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Rewrite the README sentence by sentence (closes #157) 
The old text failed the issue's prose rules: a 60-word sentence on the
content security policy, a markdown table of settings, comma-chained
lists of batch sizes and error codes, undefined jargon and an edge case
in the opening. The new text leads with what RouteWatch is, why it
exists and how to run it, then the pages, the API and the blocklists,
then the settings, memory and upaas, and last the design and the
development workflow. Every statement was checked against the code on
next. The PR body lists where the old text disagreed with the code.

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# RouteWatch
RouteWatch is an MIT-licensed Go daemon by @sneak that keeps a live copy of the
internet's BGP routing table and answers questions about IP addresses over HTTP.
BGP is the protocol by which the networks of the internet tell each other which
addresses they can reach. Each network is an autonomous system, an AS, with a
number such as `AS15169`. A prefix is a block of addresses, such as
`192.0.2.0/24`. A route says which AS announces a prefix and through which ASes
the announcement came. The AS that announces the prefix is its origin AS. The
list of ASes is the AS path.
RouteWatch does three things:
- It streams BGP updates from the RIPE RIS Live service.
- It applies them to a routing table that it keeps in memory, with a copy in a
SQLite database.
- It serves web pages and a JSON API that answer from that table.
## Rationale
RouteWatch exists to serve our other services as an internal API for information
about IP addresses. A service asks RouteWatch instead of working the answer out
for itself.
RIPE runs route collectors around the world. Many routers, the RIS peers, send
the collectors their routes. RIS Live streams every change the collectors
receive, as it happens. RouteWatch applies those changes to its own routing
table. From that table it sees directly:
- which AS each IP address is routed to
- which announced prefix holds the address, and how big that prefix is
- how many peers carry the prefix, and with which origin ASes
RouteWatch adds details of each AS from WHOIS, the public directory of the
internet registries. The details include the organisation that holds the AS and
its abuse contact. RouteWatch keeps them in its database and fetches them again
once they are 30 days old. An IP lookup answers from the stored details and
never waits for WHOIS.
An IP lookup also says which public blocklists list the address (see
Blocklists).
## Getting started
RouteWatch is built to run in Docker. Build the image, which is tagged
`routewatch`:
```bash
script/docker
```
The build runs the tests and the linter first, and fails when either fails. Run
the image:
```bash
docker run --memory=5g --memory-swap=5g -p 8080:8080 \
-v routewatch:/var/lib/berlin.sneak.app.routewatch routewatch
```
The memory limit is explained in Memory. The volume holds the database and the
copies of the blocklists.
To run the binary on the host instead, build it with `make build`. The build
needs Go and a C compiler, because the SQLite library is C:
```bash
make build
./bin/routewatch
```
`make run` builds the binary and runs it with debug logging, with a copy of the
log in `log.txt`.
Then open `http://localhost:8080/` in a browser, or ask about an address:
```bash
curl http://localhost:8080/ip/192.0.2.1
```
The routing table starts empty. RIS Live sends no routing table when a client
connects, only the changes from then on. So the table holds the routes announced
since RouteWatch first started, and it fills as the feed runs. An IP lookup
finds no route for an address until a prefix that holds it is announced. The
database keeps the table across restarts.
## HTTP
Every route answers `HEAD` as it answers `GET`, without the body. The server
listens on `PORT`, `8080` by default.
The pages and the API read routes from the routing table in memory. For each
prefix and origin AS, the table keeps the two newest routes in full, with their
AS paths and times. This document calls them the kept routes. The table keeps
only the address of every other peer that carries the prefix with that origin
AS.
### Web pages
- `/`: the home page. It has a lookup by AS number, a search of AS names and a
lookup by IP address. A card shows the `curl` command that looks up the
visitor's own address, and that command's live answer. Other cards show
figures of the routing table, with links to the AS and prefix pages:
- the newest and the oldest kept route, each with its prefix, origin AS and
time
- the AS most recently seen in an AS path, and the AS seen longest ago
- the AS that originates the most prefixes
- how many ASes originate a single prefix, and the newest kept route of
those ASes
- the number of bogon announcements, linked to `/bogons`
- the number of prefixes with more than one origin AS, linked to
`/multiple-origins`
- fifteen well-known networks, such as Apple, Google, Cogent and MIT, each
with its number of prefixes and the time of its newest kept route, newest
first
RouteWatch works these figures out once a minute, so they can be a minute
old.
