MONGOC_REFERENCE - Online Linux Manual Page

Section : 3
Updated : Feb 04, 2021
Source : 1.17.4
Note : libmongoc

NAME

mongoc_reference − Index

LIBMONGOC

A Cross Platform MongoDB Client Library for C

Introduction

The MongoDB C Driver, also known as "libmongoc", is a library for using MongoDB from C applications, and for writing MongoDB drivers in higher−level languages. It depends on libbson

to generate and parse BSON documents, the native data format of MongoDB.

Installing the MongoDB C Driver (libmongoc) and BSON library (libbson)

The following guide will step you through the process of downloading, building, and installing the current release of the MongoDB C Driver (libmongoc) and BSON library (libbson).

Supported Platforms

The MongoDB C Driver is continuously tested

on a variety of platforms including:

• Archlinux

• Debian 9.2, 10.0

• macOS 10.14

• Microsoft Windows Server 2008, 2016

• RHEL 6.2, 7.0, 7.1, 8.2

• Ubuntu 16.04, 18.04

• Clang 3.4, 3.5, 3.7, 3.8, 6.0

• GCC 4.8, 4.9, 5.4, 6.3, 8.2, 8.3

• MinGW−W64

• Visual Studio 2013, 2015, 2017

• x86, x86_64, ARM (aarch64), Power8 (ppc64le), zSeries (s390x)

Install libmongoc with a Package Manager

Several Linux distributions provide packages for libmongoc and its dependencies. One advantage of installing libmongoc with a package manager is that its dependencies (including libbson) will be installed automatically. If you choose to install libmongoc from distribution packages, use the package manager to confirm the version being installed is sufficient for your needs. The libmongoc package is available on recent versions of Debian and Ubuntu.

$ apt−get install libmongoc−1.0−0

On Fedora, a mongo−c−driver package is available in the default repositories and can be installed with:

$ dnf install mongo−c−driver

On recent Red Hat systems, such as CentOS and RHEL 7, a mongo−c−driver package is available in the EPEL

repository. To check which version is available, see

https://apps.fedoraproject.org/packages/mongo−c−driver

. The package can be installed with:

$ yum install mongo−c−driver

On macOS systems with Homebrew, the mongo−c−driver package can be installed with:

$ brew install mongo−c−driver

Install libbson with a Package Manager

The libbson package is available on recent versions of Debian and Ubuntu. If you have installed libmongoc, then libbson will have already been installed as a dependency. It is also possible to install libbson without libmongoc.

$ apt−get install libbson−1.0−0

On Fedora, a libbson package is available in the default repositories and can be installed with:

$ dnf install libbson

On recent Red Hat systems, such as CentOS and RHEL 7, a libbson package is available in the EPEL

repository. To check which version is available, see

https://apps.fedoraproject.org/packages/libbson

. The package can be installed with:

$ yum install libbson

Build environment

Build environment on Unix

Prerequisites for libmongoc

OpenSSL is required for authentication or for TLS connections to MongoDB. Kerberos or LDAP support requires Cyrus SASL. To install all optional dependencies on RedHat / Fedora:

$ sudo yum install cmake openssl−devel cyrus−sasl−devel

On Debian / Ubuntu:

$ sudo apt−get install cmake libssl−dev libsasl2−dev

On FreeBSD:

$ su −c 'pkg install cmake openssl cyrus−sasl'

Prerequisites for libbson

The only prerequisite for building libbson is cmake

. The command lines above can be adjusted to install only

cmake

Build environment on macOS

Install the XCode Command Line Tools:

$ xcode−select −−install

The cmake

utility is also required. First

install Homebrew according to its instructions

, then:

$ brew install cmake

Build environment on Windows with Visual Studio

Building on Windows requires Windows Vista or newer and Visual Studio 2010 or newer. Additionally, cmake

is required to generate Visual Studio project files. Installation of these components on Windows is beyond the scope of this document.

Build environment on Windows with MinGW−W64 and MSYS2

Install MSYS2 from msys2.github.io

. Choose the x86_64 version, not i686. Open the MingGW shell with

c:\msys64\ming64.exe

(not the msys2_shell). Install dependencies:

$ pacman −−noconfirm −Syu
$ pacman −−noconfirm −S mingw−w64−x86_64−gcc mingw−w64−x86_64−cmake
$ pacman −−noconfirm −S mingw−w64−x86_64−extra−cmake−modules make tar
$ pacman −−noconfirm −S mingw64/mingw−w64−x86_64−cyrus−sasl

Configuring the build

Before building libmongoc and/or libbson, it is necessary to configure, or prepare, the build. The steps to prepare the build depend on how you obtained the source code and the build platform.

Preparing a build from a release tarball

The most recent release of libmongoc and libbson, both of which are included in mongo−c−driver, can be downloaded here

. The instructions in this document utilize

cmake

's out−of−source build feature to keep build artifacts separate from source files. While the

prompt is used throughout, the instructions below will work on Linux, macOS, and Windows (assuming that CMake is in the user's shell path in all cases). See the subsequent sections for additional platform−specific instructions. The following snippet will download and extract the driver, and configure it:

$ wget 

https://github.com/mongodb/mongo−c−driver/releases/download/

1.17.4/mongo−c−driver−1.17.4​.tar.gz
$ tar xzf mongo−c−driver−1.17.4​.tar.gz
$ cd mongo−c−driver−1.17.4
$ mkdir cmake−build
$ cd cmake−build
$ cmake −DENABLE_AUTOMATIC_INIT_AND_CLEANUP=OFF ..

The −DENABLE_AUTOMATIC_INIT_AND_CLEANUP=OFF

option is recommended, see init−cleanup. Another useful

cmake

option is

−DCMAKE_BUILD_TYPE=Release

for a release optimized build and

−DCMAKE_BUILD_TYPE=Debug

for a debug build. For a list of all configure options, run

cmake −L ..

. If

cmake

completed successfully, you will see a considerable amount of output describing your build configuration. The final line of output should look something like this:

−− Build files have been written to: /home/user/mongo−c−driver−1.17.4/cmake−build

If cmake

concludes with anything different, then it is likely an error occurred. mongo−c−driver contains a copy of libbson, in case your system does not already have libbson installed. The configuration will detect if libbson is not installed and use the bundled libbson. Additionally, it is possible to build only libbson by setting the

−DENABLE_MONGOC=OFF

option:

$ cmake −DENABLE_AUTOMATIC_INIT_AND_CLEANUP=OFF −DENABLE_MONGOC=OFF ..

A build configuration description similar to the one above will be displayed, though with fewer entries. Once the configuration is complete, the selected items can be built and installed with these commands:

Preparing a build from a git repository clone

Clone the repository and prepare the build on the current master branch or a particular release tag:

$ git clone 

https://github.com/mongodb/mongo−c−driver.git

$ cd mongo−c−driver
$ git checkout 1.17.4  # To build a particular release
$ python build/calc_release_version.py > VERSION_CURRENT
$ mkdir cmake−build
$ cd cmake−build
$ cmake −DENABLE_AUTOMATIC_INIT_AND_CLEANUP=OFF ..

