add environment variables to all command flags

Author: maorfr

README.md

@@ -55,15 +55,14 @@ Usage:
   cain backup [flags]
 
 Flags:
-  -b, --buffer-size float           in memory buffer size (MB) to use for files copy (buffer per file) (default 6.75)
+  -b, --buffer-size float           in memory buffer size (MB) to use for files copy (buffer per file). Overrides $CAIN_BUFFER_SIZE (default 6.75)
       --cassandra-data-dir string   cassandra data directory. Overrides $CAIN_CASSANDRA_DATA_DIR (default "/var/lib/cassandra/data")
-  -c, --container string            container name to act on (default "cassandra")
-      --dst string                  destination to backup to. Example: s3://bucket/cassandra
-  -h, --help                        help for backup
-  -k, --keyspace string             keyspace to act on
-  -n, --namespace string            namespace to find cassandra cluster
-  -p, --parallel int                number of files to copy in parallel. set this flag to 0 for full parallelism (default 1)
-  -l, --selector string             selector to filter on
+  -c, --container string            container name to act on. Overrides $CAIN_CONTAINER (default "cassandra")
+      --dst string                  destination to backup to. Example: s3://bucket/cassandra. Overrides $CAIN_DST
+  -k, --keyspace string             keyspace to act on. Overrides $CAIN_KEYSPACE
+  -n, --namespace string            namespace to find cassandra cluster. Overrides $CAIN_NAMESPACE (default "default")
+  -p, --parallel int                number of files to copy in parallel. set this flag to 0 for full parallelism. Overrides $CAIN_PARALLEL (default 1)
+  -l, --selector string             selector to filter on. Overrides $CAIN_SELECTOR (default "app=cassandra")
 ```
 
 #### Examples
@@ -106,18 +105,17 @@ Usage:
   cain restore [flags]
 
 Flags:
-  -b, --buffer-size float           in memory buffer size (MB) to use for files copy (buffer per file) (default 6.75)
+  -b, --buffer-size float           in memory buffer size (MB) to use for files copy (buffer per file). Overrides $CAIN_BUFFER_SIZE (default 6.75)
       --cassandra-data-dir string   cassandra data directory. Overrides $CAIN_CASSANDRA_DATA_DIR (default "/var/lib/cassandra/data")
-  -c, --container string            container name to act on (default "cassandra")
-  -h, --help                        help for restore
-  -k, --keyspace string             keyspace to act on
-  -n, --namespace string            namespace to find cassandra cluster
-  -p, --parallel int                number of files to copy in parallel. set this flag to 0 for full parallelism (default 1)
-  -s, --schema string               schema version to restore (optional)
-  -l, --selector string             selector to filter on
-      --src string                  source to restore from. Example: s3://bucket/cassandra/namespace/cluster-name
-  -t, --tag string                  tag to restore
-      --user-group string           user and group who should own restored files (default "cassandra:cassandra")
+  -c, --container string            container name to act on. Overrides $CAIN_CONTAINER (default "cassandra")
+  -k, --keyspace string             keyspace to act on. Overrides $CAIN_KEYSPACE
+  -n, --namespace string            namespace to find cassandra cluster. Overrides $CAIN_NAMESPACE (default "default")
+  -p, --parallel int                number of files to copy in parallel. set this flag to 0 for full parallelism. Overrides $CAIN_PARALLEL (default 1)
+  -s, --schema string               schema version to restore (optional). Overrides $CAIN_SCHEMA
+  -l, --selector string             selector to filter on. Overrides $CAIN_SELECTOR (default "app=cassandra")
+      --src string                  source to restore from. Example: s3://bucket/cassandra/namespace/cluster-name. Overrides $CAIN_SRC
+  -t, --tag string                  tag to restore. Overrides $CAIN_TAG
+      --user-group string           user and group who should own restored files. Overrides $CAIN_USER_GROUP (default "cassandra:cassandra")
 ```
 
 #### Examples
@@ -158,12 +156,11 @@ Usage:
   cain schema [flags]
 
 Flags:
-  -c, --container string   container name to act on (default "cassandra")
-  -h, --help               help for schema
-  -k, --keyspace string    keyspace to act on
-  -n, --namespace string   namespace to find cassandra cluster
-  -l, --selector string    selector to filter on
-      --sum                print only checksum
+  -c, --container string   container name to act on. Overrides $CAIN_CONTAINER (default "cassandra")
+  -k, --keyspace string    keyspace to act on. Overrides $CAIN_KEYSPACE
+  -n, --namespace string   namespace to find cassandra cluster. Overrides $CAIN_NAMESPACE (default "default")
+  -l, --selector string    selector to filter on. Overrides $CAIN_SELECTOR (default "app=cassandra")
+      --sum                print only checksum. Overrides $CAIN_SUM
 ```
 
 #### Examples
@@ -182,6 +179,30 @@ cain schema \
     --sum
 ```
 
