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diff --git a/doc/developer-guide/writing-a-cloudsync-plugin.md b/doc/developer-guide/writing-a-cloudsync-plugin.md new file mode 100644 index 00000000000..907860aaed8 --- /dev/null +++ b/doc/developer-guide/writing-a-cloudsync-plugin.md @@ -0,0 +1,164 @@ +## How to write your Cloudsync Plugin + +### Background + +Cloudsync translator is part of the archival feature in Gluster. This translator +does the retrieval/download part. Each cold file will be archived to a remote +storage (public or private cloud). On future access to the file, it will be +retrieved from the remote storage by Cloudsync translator. Each remote storage +would need a unique plugin. Cloudsync translator will load this plugin and +call the necessary plugin functions. + +Upload can be done by a script or program. There are some basic mandatory steps +for uploading the data. There is a sample script for crawl and upload given at +the end of this guide. + +### Necessary changes to create a plugin + +1. Define store_methods: + +* This structure is the container of basic functions that will be called by + cloudsync xlator. + + typedef struct store_methodds { + int (*fop_download) (call_frame_t *frame, void *config); + /* return type should be the store config */ + void *(*fop_init) (xlator_t *this); + int (*fop_reconfigure) (xlator_t *this, dict_t *options); + void (*fop_fini) (void *config); + } store_methods_t; + + + Member details: + fop_download: + This is the download function pointer. + + frame: This will have the fd to write data downloaded from + cloud to GlusterFS.(frame->local->fd) + + config: This is the plugin configuration variable. + + Note: Structure cs_local_t has member dlfd and dloffset which + can be used to manage the writes to Glusterfs. + Include cloudsync-common.h to access these structures. + + fop_init: + This is similar to xlator init. But here the return value is + the plugin configuration pointer. This pointer will be stored + in the cloudsync private object (priv->stores->config). And + the cloudsync private object can be accessed by "this->private" + where "this" is of type xlator_t. + + fop_reconfigure: + This is similar to xlator_reconfigure. + + fop_fini: + Free plugin resources. + + Note: Store_methods_t is part of cs_private_t which in turn part of + xlator_t. Create a store_methods_t object named "store_ops" in + your plugin. For example + + store_methods_t store_ops = { + .fop_download = aws_download_s3, + .fop_init = aws_init, + .fop_reconfigure = aws_reconfigure, + .fop_fini = aws_fini, + }; + + +2 - Making Cloudsync xlator aware of the plugin: + + Add an entry in to the cs_plugin structure. For example + struct cs_plugin plugins[] = { + { + .name = "amazons3", + .library = "libamazons3.so", + .description = "amazon s3 store." + }, + + {.name = NULL}, + }; + + Description about individual members: + name: name of the plugin + library: This is the shared object created. Cloudsync will load + this library during init. + description: Describe about the plugin. + +3- Makefile Changes in Cloudsync: + + Add <plugin.la> to cloudsync_la_LIBADD variable. + +4 - Configure.ac changes: + + In cloudsync section add the necessary dependency checks for + the plugin. + +5 - Export symbols: + + Cloudsync needs "store_ops" to resolve all plugin functions. + Create a file <plugin>.sym and add write "store_ops" to it. + + +### Sample script for upload +This script assumes amazon s3 is the target cloud and bucket name is +gluster-bucket. User can do necessary aws configuration using command +"aws configure". Currently for amazons3 there are four gluster settings +available. +1- features.s3plugin-seckey -> s3 secret key +2- features.s3plugin-keyid -> s3 key id +3- features.s3plugin-bucketid -> bucketid +4- features.s3plugin-hostname -> hostname e.g. s3.amazonaws.com + +Additionally set cloudsync storetype to amazons3. + +gluster v set <VOLNAME> cloudsync-storetype amazons3 + +Now create a mount dedicated for this upload task. + +That covers necessary configurations needed. + +Below is the sample script for upload. The script will crawl directly on the +brick and will upload those files which are not modified for last one month. +It needs two arguments. +1st arguement - Gluster Brick path +2nd arguement - coldness that is how many days since the file was modified. +3rd argument - dedicated gluster mount point created for uploading. + +Once the cloud setup is done, run the following script on individual bricks. +Note: For an AFR volume, pick only the fully synchronized brick among the +replica bricks. + +``` +target_folder=$1 +coldness=$2 +mnt=$3 + +cd $target_folder +for i in `find . -type f | grep -v "glusterfs" | sed 's/..//'` +do + echo "processing $mnt/$i" + + #check whether the file is already archived + getfattr -n trusted.glusterfs.cs.remote $i &> /dev/null + if [ $? -eq 0 ] + then + echo "file $mnt/$i is already archived" + else + #upload to cloud + aws s3 cp $mnt/$i s3://gluster-bucket/ + mtime=`stat -c "%Y" $mnt/$i` + + #post processing of upload + setfattr -n trusted.glusterfs.csou.complete -v $mtime $mnt/$i + if [ $? -ne 0 ] + then + echo "archiving of file $mnt/$i failed" + else + echo "archiving of file $mnt/$i succeeded" + fi + + fi +done +``` |