Preparing a build on Windows with Visual Studio

On the Windows platform with Visual Studio, it may be necessary to specify the CMake generator to use. This is especially important if multiple versions of Visual Studio are installed on the system or if alternate build tools (e.g., MinGW, MSYS2, Cygwin, etc.) are present on the system. Specifying the generator will ensure that the build configuration is known with certainty, rather than relying on the toolchain that CMake happens to find. Start by generating Visual Studio project files. The following assumes you are compiling for 64−bit Windows using Visual Studio 2015 Express, which can be freely downloaded from Microsoft. The sample commands utilize cmake

's out−of−source build feature to keep build artifacts separate from source files.

$ cd mongo−c−driver−1.17.4
$ mkdir cmake−build
$ cd cmake−build
$ cmake −G "Visual Studio 14 2015 Win64" \
    "−DCMAKE_INSTALL_PREFIX=C:\mongo−c−driver" \
    "−DCMAKE_PREFIX_PATH=C:\mongo−c−driver" \
    ..

(Run cmake −LH ..

for a list of other options.) To see a complete list of the CMake generators available on your specific system, use a command like this:

$ cmake −−help

Executing a build

Building on Unix, macOS, and Windows (MinGW−W64 and MSYS2)

$ cmake −−build .
$ sudo cmake −−build . −−target install

(Note that the sudo

command may not be applicable or available depending on the configuration of your system.) In the above commands, the first relies on the default target which builds all configured components. For fine grained control over what gets built, the following command can be used (for Ninja and Makefile−based build systems) to list all available targets:

$ cmake −−build . help

Building on Windows with Visual Studio

Once the project files are generated, the project can be opened directly in Visual Studio or compiled from the command line. Build using the CMake build tool mode:

$ cmake −−build . −−config RelWithDebInfo

Visual Studio's default build type is Debug

, but we recommend a release build with debug info for production use. Now that libmongoc and libbson are compiled, install them. Components will be installed to the path specified by

CMAKE_INSTALL_PREFIX

$ cmake −−build . −−config RelWithDebInfo −−target install

You should now see libmongoc and libbson installed in C:\mongo−c−driver

For Visual Studio 2019 (16.4 and newer), this command can be used to list all available targets:

$ cmake −−build . −− /targets

Alternately, you can examine the files matching the glob *.vcxproj

in the

cmake−build

directory. To use the driver libraries in your program, see visual−studio−guide.

Generating the documentation

Install Sphinx

, then:

$ cmake −DENABLE_MAN_PAGES=ON −DENABLE_HTML_DOCS=ON ..
$ cmake −−build . −−target mongoc−doc

To build only the libbson documentation:

$ cmake −DENABLE_MAN_PAGES=ON −DENABLE_HTML_DOCS=ON ..
$ cmake −−build . −−target bson−doc

The −DENABLE_MAN_PAGES=ON

and

−DENABLE_HTML_DOCS=ON

can also be added as options to a normal build from a release tarball or from git so that the documentation is built at the same time as other components.

Uninstalling the installed components

There are two ways to uninstall the components that have been installed. The first is to invoke the uninstall program directly. On Linux/Unix:

$ sudo /usr/local/share/mongo−c−driver/uninstall.sh

On Windows:

$ C:\mongo−c−driver\share\mongo−c−driver\uninstall.bat

The second way to uninstall is from within the build directory, assuming that it is in the exact same state as when the install command was invoked:

$ sudo cmake −−build . −−target uninstall

The second approach simply invokes the uninstall program referenced in the first approach.

Additional Options for Integrators

In the event that you are building the BSON library and/or the C driver to embed with other components and you wish to avoid the potential for collision with components installed from a standard build or from a distribution package manager, you can make use of the BSON_OUTPUT_BASENAME

and

MONGOC_OUTPUT_BASENAME

options to

cmake

$ cmake −DBSON_OUTPUT_BASENAME=custom_bson −DMONGOC_OUTPUT_BASENAME=custom_mongoc ..

The above command would produce libraries named libcustom_bson.so

and

libcustom_mongoc.so

(or with the extension appropriate for the build platform). Those libraries could be placed in a standard system directory or in an alternate location and could be linked to by specifying something like

−lcustom_mongoc −lcustom_bson

on the linker command line (possibly adjusting the specific flags to those required by your linker).

Tutorial

This guide offers a brief introduction to the MongoDB C Driver. For more information on the C API, please refer to the api.

Contents

•

Tutorial

•

Installing

•

Starting MongoDB

•

Include and link libmongoc in your C program

•

Use libmongoc in a Microsoft Visual Studio Project

•

Making a Connection

•

Creating BSON Documents

•

Basic CRUD Operations

•

Executing Commands

•

Threading

•

Next Steps

Installing

For detailed instructions on installing the MongoDB C Driver on a particular platform, please see the installation guide.

Starting MongoDB

To run the examples in this tutorial, MongoDB must be installed and running on localhost

on the default port, 27017. To check if it is up and running, connect to it with the MongoDB shell.

$ mongo −−host localhost −−port 27017
MongoDB shell version: 3.0.6
connecting to: localhost:27017/test
>

Include and link libmongoc in your C program

Include mongoc.h

All libmongoc's functions and types are available in one header file. Simply include mongoc/mongoc.h

#include <mongoc/mongoc.h>

CMake

The libmongoc installation includes a CMake config−file package

, so you can use CMake's

find_package

command to import libmongoc's CMake target and link to libmongoc (as a shared library): CMakeLists.txt

# Specify the minimum version you require.
find_package (mongoc−1.0 1.7 REQUIRED)

# The "hello_mongoc.c" sample program is shared among four tests.
add_executable (hello_mongoc ../../hello_mongoc.c)
target_link_libraries (hello_mongoc PRIVATE mongo::mongoc_shared)

You can also use libmongoc as a static library instead: Use the mongo::mongoc_static

CMake target:

# Specify the minimum version you require.
find_package (mongoc−1.0 1.7 REQUIRED)

# The "hello_mongoc.c" sample program is shared among four tests.
add_executable (hello_mongoc ../../hello_mongoc.c)
target_link_libraries (hello_mongoc PRIVATE mongo::mongoc_static)

pkg−config

If you're not using CMake, use pkg−config

on the command line to set header and library paths:

gcc −o hello_mongoc hello_mongoc.c $(pkg−config −−libs −−cflags libmongoc−1.0)

Or to statically link to libmongoc:

gcc −o hello_mongoc hello_mongoc.c $(pkg−config −−libs −−cflags libmongoc−static−1.0)

If you aren't using CMake or pkg−config, paths and libraries can be managed manually.

$ gcc −o hello_mongoc hello_mongoc.c \
    −I/usr/local/include/libbson−1.0 −I/usr/local/include/libmongoc−1.0 \
    −lmongoc−1.0 −lbson−1.0
$ ./hello_mongoc
{ "ok" : 1.000000 }

For Windows users, the code can be compiled and run with the following commands. (This assumes that the MongoDB C Driver has been installed to C:\mongo−c−driver

; change the include directory as needed.)