- `/as/{asn}`: an AS, the prefixes it originates and the ASes it peers with.
When the database has no record of the AS, its handle and description come
from the AS list built into RouteWatch. The page then shows no first-seen
date.
- `/prefix/{prefix}/{length}`: a prefix, such as `/prefix/192.0.2.0/24`, with
its origin ASes and every peer that carries it. Only the kept routes show an
AS path, a next hop and a time.
- `/prefixlength/{length}`: up to 500 IPv4 prefixes with that mask length,
picked at random. Each shows the origin AS that the most peers carry it with,
and the age of its newest kept route.
- `/prefixlength6/{length}`: the same for IPv6.
- `/bogons`: the bogon announcements. A bogon announcement is a route whose
prefix or origin AS is reserved. Each row shows the prefix, the origin AS, the
number of peers and the reason. The page lists at most 1,000 rows, in prefix
order, and says how many there are in all.
- `/multiple-origins`: the prefixes that more than one origin AS announces. Each
row shows the origin ASes and how many peers carry the prefix with each. The
page lists at most 1,000 rows, in prefix order, and says how many there are in
all.
- `/status`: a dashboard of the figures of `/api/v1/stats`, refreshed every 2
seconds.
A prefix is reserved when it lies inside one of these:
- a block that the IANA special-purpose address registries mark as not globally
reachable
- the multicast space, `224.0.0.0/4` and `ff00::/8`
An AS number is reserved when it is one of these:
- an AS number for private use or for documentation
- `AS23456`, which stands in for a 32-bit AS number
- the last AS number of the 16-bit range or of the 32-bit range
Address space and AS numbers that the IANA has not handed out yet are not
counted.
### JSON API
A JSON answer is `{"status": "ok", "data": ...}`. An error answer is
`{"status": "error", "error": {"msg": ..., "code": ...}}`. Every JSON answer
also carries an `@meta` object:
- `time_zone`: always `UTC`
- `api_version`: `1`
- `execution_time_ms`: the number of milliseconds the request took
Every value with a unit is a number. The unit ends the field name: `_ms`,
`_seconds` or `_bytes`. Every time is in UTC.
The routes:
- `GET /api/v1/ip/{ip}`: what RouteWatch knows about each address in `{ip}`. See
IP lookup below.
- `GET /ip/{addr}`: the same answer as `/api/v1/ip/{ip}`.
- `GET /ip/`: the same answer, for the caller's own address. That is the address
the request came from. For a request from a trusted proxy, it is the client
address in `X-Forwarded-For` (see `TRUSTED_PROXIES` in Configuration).
- `GET /api/v1/as/{asn}`: the AS in `asn`, and the prefixes it originates in
`ipv4_prefixes` and `ipv6_prefixes`, counted in `total_count`. Each prefix has
`last_updated`, the time of its newest kept route with the AS. A prefix that
keeps no route with the AS has no `last_updated`. When the database has no
record of the AS, its handle and description come from the AS list built into
RouteWatch. The answer then has no `first_seen` or `last_seen`.
- `GET /api/v1/prefix/{prefix}/{length}`: the prefix, one route for each peer
that carries it in `routes`, and the same routes grouped by origin AS in
`origins`. `peer_count` and `origin_count` count them. Only the kept routes
have `as_path`, `next_hop` and `last_updated`.
- `GET /api/v1/search/as?q={text}`: the ASes whose handle or description
contains `{text}`, ignoring case. `data` holds:
- `query`: `{text}` without its leading and trailing spaces
- `total`: the number of ASes that match
- `results`: the first 50 of them in AS number order, each with `asn`,
`handle` and `description`
The search reads the AS list built into RouteWatch, not the database. The
list comes from
[ipverse/as-metadata](https://github.com/ipverse/as-metadata). So a match
can be an AS that the database has no record of.
