DanConwayDev
3200e7b31a
Purgatory git sync listed every needed commit id as an explicit want in
a single `git fetch <url> <oid1> <oid2> ...` and, on each upload-pack
"not our ref" rejection, dropped that one oid and re-sent the entire
remaining batch. Against a state event declaring tips that exist on no
reachable server (production evidence: the `market` repository, whose
declared-but-missing ref tips were crawled against gitnostr.com at
150-270 requests/min, 4,521 "not our ref" upload-pack errors in the
45-minute window on 2026-08-05) this degenerated into one failed
upload-pack round trip per missing tip with O(N^2) want retransmission,
pack data streamed and aborted on every failure, and nothing fetched
until the crawl finished. A single missing object failed every batch
that contained it.
fetch_oids now runs three phases through the same hardened/pinned
subprocess machinery (outbound policy authorization and DNS pinning are
unchanged and now also cover ls-remote):
1. `git ls-remote` compares the remote's advertised refs against the
needed oids; state-event ref tips and `refs/nostr/<event-id>` PR
tips surface in the advertisement, so matching oid sets suffices.
2. One batch `git fetch` of the needed oids the remote advertises.
Advertised oids are always valid wants, so "not our ref" cannot fail
this batch; if the advertisement races a ref update, the pass
degrades to per-oid fetches instead of failing.
3. Residual oids are requested one at a time, so a missing object costs
exactly one small round trip and never aborts the rest. Genuine
remote failures still feed the naughty list and stop the pass while
keeping what the batch already fetched.
Client-side observability the old debug-only retry loop lacked: one
INFO summary line per pass (needed / advertised tips / residual
attempted / residual missing / fetched) plus new counters
ngit_purgatory_git_fetch_passes_total and
ngit_purgatory_git_fetch_oids_total{kind}, so production verification
can observe gitnostr.com's own outbound behaviour rather than only the
serving side.
Reproduced by tests/sync/purgatory_fetch.rs: a real relay serves a
repository with two branch tips behind a new counting smart-HTTP proxy
(tests/common/upload_pack_counting_proxy.rs), and the relay under test
holds a state event declaring those tips plus eight unfetchable ones
(events delivered via a MockRelay bootstrap so purgatory sync takes the
immediate path). On the previous implementation the test fails with a
failed upload-pack request carrying all ten wants; with this change the
first want-carrying request is the successful batch of advertised tips
and every failed request carries at most one want.
Excluded scope: sync-pass scheduling/backoff, URL selection, and the
upload-pack serving side are untouched; the third-party crawler hitting
gitnostr.com only stops when that instance upgrades.
Validation: new scenario test fails on master and passes here (stable
across three runs); full `cargo test` suite green; clippy introduces no
new warnings.
Explanation
Understanding-oriented documentation - Concepts, design decisions, and the "why" behind ngit-grasp.
What Is Explanation?
Explanation documentation helps you understand concepts and design decisions, providing context and discussing alternatives.
Characteristics:
- ✅ Understanding-oriented (clarify concepts)
- ✅ Theoretical (ideas and design)
- ✅ Discuss alternatives
- ✅ Provide context and background
- ✅ Answer "why" questions
Not explanation:
- ❌ Step-by-step lessons (those are Tutorials)
- ❌ Problem-solving recipes (those are How-To)
- ❌ Technical specifications (those are Reference)
Available Explanation Documentation
Architecture Overview
Understand the system design and component interaction
Topics:
- Overall architecture
- Component responsibilities
- Data flows
- Technology choices
- Design patterns
Read when: You want to understand how ngit-grasp works as a system
Inline Authorization
Why we validate pushes inline instead of using Git hooks
Topics:
- The authorization problem
- Git hooks approach
- Inline approach
- Comparison and trade-offs
- Implementation details
Read when: You want to understand the core architectural decision
Design Decisions
Key architectural choices and their rationale
Topics:
- Inline authorization vs hooks
- Technology stack choices
- Storage design
- API design
- Performance considerations
Read when: You want to know why things are the way they are
Comparison with ngit-relay
How ngit-grasp differs from the reference implementation
Topics:
- Architecture comparison
- Component differences
- Trade-offs
- Migration path
- Compatibility
Read when: You're familiar with ngit-relay and want to understand differences
Purgatory Design
In-memory holding area for events awaiting git data
Topics:
- The "which arrives first?" problem
- Separate storage for state vs PR events
- Late binding for state events
- Bidirectional waiting for PR events
- Authorization during push
Read when: You want to understand how ngit-grasp handles out-of-order event/git data arrival
GRASP-02 Proactive Sync
Relay-to-relay synchronization for repository discovery