C:\> cl.exe /IC:\mongo−c−driver\include\libbson−1.0 /IC:\mongo−c−driver\include\libmongoc−1.0 hello_mongoc.c
C:\> hello_mongoc
{ "ok" : 1.000000 }

Use libmongoc in a Microsoft Visual Studio Project

See the libmongoc and Visual Studio guide.

Making a Connection

Access MongoDB with a mongoc_client_t

. It transparently connects to standalone servers, replica sets and sharded clusters on demand. To perform operations on a database or collection, create a

mongoc_database_t

mongoc_collection_t

struct from the

mongoc_client_t

. At the start of an application, call

mongoc_init

before any other libmongoc functions. At the end, call the appropriate destroy function for each collection, database, or client handle, in reverse order from how they were constructed. Call

mongoc_cleanup

before exiting. The example below establishes a connection to a standalone server on

localhost

, registers the client application as "connect−example," and performs a simple command. More information about database operations can be found in the

CRUD Operations

and

Executing Commands

sections. Examples of connecting to replica sets and sharded clusters can be found on the Advanced Connections page. hello_mongoc.c

#include <mongoc/mongoc.h>

int
main (int argc, char *argv[])
{
   const char *uri_string = "mongodb://localhost:27017";
   mongoc_uri_t *uri;
   mongoc_client_t *client;
   mongoc_database_t *database;
   mongoc_collection_t *collection;
   bson_t *command, reply, *insert;
   bson_error_t error;
   char *str;
   bool retval;

   /*
    * Required to initialize libmongoc's internals
    */
   mongoc_init ();

   /*
    * Optionally get MongoDB URI from command line
    */
   if (argc > 1) {
      uri_string = argv[1];
   }

   /*
    * Safely create a MongoDB URI object from the given string
    */
   uri = mongoc_uri_new_with_error (uri_string, &error);
   if (!uri) {
      fprintf (stderr,
               "failed to parse URI: %s\n"
               "error message:       %s\n",
               uri_string,
               error.message);
      return EXIT_FAILURE;
   }

   /*
    * Create a new client instance
    */
   client = mongoc_client_new_from_uri (uri);
   if (!client) {
      return EXIT_FAILURE;
   }

   /*
    * Register the application name so we can track it in the profile logs
    * on the server. This can also be done from the URI (see other examples).
    */
   mongoc_client_set_appname (client, "connect−example");

   /*
    * Get a handle on the database "db_name" and collection "coll_name"
    */
   database = mongoc_client_get_database (client, "db_name");
   collection = mongoc_client_get_collection (client, "db_name", "coll_name");

   /*
    * Do work. This example pings the database, prints the result as JSON and
    * performs an insert
    */
   command = BCON_NEW ("ping", BCON_INT32 (1));

   retval = mongoc_client_command_simple (
      client, "admin", command, NULL, &reply, &error);

   if (!retval) {
      fprintf (stderr, "%s\n", error.message);
      return EXIT_FAILURE;
   }

   str = bson_as_json (&reply, NULL);
   printf ("%s\n", str);

   insert = BCON_NEW ("hello", BCON_UTF8 ("world"));

   if (!mongoc_collection_insert_one (collection, insert, NULL, NULL, &error)) {
      fprintf (stderr, "%s\n", error.message);
   }

   bson_destroy (insert);
   bson_destroy (&reply);
   bson_destroy (command);
   bson_free (str);

   /*
    * Release our handles and clean up libmongoc
    */
   mongoc_collection_destroy (collection);
   mongoc_database_destroy (database);
   mongoc_uri_destroy (uri);
   mongoc_client_destroy (client);
   mongoc_cleanup ();

   return EXIT_SUCCESS;
}

Creating BSON Documents

Documents are stored in MongoDB's data format, BSON. The C driver uses libbson

to create BSON documents. There are several ways to construct them: appending key−value pairs, using BCON, or parsing JSON.

Appending BSON

A BSON document, represented as a bson_t

in code, can be constructed one field at a time using libbson's append functions. For example, to create a document like this:

{
   born : ISODate("1906−12−09"),
   died : ISODate("1992−01−01"),
   name : {
      first : "Grace",
      last : "Hopper"
   },
   languages : [ "MATH−MATIC", "FLOW−MATIC", "COBOL" ],
   degrees: [ { degree: "BA", school: "Vassar" }, { degree: "PhD", school: "Yale" } ]
}

Use the following code:

#include <bson/bson.h>

int
main (int   argc,
      char *argv[])
{
   struct tm   born = { 0 };
   struct tm   died = { 0 };
   const char *lang_names[] = {"MATH−MATIC", "FLOW−MATIC", "COBOL"};
   const char *schools[] = {"Vassar", "Yale"};
   const char *degrees[] = {"BA", "PhD"};
   uint32_t    i;
   char        buf[16];
   const       char *key;
   size_t      keylen;
   bson_t     *document;
   bson_t      child;
   bson_t      child2;
   char       *str;

   document = bson_new ();

   /*
    * Append { "born" : ISODate("1906−12−09") } to the document.
    * Passing −1 for the length argument tells libbson to calculate the string length.
    */
   born.tm_year = 6;  /* years are 1900−based */
   born.tm_mon = 11;  /* months are 0−based */
   born.tm_mday = 9;
   bson_append_date_time (document, "born", −1, mktime (&born) * 1000);

   /*
    * Append { "died" : ISODate("1992−01−01") } to the document.
    */
   died.tm_year = 92;
   died.tm_mon = 0;
   died.tm_mday = 1;

   /*
    * For convenience, this macro passes length −1 by default.
    */
   BSON_APPEND_DATE_TIME (document, "died", mktime (&died) * 1000);

   /*
    * Append a subdocument.
    */
   BSON_APPEND_DOCUMENT_BEGIN (document, "name", &child);
   BSON_APPEND_UTF8 (&child, "first", "Grace");
   BSON_APPEND_UTF8 (&child, "last", "Hopper");
   bson_append_document_end (document, &child);

   /*
    * Append array of strings. Generate keys "0", "1", "2".
    */
   BSON_APPEND_ARRAY_BEGIN (document, "languages", &child);
   for (i = 0; i < sizeof lang_names / sizeof (char *); ++i) {
      keylen = bson_uint32_to_string (i, &key, buf, sizeof buf);
      bson_append_utf8 (&child, key, (int) keylen, lang_names[i], −1);
   }
   bson_append_array_end (document, &child);

   /*
    * Array of subdocuments:
    *    degrees: [ { degree: "BA", school: "Vassar" }, ... ]
    */
   BSON_APPEND_ARRAY_BEGIN (document, "degrees", &child);
   for (i = 0; i < sizeof degrees / sizeof (char *); ++i) {
      keylen = bson_uint32_to_string (i, &key, buf, sizeof buf);
      bson_append_document_begin (&child, key, (int) keylen, &child2);
      BSON_APPEND_UTF8 (&child2, "degree", degrees[i]);
      BSON_APPEND_UTF8 (&child2, "school", schools[i]);
      bson_append_document_end (&child, &child2);
   }
   bson_append_array_end (document, &child);

   /*
    * Print the document as a JSON string.
    */
   str = bson_as_canonical_extended_json (document, NULL);
   printf ("%s\n", str);
   bson_free (str);

   /*
    * Clean up allocated bson documents.
    */
   bson_destroy (document);
   return 0;
}

See the libbson documentation

for all of the types that can be appended to a

bson_t

Using BCON

BSON C Object Notation

, BCON for short, is an alternative way of constructing BSON documents in a manner closer to the intended format. It has less type−safety than BSON's append functions but results in less code.