+## Environment variables support
+
+Cain commands support the usage of environment variables instead of flags. For example:
+The `backup` command can be executed as mentioned in the example:
+
+```
+cain backup \
+    -n default \
+    -l release=cassandra \
+    -k keyspace \
+    --dst s3://db-backup/cassandra
+```
+
+You can also set the appropriate envrionment variables (CAIN_FLAG, _ instead of -):
+
+```
+export CAIN_NAMESPACE=default
+export CAIN_SELECTOR=release=cassandra
+export CAIN_KEYSPACE=keyspace
+export CAIN_DST=s3://db-backup/cassandra
+
+cain backup
+```
+
 ## Support for additional storage services
 
 Since Cain uses [Skbn](https://github.com/nuvo/skbn), adding support for additional storage services is simple. Read [this post](https://medium.com/nuvo-group-tech/copy-files-and-directories-between-kubernetes-and-s3-d290ded9a5e0) for more information.

cmd/cain.go

@@ -89,14 +89,14 @@ func NewBackupCmd(out io.Writer) *cobra.Command {
 	}
 	f := cmd.Flags()
 
-	f.StringVarP(&b.namespace, "namespace", "n", "", "namespace to find cassandra cluster")
-	f.StringVarP(&b.selector, "selector", "l", "", "selector to filter on")
-	f.StringVarP(&b.container, "container", "c", "cassandra", "container name to act on")
-	f.StringVarP(&b.keyspace, "keyspace", "k", "", "keyspace to act on")
-	f.StringVar(&b.dst, "dst", "", "destination to backup to. Example: s3://bucket/cassandra")
-	f.IntVarP(&b.parallel, "parallel", "p", 1, "number of files to copy in parallel. set this flag to 0 for full parallelism")
-	f.Float64VarP(&b.bufferSize, "buffer-size", "b", 6.75, "in memory buffer size (MB) to use for files copy (buffer per file)")
-	f.StringVarP(&b.cassandraDataDir, "cassandra-data-dir", "", utils.GetStringEnvVar("CAIN_CASSANDRA_DATA_DIR", "/var/lib/cassandra/data"), "cassandra data directory. Overrides $CAIN_CASSANDRA_DATA_DIR")
+	f.StringVarP(&b.namespace, "namespace", "n", utils.GetStringEnvVar("CAIN_NAMESPACE", "default"), "namespace to find cassandra cluster. Overrides $CAIN_NAMESPACE")
+	f.StringVarP(&b.selector, "selector", "l", utils.GetStringEnvVar("CAIN_SELECTOR", "app=cassandra"), "selector to filter on. Overrides $CAIN_SELECTOR")
+	f.StringVarP(&b.container, "container", "c", utils.GetStringEnvVar("CAIN_CONTAINER", "cassandra"), "container name to act on. Overrides $CAIN_CONTAINER")
+	f.StringVarP(&b.keyspace, "keyspace", "k", utils.GetStringEnvVar("CAIN_KEYSPACE", ""), "keyspace to act on. Overrides $CAIN_KEYSPACE")
+	f.StringVar(&b.dst, "dst", utils.GetStringEnvVar("CAIN_DST", ""), "destination to backup to. Example: s3://bucket/cassandra. Overrides $CAIN_DST")
+	f.IntVarP(&b.parallel, "parallel", "p", utils.GetIntEnvVar("CAIN_PARALLEL", 1), "number of files to copy in parallel. set this flag to 0 for full parallelism. Overrides $CAIN_PARALLEL")
+	f.Float64VarP(&b.bufferSize, "buffer-size", "b", utils.GetFloat64EnvVar("CAIN_BUFFER_SIZE", 6.75), "in memory buffer size (MB) to use for files copy (buffer per file). Overrides $CAIN_BUFFER_SIZE")
+	f.StringVar(&b.cassandraDataDir, "cassandra-data-dir", utils.GetStringEnvVar("CAIN_CASSANDRA_DATA_DIR", "/var/lib/cassandra/data"), "cassandra data directory. Overrides $CAIN_CASSANDRA_DATA_DIR")
 
 	return cmd
 }
@@ -161,17 +161,17 @@ func NewRestoreCmd(out io.Writer) *cobra.Command {
 	}
 	f := cmd.Flags()
 
