Export Hooks: Symlink Exporter

pkg/actions/lua/lakefs/catalogexport/internal.lua

@@ -1,3 +1,4 @@
+local url = require("net/url")
 local DEFAULT_SHORT_DIGEST_LEN=6
 
 local function short_digest(digest, len)
@@ -41,7 +42,17 @@ local function ref_from_branch_or_tag(action_info)
     end
 end
 
+local function parse_storage_uri(uri)
+    local u = url.parse(uri)
+    return { 
+        protocol = u.scheme,
+        bucket = u.host,
+        key = (u.path:sub(0, 1) == "/") and u.path:sub(2) or u.path,
+    }
+end
+
 return {
+    parse_storage_uri=parse_storage_uri,
     short_digest=short_digest,
     ref_from_branch_or_tag=ref_from_branch_or_tag,
     lakefs_object_pager=lakefs_object_pager, 

pkg/actions/lua/lakefs/catalogexport/symlink_exporter.lua

@@ -0,0 +1,108 @@
+local extractor = require("lakefs/catalogexport/table_extractor")
+local hive = require("lakefs/catalogexport/hive")
+local utils = require("lakefs/catalogexport/internal")
+local pathlib = require("path")
+local strings = require("strings")
+local lakefs = require("lakefs")
+
+--[[
+    ### Default Symlink File(s) structure:
+
+    ${storageNamespace}
+    _lakefs/
+        exported/
+            ${ref}/
+                ${commitId}/
+                    ${tableName}/
+                        p1=v1/symlink.txt
+                        p1=v2/symlink.txt
+                        p1=v3/symlink.txt
+                        ...
+]]
+local function get_storage_uri_prefix(storage_ns, commit_id, action_info)
+    local branch_or_tag = utils.ref_from_branch_or_tag(action_info)
+    local sha = utils.short_digest(commit_id)
+    return pathlib.join("/", storage_ns, string.format("_lakefs/exported/%s/%s/", branch_or_tag, sha))
+end
+
+--[[
+    @repo_id: repository id
+    @commit_id: commit id of the current table
+    @table_src_path: path to table spec (i.e _lakefs_tables/my_table.yaml)
+    @options:
+    - skip_trim_obj_base_path(boolean) if true will skip removing the prefix path before the partition path. 
+]]
+local function export_it(repo_id, commit_id, table_src_path, options)
+    local opts = options or {}
+    local descriptor = extractor.get_table_descriptor(lakefs, repo_id, commit_id, table_src_path)
+    if descriptor.type ~= "hive" then
+        error("table " .. descriptor.type .. " in path " .. table_src_path .. " not supported")
+    end
+    if opts.debug then
+        print(string.format('%s table `lakefs://%s/%s/%s`', descriptor.type, repo_id, utils.short_digest(commit_id),
+            descriptor.path))
+    end
+    local base_path = descriptor.path
+    local cols = descriptor.partition_columns
+    local pager = hive.extract_partition_pager(lakefs, repo_id, commit_id, base_path, cols)
+    return function()
+        local part_key, entries = pager()
+        if part_key == nil then
+            return nil
+        end
+        local symlink_data = ""
+        for _, entry in ipairs(entries) do
+            symlink_data = symlink_data .. entry.physical_address .. "\n"
+        end
+        -- create key suffix for symlink file 
+        local storage_key_suffix = part_key
+        if #descriptor.partition_columns == 0 then
+            storage_key_suffix = descriptor.name .. "/" .. "symlink.txt"
+        else
+            if not opts.skip_trim_obj_base_path then
+                storage_key_suffix = strings.replace(part_key, base_path .. "/", "", 1) -- remove base_path prefix from partition path
+            end
+            -- append to partition path to suffix 
+            storage_key_suffix = pathlib.join("/", descriptor.name, storage_key_suffix, "symlink.txt")
+        end
+        return {
+            key_suffix = storage_key_suffix,
+            data = symlink_data
+        }
+    end
+end
+
+--[[
+    export a Symlinks that represent a table to S3 
+    @s3_client: configured client 
+    @table_src_path: object path to the table spec (_lakefs_tables/my_table.yaml)
+    @action_info: the global action object 
+    @options: 
+    - debug(boolean)
+    - export_base_uri(string): override the prefix in S3 i.e s3://other-bucket/path/ 
+    - writer(function(bucket, key, data)): if passed then will not use s3 client, helpful for debug
+]]
+local function export_s3(s3_client, table_src_path, action_info, options)
+    local opts = options or {}
+    local repo_id = action_info.repository_id
+    local commit_id = action_info.commit_id
+    local base_prefix = opts.export_base_uri or action_info.storage_namespace
+    local export_base_uri = get_storage_uri_prefix(base_prefix, commit_id, action_info)
+    local location = utils.parse_storage_uri(export_base_uri)
+    local put_object = opts.writer or s3_client.put_object
+    local it = export_it(repo_id, commit_id, table_src_path, opts)
+    for symlink in it do
+        local key = pathlib.join("/", location.key, symlink.key_suffix)
+        if opts.debug then
+            print("S3 writing bucket: " .. location.bucket .. " key: " .. key)
+        end
+        put_obj(location.bucket, key, symlink.data)
+    end
+    return {
+        location = location
+    }
+end
+
+return {
+    export_s3 = export_s3
+}