#include <bson/bson.h>

int
main (int   argc,
      char *argv[])
{
   struct tm born = { 0 };
   struct tm died = { 0 };
   bson_t   *document;
   char     *str;

   born.tm_year = 6;
   born.tm_mon = 11;
   born.tm_mday = 9;

   died.tm_year = 92;
   died.tm_mon = 0;
   died.tm_mday = 1;

   document = BCON_NEW (
      "born", BCON_DATE_TIME (mktime (&born) * 1000),
      "died", BCON_DATE_TIME (mktime (&died) * 1000),
      "name", "{",
      "first", BCON_UTF8 ("Grace"),
      "last", BCON_UTF8 ("Hopper"),
      "}",
      "languages", "[",
      BCON_UTF8 ("MATH−MATIC"),
      BCON_UTF8 ("FLOW−MATIC"),
      BCON_UTF8 ("COBOL"),
      "]",
      "degrees", "[",
      "{", "degree", BCON_UTF8 ("BA"), "school", BCON_UTF8 ("Vassar"), "}",
      "{", "degree", BCON_UTF8 ("PhD"), "school", BCON_UTF8 ("Yale"), "}",
      "]");

   /*
    * Print the document as a JSON string.
    */
   str = bson_as_canonical_extended_json (document, NULL);
   printf ("%s\n", str);
   bson_free (str);

   /*
    * Clean up allocated bson documents.
    */
   bson_destroy (document);
   return 0;
}

Notice that BCON can create arrays, subdocuments and arbitrary fields.

Creating BSON from JSON

For single

documents, BSON can be created from JSON strings via

bson_new_from_json

#include <bson/bson.h>

int
main (int   argc,
      char *argv[])
{
   bson_error_t error;
   bson_t      *bson;
   char        *string;

   const char *json = "{\"name\": {\"first\":\"Grace\", \"last\":\"Hopper\"}}";
   bson = bson_new_from_json ((const uint8_t *)json, −1, &error);

   if (!bson) {
      fprintf (stderr, "%s\n", error.message);
      return EXIT_FAILURE;
   }

   string = bson_as_canonical_extended_json (bson, NULL);
   printf ("%s\n", string);
   bson_free (string);

   return 0;
}

To initialize BSON from a sequence of JSON documents, use bson_json_reader_t

Basic CRUD Operations

This section demonstrates the basics of using the C Driver to interact with MongoDB.

Inserting a Document

To insert documents into a collection, first obtain a handle to a mongoc_collection_t

via a

mongoc_client_t

. Then, use

mongoc_collection_insert_one

to add BSON documents to the collection. This example inserts into the database "mydb" and collection "mycoll". When finished, ensure that allocated structures are freed by using their respective destroy functions.

#include <bson/bson.h>
#include <mongoc/mongoc.h>
#include <stdio.h>

int
main (int   argc,
      char *argv[])
{
    mongoc_client_t *client;
    mongoc_collection_t *collection;
    bson_error_t error;
    bson_oid_t oid;
    bson_t *doc;

    mongoc_init ();

    client = mongoc_client_new ("mongodb://localhost:27017/?appname=insert−example");
    collection = mongoc_client_get_collection (client, "mydb", "mycoll");

    doc = bson_new ();
    bson_oid_init (&oid, NULL);
    BSON_APPEND_OID (doc, "_id", &oid);
    BSON_APPEND_UTF8 (doc, "hello", "world");

    if (!mongoc_collection_insert_one (
           collection, doc, NULL, NULL, &error)) {
        fprintf (stderr, "%s\n", error.message);
    }

    bson_destroy (doc);
    mongoc_collection_destroy (collection);
    mongoc_client_destroy (client);
    mongoc_cleanup ();

    return 0;
}

Compile the code and run it:

$ gcc −o insert insert.c $(pkg−config −−cflags −−libs libmongoc−1.0)
$ ./insert

On Windows:

C:\> cl.exe /IC:\mongo−c−driver\include\libbson−1.0 /IC:\mongo−c−driver\include\libmongoc−1.0 insert.c
C:\> insert

To verify that the insert succeeded, connect with the MongoDB shell.

$ mongo
MongoDB shell version: 3.0.6
connecting to: test
> use mydb
switched to db mydb
> db.mycoll.find()
{ "_id" : ObjectId("55ef43766cb5f36a3bae6ee4"), "hello" : "world" }
>

Finding a Document

To query a MongoDB collection with the C driver, use the function mongoc_collection_find_with_opts(). This returns a cursor to the matching documents. The following examples iterate through the result cursors and print the matches to stdout

as JSON strings. Use a document as a query specifier; for example,

{ "color" : "red" }

will match any document with a field named "color" with value "red". An empty document

{

}

can be used to match all documents. This first example uses an empty query specifier to find all documents in the database "mydb" and collection "mycoll".

#include <bson/bson.h>
#include <mongoc/mongoc.h>
#include <stdio.h>

int
main (int argc, char *argv[])
{
   mongoc_client_t *client;
   mongoc_collection_t *collection;
   mongoc_cursor_t *cursor;
   const bson_t *doc;
   bson_t *query;
   char *str;

   mongoc_init ();

   client =
      mongoc_client_new ("mongodb://localhost:27017/?appname=find−example");
   collection = mongoc_client_get_collection (client, "mydb", "mycoll");
   query = bson_new ();
   cursor = mongoc_collection_find_with_opts (collection, query, NULL, NULL);

   while (mongoc_cursor_next (cursor, &doc)) {
      str = bson_as_canonical_extended_json (doc, NULL);
      printf ("%s\n", str);
      bson_free (str);
   }

   bson_destroy (query);
   mongoc_cursor_destroy (cursor);
   mongoc_collection_destroy (collection);
   mongoc_client_destroy (client);
   mongoc_cleanup ();

   return 0;
}

Compile the code and run it:

$ gcc −o find find.c $(pkg−config −−cflags −−libs libmongoc−1.0)
$ ./find
{ "_id" : { "$oid" : "55ef43766cb5f36a3bae6ee4" }, "hello" : "world" }

On Windows:

C:\> cl.exe /IC:\mongo−c−driver\include\libbson−1.0 /IC:\mongo−c−driver\include\libmongoc−1.0 find.c
C:\> find
{ "_id" : { "$oid" : "55ef43766cb5f36a3bae6ee4" }, "hello" : "world" }

