File

Description

The file vmod allows for Varnish to act as a file server as well as a means to interact with the file system from VCL.

The backend allows the serving of static files through Varnish. The backend request URL is appended to the vmod’s root directory to form a file path. If the file path resolves to a regular file and is readable to the Varnish child process, it is used as the source for this backend fetch operation. Files served this way are treated in the same manner as if they were fetched from a real backend, and so will be cached in memory according to the current configuration. TTL, grace, and keep works just like it would normally as well.

The following headers are added based on the resolved files attributes: Last-Modified, Content-type, and Content-Length.

If the file could not be read for any reason (e.g. not found, access restrictions or resolved outside of the root directory of the vmod), an appropriate error response is synthesized.

This VMOD includes a standard set of file operations and an ACL. All file objects must allow at least one path in the ACL. To use executable files, a mode of x, varnishd must be started with -p allow_exec=true.

Examples

Serve a local file system:

import file;

sub vcl_init {
  new root = file.init("/var/www/html/");
}

sub vcl_backend_fetch {
  # Set the file system as the backend
  set bereq.backend = root.backend();
}

Return the uptime of the server:

import file;

sub vcl_init {
  new fs = file.init();
  fs.allow("/usr/bin/uptime", "x");
}

sub vcl_recv {
  if (req.method == "UPTIME") {
    return (synth(200, "UPTIME"));
  }
}

sub vcl_synth {
  if (resp.reason == "UPTIME") {
    synthetic(fs.exec("/usr/bin/uptime"));
    if (fs.exec_get_errorcode() != 0) {
      set resp.status = 404;
    }
    return (deliver);
  }
}

API

arg

STRING arg(STRING str)

Allow a string literal to be used with STRANDS so it can be read in .exec() arguments.

Arguments:

• str accepts type STRING

Type: Function

Returns: String

split_args

STRANDS split_args(STRING str)

Turn a string into a STRANDS object to be read in .exec() arguments. The string is broken up in two ways, by whitespace or matching quotes. Quotes will be deliminated by a matching quote followed by any whitespace character or the end of the string. Both single and double quotes are supported. This can be used to pass in multiple arguments to .exec().

Arguments:

• str accepts type STRING

Type: Function

Returns: Strands

init

OBJECT init(STRING rootdir = 0, STRING mimedb = "/etc/mime.types", BOOL disable_symlinks = 0)

Creates a file system root. The rootdir is the base of the file system hierarchy.

The root directory, when set, will be prepended to each path used in the functions bellow (except for .exec()). Otherwise each path will be considered absolute or relative, depending on a leading slash.

Arguments:

• rootdir accepts type STRING with a default value of 0 optional

• mimedb accepts type STRING with a default value of /etc/mime.types optional

• disable_symlinks accepts type BOOL with a default value of 0 optional

Type: Object

Returns: Object.

.backend

BACKEND .backend()

Return a backend reference to this root for use during fetch.

Arguments: None

Type: Method

Returns: Backend

.allow

VOID .allow(STRING path, STRING mode = "r")

Allow path to be accessed from functions that access files through mode. At least one path must be added to allow for the object to work correctly. The mode can be any combination of read (r), write (w), or execute (x).

Arguments:

• path accepts type STRING

• mode accepts type STRING with a default value of r optional

Type: Method

Returns: None

Restricted to: vcl_init

.deny

VOID .deny(STRING path, STRING mode = "rwx")

Deny path access from functions that access files through mode. The mode can be any combination of read (r), write (w), or execute (x)

Arguments:

• path accepts type STRING

• mode accepts type STRING with a default value of rwx optional

Type: Method

Returns: None

Restricted to: vcl_init

.read

STRING .read(STRING file, STRING def = 0)

Read file and return it as a string. If file does not exist or does not pass the ACL, def is returned.

Arguments:

• file accepts type STRING

• def accepts type STRING with a default value of 0 optional

Type: Method

Returns: String

.read_blob

BLOB .read_blob(STRING file, STRING def = 0)

Read file and return it in a blob. If file does not exist or does not pass the ACL, def is returned. def refers to contents of the blob to return if there was an error reading the file.

Arguments:

• file accepts type STRING

• def accepts type STRING with a default value of 0 optional

Type: Method

Returns: Blob

.read_into_synth

VOID .read_into_synth(STRING file, STRING def = 0)

Return a file as a synthetic response body. Only accessible through sub vcl_synth and sub vcl_backend_error. If file does not exist or does not pass the ACL, def is returned.

Arguments:

• file accepts type STRING

• def accepts type STRING with a default value of 0 optional

Type: Method

Returns: None

Restricted to: vcl_synth, vcl_backend_error

.append

INT .append(STRING file, STRING str, BOOL create_path = 0, INT dir_mask = 755, BOOL lock = 1)

Append a string, str, to a file, file. If create_path = true and a directory above the file does not exist, it will be created with permission dir_perm. Must Pass ACL. If lock is true the file will be appended under a lock.

Arguments:

• file accepts type STRING

• str accepts type STRING

• create_path accepts type BOOL with a default value of 0 optional

• dir_mask accepts type INT with a default value of 755 optional

• lock accepts type BOOL with a default value of 1 optional

Type: Method

Returns: Int

.write

INT .write(STRING file, STRING str, BOOL create_path = 0, INT dir_mask = 755)

Write to a file, file, consisting of str. If create_path = true and a directory above the file does not exist, it will be created with permission dir_perm. Must Pass ACL. The file is first written to a temporary file by appending a random string to the end of the file path (/rootdir/file[.random_string]). Next, the file is renamed back to the original path. If there are multiple concurrent writers, the last write wins.