- `GET /status.json`: figures of the feed, the memory, the database and the
routing table. The figures whose names do not say what they mean:
- `uptime_seconds`: the seconds since the feed last connected, or 0 when it
has never connected
- `memory_usage_bytes`: the size of the Go heap in use
- `live_routes`, `ipv4_routes` and `ipv6_routes`: the number of peer and
prefix pairs, where each peer that carries a prefix counts once for it
- `oldest_route` and `newest_route`: the times of the oldest and the newest
kept route
- `origins_without_kept_route`: the number of prefix and origin AS pairs
that peers carry but that keep no route
- `whois_stats.current_interval_seconds`: the WHOIS fetcher's wait between
two fetches, which can include a fraction of a second
- `GET /api/v1/stats`: the `/status.json` figures plus the reconnection count,
and figures of the garbage collector, the stream and the handler queues.
`connection_duration_seconds` is the seconds the feed has been connected, or
null while it is not connected. `stream.route_churn_per_min` is the number of
announcements and withdrawals, from all peers, in the last full clock minute.
- `GET /.well-known/healthcheck.json`: the health check. It answers 200 when the
database answers and the feed is connected, otherwise 503. `data.status` is
`ok` or `error`, and `data.checks` says which check failed. The 503 answer
keeps the `{"status": "ok", "data": ...}` form.
### IP lookup
`{ip}` is an IP address, a host name, or a comma-separated list of at most 10 of
these. A host name is resolved, and only its public addresses are looked up. The
answer holds `query`, the text looked up, and `results`, with one entry for each
address. Every entry has the same fields:
- `ip`: the address
- `ptr`: the names DNS gives for the address, its PTR names, or an empty list
when it has none
- `blocklists`: the public blocklists the address is on (see Blocklists), or an
empty list when it is on none
Every other field is about the address's live route. Each is null when the
address has no live route:
- `netblock`: the most specific prefix that holds the address
- `mask_length`: the netblock's mask length
- `ip_version`: the netblock's IP version, 4 or 6
- `num_peers`: the number of peers that carry the netblock
- `asn`: the origin AS that the most peers carry the netblock with
- `num_origins`: the number of origin ASes that peers carry the netblock with
- `origin_asns`: those origin ASes, in AS number order
- `first_seen`: when RouteWatch first saw the netblock, or null when the
database has not stored the netblock yet
- `last_seen`: the time of the netblock's newest kept route, or null when the
netblock keeps no route
The fields about the AS in `asn` come from the database. Each is null when the
database does not have it:
- `handle`: the AS's handle
- `description`: the AS's description
- `as_name`: the AS's name in its WHOIS details
- `org_name`: the name of the organisation that holds the AS
- `org_id`: the organisation's ID at its registry
- `address`: the organisation's postal address
- `country_code`: the organisation's country code
- `abuse_email`: the address that takes abuse reports for the AS
- `rir`: the regional internet registry of the AS
When a host name fails, `errors` lists it with the reason. A name that does not
resolve is reported as `could not resolve host name`. A name with no public
address, such as one that resolves to a private address, is reported as
`host name has no public address`. The answer is 400 when:
- `{ip}` lists more than 10 addresses and host names
- `{ip}` comes to more than 10 addresses once its names are resolved
- nothing in `{ip}` is an IP address or a host name with a public address
Each PTR lookup gets 2 seconds. An address whose lookup takes longer is answered
without PTR names.
A successful answer carries `Cache-Control` with a `max-age` of 15 minutes, the
shortest blocklist interval. The answer for the caller's own address (`/ip/`) is
`private`, and the others are `public`.
### Errors
- 400, for:
- an AS number, prefix or mask length that does not parse
- a mask length out of range for its IP version
- an AS name search without `q`
- an IP lookup with too many addresses, or none (see IP lookup)
- 404, for:
- AS 0
- an AS that originates no prefix and has no record in the database or in
the AS list built into RouteWatch
- a prefix that no peer carries
- under `/api/v1` and `/ip/`, a path that matches no route, with the message
`Not found`
- 405, with the message `Method not allowed`, for any method other than `GET`
and `HEAD` on the routes under `/api/v1` and `/ip/`, on `/status.json` and on
the health check.
- 500: `Internal server error`. The detail goes to the log.
- 504: `Request timeout`. A request may take 30 seconds. The database reads
behind `/status.json` and `/api/v1/stats` may take 4 seconds.
