Open Connector

Open Connector is a separate, self-hosted SaaS gateway: it owns provider credentials, OAuth flows, token refresh, action policies, and provider-specific HTTP execution for 1,000+ SaaS providers. Skardi adds the relational layer on top — stable table definitions, JSON-to-Arrow conversion, pagination, safe filter and limit pushdown, optional caching, and DataFusion registration — so selected SaaS resources become ordinary SQL tables that can join against every other Skardi source.

Provider credentials never enter Skardi. Skardi is configured with only two things: the gateway URL and the name of an environment variable holding the gateway runtime token.

Status: the shared foundation is complete, and the first real provider packs have landed alongside the synthetic mock pack used by the test suite: GitHub (repositories, issues, pull requests, reviews, commits, workflow runs, releases) and Slack (conversations, users, files — message tables are gated on upstream cursor support). Further provider packs (Jira, Notion, …) ship one pack per release per the design spec; a source is advertised as supported only once its pack passes the admission gate there.

A runnable local walkthrough (bundled stub gateway, server, all three SQL interfaces, federated join) lives in the GitHub pack demo.

Configuration

An Open Connector gateway is a type: open_connector data source with hierarchy_level: catalog and a typed open_connector: block:

kind: context

metadata:
  name: saas-example
  version: 1.0.0

spec:
  data_sources:
    - name: saas                                  # catalog name in SQL
      type: open_connector
      connection_string: http://open-connector:3000
      hierarchy_level: catalog

      open_connector:
        # Environment variable holding the gateway runtime token.
        # The token value itself never appears in YAML.
        runtime_token_env: OPEN_CONNECTOR_TOKEN

        # Safety bounds (defaults shown).
        request_timeout_seconds: 30      # one gateway HTTP request
        scan_timeout_seconds: 300        # one whole scan, all pages
        max_pages: 100                   # pages per scan
        max_rows: 100000                 # rows per scan
        max_response_bytes: 16777216     # decoded bytes per response
        max_attempts: 3                  # attempts per gateway call

        # Caching: live reads by default; > 0 enables the bounded
        # in-memory TTL cache shared by all scans of this gateway.
        cache_ttl_seconds: 0
        cache_max_bytes: 268435456

        # Actions open_connector_scan may invoke. Empty by default —
        # raw-action access is default-deny.
        raw_action_allowlist:
          - github.list_repository_issues

        # Persistent stable tables: each binding becomes a schema in the
        # gateway catalog, each listed source-pack table becomes a table.
        bindings:
          - name: github_skardi          # schema name in SQL
            source_pack: github          # built-in pack
            source_pack_version: 1       # optional pin (schema stability)
            connection_alias: work       # optional Open Connector alias
            resource:                    # inputs the pack requires
              owner: SkardiLabs
              repo: skardi
            tables:
              - issues
              - pull_requests

Notes:

• Unknown keys anywhere in the block are rejected at load time — a misspelled source_pack_versions fails loudly instead of silently disabling the pin it was meant to set.
• One binding can serve tables with different resource needs: each table's requests carry only the resource keys its contract declares (Open Connector's strict action schemas reject undeclared inputs), so binding repositories alongside issues under one owner/repo resource map just works. A resource key that no bound table declares fails registration as a probable typo.
• The gateway URL must be plain http(s):// with no embedded credentials, query string, or fragment; the runtime token travels only as a Bearer header.
• The source is read-only by construction. access_mode: read_write, SQL DML, and job destinations are all rejected.
• Registration is a configuration action, not a SQL action: bindings change only through reviewed context YAML, never through DDL.

At startup Skardi validates the config, health-checks the gateway, discovers the metadata of every referenced action (bound pack tables plus the raw-action allowlist), verifies pack version pins, required resource inputs, and action-contract fingerprints, and only then registers the catalog. Query planning never performs network I/O.

Three SQL interfaces

1. Stable catalog tables

Each binding is a schema under the gateway catalog: <gateway>.<binding>.<table>. This is the interface for repeatedly queried resources and federated joins:

SELECT number, title, author_login
FROM saas.github_skardi.issues
WHERE state = 'open'
LIMIT 50;

Filters that the source pack maps faithfully (Exact) are pushed into the provider API call; everything else stays in DataFusion. LIMIT stops pagination as soon as enough rows have been emitted.

2. open_connector_query — built-in pack tables, ad hoc

Runs a built-in source-pack table without a persistent binding. Arguments: gateway, stable table ID, resource JSON, optional connection alias.

SELECT number, title, author_login
FROM open_connector_query(
  'saas',
  'github.issues',
  '{"owner":"SkardiLabs","repo":"skardi"}',
  'work'                    -- optional; defaults to the gateway default
)
WHERE state = 'open'
LIMIT 50;

It compiles into exactly the scan the YAML-bound table uses: same stable Arrow schema, filter allowlist, pagination, safety bounds, and shared cache. The table's action must have been discovered when the gateway was registered — bind the table in YAML or add its action to raw_action_allowlist; otherwise planning fails with an error saying so (planning never contacts the gateway).

3. open_connector_scan — allowlisted raw read actions

The escape hatch for actions no pack covers yet. Arguments: gateway, action ID, input JSON, row path, optional connection alias.

