oss_19_periodic_metric_reader_batch_size

[ocelotl]

PeriodicExportingMetricReader: add optional max_export_batch_size chunking (Linear OSS-19, finding M4).

Branch / worktree: oss_19_periodic_metric_reader_batch_size

Linear issue: https://linear.app/dash0/issue/OSS-19/m4-periodicexportingmetricreader-lacks-max-export-batch-size

[ocelotl]

🔒 Internal (dash0) — not for upstream.

Tracking for PeriodicExportingMetricReader max_export_batch_size.

• Linear: https://linear.app/dash0/issue/OSS-19/m4-periodicexportingmetricreader-lacks-max-export-batch-size (finding M4)
• Slug/branch/worktree: oss_19_periodic_metric_reader_batch_size
• Commit: 0fec0b5c8 · PR: oss_19_periodic_metric_reader_batch_size #25
• Validation: full metrics suite 309 passed; scope sdk + changelog.

[ocelotl]

📣 Public-facing draft — to be opened upstream in open-telemetry/opentelemetry-python. No internal references; copy verbatim.

Title: PeriodicExportingMetricReader lacks maxExportBatchSize (always exports full MetricsData in one call)

Description

The spec's periodic metric reader defines a maxExportBatchSize, but Python's PeriodicExportingMetricReader does not implement it: it always hands the entire collected MetricsData to the exporter in one export() call.

Evidence — opentelemetry-sdk/src/opentelemetry/sdk/metrics/_internal/export/__init__.py, PeriodicExportingMetricReader._receive_metrics:

with self._export_lock:
    self._exporter.export(metrics_data, timeout_millis=timeout_millis)

No batch-size parameter, no chunking.

Spec

specification/metrics/sdk.md — the periodic exporting MetricReader defines a configurable maximum export batch size so a single export call does not exceed a bounded number of data points, bounding payload/memory for exporters (e.g. OTLP) on large collection cycles.

Reference

Go implements this as WithExportMaxBatchSize / maxExportBatchSize in sdk/metric/periodic_reader.go, chunking the collected data into export calls within the configured size.

Proposed fix

Add an optional max_export_batch_size to PeriodicExportingMetricReader. When set, chunk data points into batches of at most that size and export each under the existing export lock, preserving resource/scope/metric grouping. When None, behavior is unchanged (single export). Validate > 0.