To look for a specific document, add a specifier to query

. This example adds a call to

BSON_APPEND_UTF8(

)

to look for all documents matching

{

"hello" : "world"

}

#include <bson/bson.h>
#include <mongoc/mongoc.h>
#include <stdio.h>

int
main (int argc, char *argv[])
{
   mongoc_client_t *client;
   mongoc_collection_t *collection;
   mongoc_cursor_t *cursor;
   const bson_t *doc;
   bson_t *query;
   char *str;

   mongoc_init ();

   client = mongoc_client_new (
      "mongodb://localhost:27017/?appname=find−specific−example");
   collection = mongoc_client_get_collection (client, "mydb", "mycoll");
   query = bson_new ();
   BSON_APPEND_UTF8 (query, "hello", "world");

   cursor = mongoc_collection_find_with_opts (collection, query, NULL, NULL);

   while (mongoc_cursor_next (cursor, &doc)) {
      str = bson_as_canonical_extended_json (doc, NULL);
      printf ("%s\n", str);
      bson_free (str);
   }

   bson_destroy (query);
   mongoc_cursor_destroy (cursor);
   mongoc_collection_destroy (collection);
   mongoc_client_destroy (client);
   mongoc_cleanup ();

   return 0;
}

$ gcc −o find−specific find−specific.c $(pkg−config −−cflags −−libs libmongoc−1.0)
$ ./find−specific
{ "_id" : { "$oid" : "55ef43766cb5f36a3bae6ee4" }, "hello" : "world" }

C:\> cl.exe /IC:\mongo−c−driver\include\libbson−1.0 /IC:\mongo−c−driver\include\libmongoc−1.0 find−specific.c
C:\> find−specific
{ "_id" : { "$oid" : "55ef43766cb5f36a3bae6ee4" }, "hello" : "world" }

Updating a Document

This code snippet gives an example of using mongoc_collection_update_one() to update the fields of a document. Using the "mydb" database, the following example inserts an example document into the "mycoll" collection. Then, using its _id

field, the document is updated with different values and a new field.

#include <bson/bson.h>
#include <mongoc/mongoc.h>
#include <stdio.h>

int
main (int argc, char *argv[])
{
   mongoc_collection_t *collection;
   mongoc_client_t *client;
   bson_error_t error;
   bson_oid_t oid;
   bson_t *doc = NULL;
   bson_t *update = NULL;
   bson_t *query = NULL;

   mongoc_init ();

   client =
      mongoc_client_new ("mongodb://localhost:27017/?appname=update−example");
   collection = mongoc_client_get_collection (client, "mydb", "mycoll");

   bson_oid_init (&oid, NULL);
   doc = BCON_NEW ("_id", BCON_OID (&oid), "key", BCON_UTF8 ("old_value"));

   if (!mongoc_collection_insert_one (collection, doc, NULL, &error)) {
      fprintf (stderr, "%s\n", error.message);
      goto fail;
   }

   query = BCON_NEW ("_id", BCON_OID (&oid));
   update = BCON_NEW ("$set",
                      "{",
                      "key",
                      BCON_UTF8 ("new_value"),
                      "updated",
                      BCON_BOOL (true),
                      "}");

   if (!mongoc_collection_update_one (
          collection, query, update, NULL, NULL, &error)) {
      fprintf (stderr, "%s\n", error.message);
      goto fail;
   }

fail:
   if (doc)
      bson_destroy (doc);
   if (query)
      bson_destroy (query);
   if (update)
      bson_destroy (update);

   mongoc_collection_destroy (collection);
   mongoc_client_destroy (client);
   mongoc_cleanup ();

   return 0;
}

Compile the code and run it:

$ gcc −o update update.c $(pkg−config −−cflags −−libs libmongoc−1.0)
$ ./update

On Windows:

C:\> cl.exe /IC:\mongo−c−driver\include\libbson−1.0 /IC:\mongo−c−driver\include\libmongoc−1.0 update.c
C:\> update
{ "_id" : { "$oid" : "55ef43766cb5f36a3bae6ee4" }, "hello" : "world" }

To verify that the update succeeded, connect with the MongoDB shell.

$ mongo
MongoDB shell version: 3.0.6
connecting to: test
> use mydb
switched to db mydb
> db.mycoll.find({"updated" : true})
{ "_id" : ObjectId("55ef549236fe322f9490e17b"), "updated" : true, "key" : "new_value" }
>

Deleting a Document

This example illustrates the use of mongoc_collection_delete_one(

)

to delete a document. The following code inserts a sample document into the database "mydb" and collection "mycoll". Then, it deletes all documents matching

{

"hello" : "world"

}

#include <bson/bson.h>
#include <mongoc/mongoc.h>
#include <stdio.h>

int
main (int argc, char *argv[])
{
   mongoc_client_t *client;
   mongoc_collection_t *collection;
   bson_error_t error;
   bson_oid_t oid;
   bson_t *doc;

   mongoc_init ();

   client =
      mongoc_client_new ("mongodb://localhost:27017/?appname=delete−example");
   collection = mongoc_client_get_collection (client, "test", "test");

   doc = bson_new ();
   bson_oid_init (&oid, NULL);
   BSON_APPEND_OID (doc, "_id", &oid);
   BSON_APPEND_UTF8 (doc, "hello", "world");

   if (!mongoc_collection_insert_one (collection, doc, NULL, &error)) {
      fprintf (stderr, "Insert failed: %s\n", error.message);
   }

   bson_destroy (doc);

   doc = bson_new ();
   BSON_APPEND_OID (doc, "_id", &oid);

   if (!mongoc_collection_delete_one (
          collection, doc, NULL, NULL, &error)) {
      fprintf (stderr, "Delete failed: %s\n", error.message);
   }

   bson_destroy (doc);
   mongoc_collection_destroy (collection);
   mongoc_client_destroy (client);
   mongoc_cleanup ();

   return 0;
}

Compile the code and run it:

$ gcc −o delete delete.c $(pkg−config −−cflags −−libs libmongoc−1.0)
$ ./delete

On Windows:

C:\> cl.exe /IC:\mongo−c−driver\include\libbson−1.0 /IC:\mongo−c−driver\include\libmongoc−1.0 delete.c
C:\> delete

Use the MongoDB shell to prove that the documents have been removed successfully.

$ mongo
MongoDB shell version: 3.0.6
connecting to: test
> use mydb
switched to db mydb
> db.mycoll.count({"hello" : "world"})
0
>

Counting Documents

Counting the number of documents in a MongoDB collection is similar to performing a find operation

. This example counts the number of documents matching

{

"hello" : "world"

}

in the database "mydb" and collection "mycoll".