SELECT number, title
FROM open_connector_scan(
  'saas',
  'github.list_repository_issues',
  '{"owner":"SkardiLabs","repo":"skardi","state":"open"}',
  '$.issues'
)
LIMIT 50;

Raw scans are deliberately narrow:

• Default-deny. The action must be in the gateway's raw_action_allowlist, and its discovered metadata must classify it as a non-mutating read (execution.readOnly). A missing or ambiguous classification is refused with an error naming the gap — the allowlist alone never grants execution. Both checks fire at planning time, before any HTTP request. Current-gateway caveat: Open Connector does not yet publish a read/write classification in its action metadata (verified against v1.3.1), so raw scans against today's real gateway are refused by this gate; built-in pack tables — read-only by Skardi's own review — are unaffected. The parse site is forward-compatible for when the upstream grows the field.
• Deterministic row type or planning error. The Arrow schema is derived from the discovered action output schema at the row path: declared primitives (string, integer, number, boolean, including ["T","null"] unions) become typed nullable columns; objects, arrays, wider unions, and undeclared types become JSON-string columns. If the row path does not resolve to an array of objects with declared properties, planning fails and recommends a built-in pack table or a source-pack contribution.
• One request, one page. Raw actions declare no pagination contract, so the action executes exactly once; pass any paging inputs explicitly in the input JSON. Raw scans are always live (never cached) and support no filter pushdown — provider-side filters go in the input JSON, SQL predicates are evaluated by DataFusion.

Federated joins

Open Connector tables join like any other source:

SELECT i.id, i.name, l.label
FROM open_connector_query('saas', 'mock.items', '{"workspace":"demo"}') i
JOIN 'labels.csv' l ON i.id = l.id;

Security model

• Provider credentials stay in Open Connector; Skardi holds only the gateway runtime token, read from the environment at registration.
• Tokens never appear in YAML, logs, Debug output, error messages, or the data-sources API.
• Stable tables and open_connector_query can execute only the read actions hard-coded in Skardi's source packs; bindings cannot override the pack's action, row path, pagination, or schema (unknown keys are rejected at parse time).
• open_connector_scan requires an explicit allowlist entry and a read-only classification in the discovered metadata; mutating and unclassified actions are rejected before any HTTP request.
• The integration registers no DML: INSERT/UPDATE/DELETE and read-write access modes fail with targeted errors.
• The metadata these gates read (read-only classification, executability, action-contract fingerprints) is discovered at registration and holds until the next restart or configuration reload — query planning never re-contacts the gateway. An action whose upstream definition turns mutating after registration is therefore not re-checked by Skardi inside that window.
• Open Connector's own action policies remain a second, independent enforcement boundary — and the live one during the staleness window above.

Caching and freshness

Live reads are the default (cache_ttl_seconds: 0). With a positive TTL, completed scans are cached in a bounded in-memory LRU (byte- and entry-capped) keyed by gateway, connection alias, action, source-pack version, resource inputs, translated filters, projection, LIMIT, and the Arrow schema fingerprint. Only completed scans are stored, so a truncated result can never serve a fuller query. Both stable tables and open_connector_query share one cache per gateway; raw scans bypass it.

Caching claims no transactional consistency: a live multi-page scan can observe upstream changes between pages, subject to the provider's own pagination guarantees.

Bounds, retries, and errors

Every scan is bounded by max_pages, max_rows, request_timeout_seconds, scan_timeout_seconds, and max_response_bytes; hitting a bound fails the scan rather than returning a partial result as success. Idempotent gateway calls (health, discovery) retry 429/transient 5xx with capped exponential backoff honoring Retry-After; non-idempotent execute calls retry only a pre-execution 429 and never re-send a request that may have already run. Cursor pagination that stops advancing fails as a detected loop instead of spinning forever; a continuation cursor of the wrong JSON type fails the scan as itself (only an absent, null, or empty-string cursor means end-of-collection — anything else would silently truncate). Conversion errors report the action, row path, page, row, column, and expected type — with the offending JSON kind, never the value.

Provider errors reported in-band (Slack-style HTTP 200 with ok: false

• error) are handled at one of two layers. Open Connector's own executors consume them and return the gateway's failure envelope (non-2xx), which Skardi surfaces with the provider's message — this is the path the built-in slack pack relies on. For a gateway that instead forwards such envelopes unchanged, a pack table must declare an error_path; the scan checks it before row extraction and fails with the provider's own code (bounded, value-free), never the misleading missing-row-array error. A pack whose gateway does neither would otherwise report RowPathNotFound on an in-band error page.

Compatibility and schema drift

Each pack table pins the full relational contract and an expected action-contract fingerprint captured from a live gateway (a canonicalized BLAKE3 hash of the discovered output schema; both the github and slack packs are pinned, with the captured schemas committed next to each pack under fixtures/<provider>/contracts/). At registration a pinned table's fingerprint is compared against the discovered contract and any difference — breaking or additive, since a hash cannot tell them apart — fails with a targeted error instead of silently changing a table's schema; upgrading the gateway means re-capturing the contract and re-pinning. (Additive upstream fields in row data are still simply ignored by conversion — the fingerprint gates the declared schema, not the rows.) The gate's coverage is exactly the upstream declaration: mapped columns that a provider's schema leaves to additionalProperties passthrough sit outside the fingerprint, and drift there surfaces at scan time under the conversion rules instead (a shape change fails loudly; a removed nullable field reads as NULL). Each pack pins its uncovered-column set in a test, so that gap is a reviewed fact rather than an implicit one. Bindings may pin source_pack_version so a Skardi upgrade cannot silently change a bound table's schema either.

Observability

Every scan completion emits a structured tracing event with the gateway, binding, table, action, cache hit/miss, pages fetched, rows returned, and duration — identifying fields and counters only. Scan failures emit the same identity plus the error; for failure diagnosability the error message may quote a bounded (at most 512-character) snippet of the gateway's error response — which can echo request identifiers such as an owner or repo name — and, on pagination-loop detection, the offending cursor. The client logs each retry with the operation and status. Tokens, authorization headers, provider credentials, successful-response bodies, and row data are never logged; conversion and row-path failures report JSON kinds, never values.