1 files changed, 145 insertions, 0 deletions
diff --git a/ngxtop/config_parser.py b/ngxtop/config_parser.py
new file mode 100644
index 0000000..82a2d2a
--- /dev/null
+++ b/ngxtop/config_parser.py
@@ -0,0 +1,145 @@
+"""
+Nginx config parser and pattern builder.
+"""
+import os
+import re
+import subprocess
+
+from pyparsing import Literal, Word, ZeroOrMore, OneOrMore, Group, \
+    printables, quotedString, pythonStyleComment, removeQuotes
+
+from utils import choose_one, error_exit
+
+
+REGEX_SPECIAL_CHARS = r'([\.\*\+\?\|\(\)\{\}\[\]])'
+REGEX_LOG_FORMAT_VARIABLE = r'\$([a-z0-9\_]+)'
+LOG_FORMAT_COMBINED = '$remote_addr - $remote_user [$time_local] ' \
+                      '"$request" $status $body_bytes_sent ' \
+                      '"$http_referer" "$http_user_agent"'
+
+# common parser element
+semicolon = Literal(';').suppress()
+# nginx string parameter can contain any character except: { ; " '
+parameter = Word(''.join(c for c in printables if c not in set('{;"\'')))
+# which can also be quoted
+parameter = parameter | quotedString.setParseAction(removeQuotes)
+
+
+def detect_config_path():
+    """
+    Get nginx configuration file path based on `nginx -V` output
+    :return: detected nginx configuration file path
+    """
+    try:
+        proc = subprocess.Popen(['nginx', '-V'], stderr=subprocess.PIPE)
+    except OSError:
+        error_exit('Access log file or format was not set and nginx config file cannot be detected. ' +
+                   'Perhaps nginx is not in your PATH?')
+
+    stdout, stderr = proc.communicate()
+    version_output = stderr.decode('utf-8')
+    conf_path_match = re.search(r'--conf-path=(\S*)', version_output)
+    if conf_path_match is not None:
+        return conf_path_match.group(1)
+
+    prefix_match = re.search(r'--prefix=(\S*)', version_output)
+    if prefix_match is not None:
+        return prefix_match.group(1) + '/conf/nginx.conf'
+    return '/etc/nginx/nginx.conf'
+
+
+def get_access_logs(config):
+    """
+    Parse config for access_log directives
+    :return: iterator over ('path', 'format name') tuple of found directives
+    """
+    access_log = Literal("access_log") + ZeroOrMore(parameter) + semicolon
+    access_log.ignore(pythonStyleComment)
+
+    for directive in access_log.searchString(config).asList():
+        path = directive[1]
+        if path == 'off' or path.startswith('syslog:'):
+            # nothing to process here
+            continue
+
+        format_name = 'combined'
+        if len(directive) > 2 and '=' not in directive[2]:
+            format_name = directive[2]
+
+        yield path, format_name
+
+
+def get_log_formats(config):
+    """
+    Parse config for log_format directives
+    :return: iterator over ('format name', 'format string') tuple of found directives
+    """
+    # log_format name [params]
+    log_format = Literal('log_format') + parameter + Group(OneOrMore(parameter)) + semicolon
+    log_format.ignore(pythonStyleComment)
+
+    for directive in log_format.searchString(config).asList():
+        name = directive[1]
+        format_string = ''.join(directive[2])
+        yield name, format_string
+
+
+def detect_log_config(arguments):
+    """
+    Detect access log config (path and format) of nginx. Offer user to select if multiple access logs are detected.
+    :return: path and format of detected / selected access log
+    """
+    config = arguments['--config']
+    if config is None:
+        config = detect_config_path()
+    if not os.path.exists(config):
+        error_exit('Nginx config file not found: %s' % config)
+
+    with open(config) as f:
+        config_str = f.read()
+    access_logs = dict(get_access_logs(config_str))
+    if not access_logs:
+        error_exit('Access log file is not provided and ngxtop cannot detect it from your config file (%s).' % config)
+
+    log_formats = dict(get_log_formats(config_str))
+    if len(access_logs) == 1:
+        log_path, format_name = access_logs.items()[0]
+        if format_name == 'combined':
+            return log_path, LOG_FORMAT_COMBINED
+        if format_name not in log_formats:
+            error_exit('Incorrect format name set in config for access log file "%s"' % log_path)
+        return log_path, log_formats[format_name]
+
+    # multiple access logs configured, offer to select one
+    print('Multiple access logs detected in configuration:')
+    log_path = choose_one(access_logs.keys(), 'Select access log file to process: ')
+    format_name = access_logs[log_path]
+    if format_name not in log_formats:
+        error_exit('Incorrect format name set in config for access log file "%s"' % log_path)
+    return log_path, log_formats[format_name]
+
+
+def build_pattern(log_format):
+    """
+    Build regular expression to parse given format.
+    :param log_format: format string to parse
+    :return: regular expression to parse given format
+    """
+    if log_format == 'combined':
+        log_format = LOG_FORMAT_COMBINED
+    pattern = re.sub(REGEX_SPECIAL_CHARS, r'\\\1', log_format)
+    pattern = re.sub(REGEX_LOG_FORMAT_VARIABLE, '(?P<\\1>.*)', pattern)
+    return re.compile(pattern)
+
+
+def extract_variables(log_format):
+    """
+    Extract all variables from a log format string.
+    :param log_format: format string to extract
+    :return: iterator over all variables in given format string
+    """
+    if log_format == 'combined':
+        log_format = LOG_FORMAT_COMBINED
+    for match in re.findall(REGEX_LOG_FORMAT_VARIABLE, log_format):
+        yield match
+