#include <bson/bson.h>
#include <mongoc/mongoc.h>
#include <stdio.h>

int
main (int argc, char *argv[])
{
   mongoc_client_t *client;
   mongoc_collection_t *collection;
   bson_error_t error;
   bson_t *doc;
   int64_t count;

   mongoc_init ();

   client =
      mongoc_client_new ("mongodb://localhost:27017/?appname=count−example");
   collection = mongoc_client_get_collection (client, "mydb", "mycoll");
   doc = bson_new_from_json (
      (const uint8_t *) "{\"hello\" : \"world\"}", −1, &error);

   count = mongoc_collection_count (
      collection, MONGOC_QUERY_NONE, doc, 0, 0, NULL, &error);

   if (count < 0) {
      fprintf (stderr, "%s\n", error.message);
   } else {
      printf ("%" PRId64 "\n", count);
   }

   bson_destroy (doc);
   mongoc_collection_destroy (collection);
   mongoc_client_destroy (client);
   mongoc_cleanup ();

   return 0;
}

Compile the code and run it:

$ gcc −o count count.c $(pkg−config −−cflags −−libs libmongoc−1.0)
$ ./count
1

On Windows:

C:\> cl.exe /IC:\mongo−c−driver\include\libbson−1.0 /IC:\mongo−c−driver\include\libmongoc−1.0 count.c
C:\> count
1

Executing Commands

The driver provides helper functions for executing MongoDB commands on client, database and collection structures. These functions return cursors; the _simple

variants return booleans indicating success or failure. This example executes the

collStats

command against the collection "mycoll" in database "mydb".

#include <bson/bson.h>
#include <mongoc/mongoc.h>
#include <stdio.h>

int
main (int argc, char *argv[])
{
   mongoc_client_t *client;
   mongoc_collection_t *collection;
   bson_error_t error;
   bson_t *command;
   bson_t reply;
   char *str;

   mongoc_init ();

   client = mongoc_client_new (
      "mongodb://localhost:27017/?appname=executing−example");
   collection = mongoc_client_get_collection (client, "mydb", "mycoll");

   command = BCON_NEW ("collStats", BCON_UTF8 ("mycoll"));
   if (mongoc_collection_command_simple (
          collection, command, NULL, &reply, &error)) {
      str = bson_as_canonical_extended_json (&reply, NULL);
      printf ("%s\n", str);
      bson_free (str);
   } else {
      fprintf (stderr, "Failed to run command: %s\n", error.message);
   }

   bson_destroy (command);
   bson_destroy (&reply);
   mongoc_collection_destroy (collection);
   mongoc_client_destroy (client);
   mongoc_cleanup ();

   return 0;
}

Compile the code and run it:

$ gcc −o executing executing.c $(pkg−config −−cflags −−libs libmongoc−1.0)
$ ./executing
{ "ns" : "mydb.mycoll", "count" : 1, "size" : 48, "avgObjSize" : 48, "numExtents" : 1, "storageSize" : 8192,
"lastExtentSize" : 8192.000000, "paddingFactor" : 1.000000, "userFlags" : 1, "capped" : false, "nindexes" : 1,
"indexDetails" : {  }, "totalIndexSize" : 8176, "indexSizes" : { "_id_" : 8176 }, "ok" : 1.000000 }

On Windows:

C:\> cl.exe /IC:\mongo−c−driver\include\libbson−1.0 /IC:\mongo−c−driver\include\libmongoc−1.0 executing.c
C:\> executing
{ "ns" : "mydb.mycoll", "count" : 1, "size" : 48, "avgObjSize" : 48, "numExtents" : 1, "storageSize" : 8192,
"lastExtentSize" : 8192.000000, "paddingFactor" : 1.000000, "userFlags" : 1, "capped" : false, "nindexes" : 1,
"indexDetails" : {  }, "totalIndexSize" : 8176, "indexSizes" : { "_id_" : 8176 }, "ok" : 1.000000 }

Threading

The MongoDB C Driver is thread−unaware in the vast majority of its operations. This means it is up to the programmer to guarantee thread−safety. However, mongoc_client_pool_t

is thread−safe and is used to fetch a

mongoc_client_t

in a thread−safe manner. After retrieving a client from the pool, the client structure should be considered owned by the calling thread. When the thread is finished, the client should be placed back into the pool. example−pool.c

/* gcc example−pool.c −o example−pool $(pkg−config −−cflags −−libs
 * libmongoc−1.0) */

/* ./example−pool [CONNECTION_STRING] */

#include <mongoc/mongoc.h>
#include <pthread.h>
#include <stdio.h>

static pthread_mutex_t mutex;
static bool in_shutdown = false;

static void *
worker (void *data)
{
   mongoc_client_pool_t *pool = data;
   mongoc_client_t *client;
   bson_t ping = BSON_INITIALIZER;
   bson_error_t error;
   bool r;

   BSON_APPEND_INT32 (&ping, "ping", 1);

   while (true) {
      client = mongoc_client_pool_pop (pool);
      /* Do something with client. If you are writing an HTTP server, you
       * probably only want to hold onto the client for the portion of the
       * request performing database queries.
       */
      r = mongoc_client_command_simple (
         client, "admin", &ping, NULL, NULL, &error);

      if (!r) {
         fprintf (stderr, "%s\n", error.message);
      }

      mongoc_client_pool_push (pool, client);

      pthread_mutex_lock (&mutex);
      if (in_shutdown || !r) {
         pthread_mutex_unlock (&mutex);
         break;
      }

      pthread_mutex_unlock (&mutex);
   }

   bson_destroy (&ping);
   return NULL;
}

int
main (int argc, char *argv[])
{
   const char *uri_string = "mongodb://127.0.0.1/?appname=pool−example";
   mongoc_uri_t *uri;
   bson_error_t error;
   mongoc_client_pool_t *pool;
   pthread_t threads[10];
   unsigned i;
   void *ret;

   pthread_mutex_init (&mutex, NULL);
   mongoc_init ();

   if (argc > 1) {
      uri_string = argv[1];
   }

   uri = mongoc_uri_new_with_error (uri_string, &error);
   if (!uri) {
      fprintf (stderr,
               "failed to parse URI: %s\n"
               "error message:       %s\n",
               uri_string,
               error.message);
      return EXIT_FAILURE;
   }

   pool = mongoc_client_pool_new (uri);
   mongoc_client_pool_set_error_api (pool, 2);

   for (i = 0; i < 10; i++) {
      pthread_create (&threads[i], NULL, worker, pool);
   }

   sleep (10);
   pthread_mutex_lock (&mutex);
   in_shutdown = true;
   pthread_mutex_unlock (&mutex);

   for (i = 0; i < 10; i++) {
      pthread_join (threads[i], &ret);
   }

   mongoc_client_pool_destroy (pool);
   mongoc_uri_destroy (uri);

   mongoc_cleanup ();

   return EXIT_SUCCESS;
}

Next Steps

To find information on advanced topics, browse the rest of the C driver guide or the official MongoDB documentation

. For help with common issues, consult the Troubleshooting page. To report a bug or request a new feature, follow these instructions.

