nntp-storage

https://github.com/go-while/nntp-storage

nntp-storage provides an interface via channels to read/write usenet
articles from/to storage

Flat file storage stores articles in flat text files: one for head and
one for body.

CacheDir structure creates 3 levels of directories
[0-9a-f]/[0-9a-f]/[0-9a-f]/
Files are stored in format:


"cachedir/[head|body]/[0-9a-f]/[0-9a-f]/[0-9a-f]/"+messageidhash[3:]+".[head|body]"
First 3 chars are cut from hash and used for directories.

Remaining string (missing first 3 chars) is used as filename.[head|body]

Hash of Message-ID should be md5, sha1, sha256 or better.

Choose wisely or a change may break things!

Xref_Linker
is needed to access "article|head|body|stat" via MsgNumber by creating softlinks from constructed Xref info

it creates soft(sym)links to message-ids in

"cachedir/[head|body]/groups/"+grouphash+"/"+"Msgnum"
Xref_linker eats a *redis.Pool as optional argument. If you dont want
redis: set redis_pool to nil and AskRedis = false

If you pass a *redis.Pool to Xref_linker it will create links in redis
as constant (no expiry) key/value.

When crafting read.request: only set .AskRedis = true when

requesting an "article|head|body|stat" via Msgnum, not via message-ID!

If you do xref-linking in redis: better have loads of ram and fast
storage for redis!

Redis killed my test import machine in one night...

redis-db > 30GB started swapping and bg-save will never complete with
default settings

Redis can be enabled later at any time but will only create old entries
on read if wasnt found in redis.
One can choose to disable 'do_softlinks' and run only with redis
but disabling redis later is not possible (yet) because grouphash/msgnum
links do not exist without redis
and there is yet no code to export data from redis and create symlink on filesystem.


flat_storage_reader:
provides 2 channels of type 'storage.ReadReq':

'storage.ReadCache.RC_head_chan'

'storage.ReadCache.RC_body_chan'

type ReadReq struct {
Sessionid string
File_path string
Cli_chan chan ReadItem
Cmdstring string
AskRedis bool
} // end ReadReq struct


Crafting read requests
readreq := storage.ReadReq{}
readreq.Sessionid = "anything"
// the client constructs file_path from message-id hash
readreq.File_path = "/mnt/cache/0/0/0/ffffff.[head|body]"
// create the channel where client will receive reply to readreq readreq.Cli_chan = make(chan storage.ReadItem, 1)
// Cmdstring in lowercase
readreq.Cmdstring = "[article|head|body|stat]"
readreq.AskRedis = false

// choose correct channel to put the read request for head or body

// send read request for head:
storage.ReadCache.RC_head_chan <- readreq

// send read request for body:
storage.ReadCache.RC_body_chan <- readreq

reply := <- readreq.Cli_chan

// when requesting an article:
// craft 2 requests with File_path .[head|body]
// wait for replies on Cli_chan, create one for each request
// and construct the article yourself.

// reply.Fileobj is a type []byte.
// if requesting "stat":
// reply.Fileobj[0] is: 'S' ok OR '0' not found

// do not send the reply.Fileobj as []byte to client!!
// contains LF and no CRLF pair to define end of line.
// get a sendable []string and send lines with CRLF to client
lines := utils.Bytes2Lines(reply.Fileobj)


flat_storage_writer:
provides 2 channels of type 'storage.CacheItem':

'storage.WriteCache.WC_head_chan'

'storage.WriteCache.WC_body_chan'

Pass a CacheItem object with Lines []string or Bytes []byte into the
respective channels and nntp-storage will write head/body to storage.

type CacheItem struct {
Msgidhash string
Head bool
Lines []string // use either []string
Bytes []byte // or []byte but dont supply both!
Size int
} // end CacheItem struct

type ReadItem struct {
Fileobj []byte
Err error
} // end ReadItem struct


Crafting write requests
// storage backend will not count bytes again,
// Size has to be supplied from layer above.

