1MONGOC_CURSOR_ERROR_DOCUMENT(3)    libmongoc   MONGOC_CURSOR_ERROR_DOCUMENT(3)
2
3
4

SYNOPSIS

6          bool
7          mongoc_cursor_error_document (mongoc_cursor_t *cursor,
8                                        bson_error_t *error,
9                                        const bson_t **reply);
10

PARAMETERS

12       • cursor: A mongoc_cursor_t.
13
14       • error: An optional location for a bson_error_t or NULL.
15
16       • reply: A location for a bson_t.
17

DESCRIPTION

19       This  function  checks  to see if an error has occurred while iterating
20       the cursor.
21
22       If an error occurred client-side, for example if there  was  a  network
23       error  or  timeout,  or the cursor was created with invalid parameters,
24       then reply is set to an empty  BSON  document.  If  an  error  occurred
25       server-side,  reply is set to the server's reply document with informa‐
26       tion about the error.
27

ERRORS

29       Errors are propagated via the error and reply parameters.
30

RETURNS

32       False if no error has occurred, otherwise true and error is set.
33
34       If the function returns true and reply is not NULL, then reply  is  set
35       to  a pointer to a BSON document, which is either empty or the server's
36       error response. The document is invalid after the cursor is freed  with
37       mongoc_cursor_destroy().
38

EXAMPLE

40       This example shows the difference between a client-side and server-side
41       error. If the client cannot connect to the server, for example, the er‐
42       ror message includes "No suitable servers found" and reply is set to an
43       empty BSON document.
44
45       On the other hand, if the client connects to  the  server  successfully
46       and  attempts to execute an invalid query, the error message comes from
47       the server and reply is set to the server's reply document, with fields
48       errmsg and code.
49
50          void
51          run_query (const char *uri_str, const bson_t *query)
52          {
53             mongoc_client_t *client;
54             mongoc_collection_t *collection;
55             mongoc_cursor_t *cursor;
56             const bson_t *doc;
57             bson_error_t error;
58             const bson_t *reply;
59             char *str;
60
61             client = mongoc_client_new (uri_str);
62
63             mongoc_client_set_error_api (client, 2);
64
65             collection = mongoc_client_get_collection (client, "db", "collection");
66             cursor = mongoc_collection_find_with_opts (
67                collection,
68                query,
69                NULL,  /* additional options */
70                NULL); /* read prefs, NULL for default */
71
72             /* this loop is never run: mongoc_cursor_next immediately returns false */
73             while (mongoc_cursor_next (cursor, &doc)) {
74             }
75
76             if (mongoc_cursor_error_document (cursor, &error, &reply)) {
77                str = bson_as_json (reply, NULL);
78                fprintf (stderr, "Cursor Failure: %s\nReply: %s\n", error.message, str);
79                bson_free (str);
80             }
81
82             mongoc_cursor_destroy (cursor);
83             mongoc_collection_destroy (collection);
84             mongoc_client_destroy (client);
85          }
86
87          int
88          main (int argc, char *argv[])
89          {
90             bson_t *good_query;
91             bson_t *bad_query;
92
93             mongoc_init ();
94
95             /* find documents matching the query {"x": 1} */
96             good_query = BCON_NEW ("x", BCON_INT64 (1));
97
98             /* Cause a network error. This will print an error and empty reply document:
99              *
100              * Cursor Failure: No suitable servers found (`serverSelectionTryOnce` set):
101              *     [Failed to resolve 'fake-domain']
102              *
103              * Reply: { }
104              *
105              */
106             run_query ("mongodb://fake-domain/?appname=cursor-example", good_query);
107
108             /* invalid: {"x": {"$badOperator": 1}} */
109             bad_query = BCON_NEW ("x", "{", "$badOperator", BCON_INT64 (1), "}");
110
111             /* Cause a server error. This will print an error and server reply document:
112              *
113              * Cursor Failure: unknown operator: $badOperator
114              *
115              * Reply:
116              * {"ok": 0.0,
117              *  "errmsg":"unknown operator: $badOperator",
118              *  "code": 2,
119              *  "codeName":"BadValue"
120              * }
121              *
122              */
123             run_query ("mongodb://localhost/?appname=cursor-example", bad_query);
124
125             bson_destroy (good_query);
126             bson_destroy (bad_query);
127
128             mongoc_cleanup ();
129
130             return 0;
131          }
132

AUTHOR

134       MongoDB, Inc
135

137       2017-present, MongoDB, Inc
138
139
140
141
1421.25.1                           Nov 08, 2023  MONGOC_CURSOR_ERROR_DOCUMENT(3)
Impressum