Authentication

This guide covers the use of authentication options with the MongoDB C Driver. Ensure that the MongoDB server is also properly configured for authentication before making a connection. For more information, see the MongoDB security documentation

. The MongoDB C driver supports several authentication mechanisms through the use of MongoDB connection URIs. By default, if a username and password are provided as part of the connection string (and an optional authentication database), they are used to connect via the default authentication mechanism of the server. To select a specific authentication mechanism other than the default, see the list of supported mechanism below.

mongoc_client_t *client = mongoc_client_new ("mongodb://user:password@localhost/?authSource=mydb");

Currently supported values for the authMechanism connection string option are:

•

SCRAM−SHA−1

•

MONGODB−CR (deprecated)

•

GSSAPI

•

PLAIN

•

X509

•

MONGODB−AWS

Basic Authentication (SCRAM−SHA−256)

MongoDB 4.0 introduces support for authenticating using the SCRAM protocol with the more secure SHA−256 hash described in RFC 7677

. Using this authentication mechanism means that the password is never actually sent over the wire when authenticating, but rather a computed proof that the client password is the same as the password the server knows. In MongoDB 4.0, the C driver can determine the correct default authentication mechanism for users with stored SCRAM−SHA−1 and SCRAM−SHA−256 credentials:

mongoc_client_t *client =  mongoc_client_new ("mongodb://user:password@localhost/?authSource=mydb");
/* the correct authMechanism is negotiated between the driver and server. */

Alternatively, SCRAM−SHA−256 can be explicitly specified as an authMechanism.

mongoc_client_t *client =  mongoc_client_new ("mongodb://user:password@localhost/?authMechanism=SCRAM−SHA−256&authSource=mydb");

Passwords for SCRAM−SHA−256 undergo the preprocessing step known as SASLPrep specified in RFC 4013

. SASLPrep will only be performed for passwords containing non−ASCII characters. SASLPrep requires libicu. If libicu is not available, attempting to authenticate over SCRAM−SHA−256 with non−ASCII passwords will result in error. Usernames

never

undergo SASLPrep. By default, when building the C driver libicu is linked if available. This can be changed with the

ENABLE_ICU

cmake option. To specify an installation path of libicu, specify

ICU_ROOT

as a cmake option. See the

FindICU

documentation for more information.

Basic Authentication (SCRAM−SHA−1)

The default authentication mechanism before MongoDB 4.0 is SCRAM−SHA−1

(

RFC 5802

). Using this authentication mechanism means that the password is never actually sent over the wire when authenticating, but rather a computed proof that the client password is the same as the password the server knows.

mongoc_client_t *client = mongoc_client_new ("mongodb://user:password@localhost/?authMechanism=SCRAM−SHA−1&authSource=mydb");

NOTE:

SCRAM−SHA−1

authenticates against the

admin

database by default. If the user is created in another database, then specifying the authSource is required.

Legacy Authentication (MONGODB−CR)

The MONGODB−CR authMechanism is deprecated and will no longer function in MongoDB 4.0. Instead, specify no authMechanism and the driver will use an authentication mechanism compatible with your server.

GSSAPI (Kerberos) Authentication

NOTE:

Kerberos support requires compiling the driver against cyrus−sasl

on UNIX−like environments. On Windows, configure the driver to build against the Windows Native SSPI.

GSSAPI

(Kerberos) authentication is available in the Enterprise Edition of MongoDB. To authenticate using

GSSAPI

, the MongoDB C driver must be installed with SASL support. On UNIX−like environments, run the

kinit

command before using the following authentication methods:

$ kinit mongodbuser@EXAMPLE.COM
mongodbuser@EXAMPLE.COM's Password:
$ klistCredentials cache: FILE:/tmp/krb5cc_1000
        Principal: mongodbuser@EXAMPLE.COM

  Issued                Expires               Principal
Feb  9 13:48:51 2013  Feb  9 23:48:51 2013  krbtgt/EXAMPLE.COM@EXAMPLE.COM

Now authenticate using the MongoDB URI. GSSAPI

authenticates against the

$external

virtual database, so a database does not need to be specified in the URI. Note that the Kerberos principal

must

be URL−encoded:

mongoc_client_t *client;

client = mongoc_client_new ("mongodb://mongodbuser%40EXAMPLE.COM@mongo−server.example.com/?authMechanism=GSSAPI");

NOTE:

GSSAPI

authenticates against the

$external

database, so specifying the authSource database is not required.

The driver supports these GSSAPI properties:

•

CANONICALIZE_HOST_NAME

: This might be required with Cyrus−SASL when the hosts report different hostnames than what is used in the Kerberos database. The default is "false".

•

SERVICE_NAME

: Use a different service name than the default, "mongodb".

Set properties in the URL:

mongoc_client_t *client;

client = mongoc_client_new ("mongodb://mongodbuser%40EXAMPLE.COM@mongo−server.example.com/?authMechanism=GSSAPI&"
                            "authMechanismProperties=SERVICE_NAME:other,CANONICALIZE_HOST_NAME:true");

If you encounter errors such as Invalid net address

, check if the application is behind a NAT (Network Address Translation) firewall. If so, create a ticket that uses

forwardable

and

addressless

Kerberos tickets. This can be done by passing

−f −A

kinit

$ kinit −f −A mongodbuser@EXAMPLE.COM

SASL Plain Authentication

NOTE:

The MongoDB C Driver must be compiled with SASL support in order to use SASL PLAIN

authentication.

MongoDB Enterprise Edition supports the SASL PLAIN

authentication mechanism, initially intended for delegating authentication to an LDAP server. Using the

SASL PLAIN

mechanism is very similar to the challenge response mechanism with usernames and passwords. This authentication mechanism uses the

$external

virtual database for

LDAP

support:

NOTE:

SASL PLAIN

is a clear−text authentication mechanism. It is strongly recommended to connect to MongoDB using TLS with certificate validation when using the

PLAIN

mechanism.

mongoc_client_t *client;

client = mongoc_client_new ("mongodb://user:password@example.com/?authMechanism=PLAIN");

PLAIN

authenticates against the

$external

database, so specifying the authSource database is not required.

X.509 Certificate Authentication

NOTE:

The MongoDB C Driver must be compiled with TLS support for X.509 authentication support. Once this is done, start a server with the following options:

$ mongod −−tlsMode requireTLS −−tlsCertificateKeyFile server.pem −−tlsCAFile ca.pem

The MONGODB−X509

mechanism authenticates a username derived from the distinguished subject name of the X.509 certificate presented by the driver during TLS negotiation. This authentication method requires the use of TLS connections with certificate validation.

mongoc_client_t *client;
mongoc_ssl_opt_t ssl_opts = { 0 };

ssl_opts.pem_file = "mycert.pem";
ssl_opts.pem_pwd = "mycertpassword";
ssl_opts.ca_file = "myca.pem";
ssl_opts.ca_dir = "trust_dir";
ssl_opts.weak_cert_validation = false;

client = mongoc_client_new ("mongodb://x509_derived_username@localhost/?authMechanism=MONGODB−X509");
mongoc_client_set_ssl_opts (client, &ssl_opts);

MONGODB−X509

authenticates against the

$external

database, so specifying the authSource database is not required. For more information on the x509_derived_username, see the MongoDB server

x.509 tutorial

NOTE:

The MongoDB C Driver will attempt to determine the x509 derived username when none is provided, and as of MongoDB 3.4 providing the username is not required at all.

