Message Persistence API for POSIX C SDK

Message Persistence provides real-time access to the history of all messages published to PubNub. Each published message is timestamped to the nearest 10 nanoseconds and is stored across multiple availability zones in several geographical locations. Stored messages can be encrypted with AES-256 message encryption, ensuring that they are not readable while stored on PubNub's network. For more information, refer to Message Persistence.

Messages can be stored for a configurable duration or forever, as controlled by the retention policy that is configured on your account. The following options are available: 1 day, 7 days, 30 days, 3 months, 6 months, 1 year, or Unlimited.

You can retrieve the following:

  • Messages
  • Message reactions
  • File Sharing (using File Sharing API)

History​

This function fetches historical messages of a channel. Message Persistence provides real-time access to an unlimited history for all messages published to PubNub. Stored messages are replicated across multiple availability zones in several geographical data center locations. Stored messages can be encrypted with AES-256 message encryption ensuring that they are not readable while stored on PubNub's network. It is possible to control how messages are returned and in what order, for example you can:

  • Limit the number of messages to a specific quantity using the 4th argument parameter.

Method(s)​

To run History you can use the following method(s) in the Posix C SDK:

enum pubnub_res pubnub_history (pubnub_t *p, const char *channel, const char *channel_group, unsigned count)
* required
ParameterDescription
p *
Type: pubnub_t*
Pointer to PubNub client context. Can't be NULL.
channel *
Type: const char*
The string with the channel name to fetch the history
count *
Type: unsigned
Maximum number of messages to get. If there are less than this available on the channel, you'll get less, but you can't get more.
include_token *
Type: bool
If true, include the timetoken for every message. default: false

Basic Usage​

Retrieve the last 100 messages on a channel:

// Sync
enum pubnub_res res;

pubnub_history(pn, "history_channel", 10, false);
res = pubnub_await(pn);

if (PNR_OK == res) {
  puts("Got history! Messages:");
  for (;;) {
    const char *msg = pubnub_get(pn);
    if (NULL == msg) {
      break;
    }
    puts(msg);
  }
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Rest Response from Server​

An array is returned on success. The pubnub_history() function returns a list of up to 100 messages, the timetoken of the first (oldest) message and the timetoken of the last (newest) message in the resulting set of messages. The output below demonstrates the format for a pubnub_history() response:

[
    ["message1", "message2", "message3",... ],
    "Start Time Token",
    "End Time Token"
]

Extended History​

Extended History Options structure​

Options for extended history.

Method(s)​

Declaration​

struct pubnub_history_options { bool string_token; int count; bool reverse; char const* start; char const* end; bool include_token; };

Members​

MemberTypeDescription
string_token
bool
If false, the returned start and end Timetoken values will be returned as long ints. If true, the start and end Timetoken values will be returned as strings. Default is false.
count
int
The maximum number of messages to return per response. Has to be between 1 and 100 messages. Default is 100.
reverse
bool
Direction of time traversal. Default is false, which means timeline is traversed newest to oldest.
start
char const*
If provided (not NULL), lets you select a "start date," in Timetoken format. If not provided, it will default to current time. Page through results by providing a start OR end timetoken. Retrieve a slice of the time line by providing both a start AND end timetoken. start is exclusive – that is, the first item returned will be the one immediately after the start Timetoken value. Default is NULL.
end
char const*
If provided (not NULL), lets you select an "end date," in Timetoken format. If not provided, it will provide up to the number of messages defined in the "count" parameter. Page through results by providing a start OR end timetoken. Retrieve a slice of the time line by providing both a start AND end timetoken. End is exclusive – that is, if a message is associated exactly with the end Timetoken, it will be included in the result. Default is NULL.
include_token
bool
Pass true to receive a timetoken with each history message. Defaults to false.

Initialize extended History options​

This returns the default options for publish V1 transactions. It's best to always call it to initialize the pubnub_history_options(), since it has several parameters.

