1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
|
## requesting content
In some situations, nodes only want particular files, and not everything.
(Or don't have the bandwidth to get everything.) A way to handle this,
that should work in a fully ad-hoc, offline distributed network,
suggested by Vincenzo Tozzi:
* Nodes generate a request for a specific file they want, committed
to git somewhere.
* This request has a TTL (of eg 3 or 4).
* When syncing, copy the requests that a node has, and decrease their TTL
by 1. Requests with a TTL of 0 have timed out and are not copied.
(So, requests are stored in git, but on eg, per-node branches.)
* Only copy content to nodes that have a request for it (either one
originating with them, or one they copied from another node).
* Each request indicates the requesting node, so once no nodes have an
active request for a particular file, it's ok to drop it from the
transfer nodes (honoring numcopies etc of course).
A simulation of a network using this method is in [[simroutes.hs]]
## storing requests
Requests could be stored in the location tracking file.
Currently:
time 0|1 uuid1
time 0|1 uuid2
* Use negative numbers for the TTL of a request.
* To propigate a request, set -1 * (TTL+1) in the line
for the uuid of the repository that is propigating it.
This should be done as part of the git-annex branch merging,
so if a location tracking file is merged, any open requests
get propigated to the current repository.
* When a requested file reaches a node that requested it,
the location is set to 1; this automatically clears the
request.
## generating requests
git annex request [file...]
Indicates that the file is wanted in the current repository.
(git annex get could also do this on failure, or suggest doing this)
## acting on requests
Add a preferred content expression that looks at request data:
requestedby=N
Matches files that have been requested by at least N nodes.
requested
Matches files that the current node has requested.
|