The pages give these errors as plain text.
### AS 0
An origin AS of 0 means the route has no known origin. Its AS path ends in an AS
set: a group of several ASes, any of which may have originated the route. The 0
appears in these fields:
- `origin_asn` in a route
- `asn` and `origin_asns` in an IP lookup
- the key `0` in a prefix's `origins`
The pages show such a route as having no known origin. `/as/0` answers 404, and
the AS name search never lists AS 0.
### Headers
Every answer carries `Strict-Transport-Security`, `Content-Security-Policy`,
`X-Frame-Options`, `X-Content-Type-Options`, `Referrer-Policy` and
`Permissions-Policy`. The content security policy lets a page load content only
from the server. The pages keep their CSS and JavaScript in inline `<style>` and
`<script>` blocks. Each answer's policy names a random value, a nonce, made for
that answer. The browser applies or runs only the blocks that carry it.
## Blocklists
An IP lookup reports which public blocklists list each address. Each entry in
`blocklists` has:
- `name`: the list's name, from the lists below
- `description`: what being on the list means
- `updated`: when RouteWatch last downloaded the list, or last heard from its
publisher that its copy was current
The lists:
- `dshield`: the 20 networks that DShield saw scan the most targets in the last
three days. From [DShield](https://isc.sans.edu/feeds_doc.html), downloaded
every hour.
- `feodo_tracker`: botnet command-and-control servers. From abuse.ch
[Feodo Tracker](https://feodotracker.abuse.ch/blocklist/), downloaded every 15
minutes.
- `firehol_abusers_30d`: addresses reported for comment, form or forum spam in
the last 30 days. From
[FireHOL](https://iplists.firehol.org/?ipset=firehol_abusers_30d), downloaded
every 5 hours.
- `firehol_level3`: addresses reported for attacks, spyware or viruses in the
last 30 days. From
[FireHOL](https://iplists.firehol.org/?ipset=firehol_level3), downloaded every
3 hours.
- `spamhaus_drop` and `spamhaus_dropv6`: IPv4 and IPv6 networks hijacked or
leased by spammers or cyber criminals, according to Spamhaus. From
[Spamhaus DROP](https://www.spamhaus.org/blocklists/do-not-route-or-peer/),
downloaded once a day.
- `tor_exits`: Tor exit nodes, where traffic from the Tor network leaves. From
the [Tor Project](https://check.torproject.org/torbulkexitlist), downloaded
every hour.
No list is downloaded more often than its publisher updates it or allows. Each
can be downloaded whole without an account or a key.
How RouteWatch keeps the lists:
- It holds each list in memory, so a lookup makes no outside request.
- It keeps a copy of each list in the `blocklists` directory of the state
directory (see Configuration). Each copy is a file named after its list.
- Beside each copy, a file ending in `.validators` keeps the `Last-Modified` and
`ETag` headers the publisher sent with that copy.
- At startup it loads each list from its copy. It downloads a list at once when
the copy is older than the list's interval, or when there is no copy.
- A download sends the copy's `Last-Modified` as `If-Modified-Since` and its
`ETag` as `If-None-Match`. The publisher then sends the list only when it has
changed.
- A download fails when it takes over a minute or its file is over 16 MiB.
- When a download fails, or its file does not parse, RouteWatch keeps the
previous copy and logs the failure. It tries again one interval later.
## Configuration
RouteWatch reads its settings from environment variables. It takes no
command-line flags.
- `PORT`: the port the HTTP server listens on. A whole number from 1 to 65535.
Default `8080`.
- `DEBUG`: set it to `routewatch` for debug logging. The daemon then also logs a
`System stats` line every 60 seconds, with the goroutine count and the Go
memory figures. Default empty.
- `TRUSTED_PROXIES`: the reverse proxies whose `X-Forwarded-For` header the
server believes. See below. Default: the private ranges of RFC 1918.
- `XDG_DATA_HOME`: the base of the state directory on Linux and the BSDs, when
RouteWatch does not run as root. It must be an absolute path. The Docker image
sets `/var/lib`.
- `GOMEMLIMIT`: the Go runtime's soft memory limit. The Docker image sets
`2560MiB`. See Memory.
