index that has the index.blocks.read_only_allow_delete block set, which Elasticsearch applies when disk usage crosses the flood-stage watermark. The block must be cleared manually, so this surfaces indices stuck rejecting writes. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Problem
When Elasticsearch disk usage reaches the flood-stage watermark (currently set to 95%), ES sets
index.blocks.read_only_allow_delete: trueon affected indices. This block is not cleared automatically when disk frees up. It must be reset manually, and until then the index rejects writes. We currently have no good signal for this other than pillow errors which are not monitored closely.Solution
A new
elasticsearch_customcheck (modeled oncouchdb_custom, PR #25) that queries index settings and emits a per-index gaugeelasticsearch.index.read_only_allow_delete = 1, taggedindex:<name>, for each index that is blocked.Nothing is emitted for healthy indices. I figured this would help keep the custom metric count lower since we only care about this signal when it's "on".
Testing
Plan to test manually on staging which will require a related commcare-cloud PR to get the elasticsearch_custom integration onto one of the elasticsearch machines.