-	f.StringVar(&r.src, "src", "", "source to restore from. Example: s3://bucket/cassandra/namespace/cluster-name")
-	f.StringVarP(&r.keyspace, "keyspace", "k", "", "keyspace to act on")
-	f.StringVarP(&r.tag, "tag", "t", "", "tag to restore")
-	f.StringVarP(&r.schema, "schema", "s", "", "schema version to restore (optional)")
-	f.StringVarP(&r.namespace, "namespace", "n", "", "namespace to find cassandra cluster")
-	f.StringVarP(&r.selector, "selector", "l", "", "selector to filter on")
-	f.StringVarP(&r.container, "container", "c", "cassandra", "container name to act on")
-	f.IntVarP(&r.parallel, "parallel", "p", 1, "number of files to copy in parallel. set this flag to 0 for full parallelism")
-	f.Float64VarP(&r.bufferSize, "buffer-size", "b", 6.75, "in memory buffer size (MB) to use for files copy (buffer per file)")
-	f.StringVar(&r.userGroup, "user-group", "cassandra:cassandra", "user and group who should own restored files")
-	f.StringVarP(&r.cassandraDataDir, "cassandra-data-dir", "", utils.GetStringEnvVar("CAIN_CASSANDRA_DATA_DIR", "/var/lib/cassandra/data"), "cassandra data directory. Overrides $CAIN_CASSANDRA_DATA_DIR")
+	f.StringVar(&r.src, "src", utils.GetStringEnvVar("CAIN_SRC", ""), "source to restore from. Example: s3://bucket/cassandra/namespace/cluster-name. Overrides $CAIN_SRC")
+	f.StringVarP(&r.keyspace, "keyspace", "k", utils.GetStringEnvVar("CAIN_KEYSPACE", ""), "keyspace to act on. Overrides $CAIN_KEYSPACE")
+	f.StringVarP(&r.tag, "tag", "t", utils.GetStringEnvVar("CAIN_TAG", ""), "tag to restore. Overrides $CAIN_TAG")
+	f.StringVarP(&r.schema, "schema", "s", utils.GetStringEnvVar("CAIN_SCHEMA", ""), "schema version to restore (optional). Overrides $CAIN_SCHEMA")
+	f.StringVarP(&r.namespace, "namespace", "n", utils.GetStringEnvVar("CAIN_NAMESPACE", "default"), "namespace to find cassandra cluster. Overrides $CAIN_NAMESPACE")
+	f.StringVarP(&r.selector, "selector", "l", utils.GetStringEnvVar("CAIN_SELECTOR", "app=cassandra"), "selector to filter on. Overrides $CAIN_SELECTOR")
+	f.StringVarP(&r.container, "container", "c", utils.GetStringEnvVar("CAIN_CONTAINER", "cassandra"), "container name to act on. Overrides $CAIN_CONTAINER")
+	f.IntVarP(&r.parallel, "parallel", "p", utils.GetIntEnvVar("CAIN_PARALLEL", 1), "number of files to copy in parallel. set this flag to 0 for full parallelism. Overrides $CAIN_PARALLEL")
+	f.Float64VarP(&r.bufferSize, "buffer-size", "b", utils.GetFloat64EnvVar("CAIN_BUFFER_SIZE", 6.75), "in memory buffer size (MB) to use for files copy (buffer per file). Overrides $CAIN_BUFFER_SIZE")
+	f.StringVar(&r.userGroup, "user-group", utils.GetStringEnvVar("CAIN_USER_GROUP", "cassandra:cassandra"), "user and group who should own restored files. Overrides $CAIN_USER_GROUP")
+	f.StringVar(&r.cassandraDataDir, "cassandra-data-dir", utils.GetStringEnvVar("CAIN_CASSANDRA_DATA_DIR", "/var/lib/cassandra/data"), "cassandra data directory. Overrides $CAIN_CASSANDRA_DATA_DIR")
 
 	return cmd
 }
@@ -221,14 +221,11 @@ func NewSchemaCmd(out io.Writer) *cobra.Command {
 	}
 	f := cmd.Flags()
 
-	f.StringVarP(&s.namespace, "namespace", "n", "", "namespace to find cassandra cluster")
-	f.StringVarP(&s.selector, "selector", "l", "", "selector to filter on")
-	f.StringVarP(&s.container, "container", "c", "cassandra", "container name to act on")
-	f.StringVarP(&s.keyspace, "keyspace", "k", "", "keyspace to act on")
-	f.BoolVar(&s.sum, "sum", false, "print only checksum")
-
-	cmd.MarkFlagRequired("namespace")
-	cmd.MarkFlagRequired("selector")
+	f.StringVarP(&s.namespace, "namespace", "n", utils.GetStringEnvVar("CAIN_NAMESPACE", "default"), "namespace to find cassandra cluster. Overrides $CAIN_NAMESPACE")
+	f.StringVarP(&s.selector, "selector", "l", utils.GetStringEnvVar("CAIN_SELECTOR", "app=cassandra"), "selector to filter on. Overrides $CAIN_SELECTOR")
+	f.StringVarP(&s.container, "container", "c", utils.GetStringEnvVar("CAIN_CONTAINER", "cassandra"), "container name to act on. Overrides $CAIN_CONTAINER")
+	f.StringVarP(&s.keyspace, "keyspace", "k", utils.GetStringEnvVar("CAIN_KEYSPACE", ""), "keyspace to act on. Overrides $CAIN_KEYSPACE")
+	f.BoolVar(&s.sum, "sum", utils.GetBoolEnvVar("CAIN_SUM", false), "print only checksum. Overrides $CAIN_SUM")
 
 	return cmd
 }

pkg/utils/env.go

@@ -39,3 +39,16 @@ func GetBoolEnvVar(name string, defVal bool) bool {
 	}
 	return defVal
 }
+
+// GetFloat64EnvVar returns the default value if the variable is empty, else the value
+func GetFloat64EnvVar(name string, defVal float64) float64 {
+	val := os.Getenv(name)
+	if val == "" {
+		return defVal
+	}
+	iVal, err := strconv.ParseFloat(val, 64)
+	if err != nil {
+		return defVal
+	}
+	return iVal
+}