- `MALLOC_ARENA_MAX`: the number of memory pools of the C library. A positive
whole number. The Docker image sets `2`. See Memory.
A variable set to an invalid value stops the start with an error and a non-zero
exit. An empty variable counts as unset. `TRUSTED_PROXIES` is the one exception:
set but empty, it makes the server trust no proxy.
`TRUSTED_PROXIES` works like this:
- When it is not set, the server trusts `10.0.0.0/8`, `172.16.0.0/12` and
`192.168.0.0/16`.
- When it lists addresses and CIDR ranges, comma-separated, such as
`10.0.0.0/8,192.0.2.1`, the server trusts those instead.
- When it is set but empty (`TRUSTED_PROXIES=`), the server trusts no proxy.
For a request from a trusted proxy, the request log and `/ip/` use the last
address in `X-Forwarded-For` that is not a trusted proxy. Each proxy adds the
address it received the request from to the end of the header. The entries
before that are whatever the client sent. For a request from any other address,
the log and `/ip/` use the address the request came from, whatever headers it
carries. `X-Real-IP` and `True-Client-IP` are not read.
The state directory holds the database, `db.sqlite`, and the blocklist copies:
- macOS: `~/Library/Application Support/berlin.sneak.app.routewatch/`
- Linux and the BSDs, as root: `/var/lib/berlin.sneak.app.routewatch/`
- Linux and the BSDs, as another user:
`$XDG_DATA_HOME/berlin.sneak.app.routewatch/`, or
`~/.local/share/berlin.sneak.app.routewatch/` when `XDG_DATA_HOME` is not set
- the Docker image: `/var/lib/berlin.sneak.app.routewatch/`
RouteWatch logs to standard output. It writes text when standard output is a
terminal, and JSON lines otherwise.
## Memory
The daemon keeps the whole routing table in memory. The Docker image sets
ceilings that keep it inside a 5 GiB container. Run the container with a memory
limit of 5 GiB and swap disabled:
```bash
docker run --memory=5g --memory-swap=5g ...
```
That leaves room above the ceilings for spikes and for the kernel's page cache.
The ceilings add up to 3.7 GiB:
- The Go heap: a 2.5 GiB soft limit, `GOMEMLIMIT=2560MiB`. The routing table
takes about 700 bytes for each prefix and origin AS pair. A full table has
about 1.4 million pairs, so it takes about 1 GB. The handlers' batches and
queues take up to about 0.5 GiB. The remaining 1 GiB is room for the garbage
collector. With much less, it would run almost all the time.
- SQLite: 1 GiB. The connection that does every write has a 512 MiB page cache,
the database pages it keeps in memory. It keeps the pages the writes touch
from one write to the next. The `routes` table of a full routing table takes
about 450 MB, so its pages fit. Each of the 9 reading connections has 16 MiB.
A 768 MiB soft heap limit sits above the caches, so it does not shrink them. A
1 GiB hard heap limit caps the SQLite library.
- About 0.2 GiB for everything else in the runtime.
The SQLite library gets its memory from the C library, glibc. glibc keeps freed
memory in pools called arenas, and hands it back to the kernel slowly. It
creates up to eight arenas per processor core. So on a host with many cores the
process holds far more memory than SQLite uses. `MALLOC_ARENA_MAX=2` caps the
arenas at two. Database writes already run one at a time, so two arenas cost
nothing.
What happens at each limit:
- The Go soft limit: as the heap nears `GOMEMLIMIT`, the runtime collects
garbage more often rather than growing further.
- The SQLite soft heap limit: SQLite recycles its page cache instead of
allocating more.
- The SQLite hard heap limit: a statement fails with an out-of-memory error,
which the handler logs. The prefix handler writes the routing table's changes
again in a later write. The other handlers drop their batch. The process keeps
running.
- The handler queues: each of the four handlers has a queue of at most 20,000
messages. When a queue fills, the streamer drops messages instead of waiting.
The exception is a `STATE` message, which it holds, in feed order, until there
is room. These are a few hundred bytes each, about ten a second.