head_part := storage.CacheItem{}
head_part.Msgidhash = sha256(article.messageid)
// if object is a head, set head to true, else leave out or set to false. head_part.Head = true
// Lines of head should be []string, not a MIMEheader map which is sadly
not ordered... :/
head_part.Lines = []string // use either []string
head_part.Bytes = []byte // or []byte but dont supply both! head_part.Size = head.byteSize

body_part := storage.CacheItem{}
body_part.Msgidhash = sha256(article.messageid) // use generated
msgidhash from head if we have it here. else create one!
body_part.Lines = []string // use either []string
body_part.Bytes = []byte // or []byte but dont supply both! body_part.Size = body.byteSize

// pass objects to the correct channels or
// they will get discarded with an error message only
// without interrupting the system!

storage.WriteCache.WC_head_chan <- head_part

storage.WriteCache.WC_body_chan <- body_part


There is no response to sender.

Fire to channel and forget.

Storage writes it, or Houston, we have a problem!



flat_storage.go
/*
* SETUP:
* import ( "github.com/go-while/nntp-storage" )
main() {
cachedir := "/mnt/cache"
bodycache, headcache := true, true
storage.StorageCounter.Make_SC()
storage.Make_cache_dir(cachedir, bodycache, headcache)
} // end main
*
*
*/
flat_storage_reader.go
/*
* SETUP:
* //import ( "github.com/go-while/nntp-storage" )
main() {
rc_debug_flag_head, rc_debug_flag_body := false, false

var redis_pool *redis.Pool = nil
redis_expire := 900 // redis_expire used to cache stat request in redis.
// set redis_expire to -1 to not cache stat requests at all.
// if set to 0 defaults to 300s
// better have some memory for redis!

rc_head_workers, rc_head_ncq := 100, 100000
rc_body_workers, rc_body_ncq := 100, 100000

storage.ReadCache.Load_Readcache(rc_head_workers, rc_head_ncq,
rc_body_workers, rc_body_ncq, redis_pool, redis_expire, rc_debug_flag_head)

if storage.ReadCache.RC_head_chan == nil {
log.Printf("ERROR RC_head_chan=nil")
os.Exit(1)
}
if storage.ReadCache.RC_body_chan == nil {
log.Printf("ERROR RC_body_chan=nil")
os.Exit(1)
}

} // end main
*
*
*/



flat_storage_writer.go
/*
* SETUP:
* //import ( "github.com/go-while/nntp-storage" )
main() {
//cachedir := "/mnt/cache"
cache_index_logdir := "/var/log/cache_index"
wc_debug_flag_head, wc_debug_flag_body := false, false

headcache_workers, headcache_max := 100, 1000000
bodycache_workers, bodycache_max := 100, 1000000

storage.Load_Writecache(headcache_workers, headcache_max,
bodycache_workers, bodycache_max, cachedir, cache_index_logdir, wc_debug_flag_head)

if storage.WriteCache.WC_head_chan == nil {
log.Printf("ERROR WC_head_chan=nil")
os.Exit(1)
}
if storage.WriteCache.WC_body_chan == nil {
log.Printf("ERROR WC_body_chan=nil")
os.Exit(1)
}

} // end main
*
*
*/


xref_linker

Xref Linker creates softlinks
from 'cachedir/[head|body]/groups/grouphash/msgnum'
to 'cachedir/[head|body]/[a-f0-9]/[a-f0-9]/[a-f0-9]/messageidhash[:3].[head|body]'


xref_linker.go
/*
* SETUP:
* //import ( "github.com/go-while/nntp-storage" )
main() {
//cachedir := "/mnt/cache"
workers := 1
// syncwrites limits parallel access to filesystem for xref linking
// can be less than workers, more does nothing.
// you can have more workers pushing to redis and less parallel
syncwrites
syncwrites := workers
queuesize := 100
do_softlinks := true
debug_flag := false
var redis_pool *redis.Pool = nil

storage.XrefLinker.Load_Xref_Linker(workers, syncwrites,
do_softlinks, queuesize, cachedir, redis_pool, debug_flag)

if storage.XrefLinker.Xref_link_chan == nil {
log.Printf("ERROR Xref_link_chan=nil")
os.Exit(1)
}
}
*
*
*/


Contributing
Pull requests are welcome.

For major changes, please open an issue first to discuss what you would
like to change.

License
MIT

Author
go-while

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