Authentication via AWS IAM

The MONGODB−AWS

mechanism authenticates to MongoDB servers with credentials provided by AWS Identity and Access Management (IAM). To authenticate, create a user with an associated Amazon Resource Name (ARN) on the

$external

database, and specify the

MONGODB−AWS

authMechanism

in the URI.

mongoc_uri_t *uri = mongoc_uri_new ("mongodb://localhost/?authMechanism=MONGODB−AWS");

Since MONGODB−AWS

always authenticates against the

$external

database, so specifying the authSource database is not required. Credentials include the

access key id

secret access key

, and optional

session token

. They may be obtained from the following ways.

AWS credentials via URI

Credentials may be passed directly in the URI as username/password.

mongoc_uri_t *uri = mongoc_uri_new ("mongodb://<access key id>:<secret access key>localhost/?authMechanism=MONGODB−AWS");

This may include a session token

passed with

authMechanismProperties

mongoc_uri_t *uri = mongoc_uri_new ("mongodb://<access key id>:<secret access key>localhost/?authMechanism=MONGODB−AWS&authMechanismProperties=AWS_SESSION_TOKEN:<token>");

AWS credentials via environment

If credentials are not passed through the URI, libmongoc will check for the following environment variables.

• AWS_ACCESS_KEY_ID

• AWS_SECRET_ACCESS_KEY

• AWS_SESSION_TOKEN (optional)

AWS Credentials via ECS

If credentials are not passed in the URI or with environment variables, libmongoc will check if the environment variable AWS_CONTAINER_CREDENTIALS_RELATIVE_URI

is set, and if so, attempt to retrieve temporary credentials from the ECS task metadata by querying a link local address.

AWS Credentials via EC2

If credentials are not passed in the URI or with environment variables, and the environment variable AWS_CONTAINER_CREDENTIALS_RELATIVE_URI

is not set, libmongoc will attempt to retrieve temporary credentials from the EC2 machine metadata by querying link local addresses.

Basic Troubleshooting

Troubleshooting Checklist

The following is a short list of things to check when you have a problem.

• Did you call mongoc_init(

)

main(

)

? If not, you will likely see a segfault.

• Have you leaked any clients or cursors as can be found with mongoc−stat <PID>

• Have packets been delivered to the server? See egress bytes from mongoc−stat <PID>

• Does valgrind

show any leaks? Ensure you call

mongoc_cleanup(

)

at the end of your process to cleanup lingering allocations from the MongoDB C driver.

• If compiling your own copy of MongoDB C Driver, consider using the cmake option −DENABLE_TRACING=ON

to enable function tracing and hex dumps of network packets to

STDERR

and

STDOUT

Performance Counters

The MongoDB C driver comes with an optional unique feature to help developers and sysadmins troubleshoot problems in production. Performance counters are available for each process using the driver. If available, the counters can be accessed outside of the application process via a shared memory segment. This means that you can graph statistics about your application process easily from tools like Munin or Nagios. Your author often uses watch −−interval=0.5 −d mongoc−stat $PID

to monitor an application. Performance counters are only available on Linux platforms supporting shared memory segments. On supported platforms they are enabled by default. Applications can be built without the counters by specifying the cmake option

−DENABLE_SHM_COUNTERS=OFF

. Additionally, if performance counters are already compiled, they can be disabled at runtime by specifying the environment variable

MONGOC_DISABLE_SHM

. Performance counters keep track of the following:

• Active and Disposed Cursors

• Active and Disposed Clients, Client Pools, and Socket Streams.

• Number of operations sent and received, by type.

• Bytes transferred and received.

• Authentication successes and failures.

• Number of wire protocol errors.

To access counters for a given process, simply provide the process id to the mongoc−stat

program installed with the MongoDB C Driver.

$ mongoc−stat 22203
   Operations : Egress Total        : The number of sent operations.                    : 13247
   Operations : Ingress Total       : The number of received operations.                : 13246
   Operations : Egress Queries      : The number of sent Query operations.              : 13247
   Operations : Ingress Queries     : The number of received Query operations.          : 0
   Operations : Egress GetMore      : The number of sent GetMore operations.            : 0
   Operations : Ingress GetMore     : The number of received GetMore operations.        : 0
   Operations : Egress Insert       : The number of sent Insert operations.             : 0
   Operations : Ingress Insert      : The number of received Insert operations.         : 0
   Operations : Egress Delete       : The number of sent Delete operations.             : 0
   Operations : Ingress Delete      : The number of received Delete operations.         : 0
   Operations : Egress Update       : The number of sent Update operations.             : 0
   Operations : Ingress Update      : The number of received Update operations.         : 0
   Operations : Egress KillCursors  : The number of sent KillCursors operations.        : 0
   Operations : Ingress KillCursors : The number of received KillCursors operations.    : 0
   Operations : Egress Msg          : The number of sent Msg operations.                : 0
   Operations : Ingress Msg         : The number of received Msg operations.            : 0
   Operations : Egress Reply        : The number of sent Reply operations.              : 0
   Operations : Ingress Reply       : The number of received Reply operations.          : 13246
      Cursors : Active              : The number of active cursors.                     : 1
      Cursors : Disposed            : The number of disposed cursors.                   : 13246
      Clients : Active              : The number of active clients.                     : 1
      Clients : Disposed            : The number of disposed clients.                   : 0
      Streams : Active              : The number of active streams.                     : 1
      Streams : Disposed            : The number of disposed streams.                   : 0
      Streams : Egress Bytes        : The number of bytes sent.                         : 794931
      Streams : Ingress Bytes       : The number of bytes received.                     : 589694
      Streams : N Socket Timeouts   : The number of socket timeouts.                    : 0
 Client Pools : Active              : The number of active client pools.                : 1
 Client Pools : Disposed            : The number of disposed client pools.              : 0
     Protocol : Ingress Errors      : The number of protocol errors on ingress.         : 0
         Auth : Failures            : The number of failed authentication requests.     : 0
         Auth : Success             : The number of successful authentication requests. : 0

Submitting a Bug Report

Think you've found a bug? Want to see a new feature in the MongoDB C driver? Please open a case in our issue management tool, JIRA:

•

Create an account and login

• Navigate to the CDRIVER project

• Click Create Issue

− Please provide as much information as possible about the issue type and how to reproduce it.

Bug reports in JIRA for all driver projects (i.e. CDRIVER, CSHARP, JAVA) and the Core Server (i.e. SERVER) project are public

Guides

Configuring TLS

Configuration with URI options

Enable TLS by including tls=true

the URI.

mongoc_uri_t *uri = mongoc_uri_new ("mongodb://localhost:27017/");
mongoc_uri_set_option_as_bool (uri, MONGOC_URI_TLS, true);

mongoc_client_t *client = mongoc_client_new_from_uri (uri);

The following URI options may be used to further configure TLS:

ERROR : https://linux0001.com/man : please email : johanes_gumabo@yahoo.co.id