Arguments:

• file accepts type STRING

• str accepts type STRING

• create_path accepts type BOOL with a default value of 0 optional

• dir_mask accepts type INT with a default value of 755 optional

Type: Method

Returns: Int

.write_blob

INT .write_blob(STRING file, BLOB blb, BOOL create_path = 0, INT dir_mask = 755)

Write to a file, file, with the contents of blb. If create_path = true and a directory above the file does not exist, it will be created with permission dir_perm. Must Pass ACL. The file is first written to a temporary file by appending a random string to the end of the file path (/rootdir/file[.random_string]). Next, the file is renamed back to the original path. If there are multiple concurrent writers, the last write wins.

Arguments:

• file accepts type STRING

• blb accepts type BLOB

• create_path accepts type BOOL with a default value of 0 optional

• dir_mask accepts type INT with a default value of 755 optional

Type: Method

Returns: Int

.write_req_body

INT .write_req_body(STRING file, BOOL create_path = 0, INT dir_mask = 755)

Write the request to a file, file_path, the request body. If create_path = true and a directory above the file does not exist, it will be created with permission dir_perm. This can only can be called in sub vcl_recv. std.cache_req_body() must be called before using this. The file is first written to a temporary file by appending a random string to the end of the file path (/rootdir/file[.random_string]). Next, the file is renamed back to the original path. If there are multiple concurrent writers, the last write wins.

Arguments:

• file accepts type STRING

• create_path accepts type BOOL with a default value of 0 optional

• dir_mask accepts type INT with a default value of 755 optional

Type: Method

Returns: Int

Restricted to: vcl_recv

.delete

BOOL .delete(STRING path, BOOL recursive = 0)

Delete a path. If a directory is to be deleted, recursive must be set to true. path must pass the ACL.

Arguments:

• path accepts type STRING

• recursive accepts type BOOL with a default value of 0 optional

Type: Method

Returns: Bool

.exec

STRING .exec(STRING path, STRANDS arguments = 0, STRING checksum = 0, DURATION timeout = 60, BOOL output_stdout = 1, BOOL output_stderr = 1, STRING def = 0)

Run a binary or script and return the output as a string. Must pass the ACL. Scripts must have execute permission and contain a first line of:

#! interpreter [optional-arg]

Executing a program directly from Varnish should be avoided for servers running moderate or heavy workloads.

Arguments:

• path accepts type STRING

• arguments accepts type STRANDS with a default value of 0 optional

• checksum accepts type STRING with a default value of 0 optional

• timeout accepts type DURATION with a default value of 60 optional

• output_stdout accepts type BOOL with a default value of 1 optional

• output_stderr accepts type BOOL with a default value of 1 optional

• def accepts type STRING with a default value of 0 optional

Type: Method

Returns: String

.exec_get_errorcode

INT .exec_get_errorcode()

Get the response code from the previous .exec() call. This value is -1 until the binary or script is called in .exec() and produces a response code.

Arguments: None

Type: Method

Returns: Int

.exists

BOOL .exists(STRING path, STRING mode = "r", ENUM {FILE, DIR, BOTH} type = FILE)

Check if the path exists. The mode can be any combination of read (r), write (w), or execute (x)

Arguments:

• path accepts type STRING

• mode accepts type STRING with a default value of r optional

• type is an ENUM that accepts values of FILE, DIR, and BOTH with a default value of FILE optional

Type: Method

Returns: Bool

.lastaccess

TIME .lastaccess(STRING path, ENUM {FILE, DIR, BOTH} type = FILE)

Return the time (Unix time) that the path was last accessed. This time is updated when the following system functions are called: execve(2), mknod(2), pipe(2), utime(2), and read(2) (of more than zero bytes). This function does not work when a file system is mounted with noatime, as is currently the recommended configuration for MSE volumes.

Arguments:

• path accepts type STRING

• type is an ENUM that accepts values of FILE, DIR, and BOTH with a default value of FILE optional

Type: Method

Returns: Time

.lastmodified

TIME .lastmodified(STRING path, ENUM {FILE, DIR, BOTH} type = FILE)

Return the time (Unix time) that the path was last modified. This time is updated when the following system functions are called: mknod(2), truncate(2), utime(2), and write(2) (of more than zero bytes).

Arguments:

• path accepts type STRING

• type is an ENUM that accepts values of FILE, DIR, and BOTH with a default value of FILE optional

Type: Method

Returns: Time

.laststatus

TIME .laststatus(STRING path, ENUM {FILE, DIR, BOTH} type = FILE)

Return the time (Unix time) that path last had a status change. This time is updated by writing or setting inode information (i.e., owner, group, link count, mode, etc.).

Arguments:

• path accepts type STRING

• type is an ENUM that accepts values of FILE, DIR, and BOTH with a default value of FILE optional

Type: Method

Returns: Time

.size

BYTES .size(STRING path, ENUM {FILE, DIR, BOTH} type = FILE)

Return the size of the path in bytes. Can be limited to only files, only directories, or both files and directories

Arguments:

• path accepts type STRING

• type is an ENUM that accepts values of FILE, DIR, and BOTH with a default value of FILE optional

Type: Method

Returns: Bytes

Availability

The file VMOD is available in Varnish Enterprise version 6.0.0r0 and later.