- The handler batches: while the AS, peer or prefix handler writes a batch to
the database, the updates that arrive collect in its next batch. That batch
stops at ten times the batch size:
- 300,000 updates for the AS handler, about 10 MiB
- 100,000 for the peer handler, about 10 MiB
- 250,000 for the prefix handler, about 15 MiB
The handler then takes nothing more off its queue until the write ends. The
queue fills, and the streamer drops messages as above.
To replace the image's Go soft limit, set `GOMEMLIMIT` in the environment, for
example `-e GOMEMLIMIT=3GiB`. A limit close to the routing table's size makes
the garbage collector run almost all the time. `MALLOC_ARENA_MAX` can be
replaced the same way, but raising it lets the process grow again on a host with
many cores.
## Running under upaas
What the [upaas](https://git.eeqj.de/sneak/upaas) app needs:
- Container port: `8080`.
- Volume: one, at the container path `/var/lib/berlin.sneak.app.routewatch`.
- Environment: nothing. The server trusts a reverse proxy at a private address
without `TRUSTED_PROXIES`. Set it only when the proxy connects from another
address. Leave `XDG_DATA_HOME`, `GOMEMLIMIT` and `MALLOC_ARENA_MAX` at the
image's values. `DEBUG=routewatch` is optional.
- Memory limit: `5g`. upaas sets no swap limit, so on a host with swap Docker
allows the same amount of swap again.
- Health check: the image's `HEALTHCHECK` requests
`/.well-known/healthcheck.json` on the container port. upaas reads the
container's health 60 seconds after a deploy and fails the deploy unless it is
`healthy`. In those 60 seconds, Docker 25 and later runs the check every 5
seconds, and the first pass makes the container healthy. Startup first reads
the routing table from the database, which takes about 25 seconds when the
table is full.
- Stop grace: upaas gives the container 10 seconds between `SIGTERM` and
`SIGKILL`, as `docker stop` does by default. The daemon needs 9. See Shutdown
under Design for what a stop writes and what it can lose.
## Design
### Parts
`internal/routewatch/app.go` builds and starts these parts:
- The streamer connects to RIS Live, reads the JSON stream and parses the BGP
messages. It gives each message to the handlers that want it, through one
queue per handler.
- The prefix handler keeps the routing table in memory current. Every second it
writes the table's changes to the `routes` table of the database. It also
stores each new prefix with the time it was first seen.
- The AS handler records every AS seen in an AS path in the `asns` table, with
the times it was first and last seen.
- The peer handler records every peer in the `bgp_peers` table.
- The peering handler takes the pairs of neighbouring ASes out of the AS paths
and writes them to the `peerings` table every 30 seconds.
- The WHOIS fetcher fetches the details of one AS at a time: those never
fetched, and those fetched more than 30 days ago. An IP lookup that finds an
AS with old details asks for it next. The fetcher waits between fetches. The
wait halves after a success, down to 1 second, and grows by half after a
failure, up to a minute.
- The blocklists part downloads the blocklists and answers which lists hold an
address.
- The database maintainer checkpoints the database every 5 seconds: it folds the
write-ahead log into the database file. It reclaims free space every 10
minutes and refreshes the query statistics every hour.
- The HTTP server serves the pages and the API. It reads routes from the routing
table in memory, and everything else from the database.
The parts are built and wired together with the `fx` library.
### The routing table
`internal/routetable` holds the whole routing table. For each prefix and origin
AS it keeps:
- every peer whose current route to the prefix has that origin AS, as one bit
per peer
- the two newest of those routes in full, with their AS paths and times
The prefix handler applies each update as it handles it:
- An announcement gives the peer a route to the prefix. A peer carries a prefix
with one origin AS at most.
- A withdrawal removes the peer's route. So does an announcement whose AS path
is empty or holds AS 0 anywhere.
- A `STATE` message that says the peer's BGP session went down removes every
route of the peer.
- Within one message, the withdrawals are applied before the announcements.
The address lookup finds the most specific prefix that holds the address. It
looks the address up at each mask length, longest first: at most 25 lookups for
IPv4 and 113 for IPv6. Prefixes shorter than `/8` for IPv4 or `/16` for IPv6,
such as a default route, are not used.