Topics:
- Negentropy-based event sync
- Repository announcement discovery
- Relay management and reconnection
- Layer 2 filtering
- Bootstrap and dynamic relay discovery
Read when: You want to understand how ngit-grasp discovers and syncs repositories across relays
Sync Scaling Constraints and Budgets
Relay-imposed limits and how sync spends them at scale
Topics:
- Verified relay limits (strfry, live NIP-11, our embedded relay)
- Per-connection budget ledger (live vs historic vs fallback)
- Byte-budgeted filter chunking and REQ packing
- Bounded negentropy concurrency
- Multi-connection escalation and serving-side obligations
Read when: You're changing filter construction, subscription management, or sync concurrency, and need the constraint justification
GRASP-02 Purgatory Git Data Fetching
Proactive git data fetching from remote servers
Topics:
- Identifier-based batching
- Exponential backoff with fresh start
- Domain throttling (5 concurrent, 30/min)
- Debounced delays (3min user, 500ms sync)
- 30-minute expiry
- Mock-based testability
Read when: You want to understand how purgatory automatically fetches missing git data
Unified Git Data Sync
Shared processing for git push and purgatory sync paths
Topics:
- Why unify push and sync processing
- OID syncing to owner repos
- Ref alignment logic
- Event release from purgatory
- WebSocket notification
Read when: You want to understand how git data is processed consistently regardless of arrival method
Monitoring Overview
Prometheus metrics and observability
Topics:
- Metrics philosophy
- Connection tracking
- Git operation metrics
- Nostr event metrics
- Privacy considerations
Read when: You want to understand how to monitor ngit-grasp in production
Defensive Measures & Rate Limiting
Protection against abuse, spam, and denial-of-service attacks
Topics:
- Connection and subscription management
- Event publishing rate limits
- Content filtering (blacklists/whitelists)
- Event validation plugin system (WritePolicy/QueryPolicy)
- Relay health management (naughty list, exponential backoff)
- Privacy-preserving IP tracking
- Future enhancements (per-IP rate limiting)
Read when: You want to understand how ngit-grasp protects against abuse and what defensive features are available
GRASP-05 Archive Mode
Read-only mirroring of repositories
Topics:
- Archive whitelist configuration
- Archive-all mode
- Read-only mode defaults
- Use cases for backup/mirror relays
Read when: You want to understand how to run an archive/backup relay
Repository Lifecycle
Handling repository removal, holding, archive, recovery, and purgatory
Topics:
- Repository lifecycle architecture
- Delete disrespector concept
- Preventing left-pad scenarios
- Archival policies
- Holding, recovery, purgatory, and operator curation flows
Read when: You want to understand how ngit-grasp keeps nostr state and git data aligned across deletion, vanish, moderation, recovery, and purgatory flows
Planned Explanation Documentation
GRASP Protocol Design
Status: 🔜 Planned
Topics:
- Why Nostr for Git?
- Authorization model
- Trust and verification
- Decentralization benefits
Storage Architecture
Status: 🔜 Planned
Topics:
- Why separate Git and Nostr storage?
- Indexing strategy
- Performance considerations
- Scaling approach
Testing Philosophy
Status: 🔜 Planned
Topics:
- Why test isolation?
- Integration vs unit tests
- Compliance testing approach
- Test-driven development
Performance Considerations
Status: 🔜 Planned
Topics:
- Async architecture
- Caching strategy
- Database choices
- Bottlenecks and solutions
How to Use Explanation Documentation
- Read to understand - Not to accomplish a task
- Follow your curiosity - Read what interests you
- Connect concepts - Link ideas together
- Question and explore - Think critically
Not sure if this is what you need?
- Want to learn by doing? → Tutorials
- Need to solve a problem? → How-To Guides
- Looking for technical details? → Reference
Contributing Explanation Documentation
When writing explanation:
DO:
- ✅ Discuss concepts and ideas
- ✅ Provide context and background
- ✅ Explain alternatives
- ✅ Use analogies and examples
- ✅ Connect to broader context
- ✅ Answer "why" questions
DON'T:
- ❌ Provide step-by-step instructions (link to Tutorials/How-To)
- ❌ List technical details (link to Reference)
- ❌ Assume you must be comprehensive
- ❌ Avoid opinions (explanation can be opinionated)
Template:
# Explanation: [Topic]
**Purpose:** [What concept/decision this explains]
**Audience:** [Who wants to understand this]
---
## The Problem/Question
[What are we trying to understand?]
---
## Background
[Context and history]
---
## Our Approach
[How we address it]
### Why This Works
[Explanation of benefits]
### Trade-offs
[What we gain and lose]
---
## Alternatives Considered
### [Alternative 1]
**Pros:**
- [Benefits]
**Cons:**
- [Drawbacks]
**Why we didn't choose it:**
[Reasoning]
---
## Conclusion
[Summary of understanding]
---
## Related Documentation
- [Links to relevant docs]
See Diátaxis: Explanation for detailed guidance.
Part of the ngit-grasp documentation using the Diátaxis framework.