seaweedfs/docs/usecases.rst
2015-02-03 00:31:39 +08:00

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Use cases
===================
Saving image with different sizes
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Each image usually store one file key in database. However, one image can have several versions, e.g., thumbnail, small, medium, large, original. And each version of the same image will have a file key. It's not ideal to store all the keys.
One way to resolve this is here.
Reserve a set of file keys, for example, 5
.. code-block:: bash
curl http://<host>:<port>/dir/assign?count=5
{"fid":"3,01637037d6","url":"127.0.0.1:8080","publicUrl":"localhost:8080","count":5}
Save the 5 versions of the image to the volume server. The urls for each image can be:
.. code-block:: bash
http://<url>:<port>/3,01637037d6
http://<url>:<port>/3,01637037d6_1
http://<url>:<port>/3,01637037d6_2
http://<url>:<port>/3,01637037d6_3
http://<url>:<port>/3,01637037d6_4
Overwriting mime types
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The correct way to send mime type:
.. code-block:: bash
curl -F "file=@myImage.png;type=image/png" http://127.0.0.1:8081/5,2730a7f18b44
The wrong way to send it:
.. code-block:: bash
curl -H "Content-Type:image/png" -F file=@myImage.png http://127.0.0.1:8080/5,2730a7f18b44
Securing Seaweed-FS
#############################
The simple way is to front all master and volume servers with firewall.
However, if blocking servicing port is not feasible or trivial, a white list option can be used. Only traffic from the white list IP addresses have write permission.
.. code-block:: bash
weed master -whiteList="::1,127.0.0.1"
weed volume -whiteList="::1,127.0.0.1"
# "::1" is for IP v6 localhost.
Data Migration Example
#############################
.. code-block:: bash
weed master -mdir="/tmp/mdata" -defaultReplication="001" -ip="localhost" -port=9334
weed volume -dir=/tmp/vol1/ -mserver="localhost:9334" -ip="localhost" -port=8081
weed volume -dir=/tmp/vol2/ -mserver="localhost:9334" -ip="localhost" -port=8082
weed volume -dir=/tmp/vol3/ -mserver="localhost:9334" -ip="localhost" -port=8083
.. code-block:: bash
ls vol1 vol2 vol3
vol1:
1.dat 1.idx 2.dat 2.idx 3.dat 3.idx 5.dat 5.idx
vol2:
2.dat 2.idx 3.dat 3.idx 4.dat 4.idx 6.dat 6.idx
vol3:
1.dat 1.idx 4.dat 4.idx 5.dat 5.idx 6.dat 6.idx
stop all of them
move vol3/* to vol1 and vol2
it is ok to move x.dat and x.idx from one volumeserver to another volumeserver,
because they are exactly the same.
it can be checked by md5.
.. code-block:: bash
md5 vol1/1.dat vol2/1.dat
MD5 (vol1/1.dat) = c1a49a0ee550b44fef9f8ae9e55215c7
MD5 (vol2/1.dat) = c1a49a0ee550b44fef9f8ae9e55215c7
md5 vol1/1.idx vol2/1.idx
MD5 (vol1/1.idx) = b9edc95795dfb3b0f9063c9cc9ba8095
MD5 (vol2/1.idx) = b9edc95795dfb3b0f9063c9cc9ba8095
.. code-block:: bash
ls vol1 vol2 vol3
vol1:
1.dat 1.idx 2.dat 2.idx 3.dat 3.idx 4.dat 4.idx 5.dat 5.idx 6.dat 6.idx
vol2:
1.dat 1.idx 2.dat 2.idx 3.dat 3.idx 4.dat 4.idx 5.dat 5.idx 6.dat 6.idx
vol3:
start
.. code-block:: bash
weed master -mdir="/tmp/mdata" -defaultReplication="001" -ip="localhost" -port=9334
weed volume -dir=/tmp/vol1/ -mserver="localhost:9334" -ip="localhost" -port=8081
weed volume -dir=/tmp/vol2/ -mserver="localhost:9334" -ip="localhost" -port=8082
so we finished moving data of localhost:8083 to localhost:8081/localhost:8082