The database's `routes` table has one row for each prefix and origin AS. Every
second the prefix handler writes the pairs that changed, at most 20,000 in one
write. The rest follow in the next writes. Startup reads the whole table back
into memory before the streamer connects. A full table takes about 25 seconds to
read. A crash loses only the changes not yet written.
### What the table can miss
RIS Live sends no routing table when a client connects, so the table holds only
the routes announced since RouteWatch first started. It also misses:
- the updates sent while RouteWatch is stopped
- the updates RouteWatch drops when it falls behind (see Feed handling)
- the updates lost at a stop (see Shutdown)
A lookup or a prefix page can therefore show a route that has since been
withdrawn.
Peers are known by their IP address, and a peer can have sessions on two
collectors. When its session on one goes down, the routes the other still
carries are removed too, until they are announced again.
### Feed handling
The streamer reads the stream line by line. Each line is one message as JSON. It
passes an `UPDATE` or `STATE` message to each handler that wants it, through
that handler's queue of 20,000 messages. When a queue is more than half full,
the streamer drops a share of the messages for that handler. The share rises
from none at half full to all at full. A `STATE` message is never dropped. One
that finds the queue full is held until there is room, and the handler's other
messages are dropped until the held ones are in.
The AS, peer and prefix handlers write to the database in batches. A batch is
written when it is full, or when its time is up:
- the AS handler: 30,000 updates, or after 2 seconds
- the peer handler: 10,000 updates, or after 2 seconds
- the prefix handler: 25,000 updates, or after 1 second
The peering handler writes every 30 seconds.
### Reconnection
Any end of the stream other than a shutdown marks the feed disconnected. That
includes RIS Live ending the response normally, and a stream that sends no line
for 60 seconds. The streamer then reconnects after a wait. The wait starts at 5
seconds and doubles each time, up to 320 seconds. A stream that lasted more than
30 seconds resets the wait to 5 seconds.
### Shutdown
On `SIGTERM` or `SIGINT` the daemon stops its parts in this order:
1. the streamer
2. the handlers, each of which writes what it holds
3. the WHOIS fetcher
4. the database maintainer
5. the blocklist downloads
6. the HTTP server
Last, the daemon checkpoints and closes the database. It gives all this 8
seconds and exits with status 0. When RouteWatch stops on an error, it exits
with status 1.
What a stop can lose:
- The prefix handler's last write takes at most 20,000 of the routing table's
changed pairs. A full-table peer's session going down changes about a million
pairs, which take about a minute to write. A stop in that minute leaves the
rest unwritten.
- A lost withdrawal or peer down leaves its routes in the `routes` table, and
the next start reads them back. They stay until the peer sends another update
for the prefix, or its session goes down.
- When the 8 seconds run out, the streamer and the handlers log what they could
not hand over or write. The database is then not closed. When it next opens,
SQLite rolls back any write the exit cut off.
### Code layout
```
routewatch/
├── cmd/
│ ├── routewatch/ # The daemon's entry point
│ ├── asinfo-gen/ # Builds the AS list built into RouteWatch
│ └── streamdumper/ # Prints the raw RIS Live stream, for debugging
├── internal/
│ ├── blocklist/ # Public IP blocklists: downloads and lookups
│ ├── bogon/ # Reserved prefixes and AS numbers
│ ├── config/ # Settings from the environment
│ ├── database/ # SQLite storage
│ ├── logger/ # Structured logging
│ ├── metrics/ # Feed and route update figures
│ ├── ristypes/ # The RIS Live message types
│ ├── routetable/ # The whole routing table in memory
│ ├── routewatch/ # The daemon: startup, handlers, WHOIS fetcher
│ ├── server/ # HTTP server, pages and API
│ ├── streamer/ # RIS Live client
│ ├── templates/ # HTML templates
│ ├── version/ # Build version information
│ └── whois/ # WHOIS lookups of AS details
└── pkg/
└── asinfo/ # The AS list built into RouteWatch
```
### Database schema
```sql
asns(asn PRIMARY KEY, handle, description,
as_name, org_name, org_id, address, country_code, abuse_email,
abuse_phone, tech_email, tech_phone, rir, rir_registration_date,
rir_last_modified, whois_raw,
first_seen, last_seen, whois_updated_at)
prefixes_v4(prefix PRIMARY KEY, first_seen) WITHOUT ROWID
prefixes_v6(prefix PRIMARY KEY, first_seen) WITHOUT ROWID
-- The routing table, one row per prefix and origin AS that some peer
-- carries: the peer set, and the newest two routes in full
routes(prefix, origin_asn, peers,
newest_peer, newest_as_path, newest_time,
older_peer, older_as_path, older_time,
PRIMARY KEY (prefix, origin_asn)) WITHOUT ROWID
-- The peers of the routes table, each with its number in the peer sets
route_peers(number PRIMARY KEY, address UNIQUE)
peerings(id PRIMARY KEY, as_a, as_b, first_seen, last_seen,
UNIQUE(as_a, as_b))
bgp_peers(id PRIMARY KEY, peer_ip UNIQUE, peer_asn, first_seen, last_seen,
last_message_type)
-- Nothing in the daemon writes this table
announcements(id PRIMARY KEY, prefix_id, peer_asn, origin_asn, path,
next_hop, timestamp, is_withdrawal)
```
The indexes are in `internal/database/schema.sql`.