Method(s)​

Declaration​

struct pubnub_history_options pubnub_history_defopts(void);

Parameters​

This Method has not Argument.

Basic Usage​

struct pubnub_history_options opts = pubnub_history_defopts();

Returns​

TypeValueDescription
struct pubnub_history_options
The default options for here-now.

Extended History​

The extended history. It is basically the same as the pubnub_history(), just adding a few options that will be sent.

Method(s)​

Declaration​

enum pubnub_res pubnub_history_ex(pubnub_t* pb, char const* channel, struct pubnub_history_options opt);

Parameters​

* required
ParameterDescription
pb
Type: pubnub_t*
The Pubnub context
channel
Type: char const*
The string with the channel name to get history for.
opt
Type: struct pubnub_history_options
History options.

Basic Usage​

struct pubnub_history_options opt = pubnub_history_defopts();
opt.reverse = true;
pbresult = pubnub_history_ex(pn, "my_channel", opt);

Returns​

TypeValueDescription
enum pubnub_res
PNR_STARTED
Success.
other
Indicates the type of error.

Message Counts​

Message count per channel structure​

Contains channel name (as char memory block, aka Pascal string) and message count for messages received on the channel. The message counts are the number of messages published on one or more channels since a given time.

Used to store information retrieved by pubnub_message_counts() transaction.

Declaration​

struct pubnub_chan_msg_count {pubnub_chamebl_t channel; size_t message_count; };

Members​

MembersTypeDescription
channel
pubnub_chamebl_t
Channel name as a char memory block (aka Pascal string)
message_count
size_t
Number of messages for the channel

Count channels in message count response​

Returns the number of members (key->value pairs) of JSON object channels in the response to a message count transaction.

Declaration​

int pubnub_get_chan_msg_counts_size(pubnub_t* pb);

Parameters​

* required
ParameterDescription
pb *
Type: pubnub_t*
The Pubnub context in which to parse the response

Basic Usage​

int n  = pubnub_get_chan_msg_counts_size(pb);
printf("There are %d channels in the message counts response\n", n);

Returns​

TypeValueDescription
int
-1
Error (transaction still in progress or other)
>= 0
The number of members of the channels JSON object)

Message Counts transaction​

Starts the transaction pubnub_message_counts on the context @p pb for the list of channels @p channel for messages counts starting from @p timeoken which can be a single timetoken, or list of comma-separated timetokens (corresponding to the channel list).

Unlimited message retention

For keys with unlimited message retention enabled, this transaction considers only messages published in the last 30 days.

Declaration​

enum pubnub_res pubnub_message_counts(pubnub_t* pb, char const* channel, char const* timetoken);

Parameters​

* required
ParameterDescription
pb *
Type: pubnub_t*
The Pubnub context to use for transaction
channel *
Type: char const*
The string with the channel name (or comma-delimited list of channel names) to subscribe for.
timetoken *
Type: char const*
A single token OR a comma-separated list of tokens. If single, will be used for all channels. If a list, has to have the same number of elements as @p channel and each will be used for its channel, in-order.

Basic Usage​

/** Obtain message count for
        channel 'one' since 15517035062228243 and
        channel 'two' since 15517035052228243. */
pbres = pubnub_message_counts(pb, "one,two", "15517035062228243,15517035052228243");

Returns​

TypeValueDescription
enum pubnub_res
PNR_STARTED
Started
PNR_OK
Finished with a success (can only happen in the sync interface)
other
Failed, Indicates the type of error

Example: Single token for all channels​

/** Obtain message count for channels
        'one' and 'two' since 15517035062228243 */
pbres = pubnub_message_counts(pb, "one,two", "15517035062228243");

Read all channel message counts​

On input, @p io_count is the number of allocated counters per channel (array dimension of @p chan_msg_counters). On output(@p io_count), number of counters per channel written. If there are more channel message counters in the answer than there are in the allocated array (can't fit all), that will not be considered an error, they will simply not be written to @p chan_msg_counters. To see how much elements there are (and allocate accordingly), use pubnub_get_chan_msg_counts_size().

This is an alternative to pubnub_get_message_counts(), useful for exploratory usage, as one can get all the channel message counters that are in the report, without keeping track of what were the requested channels.

Unlimited message retention

For keys with unlimited message retention enabled, this transaction considers only messages published in the last 30 days.

Declaration​

int pubnub_get_chan_msg_counts(pubnub_t* pb, size_t* io_count, struct pubnub_chan_msg_count* chan_msg_counters);

Parameters​

* required
ParameterDescription
pb *
Type: pubnub_t*
The Pubnub context to use for transaction
io_count *
Type: size_t*
On input, the number of allocated counters per channel (array dimension of @p chan_msg_counters). On output, number of counters per channel written to @p chan_msg_counters.
chan_msg_counters *
Type: struct pubnub_chan_msg_count*
An array of channel message counters, allocated by the caller, filled in by this function.

Basic Usage​

struct pubnub_chan_msg_count chan_msg_count[CHAN_COUNT];
size_t count = CHAN_COUNT;
int rslt = pubnub_get_chan_msg_counts(pb, &count, chan_msg_count);
if (0 == rslt) {
    size_t i;
    for (i = 0; i < count; ++i) {
        printf("  Channel    = '%.*s'\n", (int)chan_msg_count[i].channel.size, chan_msg_count[i].channel.ptr);
        printf("  Message count  = %z'\n", chan_msg_count[i].message_count);
    }
}

Returns​

TypeValueDescription
int
0
Success (even if there are more channel message counts than is possible to write to @p chan_msg_counters)
-1
Error, messages not read (transaction still in progress, format error...)

Example: Make sure we have room for all the channel message counters​

int n  = pubnub_get_chan_msg_counts_size(pb);
if (n > 0) {
    struct pubnub_chan_msg_count *pchmsc = malloc(n * sizeof *pchmsc);
    if (pchmsc != NULL) {
        size_t count = n;
        int rslt = pubnub_get_chan_msg_counts(pb, &count, pchmsc);
        if (0 == rslt) {
            printf("Got %z counters, should be the same as %d\n", count, n);
        }
        free(pchmsc);
    }
}

Read counters for channels​

Reads message counters for the given channels (in @p channel) from the PubNub response to pubnub_message_counts().

Array dimension for @p o_count is the number of channels from the comma-separated channel list @p channel and it (@p o_count array) is allocated by the caller.

Message counts order in @p o_count is corresponding to channel order in @p channel list respectively, even if the answer itself has the channels in a different order. If a requested channel is not found in the PubNub response, the message counter in the respective @p o_count array member has a negative value.

If there is a channel name in the answer, not to be found in requested @p channel list, that is not considered an error.

This is an alternative to pubnub_get_chan_msg_count(), useful if we already maintain the list of channels and just want to get the message counters.

Unlimited message retention

For keys with unlimited message retention enabled, this transaction considers only messages published in the last 30 days.

Declaration​

int pubnub_get_message_counts(pubnub_t* pb, char const*channel, int* o_count);

Parameters​

* required
ParameterDescription
pb *
Type: pubnub_t*
The Pubnub context to use for transaction
channel *
Type: char const*
A comma-separated list of channels to read message counters from
o_count *
Type: int*
An array of message counters, allocated by the caller, filled in by this function.

Basic Usage​

int msg_count[2];
int rslt = pubnub_get_message_counts(pb, "one,two", msg_count);
if (0 == rslt) {
    printf("message counts: one -> %d, two -> %d\n", msg_count[0], msg_count[1]);
}

Returns​

TypeValueDescription
int
0
Success (even if there are channel message counts int @p channel that are not there in the response or vice-versa)
-1
Error, messages not read (transaction still in progress, format error...)
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