## Development
The `make` targets:
- `make setup`: make a fresh clone ready for development
- `make test`: run the tests
- `make lint`: run the linter
- `make fmt`: format the Go code and the markdown
- `make check`: run the tests, the linter and the format check
- `make build`: build `bin/routewatch`
- `make run`: build the binary and run it with debug logging
- `make docker`: build the Docker image
- `make asupdate`: rebuild the AS list built into RouteWatch
The tests and the linter run only in Docker, as the `test` and `lint` phases of
the `Dockerfile`. The image cannot be built unless both pass. Every
`docker build` in `script/` passes a new `CACHEBUST` value, so each run executes
every check. Go's build cache and the linter's cache are kept between builds.
The test suite runs with `-short`, which skips `TestRouteWatchLiveFeed`. That
test streams the live feed for a few seconds. No `make` target runs it. To run
it, call `go test -run TestRouteWatchLiveFeed ./internal/routewatch/` without
`-short`.
`TODO.md` holds the working list: the next step, the steps done and the steps
planned.
### Entrypoints
This repository adheres to the
[Scripts to Rule Them All](https://github.com/github/scripts-to-rule-them-all)
standard: the scripts in `script/` are the entrypoints of the development
workflow, and the `Makefile` targets call them. The scripts:
- `script/bootstrap`: install the development dependencies: git, make, Go, the
pinned node and yarn, prettier from `yarn.lock`, and the Go modules.
- `script/setup`: make a fresh clone ready for development. It runs
`script/bootstrap`, then `script/install-precommit`.
- `script/projectname`: print the project name, `routewatch`, which
`script/docker` uses as the image tag.
- `script/test`: build the `test` phase of the `Dockerfile` alone. It runs
`go test -short -count=1 -timeout 90s -race -cover ./...`, and reruns it with
`-v` on failure.
- `script/lint`: build the `lint` phase of the `Dockerfile` alone. It runs
golangci-lint v2.14.0 with `.golangci.yml`.
- `script/fmt`: format the Go code with `go fmt` and the markdown with prettier.
It writes.
- `script/fmt-check`: check the formatting without writing.
- `script/check`: run `script/test`, `script/lint` and `script/fmt-check`.
- `script/docker`: build the Docker image, tagged `routewatch`.
- `script/cibuild`: the CI entrypoint. It runs `script/bootstrap` and
`script/check`, then builds the image.
- `script/precommit`: the pre-commit gate. It runs `go mod tidy` and `go fmt`,
then `script/check`. `go mod tidy` must leave `go.mod` and `go.sum` unchanged;
`go fmt` writes.
- `script/install-precommit`: install the git pre-commit hook that runs
`script/precommit`.
- `script/asupdate`: rebuild the AS list built into RouteWatch,
`pkg/asinfo/asdata.json.gz`, from the `as.csv` file of
[ipverse/as-metadata](https://github.com/ipverse/as-metadata). It needs the
network. When the generator finds no AS, the old list stays and the script
exits non-zero.
## License
MIT. See [`LICENSE`](LICENSE).
## Author
[@sneak](https://sneak.berlin)
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